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Two stage stationary concentrator - numerical simulation of prototype concentrators

: Goetzberger, A.; Goldbach, T.

European Commission:
Ninth E.C. Photovoltaic Solar Energy Conference '89. Proceedings of the International Conference
Dordrecht: Kluwer Academic Publishers Group, 1989
ISBN: 0-7923-0497-7
Photovoltaic Solar Energy Conference <9, 1989, Freiburg>
Fraunhofer ISE ()

In a previous paper (1) the concept of a stationary concentrator with optimized concentration ratio was proposed. It consists of a first stage, linear CPC and a second two dimensional stage (Fig. 1). It was shown that a solar cell area reduction by a factor 6 and an effective efficiency factor around 0.8 can be reached. In the present paper further work towards the realization of this principle will be reported. Numerical simulations by ray-tracing have been undertaken to investigate the efficiency and the optimal design of the concentrator. Of special importance is the performance of the second stage, the two dimensional quadratic concentrator. Whereas the linear first stage can in principle be made lossless it is known that the second stage is not ideal. Therefore it was necessary to determine the efficiency of this stage numerically. It was concluded that the mean optical efficiency of the second stage is 95%. Another question that was studied is the uniformity of illumination. The performance of the complete two-stage concentrator was also modelled. The results confirm the analytical calculations.