Combined photovoltaic thermal collector testing

A commercially available liquid-cooled thermal flat-plate collector was modified by the addition of 104 silicon cells in four parallel strings extending almost the entire length of the collector front surface. The electrical efficiency of the cell array was measured as a function of temperature for three different flow rates corresponding to temperature differences between inlet and outlet coolant ranging from 4/sup 0/C to 38/sup 0/C. The data showed a linear decrease in electrical efficiency with the temperature of the panel surface measured halfway between inlet and outlet ports. The efficiency-temperature relationship was independent of the temperature gradient. The thermal efficiency also exhibited a linear decrease with increasing difference between inlet coolant temperature and ambient temperature. The measured array efficiency (8.1 percent at 27/sup 0/C) was comparable to the measured efficiency of a single cell from the same lot.