| Concentrator photovoltaic(CPV) is an optical device which can converge sunlight on a small size of sunshine photovoltaic cells, reduce the batteries’area of focal spot by increasing concentration ratio, and increase the light intensity. Concentrator photovoltaic/thermal (PV/T) was first proposed by Kern based on the idea of comprehensive utilization of photovoltaic and thermal. They laid channel on the back of PV modules, through which the refrigerant can take away heat produced by PV modules.Through the theoretical and experimental study of flat plate type high concentrated photovoltaic/thermal (HCPV/T) system and butterfly HCPV/T system, this paper has proposed and built a Fresnel HCPV/T test system, which combines Fresnel type point focusing PV system and PV/T system efficiently. This prototype used light-concentrated and light-evenly Fresnel lens of 1090 concentration ratio. Light sensor, shaft controlled by motor drive and two-axis tracking system controlled by PLC are adopted in this system. This system used channel type heat exchanger made of aluminum material and identical distance water channel.Then we tested the Fresnel HCPV/T system under different experimental conditions and studied it’s thermoelectric performance. Results showed that:1) electrical efficiency is mainly affected by DNI and water tank temperature. And relationship of electrical efficiency and DNI looks like a upwards parabola. At first, electrical efficiency decreases with the rapid rising water temperature; After water temperature rises about 50 ℃, the downward trend speeds up. But the DNI is a main factor influencing electrical efficiency; 2) output DC current of this system is linearly increased with DNI, Output power is linearly increased with DC current and output DC voltage has little impact on Output power;3) system thermal efficiency is related to water temperature and DNI. System thermal efficiency decreases with the increasing of the water temperature. Before 13:10, DNI rose slowly and system overall efficiency drops rapidly. After 13:10, DNI declined and system overall efficiency decreased slightly; 4) System peak power reached 330 W, the highest transient electrical efficiency is 29.3%, and average electrical efficiency is 26.2%. Under the environmental condition, the highest temperature of water tank is 54.5℃, system transient thermal efficiency can reach 55.0%, average thermal efficiency is 29.0%. when water temperature rose from 25 to 40℃, system average thermal efficiency is 35.8%. when water temperature is 40-54.5℃, system average thermal efficiency is 16.3%. Water temperature declined with the declining of irradiation. System average overall efficiency is 51.5%, the instantaneous comprehensive efficiency can reach above 83.5%.Besides, we also tested a push-pull type Fresnel HCPV/T system under different experimental conditions and studied its’thermoelectric performance. Results showed that output DC current is linearly increased with DNI. Before water temperature is below 40℃, the DC voltage is little effected by the water temperature; When the water temperature is too high, the rising trend of DC voltage slows down. System peak power reached 12.1 kW. During 9:40-17:00, system electricity production is 77 kWh. The highest instantaneous electrical efficiency is 28.9%, and average electrical efficiency is 27.4%. The highest instantaneous thermal efficiency is 33.5%, and average thermal efficiency is 30.0%. System overall efficiency reached 60%.Finally, we tested a radar type Fresnel HCPV/T system under different experimental conditions and studied its’thermoelectric performance. Results showed that electrical efficiency is mainly affected by DNI and water tank temperature and DNI is the most important influencing factor of electrical efficiency. Output DC current of this system is linearly increased with DN and Output power is linearly increased with DC current. System thermal efficiency is affected by water tank temperature and DNI. System peak power could reach 9.16 kW, the highest system transient electric efficiency is 27.6%, and average electrical efficiency is 25.3%. Under the environmental condition, the highest water temperature is 63.5℃, and the highest instantaneous thermal efficiency could reach 50.7%. When water temperature was 19.2-63.5 ℃,19.2-30.0 ℃,30-50 ℃,50-63.5 ℃,60-63.5 respectively, system average thermal efficiency is 29.31%,41.32%,28.1%,15.1%,10.0%. System average overall efficiency is 53.4%, the instantaneous comprehensive efficiency reaches above 77.6%.In conclusion, electrical efficiency is mainly affected by DNI and water tank temperature and DNI is the most important influencing factor of electrical efficiency. Relationship of electrical efficiency and DNI looks like a upwards parabola. Output DC current of this system is linearly increased with DN, Output power is linearly increased with DC current and output DC voltage has little impact on Output power. System thermal efficiency is affected by water tank temperature and DNI. With water temperature increasing, system overall thermal efficiency declines. Throughout the day, the average thermal efficiency is about 30%, average electrical efficiency is more than 25%, instantaneous thermal efficiency is about 55%, and instantaneous electric efficiency is about 29%. The overall efficiency is about 55% on average, the highest instantaneous efficiency is more than 80%. |
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