Investigation On A Paraboloidal Dish Concentrating Photovoltaic/Thermal System

Based on the photovoltaic/thermal technology, from the economical, practical and industrial development point of view, the thesis proposes a novel photovoltaic/thermal(PV/T) system, and discusses aspects of the system that has been designed to produce both electricity with GaAs solar cells and hot water.In this thesis, the solar dish concentrators are made of several sub-mirrors, employing the concept of breaking up the whole into parts. The novel concentrator can be manufactured easily and cheaply, Because of the advantage of uniform light intensity distribution, the efficiency of solar cells that work on the concentrator can be raised greatly. Two new hybrid cooling scheme are proposed for cooling photovoltaic cells under a paraboloidal dish concentrator. The scheme integrates the cooling effects of a microchannel flow and jet impingement, which can cool the solar cells and collect heat energy at the same time.Considering the structure features and operation mechanism of paraboloidal dish concentrators, the concentrating characteristics of two types of concentrators have been investigated with the method of combining theoretical simulation and experimental study. The two types of concentrators are Multi-dish con-focal concentrator and Multi-plane linear combination concentrator respectively. For the Multi-dish con-focal concentrator, the concentrating characteristics of sub-dish with different apertures but the same focal length or the same rim angle are investigated respectively. In order to make a quantitative evaluation for the concentrating performance of concentrators, the concept of area efficiency factor is applied. The geometric models for simulation are established, and the average flux distribution on the receivers is simulated and drawn with the software of TracePro.The result of simulation shows that rectangle aperture is more suited for the paraboloidal dish concentraror, and the prototype has been developed with the parameters from simulation results. For Multi-plane linear combination concentrator, the concentrating characteristics and distribution of flux is investigated considering several factors, including quantity of mirrors, focal length, dimensions of plane mirror and cosine efficiency. The prototype of this kind of concentrator has been developed and detected as well.In this thesis, a numerical model for the jet impingement/channel receiver has been developed with the Fluent software and experiment is conducted to verify the computational approach. The simulation results are found to be in good agreement with the experimental results, and further numerical predictions are then performed. It is shown that the new cooling scheme has the desirable working performance and is of good application potential for the cooling of photovoltaic cells exposed to a high heat flux. Another numerical model for the microchannel receiver has been developed too. The key parameters have been optimized over a range of coolant flow rates, and these include height, thickness of fins and width of the channels. The receiver is developed and tested under Multi-plane linear combination concentrator.Experimental measurement of the thermal and electrical performance of the paraboloidal dish concentrating PV/T system is carried out. The average and maximum instantaneous thermal efficiency are35.9%and47.8%respectively. The average and maximum instantaneous electrical efficiency are16.99%and15.67%respectively; the maximum and average power are50.48W and46.67W, respectively. The fill factor of maximum is71.7%, through the experiment measurement over Multi-plane linear combination concentrator.A detailed analytical model simulating the the paraboloidal dish concentrating PV/T system is developed. Several key parameters that affect the thermal efficiency are discussed. Besides, the output characteristics of GaAs solar cells are simulated through a numerical model developed with Simulink software. The simulation about output characteristic of GaAs under different temperature and radiation flux profile are carried out through Simulink software, and the electrical power of system would be1.5kW in normal operation by predicting.