Overall feasibility of low cost conversion from PV to PVTw

Photovoltaic modules are more efficient the lower their temperature is. Photovoltaic-thermal technologies, PVT, exploit this feature by refrigerating the conventional photovoltaic module with a heat exchanger, usually based either on air or on water. The water is heated in the exchanger, so it can be used as hot water directly, saving energy. However, achieving high electrical and thermal efficiency requires specifically designed panels with the exchangers built in. This increases the cost and generally puts them out of the market. In this paper we study the possibility of building profitable generic exchangers which could be fit onto standard photovoltaic panels. In order to compensate for their low performance, they are operated allowing the water to heat a few degrees only. It would have to be heated further for domestic use, but ensures that the photovoltaic panel works at a low temperature and high electrical efficiency. A coarse estimation of the simple payback period in several scenarios is made, concluding that the energy savings in preheating water and the extra electrical production would pay for the cost of the exchangers in less than two years.