Study of a hybrid PV-Thermal solar system to provide electricity and heat in Portugal

Hybrid photovoltaic-thermal (PV-T) solar collectors are used to simultaneously obtain electricity and heat from the same collector. For the same energy output, the combined collectors lead to a lower total area than separate thermal and PV collectors. Numerical models were developed for two types of hybrid collectors, with a flat-plate and tube geometry: one using monocrystalline silicon (mono-Si) PV cells and one using amorphous silicon (a-Si) flexible PV cells. The electrical, thermal and total efficiency characteristics of both types were quantified. Application of the hybrid collectors to a system generating electricity and hot water was analysed, considering two building types: a residential building and a hotel. The electrical and thermal energies produced annually, as well as the amount of backup energy, were calculated by means of the SolTerm energy simulation program for the climatic conditions of Porto, Lisbon, Faro and Bragança (Portugal). An economical analysis was carried out by comparing the hybrid system with a conventional energy system and with a system with thermal collectors and PV modules installed separately. Finally, the environmental impact of the hybrid system was assessed and compared with a conventional energy system.