Photovoltaic/Thermal (PV/T)/ground dual source heat pump: Optimum energy and economic sizing based on performance analysis

Dual or multisource heat pumps were conceived to obviate to the defects of a single source, such as outside air, ground, water or solar radiation. Concerning the latter, the use of Photovoltaic/Thermal (PV/T or PVT) modules allows not only to partially recover the otherwise lost heat, but also to cool the PV and increase its electrical efficiency. Many studies simulated the possible behavior of combination of PVT with other sources, but generally unglazed PVT collectors were used. Only few results based on coupling glazed PVT to ground source heat pumps are available in literature. The use of glazed PVT increases thermal efficiency of the collector, and the coupling of ground allows to keep the electrical efficiency at high values without the risk of cells damage due to overheating. A refurbished building located in Northern Italy will be equipped by a PVT dual source heat pump, operating with the ground as source/sink, whereas the PVT drives the heat pump compressor and acts as a dual source. When the heat pump does not need heat or operates for summer air conditioning, the ground is the heat sink both for the heat pump and for the PVT cooling. A dynamic simulation allowed to size the plant and set up a suitable control logic of the main equipment. Very high efficiency and low primary energy consumption are demonstrated for the whole plant, thanks also to the high energy independency from the grid.