| Hybrid solar Photovoltaic/Thermal system (PV/T) is an integration of photovoltaic cells into a solar thermal collector, which offers thermal energy while generating electricity and improves the total efficiency of solar energy utilization. Concentrating PV/T system, which adds the concentrator based on the typical PV/T system, can increase the solar radiant intensity, the output of the solar cells and collector by focusing the light on the solar cells. So far, the concentrating PV/T systems which contain the Fresnel lens and parabolic reflector are studied a lot, but the system combined with the composite plane mirror cusped linear solar concentrator with flat absorber and the collector with integrative flow channels is seldom studied. The concentrator which is analogous to the Compound Parabolic Concentrator (CPC) has the advantages of non-tracing and lower cost.The analogous CPC and the aluminum collector with integrative flow channels are designed and manufactured based on the former studies, and the PV/T collector attached with monocrystalline silicon solar cells is put on the concentrator frame. The concentrating, electrical and thermal characteristics of the PV/T are theoretically and experimentally studied. The key results are shown as following.①The short-circuit current of the solar cells is proportional to the radiant intensity, but the cell temperature is less influenced. The open-circuit voltage of the solar cell is reversely proportional to the cell temperature, and is logarithmically proportional to the radiant intensity. The voltage-temperature coefficient of the solar cell is -0.0144V/K.②The concentrating radiant intensity distribution on the receiver plate is non-uniform: the actual concentrating ratio is highest in the middle of the receiver, and drops down to the both side and is lowest on the edge. The design of the concentration PV/T should consider the non-uniform distribution of solar radiant intensity.③The water fluid is serious short-circuit in the flow channel near the inlet of the collector while the volume flow rate is greater than 15L/h, which influences the uniform of the collector temperature distribution. The appropriate flow rates in the present tests are between 10L/h and 15L/h.④The increasing radiant intensity effected by the concentrating improves the power output of the cells, although the efficiency of them is decreased. The power output and efficiency both dramatically drops with the increase of cell temperature, which has a stronger influence than the radiant intensity. Therefore, it is better to cool the cells by the collector than to increase the radiant intensity by the concentrator.⑤The cell temperature is reduced and the system overall performance is improved in the use of the collector cooled by water, and the system overall efficiency ascends with the increase of coolant flow rate. The overall system efficiency reaches to the maximum value of 0.793, while the flow rate is 15L/h.
|
PDF Full Text Request