ALBERT

Description: This paper presents a new type of composite bucket foundation (CBF) for offshore wind turbines, which can be adapted to the loading characteristics and development needs of offshore wind farms due to its special structural form. There are seven rooms divided inside the CBF by steel bulkheads, which are arranged in a honeycomb structure. The six peripheral rooms with the skirt have the same proportions while the middle orthohexagonal one is a little larger. With the seven-room structure, the CBF has reasonable motion characteristics and towing reliability during the wet-tow construction process. Through extensive research into the force transfer characteristics of composite structure systems, a composite bucket foundation structure system with a curved transition part has been developed. The large bending moment and horizontal force of the wind turbine tower are transferred to and dispersed into the sea floor soil through a prestressed curved concrete transition section, the top cover of the bucket foundation, the bucket skirts, and the internal steel compartment plates. Particularly, this proposed CBF structure can effectively convert the extremely large bending moment of the turbine tower to limited tensile and compressive stresses within the foundation structure via a transition section.

Description: Dynamic line rating is a novel technique used to determine the actual value of available power transmission capacity of overhead lines being underestimated by static line rating. Contrary to static line rating method, this approach provides huge technical and economic benefits of transmitting the electrical energy under controlled constraints. Nevertheless, it is of utmost importance to have an accurate knowledge of dynamic ampacity before being practically implemented. Owing to dynamic line rating technique, an overhead conductor is rated on the basis of real-time ampacity. Furthermore, the real time ampacity contributes in combating the growing power transmission demand being observed over highly congested power transmission network. Contrary to dynamic line rating approach, building new overhead lines is a lengthy, expensive, and less reliable option. Another important advantage offered by the dynamic line rating approach is to allow excessive renewable power generation in the electricity network, particularly the wind power due to its correlation with real-time ampacity. Besides, dynamic ampacity and wind power integration, the paper also deals with risk analysis associated with conductor overloading. The risk involves increase in conductor sag as it transmits the power beyond its nominal capacity at a certain temperature. However, in this paper, the dynamic as well as the static ampacity of “VL3” overhead conductor is calculated on the basis of its nominal temperature (50 °C) to avoid the risk of its possible expansion and ultimately the deterioration. In addition to technical analysis, the economic analysis of integrating a 60 MW wind park with Fortum's 130 kV regional grid and of applying dynamic line rating approach on a periodically overloaded “VL3” overhead conductor is thoroughly investigated in this research work; to further know how beneficial it is to temporarily postpone the rebuilding and/or construction of a new overhead line in parallel to the existing overhead conductor (VL3).

Description: Growing demand of energy consumption, subsequent increase in energy generation costs, and increased greenhouse gas (GHG) emissions, as well as global warming from the conventional energy sources, encourages interest worldwide to bring a higher percentage of renewable energy sources such as biogas into the energy mix to build a climate friendly environment for the future. Moreover, due to high investment and maintenance costs, governments are not providing enough support for grid extension and delivering electricity to remote locations or rural areas, in particular, in under-developing countries like Bangladesh. Therefore, this paper presents an Energy Neutral Home System (ENHS) that can meet all its energy requirements from low-cost, locally available, nonpolluting biogas generated from animal waste, in particular, chicken and cow manure. The proposed ENHS has been developed for rural community, typically an area of 200 families, and will not only provide cooking gas and sustainable and affordable power supply to the community with low emissions, but will also facilitate high quality fertilizer for agricultural purposes. In-depth analysis clearly demonstrates that the proposed ENHS not only offers electricity and cooking gas to the community with the lowest costs, but also reduces the energy crisis and GHG emissions and can play an active role in developing socio-economic infrastructure of rural communities in Bangladesh in many ways.

Description: Energy storage plays a key role in providing more flexibility and balancing to the electric grid. With the increasing penetration of renewable energy technologies, there is a need to instantaneously match demand with supply. Energy storage has the potential to provide a back-up to intermittent renewable energy by storing electricity for use during more valuable periods. At this time, there are limited storage options, because several technologies are at very early stage of development. Pumped hydro energy storage is currently the most widely installed technology. This form of storage has some drawbacks which include the technology siting, as it cannot be implemented everywhere. This paper presents a concept that is similar to the existing pumped hydro storage technology. This concept is known as gravity storage, as it stores electricity in the form of gravitational potential energy. This storage option provides better operating characteristics and economically sounds solution over conventional pumped hydro storage, and can be placed almost anywhere electricity storage is needed. This paper proposes a methodology to optimally size the gravity storage technology and avoid system design failure. It also presents an economic analysis to investigate the value of this storage option. This work identifies the leveled cost of gravity storage and compares it to similar storage options.

Description: Firms in the power industry are currently facing challenges to maintain competitiveness while maintaining minimal environmental impacts. Responding to the above challenges, environmental management systems (EMSs) are becoming more popular within organizational policies, programs, and operating agendas. Especially in the knowledge-based photovoltaic energy industry, the learning efforts of EMSs can effectively improve technological development, managing efficiency, and firm performance at the same time. However, with rapidly changing technologies along with increasingly complicated environments, how to select a suitable project contractor for EMS has become an important issue that has never been discussed comprehensively. Through the proposed methodology, practitioners can fully understand the expected performance of each EMS contractor under various aspects, and the most appropriate EMS contractor with the best synthesized performance can be selected under the complex and dynamic environment. The methodology shall enable firms to select the most suitable EMS project contractors.

Description: In this paper, a methodology of sizing optimization of a stand-alone hybrid PV/wind/battery power generation system (HPWGS) is proposed. The main objective of this optimization is to minimize the total annual cost (TAC) of the hybrid system considering power balanced constraint and determination of the optimal number of wind turbines, PV panels, and batteries. For this purpose, a new meta-heuristic nature-inspired algorithm, called Grey Wolf Optimizer is utilized. The obtained results show that the proposed methodology finds optimal sizing of the HPWGS easily with fast convergence and lower cost. Comparing the results of this new method with the well-known published works in the literature, the superior capabilities of this proposed method are demonstrated. Moreover, the results show that the reliability characteristics are weakened with decreasing the component availability, and the supply reliability of the HPWGS is improved by increasing the inverter efficiency while the TAC is decreased. Furthermore, the HPWGS can cover the load demand variations with high reliability.

Description: Battery Energy Storage System (BESS) is a type of clean energy, which is able to enhance energy efficiency. However, the connection of the BESS with distribution systems has an impact on the conventional protection. This paper presents the BESS operation characteristics and its impact on distance protection. Optimal strategy of Zone II is analyzed from the perspective of impedance originally. The BESS has three operation statuses which will be studied separately. When a fault occurs at different locations of feeders downstream, the fault current of the BESS increases nonlinearly. By defining two original concepts, critical impedance and maximum protection impedance, the nonlinear output current is classified into two parts. Protect access capacity and protection sensitivity are analyzed under both situations. Modifying value m is presented to solve this protection-related problem. Minimum and maximum values of m are calculated to avoid overreach or blinding operation. After optimized by m , Zone II protection can trip correctly. Analysis and simulation results, based on two practical distribution systems, verified the effectiveness of the optimization strategy.

Description: With the increasing demand for environmental protection and renewable energy, bioenergy technology has been attracting considerable attention. Anaerobic digestion (AD) is the process to convert the low-grade biomass into bioenergy, in which both heat-recovery and -recycling should be treated carefully in order to improve the process efficiency. In this work, the heat-recovery and its utilization processes were reviewed, and different types of heat exchangers as well as their advantages in biogas engineering were surveyed. It shows that the recovery and utilization of the waste heat from biogas plants with an internal system, such as slurry effluent unit, the combined heat and power unit, the sanitation unit, and the internal recycle unit, are important for improving the AD efficiency of biogas production. For example, the recovery and recycling of waste heat from the effluent can result in a 2–3 °C temperature increase for the inlet manure slurry. For thermophilic AD, the heat recovery from effluent can save about 50% of the total heat requirement. The external heating process is more suitable for large- and medium-scale biogas plants, and the heat transfer coefficient of external heating (850–1000 W/m 2 K −1 ) is almost two-times higher than that of the internal heating (300–400 W/m 2 K −1 ). To utilize the waste heat in biogas plants, heat exchangers have been designed for biogas slurry. However, further improvement on the heat exchangers with anti-blockage, anti-fouling, high efficiency, and low investment is still needed. Moreover, the heat exchanger suitable for a low-temperature-difference system is specially needed in China, but the development is still in its infancy. Therefore, to tailor to the Chinese national conditions, special external heating processes should be designed and reoriented to the diversity of biomass, the climatic environmental conditions, and the renewable Chinese policies.

Description: New Zealand has a long history in producing a major part of its electricity from low-carbon resources. A major transition from a state owned and operated electricity sector to an open electricity market model and the policies adopted during this period have shaped the generation mix of New Zealand to its current form. Currently, domestic fossil fuel resources offer opportunity for economic growth, while renewable energy resources are significant and present opportunities for green growth in both domestic and global markets. What is particular about the New Zealand case is the “middle out” approach of the national renewable energy strategy, rather than the common top-down approach of many other countries. Consenting is done on a case by case basis at regional level, allowing for wide community and stakeholder participation. This paper describes the transitions in the electricity sector and renewable energy policy of New Zealand, and presents an assessment using sustainability indicators to study the impact of this transition on the level of sustainability of the country's electricity supply system. Although the electricity mix has seen a transition from hydropower towards gas, geothermal, and wind energy, there has been no significant change in the overall sustainability index of the New Zealand electricity supply. This is because the system remains based on renewable sources and gas, which scores relatively high in the model we have applied. Using the country-specific values for the indicators would give a more reliable model to assess the sustainability of the electricity system in detail from its economic, social, and environmental aspects.

Description: This paper proposes the adoption of a multilevel dc link converter for a grid connected battery energy storage system in low voltage applications. The multilevel dc link converter is the simple upgrade of a typical two level voltage source converter with the incorporation of some cascaded modular chopper cells which constitute a switched-battery circuit. With the additional chopper cells, more candidates of voltage vectors are available for switching vector selection in power control. Compared to two level voltage source converter using a look-up-table direct power control or finite control set model predictive direct power control, the multilevel dc link converter which employed the latter power control tracks the reference power with much lower power ripple, as well as results in much lower total harmonic distortion in grid current. Therefore, the power quality can be improved significantly. Simulation results are presented to verify that a 3 level dc link converter is more effective than a two level voltage source converter for the grid-connected battery energy storage systems in both generating mode and charging mode.

Description: Numerical weather prediction (NWP) of wind speed (WS) is an important input to wind power forecasting (WPF), which its accuracy will limit the WPF performance. This paper proposes three NWP correcting methods based on the multiple linear regression, a radial basis function neural network, and an Elman neural network. The proposed correction methods exhibit small sample learning and efficient computational ability. So, they are in favour of forecasting the performance of planned large-scale wind farms. To this end, a physical WPF model based on computational fluid dynamics is used to demonstrate the impact of improving the NWP WS data based forecasting. A certain wind farm located in China is selected as the case study, and the measured and NWP WS forecasts before and after correction are taken as inputs to the WPF model. Results show that all three correction methods improve the precision of the NWP WS forecasts, with the nonlinear correction models performing a little better than the linear one. Compared with the original NWP, the three corrected NWP WS have higher annual, single point, and short-term prediction accuracy. As expected, the accuracy of wind power forecasting will increase with the accuracy of the input NWP WS forecast. Moreover, the WS correction enhances the consistency of error variation trends between input WS and output wind power. The proposed WS correction methods greatly improve the accuracy of both original NWP WS and the WPF derived from them.

Description: Nowadays, solar resource estimation via clear-sky models is widely accepted when correctly validated with on ground records. In the past, different approaches have been proposed in order to determine clear-sky periods of solar radiation on-ground records: visual inspection of registers, discretization via a threshold value of clear sky index, and correlation with estimated clear sky solar irradiation. However, due to the fact that the process must be automated and the need for universality, the search for clear-sky conditions presents a challenging feat. This study proposes a new algorithm based on the persistent value of the Linke turbidity in conjunction with a transitory filter. The determinant of the correlation matrix of estimated clear-sky solar irradiance and measured irradiance is calculated to distinguish between days under clear-sky conditions and cloudy or overcast days. The method was compared and proved superior against a review of other 10 commonly used techniques at 21 sites of the Baseline Surface Radiation Network, which includes diverse climates and terrain.

Description: Thermal characteristics of a mobile thermal battery, consisting of a steel tube, metallic meshes, and the phase change material, are investigated. Concentrated solar heating of the steel tube is considered and the governing equations of heat transfer and the flow field, due to the natural convection, are solved numerically. Lithium nitrate is used as a phase change material due to its high latent heat of melting and aluminum is used as the metallic mesh material. The maximum and minimum temperature difference in the tube is predicted and the temperature parameter is introduced to assess the thermal storage performance of the mobile thermal battery. The numerical code is validated with the data reported in the early study and findings revealed that both results are in good agreement. It is found that temperature predictions agree well with the previous data. The use of metallic meshes inside the steel tube significantly improves the heat conduction in the phase change material. In this case, almost uniform temperature distribution is achieved inside the tube during the cycle of thermal energy storage. Sensible heating in the liquid phase of the phase change material results in the increase in the localized excessive temperature, which has an adverse effect on achieving a uniform temperature distribution inside the thermal battery.

Description: The Wollongong wind turbine is a new kind of vertical axis wind turbine (VAWT) with its blades rotated by only 180° for each full revolution of the main rotor. A computational study on the effect of blade chord length on the turbine output performance of a four-bladed Wollongong turbine has been conducted using the commercial computational fluid dynamics (CFD) code ANSYS 13.0. A validation study was performed using a Savonius turbine and good agreement was obtained with experimental data. Both rotating and steady CFD simulations were conducted to investigate the performance of the VAWT. Rotating two-dimensional CFD simulations demonstrated that a turbine with a blade length of 550 mm has the highest power curve with a maximum averaged power coefficient of 0.3639, which is almost twice as high as that of a non-modified Savonius turbine. Steady two-dimensional CFD simulations indicated that the Wollongong turbine has a good self-starting capability with an averaged static torque coefficient of 1.09, which is about six times as high as that of a Savonius turbine.

Description: The diffuse radiation is an important component of the global radiation affecting the output of photovoltaic (PV) collectors. This radiation depends on the view factor between the collector and sky. A simple expression for the view factor for single inclined collectors on a horizontal plane is known. However, for a photovoltaic solar field with multiple rows deployed on a horizontal or on inclined planes, the view factor is more complicated to calculate, because a collector row may obscure part of the sky for the adjacent row. More complication is added for collectors deployed on saw-tooth roofs. The present study deals with the calculation of view factors to sky for collectors deployed in multiple rows and in the presence of obscuring structures on roof tops. General and particular mathematical expressions for view factors to sky were developed for PV collectors deployed on grounds or on roof tops to determine the diffuse incident solar radiation on PV collectors, and numerical values of view factors were presented. The view factor to sky depends significantly on the inclination angle of the collector. For common deployment of collectors in multiple rows on horizontal planes, the view to sky is in the range between 0.8 and 0.9 for 30° inclination angle, whereas for 50° inclination angle, the range is between 0.6 and 0.7. The effect of the distance between collectors on the view factor is less pronounced. A wall or a fence in front of the collector may decrease significantly the view factor to sky; an increase of 1.0 to 3.0 m decreases the view to sky from 0.8 to 0.6 for 30 ° inclination, and from 0.7 to 0.4 for 50 ° inclination. The view factor to sky of vertical collectors is less than 0.5.

Description: This paper presents an improved low-voltage ride-through (LVRT) capability scheme of a grid connected doubly fed induction generator (DFIG) during any type of grid fault. In this context, an effective switching strategy based on computation of rotor current components has been suggested for the proposed passive protection circuits of a rotor side converter (RSC). Simultaneously, the RSC will control the fundamental rotor current within its available capacity for providing reactive power to the faulty grid. The proposed passive protection circuits comprise both stator and rotor side series resistor based passive compensators. The stator passive compensator will only be operated at starting and ending instant of fault to restrict rotor inrush current regardless of the type of fault. On the other hand, the rotor passive compensator is conditionally activated at the time of unbalanced fault to keep the overall rotor current under control. During both types of fault, RSC performs dual functions as partially scaled active compensator cum fractional reactive power generation controlling element. Thus, coordinated operation of passive compensator(s) and RSC will improve the LVRT ability of DFIG based wind power plants under any fault scenario. Various simulations are performed on 1.5 MW DFIG to show the advantage of this proposed control strategy.

Description: The description of wind phenomena is frequently based on the data obtained from anemometers, which usually report the wind speed and direction only in a horizontal plane. Such measurements are commonly used either to develop wind generation farms or to forecast weather conditions in a geographical region. Beyond these standard applications, the information contained in the data may be richer than expected and may lead to a better understanding of the wind dynamics in a geographical area. In this work, we propose a statistical analysis based on the wind velocity vectors, which we propose may be grouped in “wind states” associated with binormal distribution functions. We found that the velocity plane defined by the anemometric velocity data may be used as a phase space, where a finite number of states may be found and sorted using standard clustering methods. The main result is a discretization technique useful to model the wind with Markov chains. We applied such ideas in the anemometric data for two different sites in Mexico where the wind resource is considered reliable. The approximated Markov chains of both places give a set of values for transition probabilities and residence times that may be regarded as a signature of the dynamics of the site.

Description: The land-yacht robot presented in this paper aims at an Antarctic expedition which is driven by wing-sail. The wing-sail is composed by airfoil and surface roughness, which is one of the main factors affecting the aerodynamic performance of the airfoil. In order to improve the efficiency of the airfoil, stress analysis of the wing-sail and airfoil mechanism is researched and the type of airfoil is determined. For roughness size, equivalent particle roughness is introduced and a boundary layer flow separation model is a simulated roughness model. Then N-S equations and the S-A turbulence model are predicted airfoil aerodynamics in CFD (Computational Fluid Dynamics). When different sizes of a roughness strip are deposed on an airfoil surface, we obtain lift and drag coefficient, sensitive angle of attack of 6°, and 0.5 mm of sensitive roughness size. When roughness is arranged at different positions, we discover two sensitive positions, 10% chord length in suction surface and near trailing edge in pressure surface. Further analysis of the two sensitive positions in 10% chord length and aerodynamic is worse with the increasing roughness size. Near the trailing edge, there is a threshold of 0.7 mm. Lower than 0.7 mm, aerodynamics is improving; in contrast, it is worse. Finally, simulation results are verified by experiments. It shows that the predicted value conforms to the experiments and this research can provide a valuable reference for the mechanism of the land-yacht robot.

Description: In this study, the potential of solar energy in Ma'an area has been assessed and the optimal tilt angles for maximizing the collected radiation were determined using a validated model for calculating solar irradiation on south facing tilted surfaces. Ma'an area was selected for this study because it receives higher level of solar radiation worldwide, which motivates the national and the international companies to invest in solar energy. The trajectories of monthly, seasonal, bi-annual, and annual optimal tilt angles were specified. The results showed that an annual optimal fixed tilt angle of 28.7° would result in 0.20% and 16.1% extra collected radiation when compared with that collected by a surface with the latitude fixed tilt of 30.2° and horizontal surface, respectively. The increases in the yearly average collected radiation were 22.0% for monthly, 20.9% for seasonally, 17.0% for semi-annual, 40.5% for one axis tracking, and 45.9% for two axes tracking compared with that on a horizontal surface. The results suggest that adjusting the panel four times a year is recommended.

Description: Compressed air energy storage (CAES) is an economic, large-scale energy storage technology, but its further applications are limited by thermodynamic inefficiency. Although high-exergy destruction components can be highlighted through exergy analysis, the interactions among components and the true potential for the improvement of CAES are not obvious. In this study, an advanced exergy analysis was applied to the CAES system. The exergy destruction within each system component was split into four parts, namely, endogenous, exogenous, avoidable, and unavoidable. The thermodynamic properties of CAES were discussed in detail by combining the four parts. Results indicate that the unavoidable part of exergy destruction within the components of the system is larger than the avoidable part. The most important components based on the avoidable exergy destruction are combustion chambers, intercoolers, and aftercoolers. Exergy destruction can be significantly reduced by improving the main component efficiencies. More than half of the avoidable exergy destruction is exogenous, which indicates that interactions among components have a considerable impact on the CAES performance.

Description: Gasoline engines currently reject up to 40% of the total fuel energy in their exhaust. Because of increasing petroleum costs, there is a growing interest in techniques that can use this waste heat to improve the overall system efficiency. In this paper, a combined cycle system is proposed where a high-speed gasoline engine acts as the topper of the combined cycle with exhaust gases used for a bottoming cycle based on a Stirling cycle. This paper describes a mathematical model of the Stirling engine to evaluate the combined performance of the gasoline engine and the Stirling engine driven by waste heat. Simulation and experimental studies of the combined cycle system of the gasoline engine and Stirling engine reveal that the Stirling engine is a good candidate for small-scale power generation. Maximum shaft power of 535 W is recovered when the temperature of the exhaust gas reaches approximately 1000 K and the gasoline engine operates at 3000 RPM and 90% load with 50.7 kW output power. The operating pressures and temperatures of the Stirling engine are monitored in the experiment by placing three pressure sensors and 34 thermocouples in the heat exchangers.

Description: Fluctuation of wind turbine output power is one the most important drawbacks of these kinds of resources. This oscillation caused by wind speed variation is undesirable for the microgrid to which the wind turbine is connected. Therefore, reduction of output power oscillation of wind turbines is one of the most important issues related to this resource. In this paper, a new method based on Continuous Wind Speed Forecasting (CWSF) is proposed to reduce fluctuation. Output power fluctuation reduction is considered as momentary in transient power oscillations and performed using short term wind speed forecasting. The goal of this paper is to decrease the output power fluctuation of a set of wind turbines and their energy storage system by CWSF and Online Supervisory Control. The oscillation reduction is performed in both the charging and discharging modes of the ultra-capacitor. The studied wind turbine is a 50 kW wind turbine and all simulations are implemented in MATLAB SIMULINK.

Description: Renewable energy sources experience problems such as deregulation when they are used as stand-alone energy sources. This paper presents an optimal power sharing and power control strategy combining a photovoltaic (PV) array, a fuel cell (FC) stack, an ultra-capacitor (UC) module, and a set of loads. The photovoltaic is the prior energy source while the fuel cell (FC) system is added as a backup source to meet the excess power demand. The ultra-capacitor (UC) is utilized as a buffer storage to compensate the slow dynamic response of the FC during transient and regulate the DC-bus voltage. The power control strategy is designed to work on a two-level arrangement. The top level controls the entire power management, which generates references to low level individual subsystems depending upon solar radiation, temperature, and load conditions. Based on the command signals, each local controller controls the PV, FC, electrolyzer, and UC. The top level also controls the load scheduling during low solar radiation in order to sustain the system operation for 24 h. The performance of the system is tested under real-world record of solar radiation, temperature, and load conditions for Bahria town at Islamabad, Pakistan. The effectiveness of the proposed model in terms of voltage regulation, power transfer, load tracking, and grid stability is verified by Matlab simulation results.

Description: The photovoltaic (PV) industry encounters a serious oversupply problem, which has caused a fierce competition among the crystalline silicon module suppliers to get the business from the PV system assemblers. This paper has developed a mechanism to coordinate a c-Si module supplier and a PV system assembler considering the government subsidy. A centralized, a decentralized, and a joint bargaining coordination decision models in a PV supply chain are formulated and analyzed. Using the world PV industry data, the numerical and sensitivity analyses are conducted to assess the impact of key parameters on the decision models. The research result has shown that a joint bargaining coordination mechanism is optimal for the studied PV supply chain. Both a PV system assembler and a c-Si module supplier gain more profit from the joint bargaining coordination model than that from either the centralized or the decentralized decision model. Policies for the sustainable PV industry development are also recommended.

Description: To avoid environment pollution caused by internal combustion engine vehicles, compressed air engines (CAEs) have attracted much attention over the past decade. Two kinds of compressed air engines, single cylinder piston-type CAE (SCAE) and double crank link CAE (DCAE), have been investigated. However, SCAEs have low energy efficiency and output power; particularly, when rotational speed is high. To solve these shortcomings, the DCAE is proposed, which can obtain higher output power at higher rotational speeds. Using co-simulation technology, the average output power, energy efficiency, and cylinder pressure of the two kinds of CAEs were obtained. The average output power and efficiency characteristics of the SCAE were obtained by simulation and experiment; the simulation results were consistent with the experimental results, which verified that the united simulation model is accurate and effective. The results show that the pressure inside the DCAE cylinder is barely influenced by the rotational speed, and the output torque remains generally stable with an increase in the rotational speed. The average energy efficiency of both kinds of CAE declines with an increase in the rotational speed when the supply pressure is set at 2 MPa. The air power efficiency of the DCAE is about 1.86–2.86 times that of the SCAE. When the rotational speed is 800 rpm, the air power efficiency of the DCAE is 2.86 times than that of the SCAE. It is clear that the DCAE can improve the CAE performance under high rotational speeds.

Description: In the United States, approximately 65 × 10 9 square-feet of underutilized rooftop space could be appropriated for the installation of solar photovoltaic systems. Although several programs are available that assist in designing a photovoltaic (PV) system, a planning tool that can take an adaptive modeling approach towards capitalizing on the complex geometry of a rooftop does not exist. We therefore focus on the development of a parametric planning tool for retrofitting rooftops with solar photovoltaic systems. The solar planning tool exploits the existing blueprint of a building's rooftop, and via image processing, the layouts of the solar photovoltaic arrays are developed based on the building's geographical location and typical weather patterns. The resulting energy generation of a PV system is estimated and is utilized to determine the leveled energy costs. The advantage of incorporating image processing in the design of a PV system not only reduces the time required for performing a robust solar PV analysis but also enables a high-level of dimensional precision when modeling the solar arrays, thus making a rooftop solar photovoltaic system installation ultimately more cost-effective. This paper demonstrates the planning tool and verifies the output array layout, sizing of the balance of system components, and expected energy generation with the existing rooftop photovoltaic systems.

Description: This study is the first systemic cost investigation using the life cycle cost (LCC) method to analyse a municipal solid waste (MSW) incineration power plant project in China. In this study, LCC is divided into acquisition cost, maintenance cost, fault cost, and operating cost. Considering the time value of each cost, a model based on the LCC theory is established and three indexes are introduced to evaluate the MSW incineration power project, including the loan repayment period, the dynamic investment payback period, and a performance indicator. For a 12 MW MSW incineration power plant project, each cost and index are investigated under the designed runtime of 5500 h and a sensitivity analysis is performed to measure the impacts of main factors on the cost assessment results, including the annual operating hours, the government subsidies, the social discount rate, inflation rate and interest rate. The results show that the MSW project's LCC and total revenue are approximately 588 × 10 6 CNY and 746 × 10 6 CNY, resulting in an LCC performance indicator of 1.270 relative to the revenue; the acquisition cost comprises the maximum proportion of approximately 50% of the LCC, and the electricity price subsidy for utilising energy from waste (EFW) technology accounts for the largest proportion of approximately 30% of all subsidies; the loan repayment period and dynamic investment payback period are 9 and 15 years, respectively. The sensitivity analysis indicates that the variations in annual operating hours, the subsidy for disposing MSW, and the electricity price for utilising EFW technology have significant effects on the costs and indexes when compared with those of the social discount rate, inflation rate and interest rate; and that the increased acquisition cost and operating cost for denitration system may be offset by an increase in electricity subsidy by up to 0.013 CNY/kW h.

Description: The dynamic behavior of the V-shaped semisubmersible offshore wind turbine subjected to misaligned wave and wind loads in operational conditions is presented in this paper. During the life time of an offshore wind turbine, wave and wind can be misaligned which may affect the dynamic response and as a result the functionality of the floating wind turbine. Especially for asymmetric floating structures such as the V-shaped semisubmersible, the misalignment of the wave and wind may result in unexpected behavior. In the present study, integrated aero-hydro-servo-elastic analysis for coupled mooring-floater-turbine is carried out in order to investigate possible effects under misaligned wave and wind conditions. For misaligned wave and wind conditions, the wave-induced as well as the wave-wind-induced motions, tension of mooring lines, and functionality of the turbine such as power production, rotational speed, and controller actions like blade-pitch-angle are studied and presented. The results show that the V-shaped semisubmersible offshore wind turbine is not affected in an undesirable way by the misaligned wave and wind loads in operational conditions and can be considered as enough robust in such environmental conditions. Also, the functionality and power production of the current concept is not affected by the misalignment of the wave and wind. The wave-induced responses of the V-shaped floating wind turbine are relatively small compared to wave-wind-induced responses. The dynamic responses of the V-shaped semisubmersible offshore wind turbine in coupled wave-wind-induced analyses are mainly dominated by the wind loads effects.

Description: Lithium-Ion (Li-Ion) batteries are commonly used as automobile energy storage systems for powering applications due to their lucrative features. However, a battery management system with individual cell monitoring and balancing of Li-Ion batteries for long use and casualties' protection are still major issues in electric vehicle applications. This paper deals with the development of a voltage equalization control algorithm for individual cell monitoring and balancing of series connected Li-Ion battery cells. The developed states and sequences of the control algorithm manage the whole processes of battery cell monitoring, charging, and discharging, respectively. A charge equalization model is implemented with series connected 10 Li-Ion battery cells utilizing the developed control algorithm. Results show that charging and discharging, and cell balancing performance of the control algorithm are capable of quickly responding to reach the state of charge difference of 2.5% among all cells, defending the existing anomaly, providing tolerable stress to components and operating at a higher efficiency of 84.9%.

Description: In recent years, the increased use of renewable energy sources (especially photovoltaic (PV) systems) has been remarkable, and use is growing because of considerations for environmental problems. However, renewable energy sources dependent on weather conditions, such as PV systems, cause output power fluctuations. In an electric distribution system, many PV systems are connected with distribution lines, and PV systems generate unstable power and inject unbalanced power to each line. Therefore, it is possible for voltage imbalance to occur in three-phase distribution systems. In this paper, we propose a method of voltage imbalance compensation by injecting active and reactive power using inverters in Power Conditioning Systems connected to smart houses. If voltage imbalance compensation is executed considering only the distribution voltage, there is a concern that the voltage at the power receiving end will deviate. Therefore, the optimum quantity of power injection is decided depending on the proper rate of both the distribution voltage and the receiving voltage. The effectiveness of the proposed method is verified by simulation results in the MATLAB /SimPowerSystems environment.

Description: New methodologies connecting molecular structure, self-organization, and nanoelectronics are important for the construction of better bulk heterojunction solar cells. In the present work, large area conjugated polymer honeycomb thin films were prepared from poly {2, 5-bis [3-N, N-diethylamino)-1-oxapropyl]-1, 4-phenylenevinylene} (P1) and EG-C 60 (1:1 wt/wt). Further, surface morphology and conductivity of honeycomb thin films were studied using conductive-atomic force microscopy. The morphological studies clearly confirm that the EG-C60 molecules are uniformly present only at the nodes and frames of honeycomb structured blend film (which avoids the formation of exciton pair recombination of polymer), whereas the TUNA current map collected at positive and negative biases reveal holes and electrons collection networks corresponding to donor and acceptor phases at honeycomb thin films. This discovery could find applications in fully exploiting the potential of various material systems, and may open up new opportunities to improve the efficiency of organic solar cells.

Description: Due to the climate and energy crisis, many countries and vehicle manufacturers have accelerated research progress on new energy vehicles, which is significant to reduce the use of fossil fuels and decrease the pollution caused by exhaust emissions. Compressed air, as a source of energy and a non-polluting fuel in air-powered devices, is considered to be an opportunity worth trying in the new energy automotive industry. The air powered vehicle is abbreviated as APV, which mainly consists of an air tank, compressed air engine, and control system. In this paper, the current state of new energy vehicles is summarized. The compressed air system and compressed air engine, as the main technologies in air-powered vehicles, are introduced. Based on compressed air energy theory, main evaluation parameters, energy density, and energy conversion efficiency of compressed air are analyzed. The practical methods and the corresponding researches to improve the efficiency of APVs are also presented and discussed, including multistage expansion and energy recovery system. In general, the air-powered vehicle is technologically feasible and practically significant. If the energy loss of the air compression and decompression process is reduced and the utilization rate of compressed air energy is improved, the energy conversion efficiency and driving mileage of APVs will be competitive with traditional vehicles and other new energy vehicles, and its green nature will make it an important place in the future automotive market.

Description: Dye-sensitized solar cells can be considered as a future candidate to complement current photovoltaic systems; however, scaling-up the dye-sensitized solar cell is a complicated issue. One of the challenges is the module resistance, which includes the resistance of the transparent conducting oxide substrate. By increasing the substrate area, the internal module series resistance increases, resulting in a decrease of the fill factor; hence, charge collectors must be introduced in the module. In this work, silver lines are incorporated in a mini-module design and the dependence of distance between the two silver current collectors, on the working and counter electrode sides, respectively, and the module series resistance is illustrated. A module of 7 cells with 0.60 mm silver lines, and 23.8 cm 2 of active surface area reached an efficiency of 4.8%.

Description: This paper proposes a new Firefly optimized Ridge Extreme Learning Machine (RELM-FF) algorithm based maximum power point tracking (MPPT) investigation for stability study of photovoltaic (PV) interactive microgrid dynamics. The proposed MPPT study is effective by managing minimum uncertainty limits, during solar uncertainty conditions (i.e., inconsistent irradiation, partial shading, etc.), compared with conventional techniques. A two stage converter dynamics is considered for the proposed grid interactive PV system. To withstand stability during worst grid operating scenario (both PV side and grid side uncertainty), a robust nonlinear Lyapunov based finite time sliding mode (LFSM) control is proposed for PV-VSC (voltage source converter) system. As the proposed multiple distributed energy resources based microgrid is considered as weak (low short circuit ratio), and PV is considered as an active power source, the Q-V based state variables are used for the dynamic control loop. A small signal stability analysis with the two stage PV converters is presented using the proposed RELM-FF algorithm and LFSM control. The performance evaluation of the microgrid operating with the PV array is demonstrated through various case scenarios, in MATLAB/ Script environment. A hardware validation with TMS320C DSK board and embedded MATLAB coder is performed to establish effectiveness of the proposed MPPT algorithm, in real time. The superiority of the proposed MPPT over the conventional techniques is validated by comparing the stability improvement performance in grid interactive PV-VSC microgrid.

Description: Biomass is a renewable energy source with the highest potential to contribute in meeting energy needs and providing a secure and sustainable energy supply. For combustion of biogas (low calorific gas), an efficient technology is needed. It should provide stable combustion with low emission of pollutants such as CO and NOx over a wide operating range. This paper presents the experimental investigation on emission and stability of a premixed dual feed biogas swirl combustor with a pilot burner. For the experimental investigation, swirlers with swirl numbers 1.13 for the main burner and 1.98 for the pilot burner were used. The tests were performed at atmospheric conditions. The effects of carbon dioxide content, nominal thermal power, and equivalence ratio were analyzed and briefly discussed.

Description: In the present scenario, petroleum sourced fuel consumption is unsustainable; therefore, there is a high demand for the development of renewable transport fuels for environmental and economic sustainability. Microalgal fuel, with the significant feature of being carbon neutral, serves as one of the potent tools for tackling the fuel crisis. Enormous researches have been explored using fresh water species on biodiesel production; nevertheless, marine species are still in a grey area, even though reported to have higher lipid content. The current review focuses on a wide spectrum of marine microalgal sources with phycology under the criteria of open pond systems for algal oil production. The discussion on the lipid expression in the marine species have been critically analysed through the vital parameters such as solar irradiation, temperature, pH, nutrient pressure, agitation, CO 2 supply, culture depth, aeration, etc. The parameters are interdependent and, if scrutinized wisely, could result in enhanced lipid productivity. Therefore, the open pond culture of marine microalgae with top prioritized parameters such as nitrogen stress, pH, and light penetration will be a suitable combination for the efficient and effective biodiesel production.

Description: The ability to forecast the production of power by photovoltaic (PV) systems accurately and reliably is of major importance for the appropriate management of future electrical distribution systems. Several forecasting methods have been proposed in the relevant literature, and many indices have been used to quantify the quality of the forecasts. The methods can provide either deterministic or probabilistic forecasts; the latter seem to be the most appropriate to take into account the unavoidable uncertainties of PV power production. Similarly, indices were used to quantify the quality of both deterministic and probabilistic forecasting methods, but they usually do not account for the economic consequences of forecasting errors. In this paper, two advanced probabilistic forecasting approaches based on the Bayesian inference method are applied to the short-term forecasting of PV power production. Moreover, new probabilistic indices were proposed with the aim of comparing the probabilistic forecasting methods in such way that the value of the forecast is not included only by the users in their decision-making process; instead, it is partially anticipated by the forecasters in their quality-assessment process. Numerical applications also are presented to provide evidence of the performances of the Bayesian-based approaches and the probabilistic indices that were considered.

Description: In restructured electric power systems under electricity market regulations, Distribution Companies (DISCOs) mainly aim at maximizing their profit subject to safe operation of the network. In this regard, optimal planning of Energy Storage Systems (ESSs) can be a very effective method to maximize DISCOs profit. This paper addresses an optimal methodology to signify the location and capacity of ESSs in distribution network under electricity market environment. The proposed optimal ESSs planning aims at maximizing DISCO profit subject to safe and secure operation constraints (e.g., voltage and flow limits). The maximization problem is mathematically expressed as a mixed integer non-linear programming and solved using particle swarm optimization algorithm. Simulations are carried out on a typical distribution network. Simulation results demonstrate significant impact of ESSs on the network operation, security constraint, and costs. The proposed planning not only increases the DISCO profit but also guarantees the safe operation of the network. As well, several stativity analyses are carried out to indicate the impact of parameters on the planning.

Description: The main purpose of this study is to find a special set of filling and emptying parameters of a three-cylinder engine, including geometrical design of intake manifold, intake and exhaust valve timing as design variables of the multi-objective optimization problem, which lead to the best values of BSFC (Brake Specific Fuel Consumption), and torque of the engine at all working speeds as four separate objective functions. The modified Non-dominated Sorting Genetic Algorithm (NSGA-II), which is an evolutionary Pareto-based method, is used as the optimization algorithm, and the technique for order of preference by similarity to ideal solution is used as a Multi-Criteria Decision Making Method to select the trade-off design based on different design strategies through the design vectors which are proposed. Group Method of Data Handling-type of Artificial Neural Networks is used to predict the relation between the design variables and the objective functions based on a 243-sized set of samples, which are chosen by Factorial method, and the corresponding engine designs are simulated using GT-SUITE as an Engine Simulation Software. The method of simulation is verified by comparison of experiment and simulation results. The verification process shows that the engine simulation code could predict the engine's performance by 4.78% error. Convergence and start point independence of the optimization algorithm (modified NSGA-II) is also investigated. The final results show remarkable improvement in BSFC and torque at 3500 RPM and mean value of BSFC at all working speeds along with a small reduction in mean value of the engine's torque at all working speeds compared to corresponding characteristics of a similar three-cylinder engine.

Description: A 3D numerical model is established to simulate a wave-induced seabed dynamic response around composite bucket foundations and to consider the sinking processes that are due to negative pressures. The negative pressure has an influence on the pore-pressure of the seabed close to the foundation. The sinking velocity of the foundation has little influence on the wave-induced pore-water-pressure of the seabed. The liquefaction depth around the composite bucket wind turbine foundation decreased as a result of the negative pressure. The effects of the sinking process on seabed response weaken as the negative pressure dissipates.

Description: E-waste is certainly increasing to become a global issue. Fast evolution of mobile electronic devices leads to their premature replacement for always newer, faster, and nicer design and therefore may be a source of environmental pollution and contributes to global warming. Fortunately, due to the properties of the lithium ion (Li-ion) battery that powers them, there is in average 3 years of life left for the battery when the device is recycled or no longer in use after 2 years. This wastage can be valued by giving to the batteries a second life as energy storage for lighting. In fact, it can be a real opportunity for access to electricity in remote rural areas of developing countries for low cost and quality lighting. We present that used mobile phone batteries associated with a solar panel and a light emitting diode lamp can be a good replacement for candles or kerosene lamps that generate pollution, are hazardous, and only give poor lighting. Such a replacement can be done for much lower cost than current expenses, better quality of light, and contributes to poverty alleviation and job creation. This reduces wastage in developed countries and overcomes the challenges of cost and durability in small off-grid photovoltaic systems in non-electrified rural areas of developing countries. The creation of social incentive can have a real effect on the reduction of e-waste.

Description: High-frequency (50 Hz) observational data from the 200-m tower data (Reese Technology Center, Texas) have been prescribed as inflow conditions into the NREL FAST code in order to evaluate the structural impacts of Low Level Jets (LLJs) on a typical commercial wind turbine. A vertical region of interest for the analysis of interaction LLJ–wind turbine has been delimited, and the LLJ length scales have been calculated. The analysis of power spectra exhibited a deviation within the inertial subrange from the classical −5/3 slope in a log-log representation towards a lower slope, which indicated a lower rate of energy transfer when the LLJ was present. It has been observed that during a LLJ event the turbulence intensity and turbulence kinetic energy were significantly lower than those during unstable conditions; and cyclical aerodynamic loads on the turbine blades produced a negative impact on the wind turbine, mainly due to the enhanced wind shear. Dominant frequencies present in the power spectra of the incoming wind were also observed in frequencies related to the dynamic loads of the turbines. It was found that the wind turbine can mimic the signals from the approaching inlet flow, although some of the replication can be altered or annulled in a wind farm.

Description: Various topics such as CO 2 emissions, industry, human activities, and electricity distribution grids have attracted considerable attention because of the current state of crude oil production. Furthermore, estimations of solar radiation levels and of the efficiencies of photovoltaics (PVs), concentrated solar power (CSP), and solar chimney towers, as well as other renewable energy sources such as wind, tidal, and geothermal, have all been investigated. Here, an overview is presented of the potential future demands and possible supply of solar energy in relation to Iraq. Solar and wind energy sources, which are clean, inexhaustible, and environmentally friendly, are presented as renewable energy resources. Those systems that combine various sources of energy are called hybrids and they have received considerable attention in recent decades. The fundamental characteristics of solar radiation in Iraq are summarized, and the selection of those sites with potential for development of solar plants is based on the local maximum solar radiation. Furthermore, longitudinal and latitudinal orientation, wind, solar intensity, dust, temperature, rain, humidity, and pollution factors are all considered in the calculation of PV/CSP efficiencies. A study of the variation of annual radiation levels was conducted. The average UV radiation was found to comprise 3.25% of the global radiation. Therefore, most of the 47% reduction in received incoming global solar UV radiation is due to scattering and absorption in the atmosphere. Details regarding the desalination of underground or polluted water resources to support solar energy systems and plants and to preserve a clean low-dust environment are presented.

Description: The knowledge of the climatic parameters' evolution represents a determining factor for design, dimensioning, performance assessment, and energetic management of renewable energy conversion systems. In particular, the solar energy conversion systems are essentially sensitive to sunlight and ambient temperature. However, for the efficient functioning and better performance of renewable energy systems, the information of solar radiation and its components at particular location in the ground is very essential. But harvesting this energy efficiently is a huge challenge. In developing countries like ours, the number of observing stations is inadequate and direct measuring is not always available for various reasons. Therefore, the need for empirical relations becomes effective alternatives to estimate global solar radiation for the places where measurements are not carried out and for the places where measurement records are not available. In this paper, four empirical models are evaluated across four localities in Cameroon and Senegal and compared with the solar radiation values measured by the meteorological stations or obtained from different databases. The studied models are those of Hargreaves and Samani [J. Irrig. Drain. Eng., Am. Soc. Civ. Eng. 108 (3), 225–230 (1982)], Annandale et al . [Irrig. Sci. 21 , 57–67 (2002)], Bristow and Campbell [Agric. For. Meteorol. 31 , 159–166 (1984)], and Goodin et al . [Agron. J. 91 , 845–851 (1999)]. According to the simulation results, the mean yearly radiation received are 3.8414 kWh m −2  d −1 for Yaounde; 3.9869 kWh m −2  d −1 for Garoua; 2.2539 kWh m −2  d −1 for Dakar; and 5.9159 kWh m −2  d −1 for Gandon. Of all the models evaluated in this study, those proposed by Annandale et al . [Irrig. Sci. 21 , 57–67 (2002)] and Goodin et al . [Agron. J. 91 , 845–851 (1999)] produced estimates that are statistically significant at the particular confidence level, i.e., 1 − α = 99%, as the calculated t values are less than the critical t value (2.5758). Taking into account the foregoing, we can state that these models are suitable in estimating solar radiation in the localities where only air temperature data are available.

Description: Individually, sunflower oil produced from inedible sunflower seeds with hulls and sunflower meats without hulls were catalytically cracked over the ZSM-5 catalyst in a fixed-bed reactor at three reaction temperatures (450 °C, 500 °C, and 550 °C). Characterizations of hydrocarbon biofuel, distillation residual, and non-condensable gas were carried out. The reaction temperature on the hydrocarbon biofuel yield and quality from sunflower seed oil and sunflower meat oil were discussed and compared. In addition, a preliminary cost analysis of the sunflower seed dehulling was carried out. The results showed that the highest hydrocarbon biofuel yield was obtained from upgrading sunflower meat oil at 500 °C. The highest meat hydrocarbon biofuel yield was 8.5% higher than the highest seed hydrocarbon biofuel yield. The reaction temperature had a significant effect on the distribution of non-condensable gas components. Furthermore, the reaction temperature affected the yield and properties of hydrocarbon biofuel. The unit cost of producing sunflower meat oil was lower than that of producing sunflower seed oil. Comprehensively, sunflower meat could be a more economical feedstock than sunflower seed to produce hydrocarbon biofuel.

Description: An effective treatment based on the modified Hummers method was initially used to improve the electrochemical properties of multiwall carbon nanotubes (MWNTs) as high-performance electrode materials for supercapacitors. In this study, the MWNTs were treated through this modified method and characterized by transmission electron microscopy (TEM). TEM findings showed that part of the nanotubes exhibited a two-dimensional structure similar to that of the graphene sheets. The –COOH content in the MWNTs treated through the modified Hummers method in accordance with the Boehm method was 8.2%. This result indicates that the modified method can convert the hydrophobic surface of the MWNTs into a hydrophilic surface. Moreover, Brunauer–Emmett–Teller measurements suggest that the specific surface area and mesoporous volume were increased. The maximum specific capacitance of the MWNTs treated with the modified Hummers method was 179 F g −1 at a current density of 0.5 A g −1 ; this value reflected an increase of 371% in comparison with that of MWNT electrodes treated with nitric acid (38 F g −1 ). Therefore, the modified Hummers method is believed to be a good prospect for improving the electrochemical performance of the MWNT supercapacitors.

Description: Hot-wire measurements obtained in a 3 × 3 wind turbine array boundary layer are utilized to analyze high order structure functions, intermittency effects as well as the probability density functions of velocity increments at different scales within the energy cascade. The intermittency exponent is found to be greater in the far-wake region in comparison with the near-wake. At hub height, the intermittency exponent is found to be null. Extended self-similarity scaling exponents of the second, fourth, and fifth order structure functions remain relatively constant as a function of height in the far-wake; whereas in the near-wake, these are highly affected by the passage of the rotor where tip vortices reside, thus showing a dependence on physical location. When comparing with proposed models, these generally overpredict the structure functions in the far-wake region. The probability density function distributions in the far-wake region display wider tails compared to the near-wake region, and the constant skewness hypothesis based on the local isotropy is disrupted in the wake.

Description: Since the concept of “green growth” has become a main growth strategy for South Korea, the South Korean Government has consistently invested in the distribution and installation of renewable power generation systems, such as recommending that island communities install renewable power generation systems to reduce the cost of maintaining and operating the electricity grid system linking the islands to the mainland. Given the South Korean energy industry's heavy dependence on nuclear and fossil fuels, such renewable power generation systems are advised for both mainland and island communities. Therefore, the current study uses the Hybrid Optimization of Multiple Energy Resources (HOMER) program software to explore possible solutions to the installation and operation of independent and renewable electricity generation systems on Geoje Island, the second largest island in South Korea. The results show that photovoltaic panels, batteries, wind turbines, and converters can be used to organize such a system on Geoje Island. This study presents an optimized electricity generation system in the context of the total net present cost, fraction of renewables, and cost of energy (COE). The suggested system presents a 1.00 fraction of renewables at a COE of $0.472 per kW h. Implications, limitations, and future research areas are presented.

Description: We discovered an unprecedented fundamental interaction originated from the fluoroalkyl chains at the interface between light harvesting chromophore and charge transport redox electrolyte in dye-sensitized solar cells (DSSCs). A fluoroalkylated Ru complexes dye (FN719) was synthesized and upon anchoring on nanoparticulate TiO 2 electrodes, FN719 exhibits 5 times better photostability in humid air than that of the conventional N719 due to the hydrophobicity of the fluoroalkyl chains. Moreover, the lipophobicity of fluoroalkylated chains in organic electrolyte causes a size-selective steric hindrance with respect to the redox couple I − /I 3 − , leading to a more stalled diffusion of the bulky I 3 − towards dyes and TiO 2 photoanode than that of the lean I − . As such, without sacrificing the forward electron transport and quantum efficiency, the recombination in FN719-based DSSCs is suppressed to be 1.3 times slower than N719-based DSSCs studied by the photovoltage transients and electrochemical impedance spectroscopy; and the adverse I 3 − exchange with SCN − on dye is also inhibited as manifested by mass spectrometry. The J-V measurements suggest improved efficiency in FN719-based cells (9.2%) than similarly fabricated N719-based cells (8.5%).

Description: The annual average wind speed in more than 80% of the global area that can potentially be employed for onshore wind farm development is lower than 7 m/s. Onshore wind farm development has been accomplished in most regions with excellent wind resource. Based on the increasing need for onshore wind farm development in low-wind-speed sites owing to the effect of environmental factors, commercial demand of IEC-Class III wind turbine has significantly increased among the world's leading developers and wind turbine manufacturers of the wind power industry. Thus, aerodynamic design of a 3 MW wind turbine blade for low-wind-speed sites was performed in this study. The geometry was optimized to improve AEP (Annual Energy Production) and minimize the increasing rate of thrust. The performance analysis result by Blade Element Momentum method showed that the increase in thrust was limited to less than 5% and AEP was enhanced by 20% at annual average wind speed of 7 m/s compared to the reference blade. To verify the final aerodynamic design result, CFD simulation was performed. It was confirmed that AEP was increased by 15%, and the increasing rate of thrust was found to be 5.1% at the same annual average wind speed.

Description: In this paper, we report the fabrication of broadband antireflection porous nano-network on the glass substrate using the combination of candle soot and HF-based vapor phase etching method. Candle soot layer plays a key role to control the pore size during the etching process. Field emission electron microscopy results showed that the pores have the tapering profile, and the pores size was restricted to the sub-wavelength dimension. Therefore, an excellent broadband antireflection with an enhancement of ∼7% in the maximum total transmittance as compared to plain glass has been achieved. Moreover, reflectance from the etched surface remains quite low (

Description: Hot-wire anemometry measurements have been performed in a 3 × 3 wind turbine array to study the multifractality of the turbulent kinetic energy dissipation. A multifractal spectrum and Hurst exponents are determined at nine locations downstream of the hub height, bottom and top tips. Higher multifractality is found at 0.5 D and 1 D downstream of the bottom tip and hub height. The second order of the Hurst exponent and combination factor shows the ability to predict the flow state in terms of its development. Snapshot proper orthogonal decomposition (POD) is used to identify the coherent and incoherent structures and to reconstruct the stochastic velocity signal using a specific number of the POD eigenfunctions. The accumulation of the turbulence kinetic energy in the top tip location exhibits fast convergence compared with the bottom tip and hub height. The dissipation of the large and small scales is determined using the reconstructed stochastic velocities. The higher multifractality is shown in the dissipation of the large scale compared with small scale dissipation showing consistency with the behavior of the original signals. Multifractality of turbulent kinetic energy dissipation in the wind farm is examined and the effect of the reconstructed flow field via proper orthogonal decomposition on the multifractality behavior is investigated. Findings are relevant in wind energy as multifractal parameters identify the variation between the near- and far-wake regions.

Description: A parametric study of vertical axis turbines of the H-Darrieus type is conducted using state-of-the-art Computational Fluid Dynamics (CFD) and the k- ω Shear Stress Transport RANS model in its unsteady form. Although most parameters have previously been investigated individually, the effect of solidity, number of blades, tip speed ratio, Reynolds number, fixed blade pitch angle, and blade thickness on the aerodynamic efficiency of the turbine is evaluated using the same performance evaluation set-up in order to determine what would be the best aerodynamic configuration and operation parameter in a given application. The quantitative impact of 3D effects associated with the blade aspect ratio and the use of end-plates is also investigated. For high-Reynolds applications, optimal radius-based solidity is found to be around σ = 0.2 , while higher solidities show a lower maximum efficiency than what was previously published using simpler streamtube based methods. In 3D, a small blade aspect ratio ( A R = 7 ) leads to a relative efficiency drop of nearly 60% compared to the 2D prediction. Longer blades improve the 3D efficiency greatly. End-plates are found to have a positive effect on power extraction performances, as long as their size and thus their drag are limited.

Description: This paper provides a quantitative analysis of the sensitivity, amount, and the development trend of carbon emissions embodied in China's international trade. With the input-output technique, nonhomogeneous exponential growth model, and carbon transmission-relative data, the following conclusions were drawn: (a) The total (direct and indirect) carbon intensity of each industrial sector was measured. Of all the 27 industrial sectors, Production and Supply of Electric Power and Heat Power ranks first. Because of the large consumption of electric power by nearly all the industrial sectors, encouraging the electric power sectors to utilize non-fossil energy (especially wind and photovoltaics), to improve the generation efficiency, and to import electric power overseas is crucial for decreasing the overall level of China's carbon intensity. (b) The amount of carbon transmission embodied in exports and imports of each industrial sector was also measured. Owing to its enormous international trade values, the sector of Manufacture of Electrical Machinery and Equipment ranks first, with absolute predominance in both exports and imports. Adjusting China's industrial policy to decrease the net export of this sector would significantly reduce the amount of net carbon transmission in the country. (c) The future net carbon transmission of each industrial sector was forecasted. Trend analysis indicates that changes in the overall international trade situation would cause the carbon transmission amount embodied in exports in China to become less than that embodied in imports since 2015.

Description: In this paper, a novel maximum power point (MPP) tracking technique for photovoltaic system (PV) with fast convergence speed and reduced range for the MPP search operation is presented. The characteristic of this method is the limited searching area/range for the tracking. The adaptable variable duty step used in the proposed method instantaneously brings the operating point close to the MPP, thus bounding the searching area. The value of duty gets updated according to the panel temperature and irradiance, and the operating point always remains close to the MPP. By bounding the search operation, the overall tracking speed and efficiency of the tracking increase. Further enhancement of the tracking speed is obtained by varying the step size of duty ratio of the DC-DC converter used; this is done in such a manner that the size of variable duty step is large for the points far away from MPP and becomes very small at or near MPP. The projected tracking algorithm is compared with conventional Perturb and Observe MPPT method in diverse irradiance and temperature conditions, and evaluation of the proposed tracking method is reported. Finally, field performance of the proposed method has been done by using a 250 W PV system. Arduino Uno microcontroller board is used for controlling the duty of the DC-DC converter. Results obtained from the hardware implementation have been presented and is concluded that the method has fast tracking capability and better efficiency. To sum up, overall performance of the proposed Fast Mutable Duty MPP Tracking technique is appreciable.

Description: This paper presents an investigation on air compressibility in the air chamber and its effects on the power conversion of oscillating water column (OWC) devices. As it is well known that for practical OWC plants, their air chambers may be large enough for accommodating significant air compressibility, the “spring effect,” an effect that is frequently and simply regarded to store and release energy during the reciprocating process of a wave cycle. Its insight effects on the device's performance and power conversion, however, have not been studied in detail. This research will investigate the phenomena with a special focus on the effects of air compressibility on wave energy conversion. Air compressibility itself is a complicated nonlinear process in nature, but it can be linearised for numerical simulations under certain assumptions for frequency domain analysis. In this research work, air compressibility in the OWC devices is first linearised and further coupled with the hydrodynamics of the OWC. It is able to show mathematically that in frequency-domain, air compressibility can increase the spring coefficients of both the water body motion and the device motion (if it is a floating device), and enhance the coupling effects between the water body and the structure. Corresponding to these changes, the OWC performance, the capture power, and the optimised Power Take-off (PTO) damping coefficient in the wave energy conversion can be all modified due to air compressibility. To validate the frequency-domain results and understand the problems better, the more accurate time-domain simulations with fewer assumptions have been used for comparison. It is shown that air compressibility may significantly change the dynamic responses and the capacity of converting wave energy of the OWC devices if the air chamber is very large.

Description: The capabilities of modelling the performance of photovoltaic (PV) systems depend both on the available PV models and on the accuracy of the input information that the models need. The meteorological input to any model consists mainly of the solar irradiance incident in the module as well as other influencing variables (temperature, wind speed, etc.). Since incident solar irradiance on characteristic inclined surfaces is not frequently available, the performance models use to incorporate specific models for computing tilted solar irradiance from the other components (global horizontal and direct normal) with higher availability. In this work, System Advisor Model (SAM), a performance model, has been used to analyze the contribution of some well-known transposition models to the uncertainty in modelling the system performance. The study has been performed for a small-scale photovoltaic array of CdTe placed at the roof of a building in Madrid. The performance predicted by SAM is rather good with around 3% of root mean squared error in the daily AC power when the input irradiance is taken from experimental measurements at the modules tilt angle. A 3% of an additional error increase compared to the results with the experimental tilt irradiance was observed for using all of the transposition models included in SAM.

Description: Unlike horizontal axis turbines, the Darrieus-type wind turbines have less efficiency and suffer from the self-starting inability. The effects of fixed and variable blade pitch angle as an idea for improving the performance of Darrieus turbine have been investigated using the CFD analysis, and a pitching system (variable pitch Darrieus-type wind turbine) has been proposed that can reduce both the blades oscillating motion and the magnitude of angle of attack in one revolution compared to that of the Darrieus-type wind turbines. In this study, the method of computational fluid dynamics with moving mesh has been used for analyzing the unsteady two-dimensional flow simulation. The numerical results show that the SST k-ω turbulence model matches well with the experimental results and can capture the flow separation phenomenon at low tip speed ratios. Also, it was observed that a small negative fixed pitch angle of −3° can delay the separation and improve the performance of wind turbine. The numerical simulation also showed that the variable-pitch blade turbine can reduce or eliminate the flow separation on its blades at a lower tip speed ratios than that of the fixed pitch blades. This result increases the starting torque and obtaining high efficiency with decreasing in torque ripple on blades during the turbine operation compared to that of the fixed-pitch blade Darrieus turbine.

Description: Micro grids are inclined to use renewable energy sources within the availability limits. Energy storage improved the management of hybrid energy resources used in parallel with the grid. This study models the hybrid usage of wind and solar energies as a support for the grid with the availability of batteries. A mixed integer mathematical model is proposed to schedule the use of different resources minimizing the cost following the power market. Capacity, energy balancing and demand constraints are taken into account for this purpose. This model can be used as a decision support system for micro grid load planning.

Description: In this paper, a structure for a piezoelectric beam vibrator driven by a groove cam is analysed. The vibrator takes the simplified form of a piezoelectric beam model, where one end of the beam is clamped and the other end is simply supported, and is thus named the clamped/simply supported piezoelectric beam model (CSPBM). Mathematical models of the damped forced vibration and electromechanical energy conversion processes of the CSPBM are established based on the harmonic displacement excitation of the simply supported end. Factors that affect the energy generated by the CSPBM are analyzed theoretically and are simulated separately using both the MATLAB software and ANSYS software. Theoretical analysis results indicate that there is an optimal value of the ratio of the base plate thickness to the beam thickness ( α ) at which the energy generated by the CSPBM is maximum. In addition, the optimal α value of a unimorph beam is about 0.3 and is irrelevant to the material parameters of the beam. The voltage and energy generated by the CSPBM are measured on an experimental bench and the results show that the maximum generated voltage increases with increasing the first natural frequency when the α value of piezoelectric beam and the amplitude of displacement excitation are constant. In addition, the theoretical results of the generated voltage are coincident with experimental results, which confirms the validity of the theoretical model. The vibrator driven by a groove cam provides a practical form of the piezoelectric beam excited by the displacement.

Description: This article presents the research findings of an extensive model test investigation of the dynamic response to vortex-induced motions (VIMs) of the OC3 spar-type floating offshore wind turbine (FOWT). Particulars of this research are to investigate the unique and crucial effects of wind load on the spar-type FOWT, which differs considerably from other traditional spar-type floating systems utilized in the gas and oil industry, on the VIMs. The model test was performed with a sequence of current, wind, and irregular wave sea states to analyze the nature of the coupled dynamic response behavior of VIMs. Many unique characteristics were found and analyzed. The lock-in phenomenon of sway in the cross flow (CF) direction was found to occur first, followed by the lock-in phenomenon of surge in the in-line (IL) direction. For the current-only case, the remaining responses, including the other 4-degree-of-freedom motions, mooring tensions, and turbine bearing loads, were found to be coupled by sway/surge VIMs. Moreover, the oscillation amplitudes of all of the responses increased significantly with increasing current velocity, particularly after locking-in. Furthermore, the wind load had a clear suppression effect on the CF and IL VIM responses. The experimental measurements demonstrated that the wave load excites wave-induced oscillations for some CF responses and all IL responses, and it further restrains the VIM oscillation amplitudes on the foundation of the wind suppression effect. In particular, when a wind load is involved, the influence of current or wave is limited to the yaw and IL tower-top bending moment.

Description: As global warming becomes increasingly pressing, many countries have begun to adopt carbon labeling on agri-products. Thus, it is prospective and significant to conduct a study on assessing the behavioral change in buying low carbon farm products in China, a country new to carbon labelling. Using a sample of the actual buying behavior of 873 subjects in China, we first examine the impact of Attitude, Perceived behavioral control, and Subjective (i.e., declarative and injunctive) norms on Actual behavior. Then, we investigate the mediating role of Behavioral intention in Actual behavior's relation with Attitude, Perceived behavioral control, and Subjective norms, respectively. Further, we explore the role of Subjective injunctive norms in the model based on the theory of planned behavior. Declarative norms, Attitude, and Perceived behavioral control explain a significant proportion of variance in actual buying behavior of low carbon products. Intentions fully mediate the relationship between Declarative norms and Actual behavior while partially mediating for Attitude and Perceived behavioral control. Injunctive norms moderate the relationship between Declarative norms and Actual behavior while partially mediating the relationship between Declarative norms and Attitude. Perceived behavioral control partially mediates the relationship between Declarative and Injunctive norms. These results suggest potential revisions to the theory of planned behavior model and practical implications to facilitate behavioral change from diagnostic and interventional perspectives.

Description: The Savonius rotor has been attracting more and more attention in recent years owing to its appealing features, such as simplicity of the fabrication, cost-effectiveness in low wind speed areas and low noise levels. It can be used for lighting, ventilation, hydropower generation and irrigation. As a traditional single-stage two-blade Savonius rotor has two defects, researchers proposed the multi-stage two-blade Savonius rotor to overcome them. However, most of the previous studies on the multi-stage Savonius rotors focused on the comparison between one- and two-stage rotors or the effect of the aspect ratios. This paper is different from previous researches and focuses on the comparison between two-stage rotors through the wind tunnel test. It also studies the effect of the gap ratio (GR) and phase shift angle (PSA) on the performance of the two-stage rotors at different wind speeds. Results showed that the negative azimuth angle range was narrowed and the torque coefficient (C T ) values were improved as GR and PSA increased. Hence, the two-stage rotor with larger GR and PSA can overcome the two defects of the single-stage rotor. In terms of the power coefficient (C P ), the optimized performance was determined by the GRs, PSAs, and wind speeds. When the wind speed increased, the difference among C P curves of one tested rotor was reduced. Generally speaking, the rotors with GR = 1/6 exhibited the optimized performance compared with those with other GRs when the PSA = 0° and PSA = 45°. While keeping the PSA = 90°, the rotor with GR = 0 had a superior performance to the others when PSA = 90° at wind speed of 4 m/s. The rotor with GR = 1/3 gave the highest C P value of 0.303 in the vicinity of the tip speed ratio 0.9 at wind speed of 6 m/s. And the rotor with GR = 1/6 attained the best C P when the wind speeds were 8 m/s and 10 m/s.

Description: To forecast wind speed at hub-height is a challenging task for wind energy application, especially in Japan where the terrain feature is very complex and large fluctuations are observed in surface wind field. In this study, an integrated system to predict the hub-height wind speed has been developed by combining data assimilation and Kalman filter with the high resolution Weather Research and Forecasting (WRF) model. Assimilating the nacelle wind data (quality-controlled) and the Kalman filter algorithm effectively improves accuracy of the WRF model forecast by optimizing initial condition and post-processing the model output, respectively. It is found that the WRF model forecasts can be markedly improved after assimilating the nacelle wind data through the Gridpoint Statistical Interpolation analysis system, with the relative improvements of 34.3%, 23.9%, and 8.8% in ME (mean error), RMSE (root mean square error), and IA (index of agreement), respectively. The implementation of the Kalman filter can significantly reduce ME and RMSE while increases the value of IA as well. Further improvement can be achieved if the Kalman filter and nacelle wind data assimilation are implemented simultaneously. It is observed that the role of the Kalman filter is more dominant for the wind band of rated out speeds, while data assimilation is effective in reducing the random errors and becomes more important in rare or extreme weather conditions. Both data assimilation and Kalman filter modules apply the nacelle wind data which is routinely available, so the system can be easily adopted in different wind farm sites for operational use.

Description: Here, we evaluated the efficiency of a solar domestic hot water system in a dormitory in Rzeszow. Radiance exposure was analyzed based on information obtained from an online database (the meteorological station in Rzeszow-Jasionka). The mean seasonal and annual solar irradiation of a flat surface and surfaces inclined at 30°, 45°, and 60° from the horizontal plane in Rzeszow were determined. The mean monthly irradiation was compared with that in selected European cities based on the Photovoltaic Geographical Information System meteorological database. The thermal solar panel area and final consumption of solar energy in Poland from 2005 to 2014 are also presented. The characteristics of the analyzed building, distribution of the inhabitants, and consumption of hot water from 2009 to 2014 are described. The heat demand was determined by hot water consumption per day per person based on hot water consumption metering and heat metering. The solar energy conversion efficiency was determined after the solar thermal collectors were installed in the building. The relation of the heat demand calculated based on the thermal energy utilized to heat water per person and heat metering for heating water was also analyzed. We also present a method of calculating the annual (stratified by month) ratio of solar energy utilization. Energy savings for the building were calculated. Improvements that could further increase the solar energy efficiency and shorten the investment payback period are proposed.

Description: The near-wake of a vertical-axis cross-flow turbine was modeled numerically via blade-resolved k–ω shear stress transport (SST) and Spalart–Allmaras Reynolds-averaged Navier–Stokes (RANS) models in two and three dimensions. The results for each case were compared with the experimental measurements of the turbine shaft power, overall streamwise rotor drag, mean velocity, turbulence kinetic energy, and momentum transport terms in the near-wake at one diameter downstream. It was shown that 2-D simulations overpredict turbine loading and do not resolve mean vertical momentum transport, which plays an important role in the near-wake's momentum balance. The 3-D simulations fared better at predicting performance, with the Spalart–Allmaras model predictions being closest to the experiments. The SST model more accurately predicted the turbulence kinetic energy, while the Spalart–Allmaras model more closely matched the momentum transport terms in the near-wake. These results show the potential of blade-resolved RANS as a design tool and a way to “extrapolate” experimental flow field measurements.

Description: A modified suction caisson (MSC) can be used to support the offshore wind turbine. This paper presents an experimental study and a numerical simulation on the earth pressure distribution along the MSC embedded in saturated marine fine sand. Results show that the yield envelops for the MSC and the corresponding regular suction caisson in the H-M space can be represented by a linear relationship. It was also found that the Prasad and Chari method, which is popular in analyzing the earth pressure distribution along lateral loaded rigid plies, can well predict the maximum net earth pressure on the regular suction caisson. However, for the MSC, since the external skirt can resist a considerable portion of the lateral load, Prasad and Chari method overestimates the maximum net earth pressures acting on the internal compartmental shaft of the MSC. Numerical simulation results indicate that in the ultimate limit state the maximum net earth pressure acting on the external skirt wall in the loading direction is larger than that on the internal compartment wall. However, the maximum net earth pressure along the caisson embedded depth is obtained at the MSC base opposite the loading direction. In addition, the separation between the top lids of the internal compartment and external skirt occurs opposite the loading direction. The lateral load and the resulting overturning moment acting on the MSC are mainly carried by the passive earth pressure zones along the inner and outer shafts of the internal compartment and the external skirt both in the loading and opposite the loading directions and under the external skirt lid in the loading direction. The main reason of the suction caisson failure is that the sand in the lower passive earth pressure zone opposite the loading direction yields completely.

Description: The price of coal fluctuated widely in the past few years in China. It is widely believed that rising coal prices can push up the inflation; this affected the determination of the policy of controlling coal price. This paper examines whether the rising coal price determines inflation in China. Bootstrap correlation test indicates that the Consumer price index (CPI) is not always positively correlated to the coal price in preceding months. The Bootstrap Granger test shows that coal price Granger-causes the CPI with 4–6 lags. However, many regression coefficients in the Granger test are negative and significant, which is consistent with the result of the bootstrap correlation test and contradicts the cost-push theory. Based on the Vector autoregression (VAR) model, bootstrap impulse response analysis reveals that coal price affects the CPI, but the directions of the effects vary and cancel each other out over a long period. Therefore, we find no evidence that shows a rise in coal price leads to cost-push inflation. Electricity price regulations, the price filter effect in the industry chain, and the Fisher currency trading equation theory can be used to explain this phenomenon. Finally, we conclude that both coal prices and the CPI are caused by inflation (in addition to market liquidity) instead of being the cause.

Description: Calcined copper slag (CCS) catalytic steam reforming of jatropha oil was investigated in a fixed bed tubular reactor for hydrogen. The pyrolysis mechanism of jatropha oil was characterized by high performance liquid chromatograph, thermogravimetric analysis, and infrared spectroscopy. At 300–400 °C the fatty acid glycerides cracked into fatty acid, ketene, and acrolein. However, carboxyl, aldehyde, and ketone groups completely became broken bonds when the reactive temperature was 400–500 °C. Dynamic analysis of jatropha oil's thermogravimetric curves was researched by Coats-Redfern equation, where the jatropha oil pyrolysis process accorded with the Z-L-T equation. The activation energy E was 294.14–349.47 kJ/mol, and the pre-exponential factor A was 7.38 × 10 20 –3.53 × 10 25  min −1 . Four catalysts were used for catalytic steam reforming of jatropha oil, the active components of CCS were ferric oxide and other metal oxides, and ferric oxide had a good effect on C=C double bond fracture of jatropha oil.

Description: This work reports on the development of Linear Quadratic Regulator (LQR) based maximum power point tracking method for standalone photovoltaic system. The advantages of the method are faster tracking ability, transfer of maximum deliverable power and its implementation with reduced complexity. The tracking performance of the proposed LQR method is compared with that of the conventional Perturb and Observe (P&O) method in MATLAB/Simulink environment for both constant and varying irradiation conditions. The improved performance of the LQR method in terms of tracking speed and tracking efficiency is confirmed through experimental results obtained using dSPACE controller.

Description: Wind tunnel measurements for a 3 × 3 canonical wind turbine array boundary layer are obtained using hot-wire anemometer velocity signals. Two downstream locations are considered, referring to the near- and far-wake, and 21 vertical points are acquired per profile. Velocity increments and exit distances are used to quantify inverse structure functions at both downstream locations. Inverse structure functions in the near-wake show a similar profile for the main vertical locations, but diverge as the moment is increased. In the far-wake, inverse structure functions converge toward a single function for all vertical location and moments. The scaling exponents for inverse structure functions are calculated directly and relatively, using extended self similarity. Scaling exponents show strong dependence on vertical position along the wind turbine profile in the near-wake and remain relatively constant in the far-wake. Intermittency in the near-wake is indicated by the nonlinear behavior of the direct and relative scaling exponents when plotted against their respective moments.

Description: This paper proposes a fuzzy interval optimization approach to solve the Environmental/Economic Dispatch (EED) problem with uncertain parameters in the constraints and the objective functions. The objective functions considered are fuel cost and the gaseous emissions of the generating units. Two different types of fuel cost functions are considered in this study, namely, the conventional quadratic function and the augmented quadratic function to introduce more accurate modeling that incorporates the valve loading effects. The latter model presents non-differentiable and nonconvex regions that challenge most gradient-based optimization algorithms. In the proposed approach, objective functions are fuzzified and integrated to represent the fuzzy decision value. On the other hand, load uncertainties are modeled using fuzzy intervals. This fuzzy EED problem formulation provides a modeling flexibility, relaxation in constraints and allows the method to seek a practical solution. The obtained fuzzy multi-objective optimization problem is solved using non-dominated sorting genetic algorithm-II, known for its global searching capabilities, to get the best compromise among all the objectives. The performance of this solution is examined and applied to the standard IEEE 30-bus six-generator test system and the Indian power network of 82-bus by comparing its results with that of the existing methods. Different cases with different complexities have been considered in the study reported in this paper.

Description: This paper considers the effects of renewable energy strategies on energy security. Based on theoretical analysis, we conclude that energy supply shocks benefit firms with a sacrifice of consumer surplus, while the effects on social welfare depend on the degree of environmental concerns. Meanwhile, renewable energy strategies improve energy security by reducing the consumption of conventional energy and by reducing emissions. Furthermore, the total consumption of conventional energy decreases with the number of firms that adopt renewable energy. In addition, for low marginal costs of renewable energy, the efficiencies are equivalent for different covering rates of governmental subsidies. For high fixed costs or marginal costs, governmental subsidies yield excess capacity.

Description: There are few empirical studies concerning the impact of information communication technology (ICT) on energy intensity in developing countries. We introduce an expanded STIRPAT model and China's provincial data samples during 2003–2012 to fill this gap. This paper applies the Driscoll–Kraay econometric method to assess the long-term impact of ICT investment on energy intensity and employs a panel error correction model to explore the short-term influence. The results indicate that the ICT investment significantly reduces energy intensity in the long-run, while it does not in the short-run at a nationwide level. Concerning the regional diversities of China, the impact of the ICT investment on energy intensity is significantly negative in western and central regions, while is insignificant in the eastern sample. Furthermore, the negative impact grows as the ICT investment increases in central provinces. Additionally, the short-term energy intensity reduction effect exists only in eastern regions, while it does not in central provinces. The ICT investment increases the energy intensity in the short-run in the western sample.

Description: Nine-switch converter has been recently known for its higher compactness with reduced switch count as compared to the back-to-back converter. The readily available dc-link capacitor made it an appropriate alternative for ac/dc/ac conversion in microgrids. Regardless of the complicated Pulse Width Modulation control scheme, this paper proposes a novel predictive power control for the nine-switch converter which is simple and allows concurrent control of real and reactive power flow between two islanded microgrids. The proposed control scheme adopts the virtual flux vectors and a newly defined reactive power to improve the power quality under the existence of grid voltage disturbances, i.e., voltage unbalance and voltage distortion. Simulation results of the proposed predictive power control guarantee decoupled active and reactive power controls, fast response, accurate power and dc-link voltage tracking, and sinusoidal current waveforms with low harmonic distortions under the various grid conditions.

Description: The demand for electrical energy increased drastically due to the exponential growth of the world population. In the last decade, owing to environmental issues and decay of non-renewable energy resources, the development of power generation from hydrokinetic energy has grown considerably. Many individuals and companies are considering hydrokinetic power as the better solution to the prevailing energy crisis. However, there is a paucity of published literature that sheds light on the economic and environmental sides of hydrokinetic turbines (HKTs) in hybrid renewable energy systems (HRES). The prime objective of this study is to provide an economic and environmental assessment of using the HKT in combination with other renewable energy resources for cost-effective, reliable, and sustainable electrical energy supply for the rural households in Naga Hammadi, Egypt, where adequate water resources are available from the Nile River. The HKT is simulated together with photovoltaic (PV), diesel generator (DG), and battery (B) power using the well-known Hybrid Optimization of Multiple Electric Renewables software to optimize the HRES. The net present cost (NPC) of the optimum HRES is $12.7 million with minimal cost of energy of $0.158/kWh. The optimum system is capable of saving approximately $9.7 million during the project lifetime (25 years) in the form of NPC as compared to the diesel generator system. In addition, the system is capable of saving 28.971 × 10 6 l of fuel at the cost of $5.11 million during the project lifetime. Finally, it is concluded that the hybrid PV/HKT/DG/B is the more economic and environment friendly system as compared to other system configurations especially the diesel generator system, because it is able to reduce 76.29 × 10 6 kg of the amount of CO 2 emissions during the project lifetime.

Description: Energy systems with renewable sources are used around the world in order to satisfy both off-grid and on-grid load demands, and are commonly coupled to conventional sources. A good behavior of this kind of systems depends on the renewable sources availability that includes the solar irradiance and the wind speed, as well as the profile variations over the energy demand. Their main objective is to satisfy the load demand while minimizing the use of conventional sources, reducing pollutant emissions and storing the energy excess for deficit conditions. This paper presents modeling, neural forecasting and optimal sizing for hybrid energy systems, which are proposed to minimize both the overall annual cost and the use of conventional sources, which in turn represents reduction of pollutant emissions. In this paper, the use of renewable sources along with load demand variations are predicted by a High Order Neural Network trained with an Extended Kalman Filter, whereas the optimal sizing is calculated by using both a Clonal Selection Algorithm and a Genetic Algorithm. The efficiency of using neural forecasting data is illustrated through a simulation with the results showing the effectiveness of both optimization algorithms for calculating an optimal sizing of the hybrid system, which ultimately represents an optimal cost-effective system.

Description: Bi-functional catalysts consisting of platinum on aluminosilicate MCM-41 materials with Si/Al ratios between 10 and 30 were prepared via direct mixed-gel synthesis. The catalysts were tested in the hydrocracking of bio-alkanes, produced from biodiesel hydrodeoxygenation and composed of n-hexadecane and n-octadecane, for the production of bio-jet fuel. The effects of temperature, pressure, weight hourly space velocity (WHSV), and H 2 /n-paraffin weight ratio on bio-alkanes conversion and product distribution were examined. The conversion was found to be dependent on the acid strength of the catalyst supports which were proportional to the Al content. However, the catalyst selectivity decreased with the increasing Al content. The optimal Si/Al ratio, temperature, pressure, WHSV, and H 2 /n-paraffin weight ratio were determined to be 20, 330 °C, 2 MPa, 1 h −1 , and 0.20, respectively. Under these conditions, the bio-alkanes conversion and kerosene/gasoline ratio in the product reached 65.62% and 1.96, respectively.

Description: This paper highlights a new approach using high-quality ground measured data to forecast the hourly power output values for grid-connected photovoltaic (PV) systems located in the tropics. A case study using the 1-year database consisting of PV power output, global irradiance, module temperature, and other relevant variables obtained from Universiti Teknikal Malaysia Melaka is used to develop forecast models for three typical weather conditions—clear, cloudy, and overcast sky conditions. A machine learning method (Support Vector Regression—SVR) and an Artificial Neural Network method (nonlinear autoregressive) are used to produce the models and the results are compared with a benchmark model using the persistence method. Comparison with all the variables suggests that tilted global horizontal irradiance ( GHI tilt ) and module temperature ( T mod ) are the essential input variables to forecast the PV power output. It has also been observed that SVR performs well across all types of sky conditions, with the forecasting skill values between 0.65 and 0.79 when compared to the benchmark persistence method.

Description: The main objective of this research is to investigate the degree to which variations in mechanical properties of constitutive composite materials can influence the aeroelastic behavior of a wind turbine blade. First, structural behavior of a full-scale wind turbine blade is evaluated from different aspects of bending, torsional and axial rigidities. For this purpose, simplified model of the blade is constructed and it is validated with experimental data of the full-scale blade. Then, a parametric study is performed to determine the most dominant mechanical properties which have a severe impact on the structural behavior of the blade. Identified dominant properties are varied randomly and independently. Thus, stochastic analysis is performed to investigate the variations in natural frequencies of the blade as the governing parameter in defining aeroelastic behavior. Finally, susceptibility of the blade to dynamics instability is also examined. Aeroelastic effects are found to have a stronger effect on the blade with lower material properties that lead to more power reduction.

Description: The wastewater of a petroleum processing facility was used to grow the oleaginous bacterium Rhodococcus opacus PD630 to produce microbial oils. Undiluted wastewater supplemented with molasses (20 g/l) and ammonium chloride (1 g/l) provided a maximum dry biomass concentration of nearly 6 g/l in a 96 h batch culture. The lipid concentration in the bacterial broth exceeded 3 g/l and the lipid content in the dry biomass was nearly 52% by weight. Biomass and oil production were further improved using a 96-h fed-batch fermentation instead of a batch culture. The final biomass concentration exceeded 7.2 g/l and the lipid concentration was nearly 4 g/l. The lipid content of the dry biomass exceeded 54% and the lipid yield on sugars was 0.33 g/g. The lipids were similar to vegetable oils. They contained mainly long chain C16 and C18 fatty acids. Potentially such lipids may be used to replace vegetable oils in production of biodiesel.

Description: This paper proposes an iterative-analytical method to find the optimal size and site of distributed generation units in a radial distribution system to reduce the maximum possible amount of network loss. The proposed analytical method is an advanced form of the Improved Analytical approach used in other papers. Three types of distributed generation units with different capabilities of active and reactive power generation are considered. To show the efficiency of the iterative analytical approach, different scenarios are tested in 33- and 69-bus standard distribution test systems. A 49-bus real network is also used to prove the efficiency of the proposed method for applying in real-world systems. Comparison between results of the proposed and existing methods demonstrates the advantage of the proposed technique in loss reduction.

Description: The intermittent volatility of wind power integrated into the grid poses a great threat to the stable operation of power systems on the supply side. Conversely, large-scale charging of electric vehicles (EVs) also brings new challenges to dispatch on the demand side. In response, the randomness and temporal-spatial correlations of stochastic wind power generation are considered in this paper. Additionally, the EV charging infrastructure is studied. A dynamic stochastic optimal power flow (DSOPF) for wind farms and EVs integrated power system based on the chance-constrained programming model is proposed. An optimal dispatch scheme is obtained by solving the dynamic optimal power flow. After that, dynamic probabilistic power flow based on cumulants is performed under the scheme to obtain the probability distribution of state variables. The upper and lower bounds of chance constraints are adjusted according to the probability distribution function until they are all satisfied. Illustrative examples demonstrate the effectiveness of DSOPF for firming the variable wind energy, and EV charging is performed on the Institute of Electrical and Electronics Engineers systems. On this basis, different EV charging modes and the temporal-spatial correlations are specifically discussed.

Description: The very mounting demand for the electricity supply and the raising concern about global warming and climate change have motivated the electricity sector to adopt renewable and local sources of energy. The incorporation of such sources into the distribution network poses a variety of benefits as well as challenges to the Distribution System Operators. The paper analyses a real life 4.3 MVA unbalanced distribution feeder in Kerala, India for its voltage profile improvement and power loss reduction with the addition of Photovoltaic (PV) units at the specified locations with optimal sizing. A methodology based on the Learning Automata (LA) algorithm is developed in order to find out the suitable size of the PV units to be installed at suitable locations in an unbalanced distribution feeder. The LA algorithm is efficient in handling the uncertainty associated with the PV power generation which is modelled using Beta Probability Density Function. The proposed algorithm is validated using the balanced feeder in the literature and extended for several unbalanced test feeders and the selected practical distribution feeder.

Description: We screened and identified a set of efficient promoters in Saccharomyces cerevisiae that maintained their relatively strong strengths to regulate the heterologous xylose-assimilating pathway genes XYL1 and XYL2 , and native XKS1 and pentose phosphate pathway four genes, irrespective of glucose or xylose fermentation medium. In this study, we developed a rapid and efficient xylose-fermenting S. cerevisiae strain 7-1 based on balanced pathway expression levels driven by our proposed strong promoters. Next, 7-1 was used to initialize the evolutionary engineering, through first aerobic and anaerobic sequential batch cultivation. The finally evolved strain of 7-1E1 displayed a high ethanol yield (0.45 g/g) and low xylitol accumulation (0.13 g/g). Moreover, the evolved strain of 7-1E1 displays great potential for ethanol production from lignocellulosic biomass. This work reveals that efficient xylose assimilation is attributed to the elevated expression levels of xylose utilization genes, which was accomplished through the strong promoter rational regulation in the chromosome of the evolved strain.

Description: Parabolic solar troughs are amongst the most widely studied solar thermal technologies available today. Methods for improving efficiency include the use of selective coatings on the absorber which reduces dominant thermal radiation losses. In this paper, we model a different approach of reducing radiation losses: the glass cover around the absorber can be coated with a hot mirror film, which reflects infrared radiation back onto the absorber. In order to describe such a mechanism, it becomes necessary to model theoretically the long range thermal radiation interactions inside the receiver unit. Our model uses discretization of the active surfaces to account for all the dominant radiation interactions, and can be used in a simulation to establish a temperature profile for the receiver unit, from which thermal properties can be inferred. The results of the simulation are compared to existing simulations and experimental data, wherever possible.

Description: To investigate the correlation between the physicochemical and hygroscopic properties of biochar and soil, the moisture sorption properties of typical biochars and soils were observed inside a thermostatically controlled incubator at a temperature of 30 °C and humidity of 70%. Results showed that the equilibrium moisture content (EMC) of tobacco stem biochar, rice husk biochar, Hubei paddy soil, and Jiangxi red soil were 7.66%, 6.40%, 3.34%, and 2.92%, respectively. There was a synergistic interaction between biochar and soil, resulting in a higher EMC of biochar-soil mixtures with increases ranging from 0.16% to 2.52%. The porosity of tobacco stem biochar, rice husk biochar, Hubei paddy soil, and Jiangxi red soil were 82.58%, 65.05%, 59.02%, and 56.71%, respectively. Additionally, according to our findings, the biochar had higher carbon content, C/N ratio, and carbonyl groups, and lower bulk density, oxygen content, O/C ratio, and carboxyl groups than the soil. The linear correlation analysis indicated that there was a positive correlation between EMC and the physicochemical properties of biochar and soil, including porosity, carbon content, nitrogen content, and carboxyl groups. Consideration of the physicochemical properties of biochar and soil will significantly improve the overall properties of biochar used for soil amendment.

Description: This study presents a charging and discharging controller of a lithium-ion battery for charge equalization control of a battery storage system using the particle swarm optimization (PSO) algorithm. The charge equalization controller is designed using a bidirectional flyback DC–DC converter for exchanging the amount of energy from a battery series stack to an overdischarged cell to be charged and vice versa. The constant current–constant voltage charge proportional–integral (PI) control and discontinuous current mode control are applied to charge and discharge the lithium-ion battery on a flyback converter operation. This proposed system utilizes the PSO algorithm to optimize the values of the PI controller parameters. Optimization results produce the ideal values of the PI controller parameters with minimum error indices, thereby regulating the pulse-width modulation to the MOSFET switching drive of the flyback converter and upgrading the battery charge performance for charge equalization. The PSO algorithmic approach-based developed system is proven to be robust and competent for high-tech storage systems toward the advancement of sustainable electric vehicle technologies and renewable source of applications.

Description: Mitochondria were deposited via dip coating on different substrates, namely, commercial glass, copper plate (Cu), aluminum plate (Al), and poly (methylmethacrylate). Mitochondria are organelles that are found in live cells. Mitochondria produce most of the ATP via oxidative phosphorylation. First, mitochondria were extracted for the thin film, as described in the literature. Capacitance properties of thin films were measured with Agilent LCR meter. SEM analysis was used for the surface analysis. The structure of mitochondrion was characterized with FTIR, whose spectrum was measured using a Perkin Elmer Spectrum 400 spectrometer. The stretching vibration of the P-O bond was observed at 1236 cm −1 in FTIR spectrum of the thin film. The capacitance and dielectric permittivity were first measured and calculated for the substrates, and then for mitochondria plated substrates. The properties, such as dielectric permittivity, capacitance, energy density, and power density of some substrates have been changed when their surface has been coated with mitochondria.

Description: The framework of theoretical method is two-fluid model coupled with reaction process. The k-ε model is used for gas phase, and the kinetic theory of granular flow is employed for solid phase. In the simulation, gasification process consists of three parts: pyrolysis, homogenous reaction, and heterogeneous reaction. In the first stage, biomass particles crack into carbon particles and volatile gases upon entering the reactor. Subsequently, the carbon particles and volatile gases react with oxygen, which includes both homogenous reaction and heterogeneous reaction. The effect of equivalence ratio (ER) is studied. It is found that all the products have same tendency with the increase of ER. H 2 and CH 4 change linearly with ER; CO and CO 2 change cubically with ER. This is because the mechanism of formation of CO and CO 2 is more complex than that of H 2 and CH 4 . H 2 and CH 4 are consumed by O 2 , so they tend to decrease with the increase of ER, whose value corresponds to the amount of O 2 fed. For CO and CO 2 , however, things are more complicated: the extents at which CO and CO 2 decrease are converse. CO decreases significantly and then reaches a plateau and finally decreases again, while CO 2 decreases moderately at the beginning and then decreases sharply and finally becomes flat. The conclusion is that when oxygen concentration is low, increment of oxygen favors production of CO 2 , and when oxygen concentration reaches a certain level, increment of oxygen favors production of CO, and when oxygen concentration continually increases, increment of oxygen favors production of CO 2 again.

Description: Currently, many Chinese cities are suffering from the mounting pressures of deteriorating environmental quality, particularly in the form of serious air pollution that contributes to fog and haze. An important reason for urban air pollution is the rapid increase in automobile ownership and usage, which has increased gasoline consumption and waste gas production. Thus, it is important—and even necessary—to develop new energy vehicles (NEVs) to mitigate the environmental problems associated with automobile usage. However, the market share of NEVs in China is still relatively low. For the sake of boosting NEV sales, research should be conducted on this market, particularly regarding Chinese consumers' preferences for and intentions to purchase environmentally friendly vehicles. This study employs a carefully designed questionnaire survey of potential electronic vehicle consumers in seven Chinese cities. An empirical analysis based on the survey data is performed to investigate the main factors influencing the purchase of electronic vehicles. The estimation results indicate that monthly income, the number of cars a family owns, sustainability and vehicle comfort strongly influence consumers' purchasing behavior. Furthermore, age, marital status, city of residence, the number of cars a family owns, and the extent of police familiarity concerning NEVs are all proven to be significantly determinants of consumers' purchasing intentions. Moreover, based on our results, several political suggestions are provided to encourage the development of the Chinese NEV market.

Description: This work presents a simple time-lag model for biogas production from anaerobic digestion of organic wastes (biomass) in a batch digester. The model has the ability of predicting the S-shaped nature of the cumulative biogas yield with retention time that is commonly observed experimentally. The model is calibrated against biogas production data from anaerobic digestion of three types of organic waste: OFMSW (organic fraction of municipal solid waste), FVW (fruit and vegetable waste) and RH (rice husk). For these three wastes, the fit of the model to the experimental data has an average root-mean-square deviation of 9%. The time-lag model leads to the formulation of two measures or indexes of biodegradability of a particular waste. The values of these indexes are much higher for FVW compared to those for OFMSW and RH showing that the susceptibility of FVW to anaerobic digestion far exceeds that of the other two wastes.

Description: This paper presents experimental investigation of pyrolysis process of corn cob from Vojvodina (Republic of Serbia). The influence of temperature, reaction time, particle size, and heating rate on pyrolysis products yields was investigated. Studying of biomass pyrolysis kinetics led to the conclusion that thermogravimetry is an appropriate method for explaining decomposition of different biomass types. Experimental research showed that temperature increase leads to decrease in char yield and volatile yield. Mass yield of pyrolysis oil increased with higher heating rate. Methane volume fraction in pyrolysis gas increased with temperature increase, while the volume fraction of carbon dioxide decreased. Particle size affected the methane yield. It was shown that with the increase in particle size, the volume fraction of methane in pyrolysis gas decreased. Based on the char composition obtained after corn cob pyrolysis process, it was determined that char is rich in carbon (74.80%). Lower heating value of char was 26182.09 kJ/kg. High heating value of char contributes to economic justification for applying corn cob pyrolysis.

Description: To study the influence of additives on the pyrolysis behavior of microwave-heated biomass, cotton stalk pyrolysis was performed using both a particular microwave pyrolysis reactor and an electric heating system with the addition of acid (H 3 PO 4 ) and metal salts (NaCl, K 2 CO 3 , and MgCl 2 ) at 550 °C. The derived products were evaluated by environmental scanning electron microscopy, gas chromatography with mass spectrometric detection, and temperature adsorption analysis. The results indicated that microwave heating with additives was beneficial to enhance the quality of the pyrolysis products. The addition of H 3 PO 4 was favorable for liquid oil formation with higher furfural and acetic acid contents. The highest yield of oil was achieved with 8% H 3 PO 4 , while the maximum char yield and surface area were obtained at 12% H 3 PO 4 , as higher percentages caused the formation of more porous solid char. The addition of metal salts promoted the formation of char at the cost of decreasing the liquid oil production. The maximum yields of bio-oil and char were achieved with the addition of MgCl 2 , while the minimum yields were obtained by adding K 2 CO 3 . The addition of MgCl 2 (8%) promoted the formation and pore growth of char during the pyrolysis process; moreover, it was helpful for the production of furfural and acetic acid substances as well as a small amount of naphthalene. The addition of K 2 CO 3 (8%) increased the gas production significantly but decreased the specific surface area of char. The addition of NaCl (8%) increased the char yield but decreased the oil and gas yields slightly. The comparative results showed that microwave pyrolysis with H 3 PO 4 and MgCl 2 additives were beneficial for the preparation of activated char with a large specific surface area and optimal formation of bio-oil.

Description: This paper proposes a model for coordinated transmission expansion planning-reactive expansion planning (TEP-RPP) that incorporates the costs related to the operation of large-scale photovoltaic units (LPU). The model is based on the dynamic evaluation of LPU generation and the effect of it on TEP-RPP problem. In a system with the presence of LPU and conventional units, the network expansion project has been dependent on two important environmental factors, solar irradiation and ambient temperature. The TEP-RPP issue has been systematized in a multi-purpose form based on investment and operation cost, voltage deviation, and stability criterion. A multi-objective gravitational search method is implemented to extract the Pareto-archive curve of the presented multi-purpose issue. Algorithm of similarity to ideal solution is used to trade-off different points of Pareto curve. The proposed mythology has been evaluated on two different modified systems, Azarbaijan regional power system of Iran and IEEE 30 bus test system. It is indicated that the presented model can be used effectively to study the intermittent impact of LPU on the solution of the TEP-RPP problem.

Description: This work evaluates the influence of temperature and irradiation on the behavior of mono-crystalline silicon, poly-crystalline silicon, and Copper Indium diselenide (CIS), modules which have been exposed to real conditions. An outdoor experimental setup has been installed, at a Mediterranean site in north latitude 38 °, in order to collect results from current-voltage measurements that corresponded at constant radiation level in order to evaluate the effect of temperature and results from measurements realized at about the same temperature in order to study the effect of irradiation. The results present that the daily generated power normalized to the manufacturer's value is positively influenced by the irradiation and not by the negative effect of temperature. The performance of mono and poly Si appears superior to that of CIS early in the morning, while this advantage is diminished during midday, when the temperature and irradiance are highest, as CIS performance becomes comparable to the other two. However, the temperature affects the efficiency and fill factor for the mono and poly-Si modules recording the lower values on higher temperatures, while it does not the same for the CIS modules. This experimental study can provide information for locations with similar climatic conditions because it helps to take into account variation in temperatures together with variation in radiation and to avoid under-designing of photovoltaic systems and system malfunction.

Description: As one of the most promising renewable energy, wind energy plays a vital role in optimizing the configuration of energy resources in power system nowadays. However, wind generation with the intermittent and uncertain characteristics has brought new challenges for the integration of large-scale wind power into power system. Consequently, the accurate forecasting of wind power is the most effective and applicable solution to meet the challenges. A novel combined forecasting approach is proposed by integrating the ensemble empirical mode decomposition (EEMD) technique and the combination of individual forecasting methods based on optimal virtual prediction for the purpose of improving the short-term wind power prediction performance. There are three steps in this presented approach. First, EEMD is adopted to decompose the original wind power series into a number of intrinsic mode functions (IMFs) and a residue. Second, the prediction of each IMF is achieved by using four individual methods, and the prediction of the residue is obtained from the nonlinear grey Bernoulli model based on particle swarm optimization. Finally, the combined forecasting model based on optimal virtual prediction is developed, and the weight matrix in this model is optimized by a self-adaptive differential evolution algorithm, which aims to minimize the forecasting errors at the virtual prediction points. The real wind power data from a wind farm in China are used to verify the performance of the proposed model, and the simulation results show that this model has demonstrated the optimal forecasting accuracy and robustness compared with other forecasting models, which is a promising alternative for short-term wind power forecasting.