PV modules generate electricity, but the electrical output is only one component of the total energy produced by a photovoltaic array. A typical photovoltaic (PV) module has an ideal conversion efficiency in the range of 15%. The remaining energy produced is heat, which is neither captured nor utilized. This heat increases the operating temperature of the PV modules, which actually decreases their overall performance.

Recent scientific testing done in conjunction with the International Energy Agency Task 35 Project at Canada's National Solar Test Facility has shown that it is possible to capture almost two to three times more thermal energy than electricity from a PV array. Panels from various manufacturers were tested under NOCT conditions, and the results showed that when PV modules were mounted on top of SolarWall ? transpired collector panels, the total solar efficiency increased to over 50%, compared to the typical 10 to 15% for PV modules alone.

By removing the excess heat generated by the PV modules, the electrical output is increased. Modules can commonly operate at temperatures over 50 degrees C above ambient temperature, resulting in a performance reduction of more than 25%. By dissipating the heat from the module and lowering the operating temperature, significant gains can be made in system performance and the heat can be utilized for practical heating purposes. As a result of these effects, the testing showed that the payback on a PV system that incorporates a thermal component could be reduced by between one third and one half.

This paper will present the test results, and the practical and scientific implications of using a transpired solar collector with conventional PV to create a solar co-generation system.

• PV/T