| In recent years,with the development of industrialization and economy,energy crises and environmental problems have increasingly threatened the long-term stable development of mankind.Therefore,countries around the world urgently need to research and develop new energy and renewable energy technologies.Among many new energy sources,solar energy has become a promising,sustainable and clean alternative to fossil energy due to its abundant energy,wide distribution,easy use,clean and pollution-free characteristics,which has attracted wide attention.There are many technologies available for collecting and utilizing solar energy.So far,photovoltaic solar cells and solar thermal conversion technology are considered to be the most promising methods.However,for the photovoltaic conversion technology,since only photons with photon energy greater than the forbidden band width of the photovoltaic cell can excite electron-hole pairs to generate electricity.Most of the rest of the band will be dissipated as heat.The solar thermal conversion technology has high efficiency of photothermal utilization,but obtains low-grade thermal energy.Photoelectric utilization can obtain high-grade electric energy,but a large amount of irradiation cannot be utilized,and the total efficiency of solar energy utilization is low and accompanied by other unfavorable factors.Another technology for solar energy conversion is solar-thermal conversion,commonly referred to as concentrating solar power(CSP),requires large-scale initial investment and construction.Without moving parts,no chemical reactions,environmental friendliness,quietness and reliability,thermoelectric generators(TEG)are becoming a promising alternative method to using solar energy.Its combination with solar thermal conversion technology has attracted great attention in the field of solar energy for solar thermal power generators(STEG)and is seen as a potential alternative to solar power generation technology.Unlike existing solar thermal conversion processes,STEG is a solid-state device with no mechanical or moving parts,which also shows the same advantages as photovoltaic power generation.And compared to photovoltaic technology,STEGS can make use of almost all solar spectra,which contributes to higher solar energy utilization efficiency.Partial spectrum above the band gap for higher energy conversion eff-iciency.Although the first concept of STEG was proposed in 1888 and has been in development for more than a century,low energy conversion efficiencies and/or complex and cumbersome designs have hampered its application and commercialization.During this period,a large amount of theoretical and experimental research works were carried out in order to improve the efficiency of STEG.However,in the most successful experimental work reported in the literature,the STEG efficiency without optical concentration does not exceed 4.6%.In this work,the STEG general model is established based on the thermoelectric conversion theory which considers the various effects neglected by previous publications to accurately contain the temperature dependence of material properties,and to theoretically study various parasitic losses.How these losses affect STEG performance and how to minimize its impact for maximum performance are discussed.In addition,a simplified model and a theoretical model of a solar thermoelectric generator combined with a solar vacuum collector are introduced,and its scope of application is discussed.Only when the performance of the relevant material is known and the accuracy is high,the performance of the system can be optimized and predicted.In order to optimize and predict the performance of the system.In addition,through the development of a new measurement system,the self-made thermoelectric module and the STEG power generation unit were tested to verify the accuracy of the theoretical model.The verified model were used to study the key issues of improving the performance of STEG.The key components of the solar cogeneration system combined with vacuum tube heat pipe and solar thermal power generator STEG were studied.In STEG's large-scale applications,the system's electrical efficiency will decrease if the system is in the larger scale.In order to expand the STEG scale,the total heat loss will become a big problem.Combining the characteristics of solar vacuum tube collector and solar thermoelectric generator,this paper develops a high-efficiency solar cogeneration system based on TE thermoelectric technology.The system can produce electric power and hot water,and can adjust the output relationship between electric power and hot water production according to weather conditions and user demand,or implement hot water priority output,or power priority output,or simultaneous output of hot water and electricity.While improving solar energy utilization efficiency,it collects heat loss caused by expanding system scale,improves the comprehensive utilization efficiency of solar energy,and expands the application range of solar heat utilization technology for simple heat collection or power generation,and improves the comprehensive solar utilization rate and profitability.In this paper,experimental and theoretical researches were carried out in the laboratory and the outdoor actual environment The results showed that the system has higher solar energy utilization rate.And in the power generation mode,the peak electrical efficiency exceeding 5.012%of the existing literature is obtained.The experimentally validated theoretical model was used to analyze the performance of the system under different solar radiation intensity with different cooling water inlet temperature flow rates,and in different environments,and the prediction of the impact of predictable thermoelectric material performance improvement was made.The results show that when the ZT value is greater than 4,the corresponding maximum electrical efficiency will exceed 15%,and the highest instantaneous thermal efficiency exceeds 60%,showing the potential to replace the existing solar technology,and the prospects are promising. |
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