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: 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: 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: 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: 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: 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: 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: 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: 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: 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: 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: 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: 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〉