Experimental performance of an ultra-low-cost solar photovoltaic-thermal (PVT) collector using aluminum minichannels and nonimaging optics

Electricity, space heating, and hot water are ubiquitous needs among modern buildings. Solar photovoltaic/thermal (PVT) technologies are well suited to provide all of these in a distributed and renewable manner, however, the high cost of current PVT technologies remains a major barrier to implementation as the technology competes for roof space with low cost standalone PV modules. In an effort to reduce costs, a new type of solar PVT collector has been developed which replaces the traditional packaging materials with a low cost nonimaging optic and replaces sheet-and-tube heat exchange materials with a low cost and thermally efficient aluminum minichannel. A 1.2 m(2) aperture prototype built using silicon SunPower solar cells has demonstrated 57.4% thermal efficiency and 12.3% electric efficiency at ambient temperature and a maximum (stagnation) temperature around 80 degrees C. Extrapolating this performance shows the PVT collector will to generate 226 kW-hours (kWh) of electricity and 603 kWh of heat per square meter each year for a solar resource of 5.5 kWh/m(2)/day, and by doing so avoid 1280 kWh of natural gas consumption and 183.8 kg of CO2 emissions. Technical performance is comparable with commercial PVT systems today, but with a much lower estimated module cost of $81/m(2) ($0.54/W-DC). A side-by-side analysis indicates the PVT collector can be installed for 85% of the capital cost of side-by-side PV + T with only 70% of the required roof space.