Hybrid photovoltaic-thermal heat pump systems: energy and economic performance evaluations in different climates

Due to European Directives (2010/31/UE on buildings energy performance, 2009/28/CE on the use of renewable energy, 2012/27/UE on the energy efficiency) the electric and thermal energy needs of new and retrofitted buildings are faced by increasing percentages of renewable energy. Solar energy and heat pumps are the most promising technologies mainly in residential buildings as they have reached great maturity. Anyway, in most cases solar energy utilizations systems are thermal (which convert solar energy to thermal energy) and photovoltaic (which convert solar energy to electricity) used as separated collectors. Commercial photovoltaic modules have nowadays an efficiency around 15 % - 18 %. It means that the most relevant part of solar radiation is lost. PhotoVoltaic / Thermal cogeneration (PV/T) aims to utilize the same area both for producing electricity and heat. As solar cells are sensitive to temperature (their efficiency lowers when temperature increases), heat is beneficially collected even if it cannot be available at too high temperatures. For civil applications the electrical and thermal energy can be suitably used respectively to partially cover the needs for electricity and domestic hot water/space heating. An electric compression heat pump can be coupled to the PV/T panels to contribute to the space heating demand partially using the self-produced electricity. So, some Italian climates and economic incentives scenarios are taken into account with Trnsys simulations to evaluate the energy and economic viability of the proposed PV/T-heat pump hybrid technology.