Ray racing techniques applied to modelling of fluorescent solar collectors

摘要

Fluorescent solar collectors represent an alternative to flat plate photovoltaic arrays. With the emphasis on minimizing the use of silicon, the collector is usually composed of a mixture of fluorescent dyes embedded in a transparent medium. The absorbed incoming sunlight is re-emitted at a longer wavelength. A large fraction of fluorescence is totally internally reflected and transported to the edge of the collector, where the solar cell is placed. The key requirements for efficient fluorescent collectors are a good photon transport and a broad absorption of sunlight. The fundamental parameter that determines the efficiency of photon transport is the probability of reabsorption. Based on experimental results and ray-tracing simulations carried out with "TracePro", this publication illustrates the use of ray tracing to model reabsorption in collectors with different shapes as well as inhomogeneous structures, and to assess the validity of the traditional analytical approach. We show that, contrary to expectations, some novel structures (for example, "thin film" or "waveguide" collectors) do not represent an improvement over their corresponding homogeneous collectors and that any variation of the film refractive index on a glass substrate leads to an efficiency drop.