Characteristics of a water absorber in front of a silicon solar cell

In a system for converting sunlight to both electric power and heat, a selective absorber between the sun and a semiconductor solar cell may provide a substantial thermal output without seriously reducing the electrical output. Calculations for water in front of a typical silicon solar cell show, for example, that a water layer 1 cm thick absorbs 16.3% of the incident energy (chiefly photons having energies below the energy gap of silicon) while reducing the electric power output only slightly, from 13.8 to 13.1%. Experimental results confirm this finding.