A Loss Analysis for a 28% Efficient 520X Concentrator Module
A module efficiency loss analysis has been conducted by comparing the efficiency of the module on-sun (28.2% peak) to the efficiency of the bare cell measured in the laboratory (35.5% peak). This analysis suggests that there are two main loss mechanisms in the module: elevated operating temperature and an optical efficiency less than unity. This analysis also suggests that the effects of spectral and intensity non-uniformity have been well controlled
Numerical and experimental research of the characteristics of concentration solar cells
The development of automatic tracking solar concentrator photovoltaic systems is currently attracting growing interest. High concentration photovoltaic systems (HCPVs) combining triple-junction InGaP/lnGaAs/Ge solar cells with a concentrator provide high conversion efficiencies. The mathematical model for triple-junction solar cells, having a higher efficiency and superior temperature characteristics, was established based on the one-diode equivalent circuit cell model. A paraboloidal concentrator with a secondary optic system and a concentration ratio in the range of 100X–150X along with a sun tracking system was developed in this study. The GaInP/GalnAs/Ge triple-junction solar cell, produced by AZUR SPACE Solar Power, was also used in this study. The solar cells produced by Shanghai Solar Youth Energy (SY) and Shenzhen Yinshengsheng Technology Co. Ltd. (YXS) were used as comparison samples in a further comparative study at different concentration ratios (200X–1000X). A detailed analysis on the factors that influence the electrical output characteristics of the InGaP/lnGaAs/Ge solar cell was conducted with a dish-style concentrating photovoltaic system. The results show that the short-circuit current (Isc) and the open-circuit voltage (Voc) of multijunction solar cells increases with the increasing concentration ratio, while the cell efficiency (ηc) of the solar cells increases first and then decreases with increasing concentration ratio. With increasing solar cell temperature, Isc increases, while Voc and ηc decrease. A comparison of the experimental and simulation results indicate that the maximum root mean square error is less than 10%, which provides a certain theoretical basis for the study of the characteristics of triple-junction solar cell that can be applied in the analysis and discussion regarding the influence of the relevant parameters on the performance of high concentration photovoltaic systems.
E EFFECT OF CHROMATIC ABERRATIONS ON TWO-JUNCTION, TWO-TERMINAL DEVICES IN A CONCENTRATOR SYSTEM
Of the modules monitored in PVUSA (Photovoltaics for Iltiiity-Scale Applications), the one with the highest efficiency has been the ENTECH concentrator system. If the 18%-efficient Si cells in this module could be replaced by 2 6 Yo-2 8 % efficient two - t e r m i n a I, two - j u n c t i o n (Gao.5 In0.5 P/GaAs) devices, the efficiency of the system could be increased. However, two-junction, two-terminal devices present a special problem in that they must be current matched to retain their high efficiencies. This implies that variations in the spectrum caused by the focusing optics could be a potential problem. In this study we undertake to assess the severity of this problem and find that, when properly aligned, ENTECH's current lens introduces spectral nonuniformities which cause about 4% loss in power output for two-terminal Gao.5 In0.5 P/GaAs devices compared with similar four-terminal devices. The power loss increases significantly if the lens is not correctly aligned, and can be diminished somewhat by reducing the maximum refraction angle of the lens from 40" to 30". While the spectral nonuniformities reduce the power output, they also reduce the sensitivity of the system to variations in the spectrum. Thus, we conclude that, while care should be taken to minimize losses from chromatic aberrations, because of the variable spectrum, chromatic aberrations are unlikely to be a serious problem in any well designed concentrator system.