Holographic spectrum-splitting photovoltaic system using bifacial silicon cells

Abstract

In this paper a photovoltaic system is proposed that attains high energy yield by combining spectrum-splitting and bifacial photovoltaic system technologies. Spectrum-splitting photovoltaic systems achieve high conversion efficiency for the direct component of sunlight by dividing the solar spectrum among a set of photovoltaic cells with different bandgap energies and different spectral responses. Bifacial photovoltaic systems achieve high-energy yield by converting light reflected from the ground and onto the rear side of the module. The bifacial spectrum-splitting photovoltaic system described in this paper uses an array of volume holographic lenses to focus and disperse sunlight onto alternating strips of 22.5% efficient bifacial silicon and 21.1% efficient MgCdTe solar cells. The system converts 31.4% of the incident solar insolation in Tucson, AZ. Design tradeoffs in the energy yield, concentration ratio, and form factor are also analyzed, revealing that systems with practical benefits such as narrow aspect ratios and high concentration ratios can still achieve greater than 30% conversion efficiency.