Photovoltaic thermal hybrid solar collectors, sometimes known as hybrid PV/T systems or PVT, are systems that convert solar radiation into thermal and electrical energy. These systems combine a photovoltaic cell, which converts electromagnetic radiation (photons) into electricity, with a solar thermal collector, which captures the remaining energy and removes waste heat from the PV module. Photovoltaic (PV) cells suffer from a drop in efficiency with the rise in temperature due to increased resistance. Such systems can be engineered to carry heat away from the PV cells thereby cooling the cells and thus improving their efficiency by lowering resistance. There are two system types ...
PV/T liquid collector
The basic water-cooled design uses conductive-metal piping or plates attached to the back of a PV module. A working fluid, typically water, glycol or mineral oil is then piped through these pipes. The heat from the PV cells are conducted through the metal and absorbed by the working fluid (presuming that the working fluid is cooler than the operating temperature of the cells). In closed-loop systems this heat is either exhausted (to cool it), or transferred at a heat exchanger, where it flows to its application. In open-loop systems, this heat is used, or exhausted before the fluid returns to the PV cells.
PV/T concentrator (CPVT)
A concentrating system has the advantage to reduce the amount of solar cells needed. It also gets very good solar thermal performance compared to flat PV/T collectors. The main obstacles are to provide good cooling of the solar cells and a durable tracking system.