Study On Optical And Photoelectric Properties Of Modified Composite Parabolic Photovoltaic System

In order to reduce the cost of generating electrical power, based on CPCconcentrating photovoltaic system has attracted considerable attention in recent years.But CPC concentrating photovoltaic system is unsatisfactory in the practicalapplication, photoelectric conversion efficiency is low, part of the reason is thatuneven illumination is on CPC focal surface, on the other hand, light incident angleby the CPC bottom reflected is large, so as to the incident solar radiation cannot beeffectively absorbed by the solar cell. Therefore, a modified compound parabolicconcentrating photovoltaic system is proposed. The top of concentrator is paraboloid,and the bottom is planar reflector, that is CPC concentrating photovoltaic systemwith a restricted exit angle (CPC-2). The purpose of this study is to compare theoptical and electrical properties of concentrator photovoltaic systems between CPC-2and ordinary CPC (CPC-1) comprehensively.Experimental results show that for the non-concentrated solar cell, photoelectricconversion efficiency fell sharply as the solar incidence angle is greater than65°,this means that solar radiation can hardly be absorbed by the solar cell, so designingCPC concentrating photovoltaic system requires the incidence angle by the CPC exitto the solar cell limited at the range of oe=70. Consequently, for CPC-1, solarradiation reflected on the solar cell from the bottom can not used, but when existangle of CPC-2restricted in the range of e, solar radiation can be absorbed by thesolar cell effectively.Analysis shows that the annual radiation on the RWARIA（receiver with arestricted incidence angle，in short）collected by east-west oriented CPC-1and CPC-2increases with the increase of e; for fixed full CPC-1and CPC-2with identicalacceptance half-angle, annual concentrating radiation of CPC-2is slightly larger thanthat of CPC-1. Whereas for fixed truncated CPC-1and CPC-2with identicalgeometric concentration factor and acceptance half-angle, CPC-2is more efficientthan CPC-1in any day of a year. In practical applications, truncated CPC is usuallyemployed. Hence, from the perspective of concentrating radiation, the performance of CPC-2is better than CPC-1.In order to research experimentally the photoelectrical properties of themodified compound parabolic concentrating photovoltaic system, two systems weredesigned and made, one is based on CPC-1, the other is based on CPC-2, which bothhave identical acceptance half-angle, geometric concentration factor and power ofsolar cell (nonconcentrating). Results shows that for north and south oriented CPC-1and CPC-2, the projection incidence angle has a significant influence on the output,especially when the projection incidence angle is close to acceptance half-angle, theoutput efficiency of the module attenuates very quickly; for east and west orientedCPC-1and CPC-2, the output efficiency of CPC-2is larger than CPC-1whenincidence angle is0°, this is because CPC-2is limited by exist angle, light intensityon the solar cell is more uniform.