| With the frequent emergency of the coal, oil and other traditional fossil fuels, theenergy shortage had become the bottleneck of the international socio-economicdevelopment. The development of new energy would be more serious. Solar energywhich were rich resources, cleanliness without any pollution, inexhaustible and withoutthe mining and transportation had broad prospects. Its development, utilization andconversion had been become a hotspot for seeking new energy. Using of solar powerwould be an important method of new energy utilization. Concentrator photovoltaicsystems may provide many economic advantages combining with the high efficiencymulti-junction solar cells and cheap optical concentrators, if high concentration ratiowas used in a system. Considerable efforts were directed towards the development ofthe high efficient III-V based single-and multi-junction solar cells that work well underhighly concentrated light. The multi-junction approach to solar cells made possible cellefficiencies far in excess of the best efficiencies achievable, both in principle and inpractice, by conventional single-junction cells. The main idea behind high concentrationwas to achieve cost reductions through saving in semiconductor utilized. As acomparison, flat-plate PV targets cost reductions through thinner PV layers and lowercost of the PV material used itself. The problem of heat dissipation has more and moreinfluence on performance of solar cell and reliability of system in high concentrationphotovoltaic system. Aiming at heat dissipation with high heating flux and ensure solarcells working under normal temperature range in high concentration photovoltaicsystem. The two-phase closed thermosyphon radiator has been designed in this paper.The two-phase closed thermosyphon does not have capillary, and the working fluidtransfers heat though its boiling and condensing, then circumfluent by its own gravity.The structure of the two-phase closed thermosyphon is simple and processabilityconvenient, therefore it is one of the most effective way to solve heating dissipationwith high heating flux.1. Based on the concentration photovoltaic system and the characteristics of solarcells, the energy transfer characteristics in the concentration photovoltaic system oftypical cities in the world have been analyzed. In this paper, sun parameters, such assolar elevation angle, solar azimuth, direct solar radiation intensity, of six typical citieswhich are Shanghai, Lhasa, Xi’an, Berlin, Sydney and New York have been calculatedin detailed. According to the performance parameters of single crystal silicon and triple junction gallium arsenide photovoltaic modules, a detailed theoretical calculation for thedaily generating capacity of these six cities are carried out. The results show that thedaily generating capacity of the concentration photovoltaic modules is about1.85timesthan that of the single crystal silicon. Lhasa, Sydney and Xi’an are more suitable as theideal location for the development of the photovoltaic modules. The impact of thetemperature on the performance of concentration PV modules and single crystal siliconPV modules is considered and it shows that the temperature coefficient of theconcentration PV modules is lower than that of the single crystal silicon PV modulessignificantly. Therefore, it is appropriate for high concentration conditions.2. A heat pipe matching the concentration photovoltaic system is designed in thispaper. The solar cell contacts with evaporator of heat pipe, the temperature distributionof evaporator effect on solar cell performance and heat pipe efficiency significantly. Thenumerical simulation model of evaporator of heat pipe radiator is established. Theboundary condition, the energy equations and the physical parameters are set. Thetemperature distribution of heat pipe bottom surface and boiling heat transfer inside theevaporator which influence by the design parameters such as concentration ratio,inclination angle and charge of working fluid has been analyzed. The numericalsimulation is adopted to study heat transfer performance of the rectangular finned. Theimpact of the side length and pitch of fin upon heat dissipating capacity have beenanalyzed as well. The results of numerical simulation provide directions for the designand safe operation of the heat pipe radiator.3. The test of heat pipe radiator is made by putting up high concentrationphotovoltaic system. By the contrast with numerical results and experimental resultswhich are under different working fluid rate and concentration ratio, it can conclude thatthe temperature difference between solar cell and heat pipe bottom surface are about5～9K and8～12K respectively. According to the experimental results of the heat piperadiator which based on the field test, the parameters correlation formula of averageboiling heat transfer coefficient in evaporator have been obtained.4. The experiment researches the characteristics of concentration photovoltaicsystems at the concentration ratio of75X、100X、125X、150X、175X、200X. Atthe concentration ratio of200X, the average direct solar radiation intensity and theaverage temperature are600W/m2and28.9℃respectively, the average open circuitvoltage of concentration solar cell is2.72V, the average open circuit voltage of concentration solar cell is2.72V, the average short circuit current of concentration solarcell is0.65A, the average power density of concentration solar cell is2.07W/cm2, theaverage efficiency of concentration solar cell is26%, the average temperature ofconcentration solar cell is63.51℃. The power、 efficiency and fill factor ofconcentration solar cell decreases as the temperature increases.5. The mathematical model of electrical characteristic for triple-junction solar cellwhich had excellent performance both in efficiency and temperature characteristic wasestablished based on the one-diode equivalent circuit cell model. Detailed analysis onthe influence factors of output electrical characteristic of open-circuit voltage and cellefficiency for triple-junction solar cell under high concentration (120X、130X、140Xand150X) had been done, and the calculated results was compared with experimentaldate. The results show that under high concentrated light intensity, the open-circuitvoltage and cell efficiency of the triple-junction solar cell were increasing as theconcentration ratio increased. What opposite with it was the open circuit voltage andcell efficiency were decreased as the temperature of the solar cell increased. The errorsof open circuit voltage and cell efficiency between the experimental results andcalculated values were2.04%and8.4%respectively.The research is support by the Ministry of Education Doctoral DisciplineFoundation (No.200802520006) and The Innovation Fund Project For Graduate Studentof Shanghai(JWCXSL1021). |
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