Low cost photovoltaic roof tile

Static concentrator designs that achieve concentration ratios approaching the theoretical limit have been developed and demonstrated. Concentration ratios in excess of 4:1 have been predicted although this reduces to 3.6:1 for the practical design used for photovoltaic roof tile applications. A new encapsulant based on "solid white oil" has been evaluated for use in the optical cavity, exhibiting excellent optical properties while simultaneously being low cost. Prototype roof tile efficiencies of approximately 15% (not independently confirmed) are well below the expected 17-18%, due primarily to optical losses associated with the rear reflector and poor rear surface performance for the Photovoltaic devices. Good progress has been made recently with regard to the latter, although further work is required to accommodate solar grade substrates with much shorter diffusion lengths, for the bi-facial cells in this application.