Optical efficiency–concentration ratio trade-off for a flat panel photovoltaic system with diffuser type concentrator

Optical concentrators that could be used as a flat panel type stationary photovoltaic (PV) system will enable significant reduction in the cost of PV power generation. This paper presents the analysis of a concentrator based on an optically transparent planar waveguide with a diffused reflector on the rear surface and PV devices placed at the edge of the waveguide. Optical collection efficiency of the stationary concentrator for geometric concentration ratios in the range 2–1000 has been analyzed. Despite reduction in optical collection efficiency of this concentrator design compared to traditional flat PV panel or tracking type concentrator panels, for practical operation in the geometric concentration ratio up to 40, a factor of 2–10 times reduction in cost of PV modules per unit power generated can be envisioned due to ease in manufacturing (including flexible roll-to-roll production) and significant savings in materials usage. Experimental data shows a strong dependence of the optical collection efficiency on surface roughness of the diffuser.