Effect of non-uniform illumination on performance of solar thermoelectric generators

Solar thermoelectric generators (STEGs) are heat engines which can generate electricity from concentrated sunlight. The non-uniform illumination caused by the optical concentrator may affect the performance of solar thermoelectric generators. In this paper, a three-dimensional finite element model of solar thermoelectric generators is established. The two-dimensional Gaussian distribution is employed to modify the illumination profiles incident on the thermoelectric generator. Six non-uniformities of solar illumination are investigated while keeping the total energy constant. The influences of non-uniform illumination on the temperature distribution, the voltage distribution, and the maximum output power are respectively discussed. Three thermoelectric generators with 32, 18 and 8 pairs of thermocouples are compared to investigate their capability under non-uniform solar radiation. The result shows that the non-uniformity of the solar illumination has a great effect on the temperature distribution and the voltage distribution. Central thermoelectric legs can achieve a larger temperature difference and generate a larger voltage than peripheral ones. The non-uniform solar illumination will weaken the capability of the TE generator, and the maximum output power decrease by 1.4% among the range of non-uniformity studied in this paper. Reducing the number of the thermoelectric legs for non-uniform solar illumination can greatly increase the performance of the thermoelectric generator.     

Investigation of solar hybrid system with concentrating Fresnel lens,photovoltaic and thermoelectric generators

An experimental model of a solar hybrid system including photovoltaic (PV) module, concentrating Fresnel lens, thermoelectric generator (TEG), and running water heat extracting unit was created and studied. The PV module used was of c‐Si and TEG of Bi₂Te₃; the Fresnel lens (solar concentrator) and TEG share an optical train, whereas PV module was illuminated separately with non‐concentrated light. Heat extracting unit operated in thermo siphon mode. In climatic conditions of Mexico (Queretaro, 20^o of North latitude, summer time), the Fresnel lens accepted 120 W of solar radiation power, and the system generated 7.0 W of electric power and 30 W of thermal one. The discussion is made of the possible characteristics of a hypothetical hybrid system where all its elements share the same optical train. Copyright © 2016 John Wiley & Sons, Ltd.     

A comprehensive review of solar thermoelectric cooling systems

The negative environmental impacts of burning fossil fuels have forced the energy research community seriously to consider renewable sources, such as naturally available solar energy. This paper provides an overview of solar thermoelectric (TE) cooling systems. Thus, this review presents the details referring to TE cooling parameters and formulations of the performance indicators and focuses on the development of TE cooling systems in recent decade with particular attention on advances in materials and modeling and design approaches. Additionally, the TE cooling applications have been also reviewed in aspects of electronic cooling, domestic refrigeration, air conditioning, and power generation. Finally, the possibility of solar TE cooling technologies application in “nearly zero” energy buildings is briefly discussed, and some future research directions are included. This research shows that TE cooling systems have advantages over conventional cooling devices, including compact in size, light in weight, high reliability, no mechanical moving parts, no working fluid, being powered by direct current, and easily switching between cooling and heating modes.     

基于太阳能光伏热利用的光伏/热电(PV/TV)建筑一体化试验研究

将太阳能电池板、集热器、热电发电片结合起来,设计并制成了一套光伏/热电(PV/TV)系统,在利用太阳能电池发电的同时,收集热量并利用其发电。在北京地区进行了该系统的室外模拟试验,测试并讨论了该系统在不同结构和不同环境下的性能,探讨该系统在光伏建筑中的应用。试验结果表明,与单纯的光伏发电系统或太阳能热水系统相比,PV/TV系统具有占地面积小、综合效率高等优点。     

A review on photovoltaic/thermal hybrid solar technology

A significant amount of research and development work on the photovoltaic/thermal (PVT) technology has been done since the 1970s. Many innovative systems and products have been put forward and their quality evaluated by academics and professionals. A range of theoretical models has been introduced and their appropriateness validated by experimental data. Important design parameters are identified. Collaborations have been underway amongst institutions or countries, helping to sort out the suitable products and systems with the best marketing potential. This article gives a review of the trend of development of the technology, in particular the advancements in recent years and the future work required.     

A novel choice for the photovoltaic–thermoelectric hybrid system: the perovskite solar cell

Most of the recent studies about the photovoltaic cell‐thermoelectric generator (PV‐TEG) hybrid system pay their attention to silicon PV cells. This paper is to estimate the feasibility and features of the integrated system consisting of the emerging perovskite solar cells and thermoelectric modules. The results in this paper show that the temperature coefficient of the perovskite solar cell is lower than 2‰. Because of such a lower temperature coefficient, the efficiency of the perovskite solar cell‐TEG hybrid system can amount to 18.6%, while the efficiency of the single perovskite solar cell is 17.8%. Therefore, the perovskite solar cell is a reasonable choice for the PV‐TEG hybrid system. By altering the thermal concentration, the volume of the TEG material can be decreased, and the cost of the hybrid system can be remarkably reduced. To study the influence of the thermal concentration on the performance of the hybrid system, a three‐dimensional numerical model of the hybrid system is developed in this paper. When the thermal concentration ration is lower than 100, the temperature drop is lower than 3 K, and the decline in the conversion efficiency caused by the thermal concentration can be neglected for the proposed PV‐TEG hybrid system. Copyright © 2016 John Wiley & Sons, Ltd.     

Performance analysis of a hybrid solar thermoelectric generator

In this paper, a theoretical model is developed to investigate the performance of the hybrid solar thermoelectric generator (HSTEG) system, which is designed without (B-HSTEG) and with an evacuated glass tube (V-HSTEG). The heat loss, power output, thermal efficiency, and electrical efficiency of the B-HSTEG/V-HSTEG system are evaluated by analyzing the design parameters such as geometric solar concentration ratio, thermoelectric figure of merit, and cold-side inlet fluid temperature. The performance of the B-HSTEG is compared with the V-HSTEG system using two heat transfer fluids: water and Therminol VP-1. The maximum electrical efficiency of the B-HSTEG and V-HSTEG is estimated to be 12.2 and 15.6% (ZT = 3) with a corresponding thermal efficiency of about 61.9 and 60.3%, respectively. Overall, this paper provides a systematic performance analysis of HSTEG systems.     

Methodological reviews and analyses on the emerging research trends and progresses of thermoelectric generators

Thermoelectric generator is among the earliest initiated electricity‐harvesting methods. It is a very potential power harvester that can convert wasteful thermal energy into electricity. However, it often suffers from low energy conversion rate due to its inconsistent heat source, inefficient thermoelectric material (or thermoelement) performance, and incompetent structural issues. Progressively for the first time, detailed methodological surveys and analyses are made for bulk, thick, and thin films in this review. This is in order to accommodate better insights and comprehensions on the emerging trends and progresses of thermoelectric generators from 1989 to 2017. The research interests in thermoelectric generators have started back in 1989, and have continuously experienced emerging progresses in the number of studies over the last years. The methodological reviews and analyses of thermoelectric generator showed that almost 46.6% of bulk and 46.1% of thick and thin film research works, respectively, are actively progressed in 2014 to 2017. Nearly 86.2% of bulk and 44.1% of thick and thin film thermoelectric generators are realizing in between 0.001 and 4 μW cm^?2 K^?2, while 43.1% of thick and thin films are earning among 10^?6 to 0.001 μW cm^?2 K^?2. The highest achievement made until now is 2.5 W cm^?2 at a temperature difference of 140 K and thermoelectric efficiency factor of 127.55 μW cm^?2 K^?2. This achievement remarked positive elevation for the field and interest in thermoelectric power generation. Consecutively, the research trends of fundamental devices' structure, thermoelement, fabrication, substrate, and heat source characteristics are analyzed too, along with the desired improvement highlights for the applications of thermoelectric generators.     

小型太阳能光伏直流车载冰箱的实验性能研究

设计了一个小型太阳能光伏直流车载冰箱实验系统,实验验证了该系统各部件工作时的匹配性能,并测试了系统工作时的电流、冰箱温度、负载功率、蓄电池电压等数据,最后对各部分能耗进行了分析。实验结果表明：该装置能稳定运行,可满足实际冷藏要求;在完全无日照情况下,冰箱可连续运行34 h。     

A comparison study of energy and exergy performance of a hybrid photovoltaic double‐pass and single‐pass air collector

In this present paper, analysis based on energy and exergy of double‐pass hybrid photovoltaic thermal (HPV/T) air collector having air flow in the opposite direction in ducts has been carried out based on initial cost, annual savings and return on investment. Choice of the location is made to cover different climatic conditions prevailing in India e.g. hot and dry climate represented by Jodhpur, warm and humid climate represented by Mumbai, moderate climate represented by Bangalore, cold and cloudy climate represented by Srinagar and composite climate represented by New Delhi. Results of single‐pass HPV/T air collector have also been compared. It is observed that electrical, thermal and exergy efficiencies of double‐pass HPV/T air collector are higher than that of single‐pass HPV/T air collector by 10–12, 40–45 and 13–17%, respectively. Further, it is observed that cost per kWh of double‐pass HPV/T air collector reduces for all the locations covered in the study when compared with cost per kWh of single‐pass HPV/T air collector. Copyright © 2009 John Wiley & Sons, Ltd.     

On the volume power density of radial thermoelectric generators

We examine the volume power density of radial thermoelectric generators (TEGs). Radial, or tubular, TEGs have been considered as an alternative to the usual flat-plate TEGs due to its improved geometric match to typical curved heat sources and high surface power density. However, surface power density is not the only important performance index in realistic situations. Especially for TEGs with inorganic materials that have high raw material prices, volume power density can be important as well. In this note, an analytic model of a radial TEG is studied with a numerical trial-and-error approach for investigating its volume power density. At the same time, an alternative, approximate method of estimating the maximum power of the radial TEG is presented. Using these two approaches, we estimate the volume power density of a skutterudite-based radial TEG and compare the results to those of a flat-plate TEG. The volume power density of the radial TEG is significantly lower than that of the flat-plate TEG. For example, our calculation for a representative case with free convection on the cold side shows that the volume power density of the radial TEG will be 107 W/m³ at best. The result improves with forced convection, and our calculation for a representative case with forced convection on the cold side exhibits the maximum volume power density of 24 100 W/m³ . All these values turn out to be smaller roughly by one order of magnitude than the maximum volume power densities of comparable flat-plate TEGs. Such a low volume power density indicates lower economic feasibility of the radial TEG with expensive inorganic thermoelectric materials. This is also explicitly discussed by presenting the high cost per watt of the radial TEG. It is therefore suggested that radial TEGs with less expensive organic materials may be more acceptable than those with inorganic ones.     

Utility-scale solar photovoltaic hybrid system and performance analysis for eco-friendly electric vehicle charging and sustainable home

Electricity energy has a crucial importance role for social and economic developments all over the world. Nowadays, the worldwide generation of electricity mostly depends on conventional sources. These sources are limited in the environment and also responsible for ecological problems like environmental pollution. Renewable energy sources have important aspects such as feasibility, efficiency, and environment-friendly in comparison to conventional energy resources. In order to overcome environmental problems, this proposed study focuses on solar photovoltaic hybrid system for eco-friendly electric vehicle charging and house based on machine learning system. In order to realize numerical study, Homer Pro and PVSOL software are used. Various parameters of economic feasibility, sizing strategies with logical advancements, and optimization methods are numerically considered and analyzed to compare measurement one.     

Simulation of a novel hybrid solar photovoltaic/wind system to maintain the cell surface temperature and to generate electricity

A hybrid solar photovoltaic/wind system is proposed and investigated theoretically. The hybrid system is based on attaching a converging inclined duct beneath the photovoltaic (PV) panels and directed upward after the end of the panels. A wind turbine is attached at the exit of the converging duct. The converging duct will capture wind currents that at its inlet and enhances these current by buoyancy effect created by the rejected heat from the panels. The mixed convection air flow is used in cooling the PV panels and in generating electricity by driving the wind turbine at the duct exit. A mathematical model is proposed to describe the system hydrodynamic and thermal behavior. In addition to the mixed convection case, the pure free convection case, when there is no wind speed, has been tested. The design of the wind duct capturing system is not included in this study, which should be carefully manufactured to eliminate the reversed flow. The simulation results show that the integration of both systems not only enhances the performance of PV cell due to the effective cooling but also generates more electric power from the inserted turbine. At low wind speeds, it is found that the ducting system helps more in cooling the panels rather than driving the wind turbine. At these low wind speeds, the buoyancy effect may have a significant effect. However, at high wind speeds, the ducting system acts in both cooling the panels and driving the turbine, and at these high speeds, the buoyancy effect is insignificant.     

Modeling and optimization of hybrid solar thermoelectric systems with thermosyphons

We present the modeling and optimization of a new hybrid solar thermoelectric (HSTE) system which uses a thermosyphon to passively transfer heat to a bottoming cycle for various applications. A parabolic trough mirror concentrates solar energy onto a selective surface coated thermoelectric to produce electrical power. Meanwhile, a thermosyphon adjacent to the back side of the thermoelectric maintains the temperature of the cold junction and carries the remaining thermal energy to a bottoming cycle. Bismuth telluride, lead telluride, and silicon germanium thermoelectrics were studied with copper–water, stainless steel–mercury, and nickel–liquid potassium thermosyphon-working fluid combinations. An energy-based model of the HSTE system with a thermal resistance network was developed to determine overall performance. In addition, the HSTE system efficiency was investigated for temperatures of 300–1200 K, solar concentrations of 1–100 suns, and different thermosyphon and thermoelectric materials with a geometry resembling an evacuated tube solar collector. Optimizations of the HSTE show ideal system efficiencies as high as 52.6% can be achieved at solar concentrations of 100 suns and bottoming cycle temperatures of 776 K. For solar concentrations less than 4 suns, systems with thermosyphon wall thermal conductivities as low as 1.2 W/mK have comparable efficiencies to that of high conductivity material thermosyphons, i.e. copper, which suggests that lower cost materials including glass can be used. This work provides guidelines for the design, as well as the optimization and selection of thermoelectric and thermosyphon components for future high performance HSTE systems.     

A thermoelectric generator and water-cooling assisted high conversion efficiency polycrystalline silicon photovoltaic system

Solar energy has been increasing its share in the global energy structure. However, the thermal radiation brought by sunlight will attenuate the efficiency of solar cells. To reduce the temperature of the photovoltaic (PV) cell and improve the utilization efficiency of solar energy, a hybrid system composed of the PV cell, a thermoelectric generator (TEG), and a water-cooled plate (WCP) was manufactured. The WCP cannot only cool the PV cell, but also effectively generate additional electric energy with the TEG using the waste heat of the PV cell. The changes in the efficiency and power density of the hybrid system were obtained by real time monitoring. The thermal and electrical tests were performed at different irradiations and the same experiment temperature of 22°C. At a light intensity of 1000 W/m², the steady-state temperature of the PV cell decreases from 86.8°C to 54.1°C, and the overall efficiency increases from 15.6% to 21.1%. At a light intensity of 800 W/m², the steady-state temperature of the PV cell decreases from 70°C to 45.8°C, and the overall efficiency increases from 9.28% to 12.59%. At a light intensity of 400 W/m², the steady-state temperature of the PV cell decreases from 38.5°C to 31.5°C, and the overall efficiency is approximately 3.8%, basically remain unchanged.     

Improving the coefficient of performance of thermoelectric cooling systems: a review

This paper reviews research carried out to improve the coefficient of performance of thermoelectric cooling systems during the past decade. This includes development of new materials for thermoelectric modules, optimisation of module design and fabrication, system analysis and heat exchange efficiency. Several conclusions are drawn. Copyright © 2004 John Wiley & Sons, Ltd.     

Sizing optimisation of stand-alone photovoltaic generators for irrigation water pumping systems

This paper mainly presents an efficient non-conventional direct method for sizing optimisation of stand-alone photovoltaic (PV) generators for supplying AC-motor-based irrigation pumping systems. The efficiencies of various elements comprising a PV pumping system and the effects of PV-array tilt are taken into account. The strong impact of the tilt angle on the optimal sizing of a PV generator is demonstrated. Extensive analysis of the meteorological conditions of the study site is performed. An appropriate solar correlation model for the design site is determined. The optimality of the determined capacity and tilt angle for a PV generator is evaluated by calculating several optimality indicators. The proposed method is compared with the Kenna and Gillett method and the RETScreen method for suggesting the nominal power for PV generators. The results show the capability and accuracy of the proposed method in optimally sizing stand-alone PV generators for irrigation water pumping systems.     

风力/光伏/波浪能混合发电系统的应用研究

简要介绍了山东即墨大管岛风力／光伏／波浪能混合发电系统组成和功能，提出了在该项目中配套的光伏系统的设计，探讨了在海岛开发利用多种可再生能源混合发电系统的可行性。实践证明，光伏发电与其它可再生能源的最优配置是解决海岛用电问题的有效途径。     

基于相变微胶囊悬浮液的太阳能光伏热系统的研究进展

在太阳能光伏热系统中,光伏电池温度过高会导致太阳能发电效率下降。相变微胶囊悬浮液(MEPCMS)是一种潜热型功能性流体,将其作为冷却介质用于太阳能光伏热系统可以有效降低光伏电池温度,提高系统的能量利用率。针对相变微胶囊易泄露、导热性差等问题提出了改性方法,使其具有光热转换功能并提升了综合性能。基于性能评价指标分析了太阳能光伏热系统性能的影响因素。结果发现,流速、浓度和太阳辐照量是影响MEPCMS在太阳能光伏热系统中换热性能的关键因素。适当增加MEPCMS浓度和流速能提高工质的换热性能,在降低光伏板温度的同时增加太阳辐照量和系统热电产量,但需结合太阳辐照量大小合理匹配工质的浓度和流速。未来研究方向可集中在提升MEPCMS在太阳能光伏热系统中的换热性能、探究运行参数和太阳辐照量之间的匹配关系、优化集热器结构、利用其蓄热性解决太阳能间歇性等方面。     

Determinant factors in site selection for photovoltaic projects: A systematic review

The choice of great places for installation of solar power plants has become a key issue in terms of project planning because of the increased number of investments in the photovoltaic sector. This study is a systematic review of the literature that seeks to identify the determining factors in choosing the best location for solar photovoltaic power plants, through previous research on the application of renewable energy technologies in great contexts of location. Among a total of 130 academic studies filtered by the keywords “photovoltaic energy,” “power plants,” “location,” and “factor” on the bases ScienceDirect, Scopus, Web of Science, and IEEE, a total of 27 studies were identified. These articles were carefully explored, including years of publication, countries of origin, and identification of factors that each author demonstrated. It has been extracted 28 factors, organized in six points of view: socioenvironmental, location, economic, political, climatic, and orographic. It was verified that the determining factors for choosing the best locations are solar irradiation, substation distance, slope, distance of roads, distance from urban areas, and land use. The results of this research may assist academic students and investors in identifying factors that they should consider in their decision making and may also assist in the efficient planning of renewable energy management to ensure the sustainable development of power generation through the photovoltaic source.