Silicon concentrator cells in an one-axis tracking concentrator system with a concentration ratio of 300×

A solar concentrator system with one-axis tracking was developed at Fraunhofer ISE enabling a high geometrical concentration of 300×. This system uses a parabolic trough mirror and a three-dimensional second stage consisting of compound parabolic concentrators (CPCs). These CPCs are optimised for concentrating the sunlight by total internal reflection up to a geometrical concentration ratio of 7.7×. For this linear concentrator system and particularly for an easy cell integration, we have developed a rear-line-contacted silicon concentrator cell (RLCC) achieving a maximum efficiency of 25% at around 100 suns. The silicon concentrator cell has a small-sized active area of 0.2025 cm² matching with the exit area of the CPCs. The concentrator system consisting of mirror, CPCs and RLCC cells reaches an efficiency of over 16% under real outdoor conditions. In this paper outdoor measurement results of a cell string integrated in the concentrator system are presented, the performance losses are discussed in detail and a realistic estimation of the maximum efficiency of the concentrator system is given.