Optical filtering of solar radiation to increase performance of concentrator systems

Solar cell overheating due to high irradiation levels is a significant problem facing concentrator systems. Some form of cooling is needed to maintain the highest possible performance of such systems. Liquid filters may be used to inhibit unwanted solar radiation from reaching the cell and thus limit cell-operating temperatures. The performance of the cooling will depend on the optical properties of the liquid filter applied, as illustrated in this paper, on the basis of different filters. An ideal filter is identified and its effects on the systems are described. It is shown, on the basis of system modeling calculations, that cell performance could be increased by up to 25% using an ideal filter. Such a system can reach an efficiency of 22% in a realistic working environment compared to a STC value of 16%. The absorbed part of the incident radiation can be used as a heat source, so adding to the potential value of the system.

Introduction

The efficiency of silicon solar cells tends to increase with increasing irradiation, and of course the material is expensive. Solar concentrator systems might thus be a route to cheaper electricity and hence are attracting significant interest. Two principal advantages of concentrating sunlight in photovoltaic applications are [1]: