Research and development of hybrid photovoltaic thermal solar air heaters

Solar energy is used mainly in two forms, as thermal energy and as electrical energy. On the one hand, in most applications where thermal energy is used, electrical energy is also required. On the other hand, photovoltaic systems utilise only a fraction of the incident solar energy, and the rest is wasted in the form of heat. Besides, silicon cells perform poorly at high operating temperatures, thus cooling of the cells is beneficial. Though concentration of sunlight enhances photovoltaic cell output, the high temperature associated with it prohibits its effective application. A hybrid collector is designed in such a way that the surface of the collector is partially or completely covered by photovoltaic cells, while a circulating fluid stream passes through the top and/or bottom sides of the collector plate, carrying away the excess heat and thus maintaining the cells at their optimum operating temperature. For the past twenty years very few studies of actual experimentations of the photovoltaic thermal air heaters have been conducted. Most studies have concentrated on simulations to determine the performance of such systems.