| At present, the cost of the energy from photovoltaic generation is stillhigh, compared with the conventional energy generated by coal combustion,hydroelectric and so on. However, if a simple and cheap concentrator systemis used to increase solar cell’s incident solar energy, it will be possible tomake the unit area of the solar cell components to produce more output powerand reduce the price of photovoltaic generation. The concentrating solarenergy may increase the cell temperature, which will affect cell electricalperformance and life, but this thermal energy can be collected by using anactive water-cooled cycle. Hence, the system can obtain a good electrical andthermal yields. Based on this principle we designed a good photovoltaicthermal (PVT) hybrid utilization trough solar concentrator to gain moreelectrical and thermal energy.Firstly, the optimal range of the operating concentration ratio of the PVTtrough concentrator by using the conventional crystalline silicon solar cellswas discussed. The basic structures of the PVT trough concentrator and thePVT component have been described, including the method of secondarymirrors to improve the uniform illumination on the PV surface.Then, the raytracing simulation is used to optimally design and analysis the opticalproperties of various PVT trough concentrator structures under differentincident light conditions, including the concentration ratio, illuminationuniformity, and acceptance angle.According to the result of simulation, an experimental PVT troughconcentrator and an indoor concentrator performance test platform have beenestablished. The actual electrical performance of different PVT troughconcentrator structures with the dimensionless height ψHof0.883,0.979,1.095and1.220have been measured.The two-diode equivalent model was used toexplain the experimental results. The short-circuit current ISCdecreasesmainly due to the increasing of internal series resistance RS. The reduction of open-circuit voltage VOCis due to a large decrease in shunt resistance Rsh. Inaddition, the final optimized PVT trough concentrator has been figured outaccording to the simulated and experimental results.Finally, the outdoor experimental concentrating PVT system was builtwith the optimized PVT trough solar concentrator, and the electrical andthermal output performance has been monitored by a real-time data collection.Many characteristics of the concentrating PVT system have beenanalysed, including the electrical power and thermal energy power,theworking fluid’s temperaturecharacteristic, the influence of weather conditionsand circulation flow rate on the performance of concentrating PVT system andso on. When the solar irradiance is about half of the standard irradiance(1000W/m~2), the maximum electric power of the concentrating PVT systemcan reach12.28W, which is2.4times of its PV panel under the standardirradiance, and gain a maximum efficiency of14.55%. The average thermalpower and the maximum energy power of the concentrating PVT system were77.45W and2.93W separately when the sunshine amount was2.47kWh/m~2. |
