ALBERT

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 196〈/p〉 〈p〉Author(s): Zhendong Zhang, Hui Qin, Yongqi Liu, Liqiang Yao, Xiang Yu, Jiantao Lu, Zhiqiang Jiang, Zhongkai Feng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As a renewable and clean energy, wind energy plays an important role in easing the increasingly serious energy crisis. However, due to the strong volatility and randomness of wind speed, large-scale integration of wind energy is limited. Therefore, obtaining reliable high-quality wind speed prediction is of great importance for the planning and application of wind energy. The purpose of this study is to develop a hybrid model for short-term wind speed forecasting and quantifying its uncertainty. In this study, Minimal Gated Memory Network is proposed to reduce the training time without significantly decreasing the prediction accuracy. Furthermore, a new hybrid method combining Quantile Regression and Minimal Gated Memory Network is proposed to predict conditional quantile of wind speed. Afterwards, Kernel Density Estimation method is used to estimate wind speed probabilistic density function according to these conditional quantiles of wind speed. In order to make the model show better performance, Maximal Information Coefficient is used to select the feature variables while Genetic Algorithm is used to obtain optimal feature combinations. Finally, the performance of the proposed model is verified by seven state-of-the-art models through four cases in Inner Mongolia, China from five aspects: point prediction accuracy, interval prediction suitability, probability prediction comprehensive performance, forecast reliability and training time. The experimental results show that the proposed model is able to obtain point prediction results with high accuracy, suitable prediction interval and probability distribution function with strong reliability in a relatively short time on the prediction problems of wind speed.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419306958-ga1.jpg" width="159" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Jingxi Liu, Bo Xu, Lei Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gravity assist is widely applied in the deep space exploration because of its reliability and practicability. There are lots of research in the literature about the nearly coplanar situations. In this work, a three-dimensional model of gravity assist model is developed in a semi-analytical manner on the basis of the geometry relationship between the parameters of spacecraft before gravity assist and the orbital elements after gravity assist. The parameters include 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si278.svg"〉〈mrow〉〈msubsup〉〈mrow〉〈mi mathvariant="bold-italic"〉V〈/mi〉〈/mrow〉〈mrow〉〈mi〉∞〈/mi〉〈/mrow〉〈mrow〉〈mtext〉in〈/mtext〉〈/mrow〉〈/msubsup〉〈/mrow〉〈/math〉 (the hyperbolic excess velocity vector of the spacecraft before fly-by), 〈em〉H〈/em〉 (the height of fly-by) and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si279.svg"〉〈mrow〉〈mi〉θ〈/mi〉〈/mrow〉〈/math〉 (the dihedral angle between approach plane and fly-by plane). These equations can be used for analyzing the change of orbital elements in the process of gravity assist, discussing the influence of different parameters on them and deriving the condition that remains the semi-major axis unchanged. Curve fitting of the feasible region boundary of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si280.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈mi〉i〈/mi〉〈/mrow〉〈/math〉 and contour plot of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si281.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈mi〉i〈/mi〉〈/mrow〉〈/math〉 are utilized to analyze the pattern of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si282.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈mi〉i〈/mi〉〈/mrow〉〈/math〉 changing with different parameters. This method is a valuable reference for designing gravity assist trajectories to high inclination targets in the Solar system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 196〈/p〉 〈p〉Author(s): Homa Hosseinzadeh-Bandbafha, Esmail Khalife, Meisam Tabatabaei, Mortaza Aghbashlo, Majid Khanali, Pouya Mohammadi, Taha Roodbar Shojaei, Salman Soltanian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Biodiesel utilization is associated with reduced calorific value and increased nitrogen oxides emissions. Hence, various strategies are implemented to address these challenges such as water addition into diesel/biodiesel fuel blends. In line with that, this study was undertaken to explore the effect of water (3 wt.%) and aqueous carbon nanoparticles (38, 75, and 150 µM), as a novel fuel nanoadditive, on combustion and exhaust emissions of a diesel engine at a fixed engine speed of 1000 rev/min under four different engine loads ranging from 25% to 100% of full load conditions. Overall, the engine performance characteristics were improved by incorporating the aqueous carbon nanoparticles. In particular, the incorporation of carbon nanoparticles into water-emulsified biodiesel/diesel blends generally enhanced brake power and thermal efficiency while lowering specific fuel consumption. The most appealing performance features were observed for the emulsified fuel blend containing 38 µM carbon nanoparticles which increased brake power and brake thermal efficiency by 1.07 kW and 11.58% at full load operation, respectively, while it led to decreased brake specific fuel consumption by about 107.3 g/kWh. The addition of carbon nanoparticles to the water-emulsified fuel blends adversely affected unburned hydrocarbons and carbon monoxide emissions at full load conditions owing to an increase in carbon content of the fuel blends but it lowered nitrogen oxides emissions. The addition of water deteriorated the economic features of the fuel blend (i.e., the cost per kWh of power generated). However, carbon nanoparticles addition into the water-emulsified fuel blend partially neutralized the adverse economic effects of water due to its positive impacts on thermal efficiency. Overall, water-emulsified diesel/biodiesel containing 38 µM carbon nanoparticles could be regarded as the most promising emulsion fuel in terms of engine performance characteristics, nitrogen oxides emissions, as well as fuel economy.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 1 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): N.Y. Zaalov, E.V. Moskaleva〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper describes a study of the daily and yearly variability of one of the main characteristics of sporadic E layers (Es), the critical frequency (foEs). Our analysis is based on ionograms recorded by GIRO network ionosondes. The study estimates the spatial and temporal variability of the Es layer parameters and generates their statistics at different seasons and phases of the solar cycle. In turn, the statistics of the Es layer parameters can provide an assessment of the capability of the HF propagation forecasting. Further, maps of the distribution of Es layer critical frequency are produced. This paper implements the “cloud” model of Es layer in HF propagation model (Northern Ionosphere Model & Ray Tracing, NIM-RT) that can accurately reproduce many features observed in experimental measurements. Within this framework, a number of vertical sounding ionograms with the presence of Es layer are simulated based on the NIM-RT software.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Chukwuka Odibi, Meisam Babaie, Ali Zare, Md. Nurun Nabi, Timothy A. Bodisco, Richard J. Brown〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study uses the first and second laws of thermodynamics to investigate the effect of oxygenated fuels on the quality and quantity of energy in a turbo-charged, common-rail six-cylinder diesel engine. This work was performed using a range of fuel oxygen content based on diesel, waste cooking biodiesel, and a triacetin. The experimental engine performance and emission data was collected at 12 engine operating modes. Energy and exergy parameters were calculated, and results showed that the use of oxygenated fuels can improve the thermal efficiency leading to lower exhaust energy loss. Waste cooking biodiesel (B100) exhibited the lowest exhaust loss fraction and highest thermal efficiency (up to 6% higher than diesel). Considering the exergy analysis, lower exhaust temperatures obtained with oxygenated fuels resulted in lower exhaust exergy loss (down to 80%) and higher exergetic efficiency (up to 10%). Since the investigated fuels were oxygenated, this study used the oxygen ratio (OR) instead of the equivalence ratio to provide a better understanding of the concept. The OR has increased with decreasing engine load and increasing engine speed. Increasing the OR decreased the fuel exergy, exhaust exergy and destruction efficiency. With the use of B100, there was a very high exergy destruction (up to 55%), which was seen to decrease with the addition of triacetin (down to 29%).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Tingting Xu, Feng Xu, Gift Gladson Moyo, Yaya Sun, Zhihua Chen, Bo Xiao, Xun Wang, Zhiquan Hu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Syngas is an indispensable chemical raw material, which also can provide heat and power. Chemical looping reforming (CLR) with biofuels is one prospective method to produce syngas. M〈sub〉x〈/sub〉O〈sub〉y〈/sub〉 of 20 wt% (CuO, NiO and Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) supported on dolomite were prepared by the wet impregnation method used as the oxygen carriers (OCs) for syngas production in the CLR process with toluene in the lab-scale fixed bed reactor. The effects of the reduced temperature in FR and mass of OCs on the fuel conversion, syngas production and OCs utilization were studied. The study found that CuO/dolomite (CD) tended to generate CO〈sub〉2〈/sub〉, while Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/dolomite (FD) and NiO/dolomite (ND) were appropriate to syngas production. Although CD achieved the highest oxygen effective conversion of 95.90% at 950 °C and the best selectivity for CO〈sub〉2〈/sub〉, it was not a suitable OC for syngas production in CLR process since the cold gas efficiency, syngas yield and syngas purity for CD remained lowest under different reaction conditions. FD manifested the best performance at 900 °C with 30.0 g, exhibiting the highest cold gas efficiency and syngas yield of 54.23% and 1.16 Nm〈sup〉3〈/sup〉/L, and the corresponding syngas purity was 73.86%. The selection of temperature and mass of FD played a key role in the quality control of syngas. Low syngas purity and rapid deactivation in cyclic tests were main barriers for FD to behave as an excellent OC in the CLR process. Furthermore, ND was the most ideal OC of the three for syngas production with the optimum condition being at 900 °C with 20.0 g, the corresponding cold gas efficiency, syngas yield and syngas purity were 39.30%, 0.93 Nm〈sup〉3〈/sup〉/L and 90.59% respectively. ND exhibited the highest syngas purity of the three, and the satisfied H〈sub〉2〈/sub〉/CO ratios (around 2.0) were achieved under different reaction conditions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Tan Wu, Long Shao, Xinli Wei, Xinling Ma, Guojie Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The ORC (organic Rankine cycle) system has the advantages of simple structure, environmental friendliness, reliability and low capital cost. The expander is the key device of energy conversion in the ORC system, and its performance has a direct influence on that of the ORC. In this paper, a self-designed and manufactured radial inflow turbine is applied to low temperature waste heat power generation. The numerical model for the internal flow of the radial inflow turbine is established, and the numerical results show a better agreement with the experimental data. Firstly, the influence of blade stagger angles on nozzle performance is studied. The study finds that with the decrement of stagger angles under specific angle ranges, the velocity coefficient increases. However, the efficiency of the nozzle decreases sharply when the stagger angle exceeds 30°. Secondly, the influence of the blade profile on the efficiency of the rotor is investigated. The results indicate that with 〈em〉t〈/em〉 increasing, the efficiency of the rotor firstly increases, then decreases quickly. It increases by 1% compared with that of the original rotor, when the 〈em〉t =〈/em〉 1.95. At last, the performance of the turbine is researched numerically. This paper discovers that total-to-static efficiency of the turbine increases by 1.7% compared with that of the original turbine. This research provides orientation and basis for the improvement of aerodynamic design and performance of radial inflow turbine. As for practical application, the study can provide certain reference for the structure and blade profile design of nozzles and rotors to further improve the performance, and to offer some data for the operational control and tests.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Johanna Beiron, Rubén M. Montañés, Fredrik Normann, Filip Johnsson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As the share of non-dispatchable energy sources in power systems increases, thermal power plants are expected to experience load variations to a greater extent. Waste-fired combined heat and power has multiple products and is today primarily operated for waste incineration and to generate heat. To consider load variations in the power demand at these plants may be a way to provide system services and obtain revenue, however, the transient interaction between power and district heating generation for the type of steam systems used should be studied. This work describes the transient characteristics and timescales of cogeneration steam cycles to discuss the operational interactions between power and district heating generation. A dynamic model of the steam cycle of a 48 MW waste-fired combined heat and power plant is developed using physical equations and the modeling language Modelica. The model is successfully validated quantitatively for both steady-state and transient operation with data from a reference plant and is shown capable of characterizing the internal dynamics of combined heat and power plant processes. Simulations are performed to analyze steam cycle responses to step changes, ramps and sinusoidal disturbances of boiler load changes and variability in district heating inlet temperature and flow. The results give insight on the process timescales for the specific case studied; for example, with the present design a 10% boiler load change requires up to 15 min for responses to settle, while the corresponding time for a 10% change in district heating flow or temperature show settling times within 5 min. Furthermore, increasing the boiler ramp rate from 2 to 4%/min could reduce the rise time of power generation by 42%, which could be of economic significance in day-ahead power markets.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Guang Li, Zheyu Liu, Fan Liu, Bin Yang, Shuqi Ma, Yujing Weng, Yulong Zhang, Yitian Fang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Exergy-based analysis is a powerful method to evaluate, understand, and improve energy conversion processes. Compared with conventional exergy analysis, advanced exergy analysis can identify the improvement potential of each component and the interactions among components of the whole system. In this paper, the ash agglomerating fluidized bed (AFB) gasification process is simulated in Aspen Plus (version 8.0). Based on the simulation results, advanced exergy analysis is carried out to study the performance of the AFB gasification process. The exergy efficiency of the AFB gasification process is 82.13% and the total exergy destruction is 4670 kW. The result shows that 54.18% of the total exergy destruction can be avoided. The AFB gasifier has the largest potential for reducing exergy destruction. In addition, sensitivity analysis is performed to research the effects of carbon conversion, pressure and temperature on the exergy destruction of the AFB gasifier.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Juliano Pierezan, Gabriel Maidl, Eduardo Massashi Yamao, Leandro dos Santos Coelho, Viviana Cocco Mariani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the past decades, the quantity of researches regarding industrial gas turbines (GT) has increased exponentially in terms of number of publications and diversity of applications. The GTs offer high power output along with a high combined cycle efficiency and high fuel flexibility. As consequence, the energy efficiency, the pressure oscillations, the pollutant emissions and the fault diagnosis have become some of the recent concerns related to this type of equipment. In order to solve these GTs related problems and many other real-world engineering and industry 4.0 issues, a set of new technological approaches have been tested, such as the combination of Artificial Neural Networks (ANN) and metaheuristics for global optimization. In this paper, the recently proposed metaheuristic denoted Coyote Optimization Algorithm (COA) is applied to the operation optimization of a heavy duty gas turbine placed in Brazil and used in power generation. The global goal is to find the best valves setup to reduce the fuel consumption while coping with environmental and physical constraints from its operation. In order to treat it as an optimization problem, an integrated simulation model is implemented from original data-driven models and others previously proposed in literature. Moreover, a new version of the COA that links some concepts from Cultural Algorithms (CA) is proposed, which is validated under a set of benchmarks functions from the Institute of Electrical and Electronics Engineers (IEEE) Congress on Evolutionary Computation (CEC) 2017 and tested to the GT problem. The results show that the proposed Cultural Coyote Optimization Algorithm (CCOA) outperforms its counterpart for benchmark functions. Further, non-parametric statistical significance tests prove that the CCOA’s performance is competitive when compared to other state-of-the-art metaheuristics after a set of experiments for five case studies. In addition, the convergence analysis shows that the cultural mechanism employed in the CCOA has improved the COA balance between exploration and exploitation. As a result, the CCOA can improve the current GT operation significantly, reducing the fuel consumption up to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si94.svg"〉〈mrow〉〈mn〉3.6〈/mn〉〈mo〉%〈/mo〉〈/mrow〉〈/math〉 meanwhile all constraints are accomplished.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Wei Liu, Cheng Chen, Huijuan Wu, Chunhui Guo, Yuedong Chen, Wenqiu Liu, Zhaojie Cui〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a cradle-to-grave life cycle assessment was conducted on several typical domestic hot water systems across five climatic regions of China. Variations of the climate and energy supply in these regions and the energy efficiency grade of domestic hot water systems were also taken into consideration. The results suggest that evacuated tube solar systems are highly energy-efficient and low-cost, except in the region with the weakest solar radiation. Electric systems are extremely energy-intensive and uneconomical for domestic hot water use, although they have the least human and ecological toxicity potentials. Solar and air-source energy systems save energy; however, they use more materials and cause more human and ecological toxicity. From the severe cold region to the hot summer and warm winter region, the heat load of domestic hot water increases by 59%, resulting in an increase of 58–230% in primary energy demand. Accordingly, the environmental impacts of domestic hot water systems increase in varying degrees; however, few impacts decrease due to the different emission factors of different power grids. The raw materials used in the manufacture of domestic hot water systems and the energy required for the use of the systems are the most important contributors to all environmental impacts. The scenario analysis indicates that 24.5% of the primary energy demand and 25.7% of greenhouse gas emissions owing to domestic hot water use in China can be reduced by improving the energy efficiency, prompting the use of renewable energy sources, and reducing the usage of materials for domestic hot water systems, as the human and ecological toxicity potentials will increase by 0.1% and 10%, respectively, due to the increasing use of certain materials.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S019689041930946X-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Zhonghe Han, Xiaoqiang Jia, Peng Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Organic Rankine cycle (ORC) is an efficient technique to recycle the low temperature heat sources. The design method of the critical component, radial inflow turbine, is a main focus of research. A preliminary design method was developed to optimize eight critical parameters based on particle swarm optimization (PSO) algorithm. The isotropic efficiency was the objective function of the algorithm. Six working fluids were selected to conduct turbine design based on the design method. The turbine with R245fa was determined to be optimal due to its small geometry size, high exergy efficiency (0.929) and high load coefficient (1.1027). The off-design performance of R245fa turbine was investigated with the variation of pressure ratio (〈em〉PR〈/em〉), stator inlet temperature and power output. The results indicate that the turbine efficiencies increase with the reduction of 〈em〉PR〈/em〉 and turbine inlet temperature and the increase of power output. The exergy efficiency and isotropic efficiency drop slightly with the increase of turbine inlet temperature. So the turbine with R245fa exhibited good off-design performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Yifan Li, Gaoqiang Yang, Shule Yu, Zhenye Kang, Derrick A. Talley, Feng-Yuan Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The heat generated from electrochemical reactions has been considered one of the most significant issues in terms of the reliability of energy conversion devices. So far, no systematic study on the relation between heat generation and electrochemical reaction exists, especially in the form of experiments. In this study, changes of the temperature distribution and hydrogen evolution reaction (HER) on the catalyst coated membrane (CCM) in proton exchange membrane electrolyzer cells (PEMECs) are 〈em〉in-situ〈/em〉 visualized with the help of a novel PEMEC design, thermal spectroscopy and high-speed visualization system. At the channel-scale, the temperature increases rapidly for most of the active areas, and finally reaches the equilibrium state at 27 °C. The temperature distribution is non-uniform throughout the process. In addition, a series of pore-scale analyses are provided to clarify the relation between the temperature distribution and electrochemical reaction area. More interestingly, the rapid heat generation areas are found to be in a good agreement with the electrochemical reaction areas, which confirms that the heat is released during the reaction processes. Finally, the temperature evolution phenomena on the LGDL surface have also been recorded. These findings could help better understand the correlation between the cathode side electrochemical reaction and heat generation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Jiangjiang Wang, Yuzhu Chen, Noam Lior〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study integrates concentrated photovoltaic/thermal (PV/T) solar collectors into a natural gas combined cooling, heating and power (CCHP) system to both offer efficient use of solar energy and reduce greenhouse emissions. Using exergo-economic analysis based on energy level, an optimization method was proposed and used to configure and determine the PV coverage ratio on the PV/T collector for minimizing the products’ costs of the hybrid CCHP system. The optimization method considers the users’ annual variable energy loads and transforms the off-design operation conditions to the design parameters by employing the heat storage ratio of thermal storage tank and supplemental heat ratio of absorption heat pump. Based on the validated thermodynamic modeling, an exergy and exergo-economic analysis of the hybrid CCHP system are presented to reveal the influences of the PV/T configuration on the exergy efficiency and the products’ cost. As the PV coverage ratio on the PV/T collector was increased, it was found that the specific cost of the CCHP system-generated electricity rose and then slightly dropped, while the specific cost of the heat exergy decreased, and then slightly increased. The optimal coverage ratio, at which the minimal specific cost of the system products was attained, had a value of 1.0. The integration and optimization of the PV/T decreases the specific cost of the system products by 6.4%. Compared to the conventional exergo-economics analysis method, the specific cost of system electricity using the exergo-economic analysis based on energy level is 20.3% higher, and the costs of heat exergy are decreased.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Nicu Bizon〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, a real-time strategy for a fuel cell hybrid power system based on fuel optimization and load-following is analyzed to identify the critical parameters of the optimization problem. Because the dither’s frequency dictates the searching speed of the optimum in the perturbed extremum seeking algorithm, this parameter has been selected from multiple parameters involved in the optimization problem to improve the fuel economy based on sensitivity analysis. The sensitivity analysis reveals the multimodal behavior of the fuel economy, but also the best choice for the dither. The fuel cell hybrid power system is a highly dynamic system, so the optimization and control loops have been designed for a robust but efficient operation of the system based on new perturbed extremum seeking algorithm to track the optimum. Considering the recommended 100 Hz sinusoidal dither, the improvement in fuel economy is of 47.9 L for an 8 kW/12 s load cycle. Also, the electrical efficiency of the fuel cell system increases with 7.83%. Both improvements were estimated compared to a commercial strategy, called in the literature as static feed-forward strategy.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Minda Ma, Xin Ma, Weiguang Cai, Wei Cai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Carbon-dioxide mitigation in residential building sector (CMRBS) has become critical for China in achieving its emission mitigation goal in the “Post Paris” period with the growing demand for household energy service in residential buildings. This is the first paper to investigate the factors that can mitigate carbon-dioxide (CO〈sub〉2〈/sub〉) intensity and further assess CMRBS in China based on a household scale via decomposition analysis. The core findings of this study reveal that: (1) Three types of housing economic indicators and the final emission factor significantly contributed to the decrease in CO〈sub〉2〈/sub〉 intensity in the residential building sector. In addition, the CMRBS from 2001 to 2016 was 1816.99 MtCO〈sub〉2〈/sub〉, and the average mitigation intensity during this period was 266.12 kgCO〈sub〉2〈/sub〉·(household·year)〈sup〉−1〈/sup〉. (2) Ridge regression indicated that the robustness of the decomposition approach was sufficient for achieving reliable results for the decomposition analysis and CMRBS assessment. (3) The energy-conservation and emission-mitigation strategy caused CMRBS to effectively increase and is the key to promoting a more significant emission mitigation in the future. Overall, this paper covers the CMRBS assessment gap in China, and the proposed assessment model can be regarded as a reference for other countries and cities for measuring the retrospective CO〈sub〉2〈/sub〉 mitigation effect in residential buildings.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉a. Changes of CO〈sub〉2〈/sub〉 emission per household (CO〈sub〉2〈/sub〉 intensity) in the Chinese residential building sector via decomposition analysis; b and c. Total and intensity values of CO〈sub〉2〈/sub〉 mitigation in the residential building sector (2001–2016); d and e. CO〈sub〉2〈/sub〉 mitigation per capita and CO〈sub〉2〈/sub〉 mitigation per floor space in the residential building sector (2001–2016).〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419309069-ga1.jpg" width="406" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Hang Li, Zunlong Jin, Yi Yang, Yaowu Huo, Xiao Yan, Pan Zhao, Yiping Dai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nuclear energy with attractive expectation can be efficiently used by the supercritical carbon dioxide power system. However, amounts of the cooling heat is wasted in the nuclear power plant. Two conceptual designs of combined heat and power systems based on the supercritical carbon dioxide power system are proposed to exploit the waste heat. A comparison research is performed in thermodynamics and economics. Several key physical parameters are selected to investigate their effects on system performance, and multi-objective optimization using the Non-dominated Sorting Genetic Algorithms-II is carried out with the target of gaining maximum system exergy efficiency and minimum total product unit cost. The results of parameter analysis exhibit that there exist optimal values for two target functions with the increasing compressor pressure ratio for three thermal systems, and the system with heat pump needs the highest pressure ratio. Better system performance can be achieved by increasing the turbine inlet temperature and evaporator temperature. The multi-objective optimization results of genetic algorithm display that proposed two systems can gain an improvement by 7.02% and 8.45% for the system exergy efficiency, and 11.95% and 13.48% for the total product unit cost compared with the stand-alone supercritical carbon dioxide system, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): S.S. Rao, Monti Chakraborty, R. Pandey, A.K. Singh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research work, we have analyzed the data of critical frequency of the F〈sub〉2〈/sub〉 region ionosphere over southern low latitude station COCO (Keeling) Island (Geog. Lat. 12.20⁰S; Geomag. Lat. 22.83⁰S; Geog. Long. 96.80⁰E) for the period 2009-2013 and result thereof have compared with the IRI-2016 model. Our analysis shows a good correlation between variations in 〈em〉fo〈/em〉F〈sub〉2〈/sub〉 and solar flux at F10.7 cm wavelength. With concern to geomagnetic activity during the period 2009-2013, it has found that the variability in the monthly mean Ap index remained below 20 nT throughout the period 2009-2013. Concerning quiet time F〈sub〉2〈/sub〉 region variability, our results explicated the solar cycle, semiannual, and seasonal/annual variation in 〈em〉fo〈/em〉F〈sub〉2〈/sub〉. Similar oscillations in 〈em〉fo〈/em〉F〈sub〉2〈/sub〉 have been explored using the Lomb-Scargle Periodogram technique. We have also observed the fundamental mode (27 days) and its overtones (9 and 13-day) in the geomagnetic activity parameter (Ap). Analysis of 〈em〉fo〈/em〉F〈sub〉2〈/sub〉 showed the consistent presence of the semiannual anomaly and absence of the winter anomaly during the ascending phase of solar cycle-24. A presence of an annual component in normalized 〈em〉fo〈/em〉F〈sub〉2〈/sub〉 has been examined using regression analysis. A comparative study of ionosonde observed 〈em〉fo〈/em〉F〈sub〉2〈/sub〉 with IRI-2016 modeled 〈em〉fo〈/em〉F〈sub〉2〈/sub〉 showed that the general ionospheric trends in IRI predictions are consonant with the observations for the diurnal, seasonal, and solar cycle variation. However, a deviation in the amplitude of 〈em〉fo〈/em〉F〈sub〉2〈/sub〉 up to the order of 5 MHz depending upon local time, seasons, and phases of the solar cycle has observed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): K. Chopra, V.V. Tyagi, Atin K. Pathak, A.K. Pandey, Ahmet Sari〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In this study, the thermal performance of a novel solar collector integrated with stearic acid as phase change material has been investigated. In this design, the solar radiation was collected by heat pipe equipped evacuated tubes and then stored in manifold integrated with phase change material. The stored thermal energy of phase change material then transferred to water flowing through bundle of finned copper pipes placed inside the manifold. In present study, the design, the operating principle and the experimental investigation of the developed system have been presented. The developed system was investigated with different mass flow rates and also discussed the influence of varying mass flow rate on the thermal performance of system. The experimental investigation of designed and developed system has been carried out for two modes i.e. mid-day charging mode and full-day charging mode. It has been observed that for considered mass flow rates, thermal efficiency of the system was varied in the range of approximately 52–62% for full-day charging mode while for mid-day charging mode, it was varied between 55 and 72%. The maximum value of thermal efficiency was approximately 72.52% at mass flow rate of 24 LPH for mid-day charging mode. The efficiency of phase change material for both modes was varied in the range of approximately 61–64%. The annual cost and annual fuel cost of the developed system are much lower than conventional system. Also, the initial capital cost for the developed system can be recovered after 6 years of operation. However, there is no recovery of initial investment for electricity based water heating system.〈/p〉 〈p〉The proposed system overcomes two problems associated with conventional heat pipe evacuated tube solar collector: elimination of heat pipe overheating problem and low thermal conductivity of phase change materials. By this novel design of manifold, the influence of thermal stratification on the thermal performance of solar collectors can be completely eradicated.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): M.E. Demir, G. Chehade, I. Dincer, B. Yuzer, H. Selcuk〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The synergistic effects of titanium dioxide photocatalysis in combination with Fenton-like reactions for photoelectrochemical based hydrogen production and wastewater treatment is investigated in a newly designed photoelectrochemical reactor. Here, titanium dioxide nanoparticles are coated on the anode to enhance both hydrogen production and wastewater treatment processes. The reactor is tested under 600 W/m〈sup〉2〈/sup〉 of solar irradiance and is characterized using electrochemical, chemical oxygen demand, absorbance, and ultraviolet–visible absorption spectroscopy techniques. The results show that the oxygen evaluation in the anolyte is substituted by iron(II)/iron(III) ions and the presence of hydrogen peroxide forms up the hydroxyl radicals via Fenton like process for degradation of organics in wastewater. While, hydrogen gas production in the catholyte is improved up to 8% by the means of proton reduction at the cathode in an acid medium. Also, 33% chemical oxygen demand removal efficiency of the synthetic textile wastewater (Reactive Black 5) is recorded in 17 h. This new hybrid configuration combines three different photo-assisted advanced oxidation processes such as ultraviolet/Fenton, ultraviolet/titanium dioxide, and ultraviolet/hydrogen peroxide with electrolysis process which increases hydrogen gas production rate and treats the wastewater.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308945-ga1.jpg" width="347" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Mohammad Javad Kalaee, Yuto Katoh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We consider the equatorial region of the magnetosphere, where the magnetic field is perpendicular (or near to perpendicular) to the density gradient and mode conversion process from UH to LO-mode waves or reverse process are expected. We review and study the mode conversion from UH (upper hybrid) to LO (left hand polarized ordinary) mode waves by a spatially two dimensional plasma fluid code. Several simulations with different initial wave vectors under the same background plasma condition have been performed. We focus on the conversion efficiency from the UH-mode waves with purely perpendicular wave normal angle to the LO-mode waves, since one of the source of generation UH wave can be Bernstein mode as the purely perpendicular electrostatic waves. For this special case, the UH wave normal is kept in perpendicular direction with respect to the magnetic field, and difficult to be in matching direction for conversion to LO mode〈em〉.〈/em〉 Simulation results show that the mode conversion efficiency in this particular case is very weak, since two branches of Z-mode wave and LO mode wave in the dispersion relation are disconnected. We present a discussion to show that for this case (purely perpendicular propagation) a special angle (except 90 degrees), between the magnetic field and the density gradient is necessary for occurrence of efficient mode conversion. For the case (purely perpendicular propagation and the magnetic field perpendicular to the density gradient), the mode conversion just occurred via the tunneling effect, where a steepness of the inhomogeneity plays an essential role.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Yanguang Fu, Xinghua Zhou, Dongxu Zhou, Jie Li, Wanjun Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sea level variability in the South China Sea (SCS) was investigated by means of satellite altimetry and tide gauge data over a 24 years period 1993–2016. The sea level anomalies (SLAs) retrieved from satellite and tide gauge data were compared. The differences between the two datasets showed a normal distribution with 87% within ±10 cm. Considering the individual time series, the results revealed that satellite and tide gauge SLAs are in good agreement, with root mean square deviations in the range 0.9–9.9 cm (average value is 2.7 cm), and correlation coefficients exceeding 0.7 for 85% of stations. Positive linear trends of sea level were estimated for both datasets, with good agreement in most cases. The averaged linear trend of SLAs in the SCS showed a rise of 4.4±0.3 mm year〈sup〉–1〈/sup〉 during 1993–2016, consistent with the nonlinear trend of satellite and tide gauge (4.3±0.3 and 3.9±0.1 mm year〈sup〉–1〈/sup〉, respectively) extracted through empirical mode decomposition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Dechao Wang, Lijun Jin, Yang Li, Baoyong Wei, Demeng Yao, Haoquan Hu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To understand the effect of reducibility of transition metal oxides (TMOs) on tar conversion, four TMOs including Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, MnO〈sub〉x〈/sub〉, CuO, and NiO were selected and in-situ oxidative catalytic cracking of coal pyrolysis tar on a two-stage fixed bed reactor at 550 °C was performed. The reducibility of TMOs was measured by H〈sub〉2〈/sub〉-temperature programmed reduction (H〈sub〉2〈/sub〉-TPR). The effect of reducibility of TMOs on the pyrolysis products distribution and conversion was investigated. The changes of TMOs before and after reaction were also analyzed by several characterizations. The addition of TMOs results in the decrease of tar yield and heavy tar content, and the increase of gas yield. The reduction temperature of TMOs affects the products distribution and heavy tar conversion. Among these four TMOs, Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 shows the highest reduction temperature (390–700 °C with peak centered on 570 °C) and the largest heavy tar conversion (75.3 wt%). CuO shows the lowest reduction temperature (190–470 °C with peak centered on 326 °C) and heavy tar conversion (45.8 wt%). The main reactions on CuO is complete oxidation with high water yield (12.8 wt%) and CO〈sub〉2〈/sub〉 formation (110 mL/g.coal〈sub〉daf〈/sub〉). The coke formed on the used Fe〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 is amorphous or disordered carbon, and shows the largest yield being 5.5 wt%.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308532-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Diego Vittorini, Roberto Cipollone, Roberto Carapellucci〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The full exploitation of the upper thermal source is the key for enhanced energy performances of ORC-based units for medium and low-grade waste heat recovery. The adoption of a dual evaporation pressure cycle layout has the potential to reduce the heat exchange irreversibility at the evaporation section and to assure a higher net power available at the expander shaft, particularly in small scale units and in presence of upper thermal sources with a highly variable heat release characteristic. The adoption of the dual evaporation pressure technology to small scale recovery units represents a major technological breakthrough and an element of novelty, observing that, at present, the possibility to split the evaporation process in multiple pressure levels is considered mostly with reference to steam generators and boilers. The study investigates the potential energy and exergy advantage of a dual pressure heat recovery vapor generator, with respect to a base-single evaporation pressure layout, for a recovery unit with a mechanical power in the 1–15 kW range, for stationary (100 °C–150 °C hot source temperature) and on-board (350 °C–300 °C hot source temperature) applications. A dedicated optimization procedure allows the maximization of either the net power recovered or the cycle energy efficiency, dependently on the final application of the unit. The exergy efficiency of the heat recovery vapor generator is assessed and its dependence on the fluid characteristics and the main cycle variables discussed, along with the relationship between the energy and exergy gain for the enhanced heat exchange. A preliminary economic analysis provides a first indication of the financial merit of the dual evaporation pressure layout with respect to a base single evaporation pressure configuration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Seyed Sina Hosseini, Mehdi Mehrpooya, Ali Sulaiman Alsagri, Abdulrahman A. Alrobaian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The object of this paper is to develop and exergetically assess a multi-generation system comprised of a Molten Carbonate Fuel Cell (MCFC) coupled with Steam Methane Reforming (SMR), Methanol Synthesis Process (MSP) with distillation process, and combined heat and power cycle (CHP) including gas turbine, Rankine cycle (RC), Organic Rankine Cycle (ORC) and District Heating (DH) line. The combination of the MCFC, CHP and MSP can be considered as an innovative breakthrough in the field of energy systems, in light of the fact that the reforming compartment can mutually feed both MCFC and MSP, and the whole process can simultaneously produce electricity, pure methanol and hot water. The SMR at 800 kPa and 600 °C was applied to produce synthetic gas required by MCFC and MSP. The simulation was performed by Aspen Hysys, considering several operational conditions and the best was selected according to exergetic performance assessment. The structure produced 110,544 kW net electricity (34% MCFC, 33.4% gas turbine, 18.4% RC and 14.2% ORC), pure methanol (99.9%) at 271.7 kgmole/h, and hot water at 80 °C and 65398.7 kgmole/h. About 23% and 21% of the overall destructed exergy belonged to combustion chamber and MCFC, respectively. The overall exergy destruction, exergy efficiency and energy efficiency of the integrated system were obtained 116,353 kW, 58.4% and 83.7%, respectively. Finally, the performance of the proposed hybrid system was compared with similar studies and it was found that the hybrid MCFC-MSP-CHP system can outstandingly enhance the overall efficiency and reduce CO〈sub〉2〈/sub〉 emissions.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S019689041930860X-ga1.jpg" width="357" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 200〈/p〉 〈p〉Author(s): Ranjana Chowdhury, Shiladitya Ghosh, Dinabandhu Manna, Sumona Das, Sambit Dutta, Sabine Kleinsteuber, Heike Sträuber, Md. Kamrul Hassan, Suvi Kuittinen, Ari Pappinen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lignocellulosic biomass (LCB), the most abundant renewable feedstock for bioenergy generation, is commonly converted to second generation bioalcohols, the main drop-in fuels for petroleum gasoline, through three technologies based on sugar, carboxylic acid and syngas platforms. The hybridization of either any two or three platforms altogether is a novel concept aimed at improvement of yield and quality (high heating value) of bioalcohols. This article reviews the present status of the integration techniques of hybrid platforms with an overall assessment of their advancement with respect to their individual counterpart as well as the challenges involved. It has been indicated that to extract the maximum benefit of hybridization, research studies should be spurred in the fields of kinetic analysis of all thermochemical and biochemical processes, microbial interaction, optimization of process parameters (pH, temperature), performance analysis of engine for the utilization of mixed product bioalcohols, sustainability analysis through the development of mathematical models for lab-scale operations and process simulation models for large scale units along with life cycle assessment. Moreover, pyrolysis of LCB has been identified as a unique central process for the supply of all intermediate compounds, namely, sugar, carboxylic acid and syngas during the hybrid networking of three platform technologies. In this context, the scheme of CONVER-B, a joint research project under the INNO-INDIGO partnership program, aiming at sustainable integration of the platforms to produce bio-alcohols from LCBs leaving zero effluent simultaneously with carbon sequestration potential has been introduced and discussed.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419311173-ga1.jpg" width="279" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 200〈/p〉 〈p〉Author(s): Tiancheng Ouyang, Zixiang Su, Guicong Huang, Zhongkai Zhao, Zhiping Wang, Nan Chen, Haozhong Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The severe energy crisis and environmental deterioration we face today requires the development of novel methods to control emissions and enhance energy savings. In this investigation, based on the thermodynamic theory, a combined system including a dual-loop organic Rankine cycle, absorption refrigeration, and flue gas purification is modeled. The system can use various forms of waste heat to realize cascade utilization. Initially, through comparisons with existing experimental data, we verified the accuracy of the numerical simulation. The parameters affecting system performance are analyzed and discussed comprehensively. In addition, considering the contribution of the refrigeration system, a genetic algorithm is used to calculate the equivalent system output power. The optimized equivalent output power, thermal efficiency, and exergy efficiency are calculated as 1668.47 kW, 59.6%, and 57.29%, respectively. The results of the emission reduction analysis indicate that the purification system exhibits excellent removal performance with a desulfurization and denitrification efficiency of 99.8% and 45.52%, respectively, and the energy regulatory metrics meet the 2020 emission requirements. Therefore, this novel design can be considered as a feasible method to resolve energy inefficiency and emission reduction in ships.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419311082-ga1.jpg" width="212" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 200〈/p〉 〈p〉Author(s): Minghui Ge, Xiaowei Wang, Yulong Zhao, Shixue Wang, Liansheng Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The gasification process of liquified natural gas (LNG) releases a significant amount of cold energy. Traditional vaporizers release cold energy directly into the environment, resulting in energy wastage. In this study, a novel type of vaporizer with a thermoelectric generator (VTEG) that combines an air-heated vaporizer and thermoelectric power generation technology is designed. The heat transfer and generation characteristics of the VTEG are analyzed based on the modeling and calculations. The results reveal that compared with the traditional vaporizer, the outer wall temperature of the VTEG increases by 18.4–35.6 K, which mitigates the frosting problem on the surface of the vaporizer. When the fluid is in the liquid-phase and two-phase region, the generation efficiency is maintained between 1.57% and 2.12%. In the gas-phase region, a gradual decrease in the generation efficiency is observed in accordance with an increase in the natural gas temperature. Moreover, the low generation efficiency of the VTEG can be attributed to the low natural convection heat transfer coefficient outside the tube. An increase in tube length first results in an increase in the output power of the VTEG, which then decreases. An optimal tube length exists at which the VTEG output power is maximum value. In addition, the influence of the flow on the single-phase regions is more significant, wherein an approximately linear increase in the optimal tube length and maximum output power occur in accordance with an increase in the flow. Therefore, suitable selection of tube length of the VTEG is very important.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Jun Hou, Ziyou Song, Heath Hofmann, Jing Sun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hybrid energy storage systems have been widely used in transportation, microgrid and renewable energy applications to improve system efficiency and enhance reliability. However, parameter uncertainty can significantly affect system performance. In order to address this issue, an adaptive model predictive control is developed in this paper. Online parameter identification is used to mitigate parameter uncertainty, and model predictive control is used to optimally split power, deal with constraints, and achieve desired dynamic responses. A sensitivity analysis is conducted to identify major impact factors. In order to validate the proposed method, both simulation and experiments are performed to show the effectiveness of the proposed adaptive model predictive control. Compared to the model predictive control without online parameter identification, the power loss reduction can be as high as 15% in the experiments. This study focuses on all-electric ship energy management to mitigate load fluctuations and improve system efficiency and reliability. The proposed method could also be used in other applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Abdullah Nsair, Senem Önen Cinar, Hani Abu Qdais, Kerstin Kuchta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work has investigated the effect of stirring on the performance of two anaerobic digesters for a period of six years. In each digester, two propellers and one hydro-mixer were installed. 〈strong〉Five different stirring scenarios were tested and adopted for this large scale biogas plant. Agricultural residuals were used as feedstock for this biogas plant.〈/strong〉 The results showed that the optimization of the operating duration of the stirrers has led to an increase of the specific electricity yield and a reduction of the electricity consumed by the stirrers by 21.5% and 13.5%, respectively. Furthermore, the investigation found that the long turning off periods of the stirrers (45 min or longer) has led to a faster creation of sedimentation and lowering the biogas yield. The optimal operation durations were found to be 3–5 min with breaks of 25–30 min. The electricity yield and efficiency, as well as the homogeneity of the biodegradable feedstock in the fermenters, were used to evaluate the stirring scenarios. 〈strong〉Moreover, a computational fluid dynamic model was used to assist in evaluating the stirring inside the fermenters at different total solid values and to examine the use of different mechanical stirring technologies on preventing the creation of dead zones.〈/strong〉〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419309227-ga1.jpg" width="447" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Ruiyu Chen, Quanwei Li, Xiaokang Xu, Dongdong Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pyrolysis is considered as a promising method to dispose polymer waste. To provide guidance for pyrolysis recycling of representative non-charring polymer namely poly(methyl methacrylate) (PMMA) waste with micron particle size, the pyrolysis kinetics and reaction mechanism of micron PMMA waste in nitrogen are studied in the present study. Thermogravimetric analyses at 5, 10, 20, 30 and 40 K/min coupled with two model-free methods including Senum-Yang and advanced Vyazovkin method as well as one model-fitting method namely Coats-Redfern method are employed. Results indicate that the micron PMMA waste pyrolysis may be nominally considered as one-step reaction. The reaction model and mechanism in charge of the micron PMMA waste pyrolysis may be 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si80.svg"〉〈mrow〉〈mi〉g〈/mi〉〈mrow〉〈mo stretchy="false"〉(〈/mo〉〈mi〉α〈/mi〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈msup〉〈mrow〉〈mfenced close=")" open="("〉〈mrow〉〈mrow〉〈mn〉1〈/mn〉〈mo〉-〈/mo〉〈mi〉α〈/mi〉〈/mrow〉〈/mrow〉〈/mfenced〉〈/mrow〉〈mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈mo stretchy="false"〉/〈/mo〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈mo linebreak="badbreak" linebreakstyle="after"〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/math〉 and chemical reaction, respectively. The average values of the activation energy and pre-exponential factor are 243.69 kJ/mol and 1.19 × 10〈sup〉19〈/sup〉 min〈sup〉−1〈/sup〉, respectively, which are both larger than those of traditional PMMA with particle size in millimeter or larger level. Based upon the one-step reaction model and the obtained kinetic parameters, the predicted thermogravimetric data agree well with the experimental results not only at heating rates of 5, 10 and 20 K/min which are employed to calculate the kinetic parameters, but also at heating rates of 30 and 40 K/min beyond those used to calculate the kinetic parameters.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Fernanda Cristina Nascimento Silva, Daniel Flórez-Orrego, Silvio de Oliveira Junior〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉On offshore platform applications, power and heat are normally supplied by simple open cycle gas turbine (OCGT) and heat recovery steam generators (HRSG) at lower efficiencies if compared to onshore combined cycle systems. Certainly, due to the reduced available space and the weight constraints, combined cycles are not commonly considered as cogeneration systems on conventional offshore petroleum platforms. However, more stringent environmental policies for the natural gas and oil production activities have motivated the integration assessment of advanced technological solutions that aim to mitigate the environmental impact that conventional offshore platforms are responsible for. Accordingly, in this paper, the effect of the integration of a low emission, oxyfuel gas turbine cycle is analyzed and compared against an amines-based post-combustion system and a conventional offshore petroleum platform operation in terms of its exergy efficiency and reduced atmospheric CO〈sub〉2〈/sub〉 emissions. Indeed, although the conventional configuration is the most efficient, the oxyfuel powered platform configuration presents close power cycle efficiency of 27.10% and the lowest specific CO〈sub〉2〈/sub〉 emissions of 0.014 kg〈sub〉CO〈sub〉2〈/sub〉〈/sub〉/t〈sub〉oil〈/sub〉, whereas the amines-based layout provides the best cogeneration efficiency (55.34%) of the advanced configurations. Moreover, an energy integration analysis is performed to identify the heat recovery potential, while the exergy method is used to evaluate and quantify the most critical components that lead to the largest irreversibilities along the primary separation, cogeneration and gas compression systems. As a result, the study points to ways of decarbonizing offshore applications in the oil and gas sector.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 13 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Pascal Willis〈/p〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Z. Yan, A. He, S. Hara, N. Shikazono〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a modeling framework is proposed for the optimization of the solid oxide fuel cell (SOFC) electrode microstructures. This involves sequential simulations of the SOFCs from initial powder to final electrochemical performance with artificial intelligence-assisted multi-objective optimization. The effects of starting powder parameters such as particle size, particle size distribution (PSD) and pore former content on cathodic overpotential and degradation rate of SOFCs are studied. It is shown that fine particle size and/or low pore former content lead to low cathodic overpotential but high degradation rate in the investigated range of the parameters. Predictive models for the cathode overpotential and degradation rate are established by an artificial neural network using the simulation data. The Sobol global sensitivity study suggests that particle size and pore former content play important roles in determination of the cathode overpotential and degradation rate while the PSD effect is insignificant. A multi-objective genetic algorithm (MOGA) is used to minimize both the overpotential and degradation rate of the cathode. The Pareto front is obtained for the optimal design of cathode microstructures. Compared to the grid search method, the MOGA proves to be more robust and efficient for SOFC electrode microstructure optimization.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419309070-ga1.jpg" width="324" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Ahmad Hajatzadeh Pordanjani, Saeed Aghakhani, Masoud Afrand, Boshra Mahmoudi, Omid Mahian, Somchai Wongwises〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper a brief review on application of nanofluids in heat exchangers has been addressed. One of the barriers to increase the capacity of different industries is the lack of response of heat devices in higher capacities. In addition, increasing capacity leads to an increase in pressure drop and this is one of the most important restrictions on the large industries. Conventional methods of increasing heat transfer greatly increase the pressure drop, and according to the results of previous studies, using the special nanofluids, the thermal efficiency of the heat exchanger can be increased significantly, which is one of the most important thermal devices in the industry. In this research, firstly a review of nanofluids studies and introduction of nanofluids is presented, then their simulation methods are investigated, and finally, studies on the used tubes in the heat exchangers have been investigated, and studies of the plate heat exchanger, helical heat exchanger, shell and tube heat exchanger, and double-tube heat exchanger have been examined. The enhancement of thermal and hydraulic performance of heat exchangers is very important in terms of energy conversion, and also is important in the economic recovery of systems through savings. This paper examines previous studies on heat exchangers and using of nanofluids in them. The purpose of the paper is not only to describe the previous studies, but also to understand the mechanisms of heat transfer in the field of using nanofluids in heat exchangers, and also to evaluate and compare different heat transfer techniques. Finally, it can be concluded that the nanofluids in most cases improve heat transfer, which reduce the volume of heat exchangers, saving energy, consequently water consumption and industrial waste.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Wenlei Xie, Fei Wan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the current research, a porous solid base catalyst (ZIF-90-Gua) was prepared through covalent post-functionalization of zeolitic imidazolate framework ZIF-90 with organic guanidine 〈em〉via〈/em〉 an imine condensation reaction. Various techniques such as XRD, SEM, FT-IR, XPS, EDX, TPD, Hammett indicator titration and nitrogen porosimetry measurements were employed to characterize the as-prepared solid catalyst. It was shown that the organic guanidine had been bound on the ZIF-90 frameworks by covalent imine linkages, and the primary crystalline structure of the imidazolium-based ZIF-90 was essentially maintained after the guanidine incorporation. This ZIF-90-Gua catalyst possessed an enhanced basicity, and interconnectivity, leading to highly catalytic activities. As a robust catalyst, the catalytic performances were evaluated in the heterogeneous transesterification of soybean oil with methanol for biodiesel production, and the maximum oil conversion to biodiesel of 95.4% was attained at reaction temperature of 65 °C, with a methanol/oil molar ratio of 15:1, catalyst dosage of 1 wt% (based on the oil mass) within reaction duration of 6 h. The solid catalyst could be easily recovered by filtration and reused for five times without significant decay of the catalytic activity, showing that it has great potential to be used as an efficient and durable catalyst for the clean production of biodiesel.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419309136-ga1.jpg" width="459" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Young Choi, Assmelash Negash, Tae Young Kim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, thirty of customized bismuth-telluride (Bi〈sub〉2〈/sub〉Te〈sub〉3〈/sub〉) thermoelectric modules (TEMs) were fabricated for waste heat recovery of a diesel engine using a thermoelectric generator (TEG). By installing a plate-type porous medium whose porosity ranges from 0.121 to 0.516 in the TEG, the effects of the porosity on energy harvesting performance were investigated. Experimental results show that at the highest engine rotation speed of 1400 rpm, a maximum power output of 98.3 W was obtained using the lowest porosity (0.121), and a maximum energy conversion efficiency of 2.83% was obtained using the optimal porosity (0.416). The most significant improvements in the power output and conversion efficiency compared with the base case without porous media were 44.5% and 10.1% with porosities of 0.121 and 0.416, respectively, at the lowest engine speed of 1000 rpm. We concluded that the conversion efficiency and power output of the present TEG can be maximized via application of porous media with porosities of 0.461 and 0.32, respectively. The use of a porous medium with a porosity of 〈0.32 in the present TEG configuration should be avoided, as the backpressure would exceed the allowable limit of ~3 kPa for a passenger vehicle.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research, Volume 64, Issue 6〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research, Volume 64, Issue 6〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Jia Wang, Jianchun Jiang, Xiaobo Wang, Peng Liu, Jing Li, Guanghua Liu, Kui Wang, Mi Li, Zhaoping Zhong, Junming Xu, Arthur J. Ragauskas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Catalytic conversion of rubber wastes to produce an alternative fuel resource is a promising approach to dispose of solid wastes and address environmental issues. In this study, catalytic fast pyrolysis (CFP) of rubber wastes over acidic zeolites was conducted, and the effect of SiO〈sub〉2〈/sub〉/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 mole ratio of USY zeolites on the formation of aromatic hydrocarbons was explored. Experimental results indicated that alkenes and aromatic hydrocarbons were the main pyrolytic products obtained from fast pyrolysis of rubber wastes, and the pyrolysis temperature played a vital role in the formation of aromatics with the highest concentration achieved at 750 °C. Moreover, catalyst types also affected the catalytic degradation of rubber wastes since limonene was completely decomposed in the presence of zeolites. Compared to SAPO-34, zeolites with higher external surface area, stronger Brønsted acid sites, and larger pore size, including USY, HY, and Hβ, were more effective in the production of aromatic hydrocarbons with the highest content obtained from USY catalyzed run. Given the observed effect of SiO〈sub〉2〈/sub〉/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 mole ratio of USY zeolites on the formation of aromatic hydrocarbons during the CFP of rubber wastes, USY with low SiO〈sub〉2〈/sub〉/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 ratio of 5.3 was more beneficial to the generation of aromatic hydrocarbons, while that with higher SiO〈sub〉2〈/sub〉/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 mole ratio (11.5) facilitated the formation of alkenes. Simultaneously, the product distribution of aromatic hydrocarbons obtained from CFP of rubber wastes over USY zeolites was dominated by xylenes, alkylbenzenes, and toluene, and USY with SiO〈sub〉2〈/sub〉/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 mole ratio of 5.3 was more active in the production of toluene and xylenes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): S.C.S. Alcântara, A.A.V. Ochoa, J.A.P. da Costa, P.S.A. Michima, H.C.N. Silva〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work presents an energy and financial analysis of an energy trigeneration system, in which electricity, steam and chilled water are produced simultaneously using natural gas as source of input. The system consists of an internal combustion engine, a domestic heat recovery unit, a LiBr/H〈sub〉2〈/sub〉O absorption chiller to produce chilled water and a recovery boiler to produce steam. In this system, the exhaust gases produced by the engine are used to drive an absorption chiller through a heat exchanger and can also drive a recovery boiler. According to the final results, and considering total engine load, the overall system of trigeneration presented an energy utilization factor of 74%, with average electricity, cooling and heating production of 214.1 kW, 35.7 kW and 162.1 kW, respectively. A case study based on the energy demands of an ice cream industry is presented in this article for the financial analysis of the system. In order to determine the best configuration for the company, the one that presented a higher financial return, three scenarios were developed for the application of cogeneration or trigeneration in the company. They were analyzed on the financial methodology of calculation of return on investment, using as parameters the net present value (NPV), the internal rate of return (IRR) and the simple payback, based on an interest rate of 6.4% and a project period of 10 years. The first two scenarios created were not economically viable, presenting a negative NPV. However, scenario 3 presented good financial return result, presenting a NPV of $ 269,390.40, a 26.32% IRR and a 3.4 year simple payback, making it the best financial scenario for the company. The results of this work indicate that the configuration proposed in scenario 3 provides several useful results with high efficiency and a good financial return for the company.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Scheme of the Trigeneration System – An energetic and economic assessment.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308428-ga1.jpg" width="309" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Jing Luo, Tatiana Morosuk, George Tsatsaronis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A combined cycle coupling a supercritical power cycle with a transcritical refrigeration cycle with carbon dioxide as working fluid is evaluated and optimized from the exergoeconomic viewpoint. The system is designed to produce power, refrigeration, and heating simultaneously. If no net power is generated, the system can be described as a cogeneration. First, the cogeneration system working with various evaporation temperatures is optimized for having the lowest average cost of the products, which indicates that the system is preferred to operate at the lower evaporation temperature. Then for tri-generation, by increasing the power output and the pressure merging two sub-systems, the cost of the products (average and individual) reduces and the efficiency of the overall system increases. In addition, the cost of the power is the lowest while the cost of the refrigeration is the highest, and the cost of the heating is sensitive to the operation conditions of the overall system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 7 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Kaishi Zhang, Wenhai Jiao, Liang Wang, Zishen Li, Jianwen Li, Kai Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Global Navigation Satellite System (GNSS), once dedicated to military and geodetic applications, is entering civilian life with the development of low-cost internal multi-GNSS chips in mass-market smart devices. The recently enabled Application Programming Interface (API) to GNSS raw measurement in Android Nougat operating system, make it possible to implement precise positioning technology on Android smart devices, such as Real-Time Kinematic Positioning (RTK) and Precise Point Positioning (PPP). An optimized kinematic positioning approach on Android smart devices with Doppler-Smoothed-Code (DSC) filter and Constant Acceleration (CA) model is assessed in this paper. In this optimized approach, DSC filter is used to reduce the code measurement noise, which is extremely high on smart devices and CA model is used to accurately predict the kinematic state of smart devices. The optimized approach is named Smart-RTK for its applicability to smart devices, respectively. The performance of the Smart-RTK approach is validated by two Google/HTC Nexus 9 tablets separately under stationary, walking, and vehicular condition. The numerical experiments show the significant improvement on positioning accuracy and continuity. The positioning Root Mean Square Error (RMSE) in horizontal component reaches about 0.3–0.6 m in stationary condition and 0.4–0.7 m in walking condition, improved by about 85% compared with that of chipset original solutions. In the subsequent vehicular experiment, the horizontal positioning RMSE is about 0.85 m, 50% better than that of chipset solutions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Ali Zahedi Miran, Arash Nemati, Mortaza Yari〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present study, a transcritical refrigeration cycle’s performance with dedicated mechanical subcooling (MS) is investigated from the energy, exergy and exergoeconomic viewpoints. Three different refrigerants containing CO〈sub〉2〈/sub〉 (R744), N〈sub〉2〈/sub〉O (R744A) and ethane (R170) are considered as the transcritical cycle’s refrigerant. A thorough parametric study is carried out on the system and finally, the effect of dedicated subcooling system is checked out on the energy, exergy and exergoeconomic perimeters. Based on the results, value of the COP and exergy performance for N〈sub〉2〈/sub〉O, unlike the CO2, is the highest. In other words, the CO〈sub〉2〈/sub〉 refrigerant shows the best economic performance. By comparing the system with and without subcooling cycle, it can be concluded that utilizing subcooler improves performance of the system and increases the unit product cost. However, the unit product cost increment is much lower than COP improvement which makes the subcooling an effective and economical way to improve the refrigeration system’s performance. Application of subcooler leads to an enhancement of 30.74%, 26.48% and 36.1% in COP for CO〈sub〉2〈/sub〉, N〈sub〉2〈/sub〉O, and ethane, respectively while the unit product cost increment is 9.04%, 8.37% and 10.63% for the mentioned refrigerants, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Kai Shen, long Chang, Hong Chen, Zhendong Zhang, Bo Wang, Yingjie Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Over the decades, unremitting efforts have been made to achieve energy conservation and emission reduction throughout the world. While for a vehicle engine, a great deal of the fuel energy is wasted as exhaust heat. Based on a novel exhaust heat recovery system devised and modified on a vehicle exhaust channel, the chief objective of this study is to improve the vehicle economy and emissions under cold start. Therefore, a detailed experimental investigation was conducted on the chassis dynamometer (CD) under cold start NEDC at 25 °C and −7 °C temperatures. And the method of comparative analyses of the coolant temperature, gasoline fuel consumption and exhaust emissions including total hydrocarbon (THC), carbon monoxide (CO) and nitrogen oxide (NO〈sub〉X〈/sub〉) have been obtained to reveal the effects of EHRS on vehicle economy and emissions under cold start. The results show that, since the coolant temperature can be quickly increased with EHRS to shorten engine warm-up time under cold start, vehicle economy is enhanced during NEDC. Moreover, the device of EHRS can effectively alleviate the combustion deterioration and wall frame quenching effect in the cylinders under cold start, which greatly decreases THC emission. Although the excess air coefficient cannot be changed by EHRS, it can improve the combustion environment in cylinders, which contributes to the reduction of CO emission. It is unexpected to find that NO〈sub〉X〈/sub〉 emission is also decreased with EHRS actuation, which can be explained by a new theory called Fenimore mechanism. All these aims to provide helpful preliminary work for vehicles to meet the upcoming stringent limit of the real driving emission (RDE) of CHINA 6.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308817-ga1.jpg" width="270" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Baomin Dai, Kai Zhu, Yabo Wang, Zhili Sun, Zekuan Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydrocarbons (HCs) are characterized by extremely low global warming potential (GWP) and are promising working fluid for organic Rankine cycle (ORC). A comprehensive advanced evaluation model is developed to study the energetic, advanced exergy and economic performance of ORC system by using twelve HCs, considering the heat recovery from geothermal, low-temperature solar, engine waste gas heat, and high-temperature solar applications. The results show that cyclohexane obtains the highest value of thermal efficiency for high-temperature solar energy. The exergy efficiency of ORC is improved by about 20% after the system optimization through the advanced exergy analysis. In addition, the recoverable effect for the four major components can be ranked as expander, evaporator, condenser, and pump. Exergetic improvement potential ratio of expander by employing propyne and isopentane obtains the highest value of 12.41% and 12.60% at the heat source temperature of 115 and 140 °C, respectively. The lowest value of levelized energy cost are propyne, pentane, cyclohexane, and cyclohexane, which are 1.46, 1.28, 1.05, and 0.95 USD/kWh. Isobutene, isopentane, cyclohexane, and cyclohexane obtain the highest endogenous avoidable cost corresponding to the four heat sources. The endogenous avoidable cost is relatively sensitive to the heat source temperature, and it is reduced by 28% with the heat source temperature increasing from 100 to 150 °C, while it is insensitive to the expander efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 6 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Prabhakar Tiwari, Navin Parihar, Adarsh Dube, Rajesh Singh, S. Sripathi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study we present the behaviour of sporadic E-layer during a total solar eclipse (TSE) which occurred during the dawn/sunrise hours over a site located in the path of totality. A Canadian Advanced Digital Ionosonde (CADI) was operated at Allahabad (25.4° N, 81.9° E), a low latitude station located near the crest of equatorial ionization anomaly (EIA) in the Indian subcontinent to study the ionospheric effects of 22 July 2009 TSE. Corresponding to the eclipse period, a gradual increase of ftEs (top frequency of Es layer) in the 4–5 MHz range was seen on the control days. On 22 July (the TSE day), correlated changes in ftEs coinciding with the TSE progression was noted – (i) sharp decrease near first and second contact of TSE, (ii) an increase after first and second contact, and (iii) wavelike fluctuations in ftEs variation during eclipse hours and beyond. Much higher ftEs values were noted during the TSE hours in comparison to that seen on usual days. Strong blanketing Es layer developed during the TSE hours and persisted for slightly longer duration than its usual occurrence time. Near the TSE totality, slight lowering of the base height of Es layer was also noted.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Xin Huang, Weihong Liu, Xiangqian Yu, Tingfen Ke, Xiang Ling, Yang Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Humidification–dehumidification technology is an innovative desalination technology which is promising for small-scale desalination applications. The relative low energy efficiency made the early system less competitive. Multi-stage humidification–dehumidification technology is one of the approaches that effectively improve the system energy efficiency. In this study, an air extraction/injection two-stage humidification–dehumidification system with reflux configuration is proposed. The reflux configuration is introduced into the two-stage system to improve the energy efficiency by eliminating the difference between the air temperatures at the extraction and injection points. A thermodynamic model is developed to investigate the system performance. It is found that the air temperatures at the extraction and injection points are only identical when the pinch point heat capacity rate ratio of first-stage dehumidifier less than unity and that of second-stage dehumidifier greater than unity. The influence of liquid-to-air mass flow rate ratio in the second stage on the energy efficiency of the system is negligible when the pinch point heat capacity rate ratio of first-stage and second-stage dehumidifier both greater than unity. The energy efficiency peaks when the pinch point heat capacity rate ratio of first-stage or second-stage dehumidifier equals unity. Additionally, the reflux configuration can improve the energy efficiency of two-stage system by 30%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 19 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Jianfeng Duan, Zhaokui Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The 〈strong〉Magpie Bridge〈/strong〉 mission is a part of the Chang’E-4 mission, it is the first Chinese spacecraft carries out Earth-Moon communication mission at Earth-Moon libration points. The 〈strong〉Magpie Bridge〈/strong〉 operations team utilizes the Beijing Aerospace Control Center (BACC) Orbit Determination and Analysis Software (BODAS) to obtain the orbit, the measurements include range, Doppler and relay, relay-rate from China Deep Space Network (CDSN) and Very Long Baseline Interferometry (VLBI) system respectively. In order to effectively improve the accuracy of the orbit, we provided the solar radiation model with multiple characteristic surfaces. The new model is based on the structure and the real-time attitude of the satellite to solve the real-time solar pressure equivalent area. Compared with the cannon-ball model, it can calculate the solar pressure equivalent area of the satellite more accurately in orbit determination. By the analysis of the tracking measurement data, we found that the new solar radiation pressure model reduces the error of position and velocity compared to the cannon-ball model.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 19 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Mohammadreza Saghamanesh, Ehsan Taheri, Hexi Baoyin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the fundamental tasks in space mission design is to choose a set of inter-disciplinary mission-critical parameters that are used for both sizing spacecraft sub-systems and designing optimal trajectories. Trajectory design and sub-system sizing are tightly coupled tasks and mission designers are interested in algorithms that not only improve fidelity of the underlying models, but also facilitate comprehensive trade-off studies using dependable algorithms. This paper presents a systematic-design/computationally-efficient framework that makes use of a recently developed hybrid optimization method, which is a fusion between homotopic approach and particle swarm optimization to perform a robust homotopic approach. A salient feature of this framework is the flexibility in altering the fidelity of the dynamical models to beyond the conventional two-body model by including perturbations due to: 1) other planets of the Solar System, 2) solar radiation pressure, and 3) the oblateness effects of the Earth. Moreover, a comprehensive study on the impact of using different types of thrusters, different hyperbolic excess velocity values, and different launch opportunities is conducted. Extensive numerical simulations are performed for a heliocentric rendezvous mission from Earth to Mars and the results are compared against those in the literature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Li-qun Jiang, Ya-xiang Wu, Xiao-bo Wang, An-qing Zheng, Zeng-li Zhao, Hai-bin Li, Xin-jun Feng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Saccharification is a major step in the conversion of lignocellulose, and pretreatment is a vital process to modify the component and structure of lignocellulose for efficient saccharification. Crude glycerol pretreatment was used to facilitate selective saccharification of corncobs via fast pyrolysis and enzyme hydrolysis. Based on the reduction of alkaline and alkaline earth metals and removal of lignin fraction, the crude glycerol pretreated sample exhibited a higher levoglucosan selectivity (30.5%) than those from glycerol pretreated (9.5%) and un-treated corncobs (2.4%) in fast pyrolysis. The crude glycerol pretreated corncobs also gave a higher glucose yield (83.7%) as compared to those of un-treated (19.1%) and glycerol pretreated (41.1%) samples in enzyme hydrolysis. Additionally, after crude glycerol pretreatment, the recovered glycerol could also be used as an attractive fermentable substrate for D-lactate production. In accordance, this manuscript provided an economically-viable and environmentally-benign approach to maximize the value of crude glycerol, meanwhile minimize the cost of pretreatment and improve the efficiency of saccharification for lignocellulose.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308829-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Lorenzo Talluri, Giampaolo Manfrida, Daniele Fiaschi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The proposed Thermo-Electric Energy Storage (TEES) system addresses the need for peak-load support (1–2 daily hours of operation) for small-distributed users who are often owners of small/medium size PV systems (4 to 50 kWe) and wish to introduce a reliable storage system able to compensate the productivity/load mismatch. The proposed thermoelectric system relies on sensible heat storage: a warm resource at 120/160 °C (a hot water reservoir system), and a cold resource at −10 /−20 °C (a cold reservoir system containing water and ethylene glycol). The power cycle operates through a 〈em〉trans〈/em〉-critical CO〈sub〉2〈/sub〉 scheme including recuperation; in the storage mode, a supercritical heat pump restores heat to the hot reservoir, while a cooling cycle (using a suitable refrigerant) cools the cold reservoir. The power cycle and the heat pump benefit from geothermal heat integration at low-medium temperatures (80–120 °C), thereby allowing to achieve a marginal round-trip efficiency (electric-to-electric) in the range from 50 to 75% (not considering geothermal heat integration).〈/p〉 〈p〉The three systems are analyzed with different resource conditions and parameters setting (hot storage temperature, pressure levels for all cycles, ambient temperature…); exergy and exergo-economic analyses are performed to evaluate the economic competitiveness and in order to identify the critical items in the system. A sensitivity analysis on the main parameters affecting the produced power cost of the system per unit electric energy is carried out.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Mojtaba Mirzaee, Reza Zare, Milad Sadeghzadeh, Heydar Maddah, Mohammad Hossein Ahmadi, Emin Acıkkalp, Lingen Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Distributed generation as a viable solution to the energy crisis has gained popularity in recent years due to reduced transmission losses and improved efficiency. In this study, nine scenarios are considered to analyze and evaluate a cogeneration system in various conditions. The cogeneration system that includes a gas turbine, absorption chillers, boilers, and heat exchangers is modeled in EES software. The system is studied in multiple scenarios. Values of energy efficiency (EE), used energy (UE), and utility fuel ratio (UFR) are calculated to assess the system. In addition, the amount of CO〈sub〉2〈/sub〉 production is also investigated for each of the scenarios. It is found that the system used in scenario No. 5 which consists of two absorption chillers installed in series, with UFR of 45325.50 kJ/kg has the optimum performance in terms of simultaneous electricity and cooling generation. For electricity and heating generation, scenario No. 7 in which heat can be completely recovered, with UFR of 39541.90 kJ/kg is the optimum configuration. It is monitored that scenario No. 1 and scenario No. 6 have the highest amount of carbon dioxide production among the studied scenarios, 88.18 kg/s.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Vegard Ophaug, Kristian Breili, Ole Baltazar Andersen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The coastal mean sea surface (MSS) has applications within oceanography as well as geodesy. Together with a geoid model, it forms an important component for geodetic mapping of ocean surface currents that are in geostrophic balance. Furthermore, it forms a bridge between open ocean MSS and in situ measurements of mean sea level at or close to land, it contributes to the mapping of the geoid and the marine gravity field, and it is essential for connecting tidal nautical chart datums to physical height systems or global geodetic reference frames.〈/p〉 〈p〉In this study, we determine a coastal MSS with an associated error field for Norway. The MSS is solely based on new-generation altimetry data, i.e., SAR(In) data from Sentinel-3A and CryoSat-2, as well as Ka-band data from SARAL/AltiKa. The data sets partly overlap in time and cover the time period from 2010 to 2017 inclusive. We have chosen these altimeters because they represent evolutions of conventional altimetry, with reduced footprint sizes as a main benefit. This is especially advantageous in the coastal zone, as a smaller footprint reduces the probability of radar pulses being contaminated by energy backscattered from land areas.〈/p〉 〈p〉The satellite missions were harmonized by applying inter-mission biases determined in a regional crossover analysis. Furthermore, in a zone closer to land than 25 km, we have replaced the global ocean tide model with a regional ocean tide model provided by the Norwegian Mapping Authority (NMA). We use an optimal interpolation technique to determine a coastal MSS grid and discuss it in context of the estimated error field.〈/p〉 〈p〉We assess our coastal MSS by comparison to state-of-the-art MSS products along three sections perpendicular to the coast, as well as ellipsoidal mean sea level as observed by an array of permanent tide gauges within the study area. In addition, we assess a higher-resolution version of our MSS in the NMA testbed for vertical datums, by comparison with temporary tide gauges. We find that the coastal MSS outperforms the global MSS models directly at the coast, with standard deviations of differences of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si19.svg"〉〈mrow〉〈mo〉~〈/mo〉〈/mrow〉〈/math〉8 cm to the tide gauges, compared to 14–22 cm, obtained with the global MSS models. All MSS models largely agree along three sections perpendicular to the coast, with standard deviations of differences of 2–4 cm. The higher-resolution version of the coastal MSS performs similarly to the coastal MSS in comparison with the temporary tide gauges (standard deviation of differences of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si20.svg"〉〈mrow〉〈mo〉~〈/mo〉〈/mrow〉〈/math〉8 cm), but its formal error field also quantifies large uncertainties at the coast and in the fjords, mainly due to the lack of altimetry observations. A trustworthy error field is decisive for the combination of altimetry with other sea-level observations.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Da-wei Qi, Le-ping Yang, Yuan-wen Zhang, Wei-wei Cai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As a novel approach to control the relative motion of a satellite formation, electromagnetic formation flight (EMFF) has some prominent advantages, such as no propellant consumption and no plume contamination, and has a broad prospect of application in such fields as on-orbit detection and optical interferometry. The current paper investigates the optimal control for the reconfiguration of a two-satellite electromagnetic formation using the nonlinear quadratic optimal control technique. Specifically, the effects of the Earth’s magnetic field on the EMFF satellites are analyzed, and then the nonlinear translational dynamic model of a two-satellite electromagnetic formation is derived by utilizing the analytical mechanics theory. Considering the high nonlinearity and coupling in the dynamic model and the actuator saturation, a closed-loop robust suboptimal control strategy based on the indirect robust control scheme and the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si34.svg"〉〈mrow〉〈mi〉θ〈/mi〉〈mo linebreak="badbreak" linebreakstyle="after"〉-〈/mo〉〈mrow〉〈mi mathvariant="bold-italic"〉D〈/mi〉〈/mrow〉〈/mrow〉〈/math〉 technique is proposed with robust stability and optimality. To ensure a further reduction of control input, the designed suboptimal controller is modified by applying the Tracking-Differentiator. The feasibility of the derived translational dynamics and proposed control strategy for the robust reconfiguration mission is validated through theoretical analysis and numerical simulations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Patrick Mungufeni, Babatunde A. Rabiu, Daniel Okoh, Edward Jurua〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study characterised the Total Electron Content (TEC) over the African region during the years 2008 - 2015. The TEC data used were the integrated electron density observed during Radio Occultation (RO) event associated with Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites. These TEC data were referred to as COSMIC TEC. The results indicate that the COSMIC TEC captures the well known features of the ionosphere such as: (i) occurrence of minimum and maximum TEC during 0:00 - 08:00 LT and 12:00 - 16:00 LT respectively, (ii) occurrence of secondary TEC enhancement (maximum) during 16:00 - 20:00 LT, (iii) lowest TEC values being observed in June solstice and highest TEC values observed in March equinox, (iv) TEC values increase as solar activity changes from low to high, (v) mid latitude TEC values are lower than those of low latitude regions, and (vi) occurrence of equatorial ionisation anomaly. In addition, we validated RO TEC observations of COSMIC satellites using Ground-based Global Navigation Satellite System (GNSS) receiver TEC observations (Ground TEC). To achieve this, we quantified the difference between Ground TEC and COSMIC TEC that were simultaneously observed within the vicinity of the ground receiver. The Upper Quartiles, UQ, of the magnitudes of the differences of coincident COSMIC and Ground TEC over southern mid-latitude regions were 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si19.svg"〉〈mrow〉〈mo〉〈〈/mo〉〈/mrow〉〈/math〉 4 TECU, while over low-latitude and northern mid-latitude regions, the values ranged from 6.17 - 11.20 TECU. The high TEC differences over low latitude regions compared to those over southern mid latitudes could have resulted from errors due to the spherical symmetry assumption during the RO retrievals. The question that remains is, why there are large TEC differences over the northern mid-latitude regions. Since COSMIC TEC captures the well known features of the ionosphere, it might in future be used for empirical modeling over African region, thus, making this study crucial.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Arunava Banerjee, Syed Muhammad Amrr, M. Nabi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper proposes an optimal integral sliding mode control (ISMC) scheme for attitude regulation of the rigid spacecraft. This control technique is capable of handling inertial matrix uncertainties as well as external disturbances. To incorporate optimality into the robust control law, the ISMC is integrated with Legendre pseudospectral method (LPSM). The minimization of the cost function and constraint handling of the spacecraft is obtained by LPSM, while the ISMC provides disturbance rejection. LPSM is chosen for its relatively high rate of convergence and its capability of solving a wide range of challenging optimal control problems. Theoretical stability analysis of closed loop system using Lyapunov theorem guarantees the convergence of attitude states. A comparative analysis between the proposed LPSM-ISMC and Chebyshev Pseudospectral Method (CPSM) based ISMC, is also presented in this paper. The effectiveness of the proposed robust-optimal control strategy is established through simulation results.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Juncheng Guo, Hanxin Yang, Houcheng Zhang, Julian Gonzalez-Ayala, J.M.M. Roco, A. Medina, A. Calvo Hernández〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to investigate the performance of a class of thermally driven refrigerators, usually driven by low-grade thermal energy, a generic thermodynamic model of three-heat-source refrigerator without involving any specific heat-transfer law is put forward by adopting low-dissipation assumptions. Based on the proposed model, the analytical expressions for the coefficient of performance (COP) and cooling power of the system are derived in terms of well-defined dissipation parameters and contact time durations between the system and heat reservoirs. One essential parameter accounting for the size ratio of the two coupled subsystems inside the overall system is introduced in light of the practical meaning of the reversible entropy change. With the help of the aforementioned parameter, the optimal relation between the COP and cooling power is obtained. The optimal operation region and optimal construction of the overall system are further determined for the first time. In addition, the influences of the dissipation and temporal symmetries are discussed in detail, according to which the upper and lower bounds of the COP at maximum cooling power are firstly obtained under two extreme situations. Experimental and simulated data from previous reported works are collected to illustrate the validity and practical significance of the proposed model and associated results. A limit case is presented to highlight the generality of the model.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419309082-ga1.jpg" width="484" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Xiaoqiong Li, Yufeng Zhang, Lei Fang, Zhendong Jin, Yan Zhang, Xiaohui Yu, Xuelian Ma, Na Deng, Zhangxiang Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel integrated system consisting of a high-temperature heat pump providing 120–130 °C heat and a gas separation unit was developed to recover the industrial waste heat and replace the low-pressure steam used in traditional refinery process. An energy, exergy, economic, and environmental analysis was carried out to evaluate the performance of such integrated system according to its operational data of the project. Energy and exergy analyses provide an insight into the quantity and quality of the energy conversion of the integrated system. The results show that the coefficient, which evaluates the performance of the system in a stable operation mode, are 8.05 and 4.45 in the presence and absence of the waste heat recovery mechanism, respectively. The total exergy efficiency decreases from 34.57% to 33.03% in the ambient temperature range of −10–40 °C. When an electricity price of 0.109 $/kW·h and a steam price of 22.361 $/t are considered, the annual net profit of the integrated system measures a minimum of 187.4*10〈sup〉3〈/sup〉 $/year and 169.8*10〈sup〉3〈/sup〉 $/year, the payback period measures a maximum of 2.21 years and 2 years, with and without considering the penalty cost induced by emission reductions. Assuming a 8000 h/year operating time, the reduction of CO〈sub〉2〈/sub〉, SO〈sub〉2〈/sub〉, and NO〈sub〉x〈/sub〉 emissions reaches 3348 t, 101 t, and 50 t, respectively. These results indicate that the integrated system operates with a high performance and provides significant economic and environmental benefits.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): R. Ben-Abdallah, D. Leducq, H.M. Hoang, L. Fournaison, O. Pateau, B. Ballot-Miguet, A. Delahaye〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Display cabinets are widely used in supermarkets and represent an important part of their energy consumption. Adding PCM to a refrigerated display cabinet can increase its compressor cutoff time as the cold energy accumulated by PCM can replace the refrigeration system during a certain period of time. This technology can be considered as a solution to increase the electricity flexibility in order to match the demand and the production of a supply network, to manage energy flows on the grid and to boost the use of intermittent renewable energy sources. The present study is focused on the performance of the display cabinet with integrated phase change material (PCM). The PCM is selected according to the temperature range of the application. To enhance the heat transfer and facilitate the PCM melting and freezing, PCM is inserted in a heat exchanger. The experimental results show an important potential of PCM to maintain the air and product temperature when the compressor is off (up to 2 h).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Ahmed A. Abdel-Rehim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fuel cell technology is a promising alternative energy source which can provide cleaner environment and can satisfy part of the required energy demand. The objective of the present work is to investigate the influence of relatively low electromagnetic field (16 and 26 mT) on the operation and performance of a PEM fuel cell stack composite of multiple fuel cells. An electromagnetic coil was designed to enclose the fuel cell in the center of a ring. The magnetic field lines will surround the whole fuel cell stack. In this case the flow direction and the arrangement do not imply a certain direction relative to the fuel or air flow. Accordingly, the effect will extend to cover both cathodes and anodes. The results showed that electricity production of PEM fuel cells could be substantially promoted by applying magnetic fields even at relatively low magnetic strength. The fuel cell stack showed an enhancement in its efficiency by about 10% when exposed to the magnetic force. It was found also that the magnitude of the magnetic intensity has greater impact relative to the magnetic field direction which did not affect the stack performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Young Joon Park, Gyubin Min, Jongsup Hong〈/p〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Maghsoud Abdollahi Haghghi, Shahriyar Ghazanfari Holagh, Ata Chitsaz, Kiyan Parham〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The thermodynamic assessment of a novel multi-generation system producing electrical power, cooling load, potable and sanitary water, and hydrogen is conducted from the viewpoints of energy and exergy analyses. The proposed system consists of a solid oxide fuel cell as the prime mover, a gas turbine, a biomass combustion subsystem, an organic Rankin cycle integrated with an ejector refrigeration cycle, a desalination subsystem, and a proton exchange membrane electrolyser subsystem. The produced fresh water is utilized to produce potable and sanitary water, and hydrogen. Considering the fact that flat plate collectors are employed to raise the water temperature to the operating temperature of the electrolyser, 12 daylight hours of a day are dedicated to sanitary water and hydrogen production by means of the electrolyser and the rest night hours are devoted to potable water production. During the commissioning period of the hydrogen production subsystem, the effect of three crucial parameters including, current density, fuel utilization factor, and solid oxide fuel cell inlet temperature on several variables related to the system has been investigated. It is concluded that under the baseline design conditions, the net electrical power, the cooling load, and the overall energy and exergy efficiencies are correspondingly equal to 4392 kW, 164.2 kW, 77.58%, and 47.14%. Furthermore, the molar rate of the potable and sanitary water, and hydrogen production are 53.27, 52.50, and 0.7695 mol/s, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Biao Liu, Huicui Chen, Tong Zhang, Pucheng Pei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The lifetime of vehicular proton exchange membrane fuel cell is one of the key factors restricting the commercialization of fuel cell vehicles. It’s well recognized variable load conditions have the greatest impact on fuel cell degradation. Studying dynamic load characteristics is very crucial for fuel cell long-life design and optimal control. Since experiments are not easy to monitor fuel cell internal distribution, the dynamic response studying is commonly implemented in model simulation. The fuel cell system has complicated structures and large differences in length scale, to make up for the insufficient precision and limited research content in existing models, this paper uses an innovative modeling method, Simulink and Fluent co-simulation method to establish a fuel cell system-level model. It can obtain not only response characteristics of auxiliary subsystems and the system dynamic performance, but also the internal physical quantities distribution changes. Multiple simulations and comparisons are made to observe voltage dynamic response and internal concentration distribution. Impacts of subsystem’s response characteristics and system’s critical operational parameters and mechanism behind them are analyzed. The co-simulation method and obtained results in this paper can be used for future research of fuel cell system-level modeling and provide theoretical basis for dynamic capacity optimization.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): D.V. Blagoveshchensky, M.A. Sergeeva〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Variations of ionospheric parameters Total Electron Content (TEC) by GNSS, critical frequency (foF2) by vertical sounding and electron density (Ne) by low-altitude satellite were studied at high, mid and low latitudes of the European sector during the magnetic storm of August 25-26, 2018. During the main phase of the storm the ionospheric F2-layer was under the positive disturbance at mid and low latitudes. Then the transition from the positive to negative ΔfoF2 values occurred at all latitudes. The recovery phase was characterized by negative ionospheric disturbance at all latitudes. This is due to the decrease of thermospheric O/N2 ratio during the recovery phase of the storm. The intense Es layers screened the reflections from the F2-layer on August 26〈sup〉th〈/sup〉 at high and at low latitudes but at different times. Some blackouts occurred due to the high absorption level at high latitudes. In general, foF2 and TEC data were highly correlated. The major Ne changes were at the low latitudes. In general, Ne data confirmed the ionospheric dynamics revealed with foF2 and TEC.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Jiawei Li, Pengqi Gao, Ming Shen, You Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The bistatic radar system has been one of the effective methods to detect the space debris in low earth orbit (LEO). Tianlai radio array with cylindrical-parabolic antennas is designed for dark energy detection, which has large field of view and high sensitivity, offering a fan-beam during the observation. We propose a bistatic radar system, which consists of Tianlai radio array and an incoherent scattering radar (ISR) assumed as a transmitter in the Qujing city of China, to detect space debris. In this paper, we calculate and analyze the detection capabilities of this system. The results show the bistatic radar system has the potential to detect small space debris of less than 10 cm in LEO. We provide a space debris detection method to obtain the position of the cross-beam satisfying the observation requirement with the TLE data of the space debris. The method can solve the problem of space synchronization between the radio array and ISR. We used the long-short baseline method of the radio array to locate the space target. The relationship among positioning error, the azimuth and the elevation angle are also discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Jian-zhao Wang, Ying Wang, Shu-wu Dai, Chen Wang, Ji-nan Ma, Xiao-yu Jia, Yan-cun Li, Dai Tian, Jia-wen Qiu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new solar electron event model is developed based on Virtual Timeline Method (VTM). We study events individually by analyzing the 17-year data of 3DP instrument on WIND spacecraft. This model is established in different solar cycle phases and is based on statistics of duration, fluence, and waiting time of solar electron events. The fluences follow a log-normal distribution and logarithmic durations fit well with logarithmic fluences linearly. We prove that waiting times of events significantly deviates from the Poisson process by investigating the stationary and event independence property of Poisson distribution. After a comparison study on waiting times, we choose the Lévy distribution in solar minimum and maximum years. During solar minimum, the event frequency is much lower than that of solar maximum, but the event magnitude is independent of solar cycle period. Large events also happen in solar minimum years. In different solar cycle phases, this model can output a spectrum with confidence level and mission duration by generating many series of virtual timelines composed of many pseudo-events based on Monte Carlo method. On the other hand, spectra in solar minimum years are softer than that in solar maximum years. The fluences in solar maximum years are about one order of magnitude higher than that in solar minimum years in a given mission period. We also compare this model with Interplanetary Electron Model (IEM) quantitatively and prove that this model is advanced.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Junmi Gogoi, Kalyan Bhuyan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The geomagnetic storm is an important weather issue in the earth’s ionosphere-magnetosphere system. Many linear and nonlinear systems are involved in this earth-space environment. In order to understand the nonlinearly evolving dynamical system of magnetosphere and ionosphere, Time series analysis of foF2 data, Disturbance Storm Index Dst, Geomagnetic activity Index Ap and some other parameters during various solar cycles has been carried out in this work. The hourly data of critical frequency of F2 layer (foF2) for three ionosonde stations [Townsville (TV51R) 19.7°S, 146.9°E; Canberra (CB53N) 35.3°S, 149.1°E; Juliusruh (JR055) 54.6°N, 13.4°E] have been noted for 4 solar cycles viz., Solar Cycle 20, 21, 22 and 23. Hourly time series analysis has been performed to achieve some functional approaches such as statistical, analytical and spectral approach etc. to examine for the presence of periodicities in the data. Time Series is a sequential set of data which can be measured over time, and since the data being used for this work had been recorded as a function of time under various conditions, the appearance of missing observations in time series data is a very common issue. Different series may require different approaches to estimate these missing values. As such, to vanquish the problem of missing data we have attempted to estimate the missing value of foF2 data for various stations using the technique of Singular Value Decomposition (SVD). Another important method, Lomb Scargle Periodogram (LSP) has been performed on the Empirical Orthogonal Functions (EOFs) u1 and u2 (that has been obtained by SVD) along with the solar parameters such as solar flux f10.7, sun spot number (SSN) etc. and geomagnetic indices such as Dst index, Kp index & Ap index etc. for the four solar cycles to find the correlation, if any. For all the plots after performing LSP the power has been found out at 99% confidence level to see how much significant the generated data with respect to the parameters is. The periodicity obtained after performing LSP are divided into three terms namely:– (a) short-term periodicity, in which 27 days periodicity is found to be prominent, (b) mid-term periodicity, in which 1.3 year periodicity is found to be very common and (c) long-term periodicity, in which 11 years periodicity is very regular in almost among all the parameters and in the EOFs.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Hao Sun, Yingjie Li, Zhiguo Bian, Xianyao Yan, Zeyan Wang, Wenqiang Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermochemical energy storage based on CaO/CaCO〈sub〉3〈/sub〉 cycles is a promising technique used in concentrated solar power plant. The high global efficiency can be achieved under high carbonation pressure and temperature. In this work, limestone and carbide slag were chosen as the representatives of Ca-based natural and waste materials, respectively. The thermochemical energy storage performances of the limestone and the carbide slag under high carbonation pressure condition (〉1.0 MPa) during CaO/CaCO〈sub〉3〈/sub〉 cycles were studied in a pressurized dual fixed-bed reactor. The effects of carbonation temperature, calcination temperature and number of energy storage cycles under high carbonation pressure condition were also researched. The energy storage capacities of two Ca-based materials are enhanced significantly with increasing the carbonation pressure. The carbonation conversion and energy density of the limestone carbonated under 1.3 MPa are about 0.83 and 2626 kJ/kg after 10 cycles, respectively, which are 1.76 times as high as those carbonated under 0.1 MPa. The carbide slag carbonated under high pressure exhibits higher cyclic stability than the limestone during long-term energy storage cycles. In addition, the optimum temperatures for the energy storage of the limestone and the carbide slag carbonated under 1.3 MPa are 850–900 °C and 800–850 °C, respectively. High carbonation pressure can mitigate the sintering and pore-plugging of CaO. The average grain size of CaO carbonated under higher pressure increases more slowly with the number of energy storage cycles. The microstructure of the Ca-based material carbonated under high pressure appears more porous than that carbonated under atmospheric pressure. Increasing carbonation pressure is an effective method to improve the energy storage capacity of Ca-based material. The carbide slag is also a good candidate for long-term thermochemical energy storage under high pressure.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 2 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Robyn M. Millan, Rudolf von Steiger, Meir Ariel, Sergey Bartalev, Maurice Borgeaud, Stefano Campagnola, Julie C. Castillo-Rogez, René Fléron, Volker Gass, Anna Gregorio, David M. Klumpar, Bhavya Lal, Malcolm Macdonald, Jong Uk Park, V. Sambasiva Rao, Klaus Schilling, Graeme Stephens, Alan M. Title, Ji Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This is a COSPAR roadmap to advance the frontiers of science through innovation and international collaboration using small satellites. The world of small satellites is evolving quickly and an opportunity exists to leverage these developments to make scientific progress. In particular, the increasing availability of low-cost launch and commercially available hardware provides an opportunity to reduce the overall cost of science missions. This in turn should increase flight rates and encourage scientists to propose more innovative concepts, leading to scientific breakthroughs. Moreover, new computer technologies and methods are changing the way data are acquired, managed, and processed. The large data sets enabled by small satellites will require a new paradigm for scientific data analysis. In this roadmap we provide several examples of long-term scientific visions that could be enabled by the small satellite revolution. For the purpose of this report, the term “small satellite” is somewhat arbitrarily defined as a spacecraft with an upper mass limit in the range of a few hundred kilograms. The mass limit is less important than the processes used to build and launch these satellites. The goal of this roadmap is to encourage the space science community to leverage developments in the small satellite industry in order to increase flight rates, and change the way small science satellites are built and managed. Five recommendations are made; one each to the science community, to space industry, to space agencies, to policy makers, and finally, to COSPAR.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Ehsan Esmailian, Hassan Gholami, Harald Nils Røstvik, Mohammad Bagher Menhaj〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Shipping has been facing significant challenges due to strict limits imposed by the International Maritime Organization (IMO) to become more environmentally sustainable. In this regard, the use of solar energy, as a viable way to deal with the pollutant emissions caused by ships, has been attracted considerable attention. However, considerable investment costs, high area demands, and low performances of ships equipped with the photovoltaic systems have until recently been some of the significant challenges in the use of solar energy in the shipping industry. This paper proposes a novel method for the optimal performance of ships through the simultaneous optimisation of the hull-propulsion-building integrated photovoltaic (BIPV) system. Using the proposed method, the interaction effects among the ship hull, the BIPV system, and the propulsion system, as well as the impact of the wind and ship speeds on the BIPV system efficiency are considered. Ship operational conditions, including the sunshine duration, the clearness index, the ambient temperature, the latitude of the region, the view factor of the sky to ground, the wind and ship speeds, and the ship lifetime hour are also examined. Moreover, a probabilistic speed profile is employed to avoid a suboptimal design at a single ship speed. The performance of the suggested method is evaluated by designing a planing ship equipped with a waterjet propulsion system that operates in the Karun river, Iran. The non-dominated sorting genetic algorithm (NSGA-II) is used to solve the multi-objective optimisation problem of a planing hull-waterjet-BIPV system. Eight cases are compared to demonstrate the effectiveness and the promise of the proposed approach in different ship design problems with different displacements and BIPV area-to-deck area ratios. The results show the high performance of the adopted approach in cutting operating costs and greenhouse gas (GHG) emissions. Based on the results, the investment costs due to the BIPV system have been recouped within a year in different studied cases and scenarios. It is also found out that the interaction effects among the ship hull, the BIPV system, and the propulsion system are important to ensure the optimal performance of a ship.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Zhao Zhen, Zhiming Xuan, Fei Wang, Rongfu Sun, Neven Duić, Tao Jin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For minute time scale solar photovoltaic (PV) power forecasting, the motion of clouds over PV power plant mainly contribute to the fluctuant and intermittent nature of solar PV power output. Therefore, research on cloud motion displacement (CMD) calculation to realize cloud motion prediction is a key sub-process for minute time scale solar PV power forecasting approaches. Fourier phase correlation theory (FPCT) is widely applied in CMD calculation for its superiority of simplicity and less computation, then an improved algorithm based on image-phase-shift-invariance (IPSI) is proposed to reduce the outlier probability of CMD results. However, at present, the current IPSI algorithm still has limitations and cannot avoid the occurrence of outliers altogether. In this paper, we presented a novel method, termed IPSI based multi-transform-fusion (MTF) method, to further improve the effectiveness compared with traditional FPCT and affine transform based IPSI method. First, three image transform methods satisfying IPSI condition, respectively wavelet transform (WT), affine transform (AT), and convolution transform (CT), are explored. Then the information increment of the transformed sky images using the above three methods is analyzed, respectively. Second, we determine the suitable image transform method for IPSI algorithm under specific cloud condition according to the corresponding information increment. Third, an IPSI based MTF method for CMD calculation in sky images is proposed. The original sky images are transformed through WT, AT, and CT to generate multiple images that maintain the same object motion information, then calculate the CMDs in each generated image. Finally, we apply Gaussian distribution to fit the multiple CMD values and taking its mathematical expectation as final CMD result. Various experimental results in 4 different scenarios show that the performance of the proposed approach is better than FPCT, AT based IPSI, and OF method, by reducing plenty of CMD outliers, thus delivering greater accuracy and robustness.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Yuzhu Chen, Jiangjiang Wang, Chaofan Ma, Guohua Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The objective of this work is to propose a hybrid ground source heat pump system integrated with solar energy and investigate its multicriteria performances. A compound parabolic concentrated-photovoltaic thermal solar collector to output electricity and heat is comprehensively integrated with a basic ground source heat pump system. The thermodynamic models of subsystems were established and validated by comparing the simulation results to those from existing studies. The renewable resources were levelized to fossil fuels based on their contributions. The multicriteria performance of the hybrid system was analyzed by using the annual operation conditions of a hotel building. The results indicated that the primary energy ratio and exergy efficiency of the hybrid system are always higher than those of the conventional ground source heat pump system. Various inlet temperatures of solar and thermal tank subsystems in the proposed system was compared and analyzed in terms of the sustainability index, primary energy saving ratio, carbon dioxide emission reduction ratio, and annual cost saving ratio and the results indicated that their appropriate temperatures are 25 °C and 60 °C, respectively. A sensitivity analysis showed that except for the interest rate, the unit cost of electricity, service life, and maintenance coefficient have positive influences on the economic performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Fukang Ren, Jiangjiang Wang, Sitong Zhu, Yi Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aim of this study is to optimize the integrated performance of a hybrid combined cooling, heating, and power system driven by natural gas as well as solar and geothermal energy resources from the energy, economy, and emission perspectives. A basic natural gas system with a prime mover unit, absorption chiller, and electricity and thermal storage components is coupled with solar photovoltaic panels and a ground source heat pump. A multi-objective optimization method is proposed and employed to optimize the configurations of the hybrid system and thereby achieve optimal performances using non-dominated sorting genetic algorithm II. Accordingly, the variable output ratio of ground source heat pump is optimized to match the heat to electricity ratios between the system and users. The hybrid system’s schemes of a specific case building that operates in different modes are optimized and compared; these schemes include following electric load, following thermal load, and following hybrid load. The impacts of natural gas and grid electricity prices on system performance are investigated. The results demonstrate that the configurations of the hybrid system that operates using the following electric load strategy achieves better performances than other modes. The proposed optimization method herein can be effective in optimizing the configurations of a hybrid system and consequently improve system performances.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Youcai Liang, Xingyan Bian, Weiwei Qian, Mingzhang Pan, Zhibo Ban, Zhibin Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Supercritical carbon dioxide Brayton cycle is considered one of the most promising systems for waste heat recovery of engines because of its compactness and high energy efficiency. To further improve the fuel utilization ratio and solve the difficulties of waste heat recovery of high temperature exhaust gas, a regenerative supercritical carbon dioxide Brayton cycle/organic Rankine cycle dual loop is proposed for cascade utilization of exhaust heat from a dual-fuel engine. The regenerative supercritical carbon dioxide Brayton cycle of the proposed system is powered by the waste heat contained in the exhaust gas. The working fluid in the organic Rankine cycle is pre-heated by CO〈sub〉2〈/sub〉 exiting the regenerator and then further heated by the residual heat of the exhaust gas. The flow rates of the working fluids in both sub cycles are adjusted to match the waste heat recovery system to respond to the changing conditions of the dual-fuel engine. The results revealed that the maximum net power output of this system is up to 40.88 kW, thus improving the dual-fuel engine power output by 6.78%. Therefore, such a regenerative supercritical carbon dioxide Brayton cycle/organic Rankine cycle dual loop system design enables the thorough recovery of high temperature exhaust heat, leading to higher energy efficiency and lower fuel consumption of the engine.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 199〈/p〉 〈p〉Author(s): Yuekuan Zhou, Sunliang Cao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The energy flexibility of the sophisticated building energy systems with the integration of renewable systems, diversified energy storages, advanced energy conversions and electric vehicles, has attracted increasing attention. However, there are limited studies on the energy flexibility quantification and enhancement of the sophisticated building energy systems. In this study, a nonlinear component-based model, integrating building integrated photovoltaics and vehicle integrated photovoltaics, was developed for the energy flexibility assessment. A generic methodology with a series of quantifiable energy flexibility indicators (the off-peak renewable-discharging ratio and the off-peak grid-discharging ratio) has been presented to quantify the energy flexibility of the hybrid grid-connected building–vehicle system. Two dynamic advanced grid-responsive energy control strategies have been proposed for the energy flexibility enhancement. Techno-economic feasibility has been discussed regarding different off-peak electricity tariffs and different rated renewable capacities. Moreover, a technical solution is presented to solve the energy congestion contradiction regarding the exploitation of the off-peak grid electricity and the on-site renewable energy through electrical storage systems. The research results showed that the proposed renewable-to-demand and the off-peak grid-supported storage control (Control Strategy 3) shows the robustness and competitiveness, in terms of activating both the on-site renewable system and the grid to participate in the building energy system. By implementing the Control Strategy 3, 96.8% of the grid electricity can be shifted from the off-peak period to the peak period for the usage of the office building. Depending on the critical static battery capacity at 10 kWh for each floor, the energy congestion contradiction can be solved by managing the off-peak grid-battery charging power to minimise the energy-based operational cost. This study formulates a flexible energy management system and a flexible energy control strategy, which are important for the promotion of energy flexible buildings, with participation of both the policymakers and the householders.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Yuanchao Qiu, Chengqing Yuan, Jinrui Tang, Xujing Tang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The integration of a photovoltaic (PV) system into a ship power grid has recently become an important strategy of saving energy and reducing emissions from ships. Since the close relationship between the energy derived from the PV system and the navigation plans of ships including location, navigation routes and times, the techno-economic evaluation of the PV systems integrated into ship power grid is very important to ensure their proper application in ships. In this study, a ship-PV grid-connected power system incorporating in the COSCO TENGFEI pure car and truck carrier is selected as a case to conduct a comprehensive techno-economic analysis and an environmental performance assessment based on single and multi-criteria evaluation methods. Taking into account the uncertainty of navigation plan, the techno-economic efficiency of the power system along six main navigation routes are evaluated separately. The evaluation results show that the hybrid power system has high financial feasibility and environmental performance. Furthermore, the Asia-Malacca-Gibraltar-Europe navigation route has the best feasibility while the Asia-Bering-Europe navigation route has the worst feasible among the six main navigation routes. This case study provides a reliable reference for investment of hybrid power system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 14 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Angelica Tarpanelli, Stefania Camici, Karina Nielsen, Luca Brocca, Tommaso Moramarco, Jérôme Benveniste〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The monitoring of rivers is not the primary objective of the Sentinel-3 mission. The first satellite of the constellation was launched in February 2016 and so far no study has investigated the joint use of altimeter, near-infrared and thermal sensors for discharge estimation. Nevertheless, similar sensors onboard other platforms have showed their ability to estimate river discharge also in scarcely gauged areas. The advantage of altimetry lies in the observation of water surface elevation, which can be proficiently used in approaches based on rating curve, empirical formulae or hydraulic modeling. Even though their use is limited, near-infrared sensors are successfully used to detect the variability of river discharge thanks to their high capacity to discriminate water from land. Thermal sensors are nearly completely unused, but the unique study that uses the difference in temperature of the river water between day and night for the estimation of water level, encourages its use for river discharge assessment as well. To improve the estimation of river discharge and foster studies that are aimed at monitoring ungauged rivers, the combination of the sensors is considered a viable path. The aim of this manuscript is to review these studies to show the limitations and the potentials of each sensor onboard the Sentinel-3 satellite and to investigate the added value of using these three sensors co-located on the same platform for river discharge monitoring.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Ming Liu, Xuwei Zhang, Kaixuan Yang, Bo Wang, Junjie Yan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The supercritical CO〈sub〉2〈/sub〉 (SCO〈sub〉2〈/sub〉) power cycle, which is highly efficient and cost effective and features a compact structure, is expected to replace steam Rankine cycle and bring technological revolution to coal-fired power plants. To obtain the quantitative energy saving potentials of the SCO〈sub〉2〈/sub〉 power cycle, this study compared the thermodynamic performances of coal-fired power plants with SCO〈sub〉2〈/sub〉 cycle and 10 in-service coal-fired power plants with steam as the working fluid. The efficiencies of 538 °C, 566 °C, and 600 °C typical power plants were increased by the SCO〈sub〉2〈/sub〉 cycle by 2.52%, 2.39%, and 2.84%, respectively. Exergetic analysis revealed that the decrease in heat transfer irreversibility in the boilers mainly caused the efficiency enhancement. Then, the main devices’ performance parameters, including the isentropic efficiency of the compressor, isentropic efficiency of the turbine, pressure drops of the heat exchangers, regenerator terminal temperature difference, and leakage ratio, were analyzed in terms of their sensitivity to the efficiency enhancement of coal-fired power plants integrated with the SCO〈sub〉2〈/sub〉 cycle. The influence of these parameters on the internal irreversibility of coal-fired power plants was also studied. With a 600 °C power plant as an example, the energy saving limits of the main devices’ parameters of SCO〈sub〉2〈/sub〉 cycle in comparison with the steam Rankine cycle are as follows: the compressor isentropic efficiency exceeded 75%, the turbine isentropic efficiency exceeded 86%, the pressure drop of the heat exchanger was less than 0.35 MPa, the temperature difference of the regenerator terminal was less than 21 °C, the leakage ratio was less than 2.5% when the leakage was not recovered, and the leakage ratio was less than 16% when the leakage was recovered.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Ayat Gharehghani, Hossein Pourrahmani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Today’s researchers have made concerted efforts to benefit from biodiesel and to achieve better combustion due to its higher cetane number in comparison to that of diesel. The major drawback of utilizing biodiesel-diesel blend is the corresponding increase in the NOx emission, which can be solved using water. However, water results in higher HC and CO emissions that can be handled by the addition of metal-based nano-particles such as cerium oxide (CeO2). In this study, 36 different cases of these input parameters (different values of biodiesel, water, and nano-particles) have been examined experimentally, and the results are used to train an artificial neural network (ANN) model to produce 8866 data. Then, these data were utilized to find the maximum brake thermal efficiency while the value of output emissions and brake specification fuel consumption are minimum. In this regard, a new parameter called performance evaluation of diesel engine (PEDE) was introduced to decrease the number of output parameters into one. However, the results of sensitivity analysis on the PEDE indicated that the share of output parameters on this newly defined PEDE are not the same, and it demands modifications. Therefore, the exponents of each output parameter were modified by the application of sensitivity analysis. Finally, a modified PEDE that can predict the performance of diesel engines properly was introduced, and the optimum values were presented. Results indicated that the best performance occurs when the amount of cerium oxide nano-particles is 80 ppm, while the shares of biodiesel and water are 6 percent.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419309124-ga1.jpg" width="353" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Alireza Rafiei, Ali Sulaiman Alsagri, Shuhaimi Mahadzir, Reyhaneh Loni, Gholamhassan Najafi, Alibakhsh Kasaeian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research paper, a hybrid solar desalination system has been employed. The hybrid solar desalination system includes photovoltaic thermal panels, solar dish concentrator, and humidification-dehumidification desalination unit. The humidification-dehumidification desalination unit comprises a closed-air open-water flow configuration, and the solar dish concentrators are utilized for water heating. Examination of three different shapes of cavity receiver including cylindrical, cubical and hemispherical, as the solar dish absorbers, was carried out. Thermal oil was considered as the solar working fluid. The absorbed solar heat was transferred to the desalination unit using a heat exchanger. In the hybrid solar desalination, photovoltaic panels were used to generate the required power. Water flow was considered at the back of the photovoltaic panels for preheating and improving the photovoltaic efficiency. The principal aim of the current study is to propose hybrid solar desalination system to generate power, and produce freshwater. The solar desalination's performance was examined in terms of various solar dish parameters and different humidification-dehumidification desalination parameters. Examination of various solar dish parameters, including the solar working fluid's inlet temperature and the cavity shapes, was carried out. Also, some humidification-dehumidification desalination parameters, including the water to air flow ratio and the water flow rate, were considered. The effects of these four parameters were investigated on the water production and the gain output ratio. Based on the results, it was found that there was an increase in the production of freshwater by raising the water flow rate, decreasing the solar working fluid inlet temperature and increasing the air flow rate. Besides, there was an increase in the gain output ratio by increasing the water flow rate, increasing the inlet temperature, and increasing the air flow rate. Finally, the highest freshwater production and lowest gain output ratio were resulted by the hemispherical cavity receiver.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 10 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Yekoye Asmare Tariku〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper mainly focuses on the evaluation of efficiency of the Sunspot Number (SSN) and the 10.7 cm Solar Radio Flux (F10.7) indices as a cause for the variation of the performance of the latest versions of the International Reference Ionosphere model (IRI 2016 with NeQuick, IRI01-corr and IRI2001 options for the topside electron density) and the IRI Extended to the Plasmasphere (IRI-Plas 2017) for the modeling of the Total Electron Content (TEC) over the West Pacific regions during the recent solar maximum (2012-2014) years. The Global Positioning System (GPS)-derived TEC data obtained from the dual frequency GPS receivers located at Observation Rock〈strong〉,〈/strong〉 OBSR (geog 46.90°N, 238.18°W, Geom. 52.46°N) and Husband, HUSB (44.12°N, 238.15°W, Geom. 49.73°N) have been considered for the validation of the performance of the models. The results show that both the GPS-derived TEC (GPS VTEC) and modelled (IRI 2016 and IRI-Plas 2017 VTEC) seasonal diurnal values tend to peak at 00:00 UT (16:00 LT) and 20:00 (12:00 LT) with the highest being observed mostly at 20:00 (12:00 LT); while, their minima are mostly observed at about 13:00 UT (05:00 LT). In addition, in utilizing the SSN, the best performance is generally observed in the June solstice months, especially by the IRI-Plas 2017 model. However, for the equinoctial and December solstice months, the best performance is generally observed by the IRI 2016 model with NeQuick and IRI01 options. It has also been shown that the root-mean-square deviations between the GPS-derived and modelled VTEC diurnal variation in using the F10.7 index are generally less than those of the SSN option in all months, revealing that both the IRI 2016 and IRI-Plas 2017 models generally show better performance using F10.7 index than the SSN. Hence, the F10.7 option is recommended for better TEC modeling employing the IRI 2016 and IRI-Plas 2017 models during the recent solar maximum years over the West Pacific region. In addition, both models cannot effectively estimate the geomagnetic storm time TEC variation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Carlos Mateu-Royo, Adrián Mota-Babiloni, Joaquín Navarro-Esbrí, Bernardo Peris, Francisco Molés, Marta Amat-Albuixech〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nowadays, a high amount of industrial thermal energy is still lost due to the lack of competitive solutions for energy revalorization. Facing this challenge, this paper presents a novel technology, based on a reversible High-Temperature Heat Pump (HTHP) and Organic Rankine Cycle (ORC). The proposed system recovers low-grade waste heat to generate electricity or useful heat in accordance with consumer demand. Compressor and expander semi-empirical models have been considered for the reversible system computational simulation, being HFC-245fa the working fluid selected. The built-in volume ratio and Internal Heat Exchanger (IHX) effectiveness have been optimized to reach the maximum energy efficiency in each operating condition. Although HFC-245fa exhibits energy performance attributes, its high Global Warming Potential (GWP) is an issue for climate change mitigation. Hence, multi-objective optimisation of the environmentally friendly working fluids Butane, Pentane, HFO-1336mzz(Z), R-514A, HCFO-1233zd(E) and HCFO-1224yd(Z) has been carried out. The results show that the system proposed, working with HFC-245fa, achieves a Coefficient of Performance (COP) of 2.44 for condensing temperature of 140 °C, operating in HTHP mode, whereas the ORC mode provides a net electrical efficiency of 8.7% at condensing temperature of 40 °C. Besides, HCFO-1233zd(E) and HCFO-1224yd(Z) are both appropriate alternatives for the HFC-245fa replacement. These working fluids provide a COP improvement of 9.7% and 5.8% and electrical net efficiency improvement of 2.1% and 0.8%, respectively, compared to HFC-245fa. This paper provides a reference study for further designs and developments of reversible HTHP-ORC systems used for industrial low-grade waste heat recovery.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308994-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Shannan Xu, Mahdy Elsayed, Gehan A. Ismail, Chunhou Li, Shuang Wang, Abd El-Fatah Abomohra〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study aimed to evaluate the energy recovery through biodiesel and bioethanol production from 〈em〉Scenedesmus obliquus〈/em〉 in a sequential route of lipid extraction followed by fermentation, with recycling of waste glycerol (WG) as a nutrient supplement into the culture. Low WG concentrations significantly enhanced the cellular dry weight over the control, recording the maximum significant value of 3.63 g L〈sup〉−1〈/sup〉 using 2.5 g L〈sup〉−1〈/sup〉 of WG (WG2.5). In addition, the maximum carbohydrate and lipid contents were recorded in WG2.5, which represented 16.4% and 21.7%, respectively, over the corresponding control, with simultaneous reduction in protein content. Moreover, total fatty acid methyl esters (FAMEs) recovery from biomass increased after WG2.5 supplementation, recording an increase of 24.6% over the control. Fermentation of lipid-free biomass increased the rate of bioethanol production, reaching its peak of 4.82 g L〈sup〉−1〈/sup〉 at the 27〈sup〉th〈/sup〉 day. However, using of WG2.5 for microalgal growth and the residual lipid-free biomass for fermentation showed the highest bioethanol production peak of 5.58 g L〈sup〉−1〈/sup〉 at day 27. Due to the accumulation of carbohydrates under WG, the biomass treated with WG2.5 showed increase in maximum bioethanol productivity up to 0.185 g L〈sup〉−1〈/sup〉 h〈sup〉−1〈/sup〉. However, sequential fermentation after lipid extraction enhanced the maximum bioethanol productivity by 32.3% and 15.1% over the whole cells from synthetic wastewater (WW) and lipid-free biomass from WW, respectively. The highest gross energy output of 21.4 GJ ton〈sup〉−1〈/sup〉 dry microalgae was estimated from the integrated route where 〈em〉S. obliquus〈/em〉 was grown in WG-enriched medium and sequential fermentation was applied for the residual biomass after lipid extraction, with the highest recorded energy conversion efficiency of 62.9%. These findings provide an innovative practical integrated approach for waste recycling and high conversion efficiency of microalgal biomass for liquid biofuel production.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308982-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Le Wu, Yuqi Wang, Lan Zheng, Peiyu Wang, Xiaolong Han〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The co-processing of bio-oil and vacuum gas oil (VGO) in an existing fluid catalytic cracker (FCC) for productions of gasoline and diesel has been proposed and regarded as a possible technique to realize partial replacement of fossil fuels. A techno-economic analysis (TEA) was conducted to evaluate the economics of two co-processing scenarios, the co-processing of VGO and the fast pyrolysis oil or the catalytic pyrolysis oil. As revealed by the TEA results, the capital cost can be reduced significantly by using the existing refinery infrastructures and the minimum gasoline selling prices under the two scenarios were $2.63 and $2.60 per gallon respectively, which can be competing with that of petroleum-derived gasoline. As shown by the sensitivity analysis, the gasoline price was extremely sensitive to the fluctuations of the fuel yields, VGO and diesel prices, and FCC capability. Therefore, the co-processing technique to produce bio-transportation fuels can be identified as a partial replacement for the petroleum-derived fuels.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308921-ga1.jpg" width="327" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Kun Yang, Neng Zhu, Daquan Wang, Chen Chang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, exergy and exergoeconomic cost analyses are applied to biomass and natural gas co-firing in a combined cooling, heating, and power (CCHP) system, based on the structural theory of thermoeconomics. The thermoeconomic model for the investigated co-firing CCHP system is defined to quantify the productive relationships among the various components. The unit exergy/exergoeconomic cost of all flows in the productive structure are calculated by solving the characteristic equations and exergy/exergoeconomic cost equations together with the auxiliary cost allocation equations. A comparative analysis between the previous auxiliary cost allocation method and the method based on energy level is presented. Moreover, the production performance of components under summer and winter conditions are evaluated based on the exergy cost analysis. The results show that, compared with the previous method, the exergoeconomic costs of electricity with higher energy level increase 21.10 and 22.90 USD/MWh under summer and winter conditions, respectively, while the costs of other products with lower energy level decrease. Furthermore, a sensitivity analysis is presented to analyze the variation of the unit exergoeconomic cost of products with fuel prices and some non-energy factors. In conclusion, the structural theory of thermoeconomics integrated with auxiliary cost allocation equations based on the energy level can provide reasonable and accurate results for multi-product energy systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Shilei Lu, Qiaoping Li, Li Bai, Ran Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉With rapid development of artificial intelligence, data-driven prediction models play an important role in energy prediction, fault detection, and diagnosis. This paper proposes an ensemble approach using random forest (RF) for hourly performance predictions of GSHP system. Two years of in situ data were collected in an educational building situated in severe cold area in China. Prediction models were established for performance indicators, and results indicate that the average error for COP〈sub〉s〈/sub〉, COP〈sub〉u〈/sub〉, EER〈sub〉s〈/sub〉 and EER〈sub〉u〈/sub〉 were all controlled within 5%. The model established by small amount of data can accurately predict long-term performance, thereby reducing time and difficulty of data collection. RF models, trained with different parameter settings were compared, results indicate that model accuracy was not very sensitive to variables numbers. The impact of input variables on prediction performance was analyzed, and importance ranking changed with period and performance indicators. By comparing the variable importance list, it was possible to establish which parameters were abnormal and lists of different periods can reflect whether the energy structure of building has changed.〈/p〉 〈p〉The overall superiority of RF was verified by comparing with back propagation neural network (BPNN) from robustness, interpretability, and efficiency. First, since GSHP system involving multiple indicators, the robustness, measured by average accuracy, was used to evaluate the accuracy level. According to CV-RMSE, robustness of RF is approximately 3.3% higher than that of BPNN. Second, RF is highly interpretive but BPNN is typical black box model. Finally, modeling complexity and training time of BPNN were much greater than RF.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Hanning Wang, Xian'en Wang, Junnian Song, Jingzheng Ren, Haiyan Duan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the rapid economic growth and urbanization, China is suffering from serious challenges on energy security and the problems regarding waste treatment and emissions mitigation. Converting urban wastes into energy has been recognized as a promising way to achieve circular economy. In this study, combustible waste, food waste, industrial organic wastewater, and breeding-farm manure are considered to be utilized for energy recovery through waste-to-energy (WtE) technologies. Accordingly, four WtE sectors for power generation are formed and introduced into the socioeconomic activities. A methodological framework is established by combining econometrics, physical input-output model and baseline method of clean development mechanism to evaluate the energy and environmental benefits in China’s 31 provincial regions during the period 2016–2025. The results reveal that the regions with more waste generation and power generation are Guangdong (11.82 billion kWh in 2025) and Jiangsu (11.43 billion kWh in 2025). Hebei has the largest accumulative mitigation potentials for the emissions of greenhouse gases, sulfur dioxide, nitrogen oxides, and soot and dust (577.57 Mt carbon dioxide equivalent, 1.79 Mt, 0.89 Mt and 16.22 Mt, respectively), followed by Guangdong and Zhejiang. Less developed regions in northwestern China such as Gansu, Qinghai and Ningxia have less energy recovery and mitigation potentials. Meanwhile, the changes in industrial structure contribute to more mitigations in the sectors of power and heat, coal mining, and oil and gas extraction. The quantification of the energy and environmental benefits and revelation of the features and disparities of waste utilization for energy recovery across regions can provide insights and managerial implications for better policy-making regarding regional waste management.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Kangping Li, Liming Liu, Fei Wang, Tieqiang Wang, Neven Duić, Miadreza Shafie-khah, João P.S. Catalão〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Time of use (TOU) rate has been regarded as an effective strategy to associate utility companies to avoid peak time financial risks and make the most profit out of the market, while most programs are not effective as expected to reduce peak time demand of residents. Exploring the impact factors of peak demand reduction (PDR) can help policy makers find reasons that weaken effects of programs and corresponding measures can be carried out to maximize the benefits. However, averaging quantitative indicators for program assessment and incomplete impactor analysis method in existing research show limitations of revealing the complex reasons behind it. In this paper, an association rule mining based quantitative analysis framework is built to explore the impact of household characteristics on PDR under TOU price making up for the deficiencies in current research. Firstly, a probability distribution based customer PDR characterizing model is proposed, in which difference-in-difference model is adopted to quantify the effect of PDR and probability distribution fitting method is used to characterize the feature of PDR for households. Then a comprehensive association rule mining analysis using Apriori algorithm is presented to explore the impacts factors of PDR covering four categories of household characteristics including dwelling characteristics, socio-demographic, appliances and heating and attitudes towards energy. Finally, analysis results of a case study based on 2993 household records containing smart metering data and survey data illustrate that PDR level cannot be obtained simply based on the appliance’s ownership and its usage habits. Socio-demographic information of households should be taken into consideration together; Internet connection and good house insulation contribute to the increase of PDR level. Moreover, the percentage of renewable generation for households also show a certain relationship with PDR. The proposed analysis framework and findings will associate retailer to improve the benefits of TOU programs and guide policy makers to design more efficient energy saving policies for residents.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 198〈/p〉 〈p〉Author(s): Bourhan Tashtoush, Almutaz Ballah R. Algharbawi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of ejector area variation to account for the unsteadiness of the driving low-grade solar energy source on the cycle performance of a combined variable geometry solar ejector cooling Organic Rankine Cycle under different operating conditions was studied. An Organic Rankine Cycle was combined with the ejector cooling cycle to utilize the excess solar heat in peak hours and to generate power. Simulation and modeling of the system were conducted using the Engineering Equation Solver and Ebsilon Software. Conservation principles and laws of mass and energy transfer were applied to all components of the system and a one-dimensional thermodynamic model was used to model the ejector. It was found that the effect of the ejector area ratio and evaporator pressure were more predominate on the cycle performance than that of the generator pressure. An improvement of 78% of the system coefficient of performance compared to the standard ejector cooling cycle could be achieved using the Variable Geometry Ejector. In addition, further enhancement in the system coefficient of performance could be achieved by regulating the generator and evaporator pressures. The Organic Rankine Cycle efficiency was found to be 5.8% with a total system efficiency of 11.35%. The system cooling capacity was improved by 81% compared to the standard ejector cooling cycle. The proposed system was found economically feasible in countries, where the electricity price is higher than 15 c$/kWh.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 7 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Tao Chen, Zhen Zhao, Stephen R. Schwartz, Caishan Liu, Qi Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, we study the conveying dynamics in the helical groove of an auger drilling into lunar simulant. We demonstrate that the stress-coupling effect of the conveyed granules by the groove of a drill auger plays a significant role on the dynamics of conveyance. For this, a discrete element method (DEM) is adopted first to uncover the motion and the stress characteristics of conveyed granules in a working auger. Then, a simplified dynamic model following the stress characteristics of DEM is established. The simplified model can not only reflect the results by the discrete element method, but can also explain well the proportional relationship between the maximum conveying rate and the rotating speed of the auger in the experiment (Zhao et al., 2019).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Weicong Xu, Shuai Deng, Li Zhao, Dongpeng Zhao, Ruihua Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Attributing to the research on key parameters analysis and working fluid selection, this paper attempted to propose a quantitative method for the performance of zeotropic working fluids used in subcritical organic Rankine cycle. Based on the graphical analysis method in temperature-entropy diagram, the limiting performances, which could be measured using limiting thermal efficiency and limiting thermodynamics perfection, of 4 typical zeotropic working fluids used in simple and regenerative organic Rankine cycle were proposed and calculated. The key affecting parameters and variation mechanism were analyzed as well. The results show that the limiting thermal efficiency of simple organic Rankine cycle increases with the increasing of latent heat of vaporization in both evaporation and condensation process, slope of working fluid saturated liquid line and the decreasing of temperature glide in both evaporation and condensation process, specific heat capacity of liquid working fluid at constant pressure. In addition to the impact of temperature glide in condensation process on limiting thermal efficiency of regenerative organic Rankine cycle, which should be determined according to specific working fluid, the impact of other parameters on limiting thermal efficiency of regenerative organic Rankine cycle is the same as that of simple organic Rankine cycle. The quantitative description of the limiting performance of zeotropic working fluid is of great significance to the analysis and improvement of cycle performance with an in-depth understanding on mechanism and could guide the selection or design of zeotropic working fluid.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Haoye Lin, Bo Xu, Jingxi Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The accuracy in pulsar-based navigation system can be improved with a well-designed observation scheme. In this paper, based on the idea that minimises the size of position probability ellipsoid at each updating time, four strategies are put forward for determining observation order. As the calculation of posterior probability ellipsoid only requires a priori orbit information, the observation scheme can be designed during preliminary mission analysis. These strategies can be employed in both situations with single detector and multiple detectors. Numerical simulations show that the proposed observation strategies achieve good performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Adam Łyszkowicz, Anna Bernatowicz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Sea level is a unique indicator in climate impact studies on any changes on the surface of the Earth. Traditionally, tide gauges allow observation of relative (relative to land) sea level changes at specific locations with a high resolution in time. Common method of sea level determination in XXI century is the combination of tide gauge observations with satellite observation data. So determined sea level changes are absolute changes and they are referred to the beginning of the ITRF system.〈/p〉 〈p〉Geocentric changes in the Baltic Sea level are monitored, inter alia, by the SONEL network. This network system does not include the southern coast of the Baltic Sea. The aim of this work is to fill this gap and to compute geocentric changes in the Baltic Sea at the stations: Hel, Władysławowo, Łeba, Ustka, Kołobrzeg, Świnoujście.〈/p〉 〈p〉The tide gauge data needed for the analysis were made available by the Institute of Meteorology and Water Management and the GNSS data was taken from web page Nevada Geodetic Laboratory. The analysis of the time series of tide gauge and GNSS observations was carried out using the TSAnalyzer software. We assumed that GNSS and tide gauge series have a seasonal signal (annual plus semi-annual) and a trend. First the outliers were removed from observation, then the jumps were viewing. The trend, annual and semi-annual terms were calculated for GNSS and tide gauge series.〈/p〉 〈p〉The results of the work are calculated geocentric changes in the Baltic Sea level along southern coast and they are at a level of 0.3 mm/year except Ustka where it reach value 4.68 mm/year.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Patrick Juvet Gnetchejo, Salomé Ndjakomo Essiane, Pierre Ele, René Wamkeue, Daniel Mbadjoun Wapet, Steve Perabi Ngoffe〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To evaluate the performance of a photovoltaic panel, several parameters must be extracted from the photovoltaic. Among the methods developed to extract photovoltaic parameters from current-voltage (I-V) characteristic curve, metaheuristic algorithms are the most used nowadays. The aim of this paper is to present the inaccuracies occurred in the parameter’s identification of the photovoltaic cell using metaheuristic technics published in Energy Conversion and Management. The results presented by different authors do not meet the objective function. To prove it, an algorithm is proposed to check the accuracy of the proposed results; a simple tool, General Algebraic Modeling System is also proposed to extract the best values of parameters of a photovoltaic cell.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Wojciech Kostowski, Krzysztof Pajączek, Agnieszka Pociecha, Jacek Kalina, Piotr Niedzielski, Adam Przybył〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉This document deals with waste heat recovery from a natural gas compressor station driven by a set of 7 gas engines. Attention is paid to waste heat from engine exhaust gases. Possible options of energy recovery include: a) direct heat recovery with optional thermal energy storage, b) conversion of waste heat to electricity via an ORC module, or c) integration of gas expanders into the gas supply line in junction with waste heat recovery.〈/p〉 〈p〉Options for direct utilization of the recovered waste heat comprise: a) supply of heat for the in-house demand of the CS object, b) supply of heat of a larger residential consumer c) supply of heat for a dedicated consumer, intentionally located next to the CS. For external supplies heat can be supplied by pipeline or via a mobile PCM storage.〈/p〉 〈p〉The studied options were related with the possible pilot plant design bottoming 1 or 2 engines with a waste heat recovery system. For the potential pilot plant, the total rate of waste heat recovery from the CS is low, ranging from 3.1% to 11.6% for the studied cases. Effects related only to the given engine represent between 19.3 and 41.4% recovery rate. Simultaneously, these effects are significant for the studied consumers, being able to cover between 33.7 to even 98.1% of their demand from the waste heat recovery source.〈/p〉 〈p〉A PCM storage has a weak and non-uniform effect on system performance, depending on the profile of source and consumer.〈/p〉 〈p〉Direct heat recovery is recommended for a pilot plant, and the recovered quantity of waste heat may reach 900 MWh/year from a single engine if operated continuously. Electricity generation may reach 530 MWh year (gas expander system) or about 300 MWh/year (ORC system), however, the latter should be recommended for more than one engine as waste heat source.〈/p〉 〈p〉Intentional location of a heat consumer near the waste heat source as well as increasing the time of operation of the bottomed engine are two recommendations of this study.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Space Research〈/p〉 〈p〉Author(s): Lionel Métrailler, Guillaume Bélanger, Peter Kretschmar, Erik Kuulkers, Ricardo Pérez Martínez, Jan-Uwe Ness, Pedro Rodriguez, Mauro Casale, Jorge Fauste, Timothy Finn, Celia Sanchez, Thomas Godard, Richard Southworth〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetosphere sustained by the rotation of the Earth’s liquid iron core traps charged particles, mostly electrons and protons, into structures referred to as the Van Allen Belts. These radiation belts, in which the density of charged energetic particles can be very destructive for sensitive instrumentation, have to be crossed on every orbit of satellites traveling in elliptical orbits around the Earth, as is the case for ESA’s 〈em〉INTEGRAL〈/em〉 and 〈em〉XMM-Newton〈/em〉 missions. This paper presents the first working version of the 5DRBM-e model, a global, data-driven model of the radiation belts for trapped electrons. The model is based on in situ measurements of electrons by the radiation monitors on board the 〈em〉INTEGRAL〈/em〉 and 〈em〉XMM-Newton〈/em〉 satellites along their long elliptical orbits for respectively 16 and 19 years of operations. This model, in its present form, features the integral flux for trapped electrons within energies ranging from 0.7 to 1.75 MeV. Cross-validation of the 5DRBM-e with the well-known AE8min/max and AE9mean models for a low eccentricity GPS orbit shows excellent agreement, and demonstrates that the new model can be used to provide reliable predictions along widely different orbits around Earth for the purpose of designing, planning, and operating satellites with more accurate instrument safety margins. Future work will include extending the model based on electrons of different energies and proton radiation measurement data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Cong Qi, Tao Luo, Maoni Liu, Fan Fan, Yuying Yan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal performance and pressure drop of TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O nanofluids in double-tube heat exchangers are investigated. The influence of the thermal fluid (water) volume flow rates (〈em〉q〈sub〉v〈/sub〉 =〈/em〉 1–5 L/min), nanoparticle mass frictions (〈em〉ω〈/em〉 = 0.0%, 0.1%, 0.3% and 0.5%), nanofluids locations (shell-side and tube-side), Reynolds numbers of nanofluids (〈em〉Re〈/em〉 = 3000–12000), and the structures of inner tubes (smooth tube and corrugated tube) is analyzed. Results indicate that nanofluids (〈em〉ω〈/em〉 = 0.1%, 0.3% and 0.5%) can improve the heat transfer rate by 10.8%, 13.4% and 14.8% at best compared with deionized water respectively, and the number of transfer units (〈em〉NTU〈/em〉) and effectiveness are all improved. The pressure drop can be increased by 51.9% (tube-side) and 40.7% (shell-side) at best under the condition of using both nanofluids and corrugated inner tube. When the nanofluids flow in the shell-side of the corrugated double-tube heat exchanger, the comprehensive performance of nanofluids-side is better than that of the smooth double-tube heat exchanger.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Schematic diagram of experimental system.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419308593-ga1.jpg" width="336" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Sarbajit Paul, Junghwan Chang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present work proposes the design process of a novel dual-core electromagnetic energy harvester (EMEH) for the use in a deicing robot, used on power transmission lines. The EMEH is designed with a dual-core where Silicon (Si) and Nickel (Ni) steels have been used in order to take advantage of both materials characteristics. An analytical model for the EMEH has been proposed in this paper which is compared with the 3D finite element method (FEM) based model of the EMEH under the same design specification. Moreover, considering the magnetic equivalent circuit model of the EMEH, equivalent circuit parameters are determined. Furthermore, to obtain the impedance matching and to extract the maximum real power from the EMEH, power optimization circuit consisting of a capacitor and a buck-boost converter is proposed and the parameters for the power optimization circuit are evaluated. To validate the effectiveness of the EMEH and its power optimization circuit, a co-simulation design platform is developed using the 3D-FEM and MATLAB coupled in a python-based environment. On the co-simulation platform, the charging of a rechargeable battery of 15 V is verified.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 197〈/p〉 〈p〉Author(s): Wan Sun, Feng Guo, Jongwon Seok〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A two degrees of freedom (DOF) vibro-wind galloping energy harvester with a nested structure is proposed to improve wind energy harvesting efficiency. Unlike traditional wind energy harvesters configured in a single bluff body-beam structure, the proposed system comprises outer and inner square cross-sectional bluff bodies in tandem, connected with elastic cantilevered beams to allow separate oscillations. The generated power performance of a conventional single-DOF wind galloping energy harvester and the proposed system is compared through wind tunnel tests. Aerodynamic interactions between the two oscillating bluff bodies are analyzed by varying the gap distances and the coupling mechanism is determined by analyzing their power spectral density (PSD). Experimental results show that the outer bluff body has a dominant influence on the inner bluff body at low wind speed, which is a secondary cause of inner body vibration after the plain galloping directly induced by the incoming wind. The proposed system exhibits excellent performance with a significant power density increase of 27.8%. Moreover, the interference effects between the two bluff bodies can be reinforced by reducing their gap distance. We conclude that the inner bluff body plays a key role in enhancing output power, specifically at relatively high wind speed.〈/p〉〈/div〉 〈/div〉