Low cost solar photovoltaic-thermal (PVT) collector using aluminum minichannels and nonimaging optics

Solar photovoltaic / thermal (PVT) technologies are well suited to provide distributed and renewable electricity, space heating, and hot water in buildings. The high cost of current PVT technologies, however, remains a barrier to implementation as they compete for roof space with low cost PV. To reduce costs, a new kind of PVT collector has been developed which replaces traditional packaging materials with a low cost nonimaging optic and thermally efficient aluminum minichannel. A 20-tube (~2.4 m² aperture) prototype has been fabricated, demonstrating 57.4% thermal efficiency and 12.3% electric efficiency at 20 °C, with a stagnation temperature of ~80 °C. Based on this data we estimate the PVT collector will generate 226 kilowatt-hours (kWh) of electricity and 603 kWh of heat per square meter each year for a solar resource of 5.5 kWh/m²/day. In doing so, each installed square meter will replace 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/m² ($0.54/WDC). A side-by-side analysis indicates the PVT system would cost 15% less and use 30% less roof space than an equivalently sized PV+T system.