Photovoltaic-thermal heat pump based on bio-based surface coating achieves 77.32% overall efficiency

Photovoltaic-thermal heat pump based on bio-based surface coating achieves 77.32% overall efficiency

A research group in Iraq has developed a direct-expansion photovoltaic-thermal (PVT) heat pump system featuring a bio-based titanium dioxide (TiO₂) and linseed oil coating.

“The scientific gap addressed in the present work is not the individual use of PVT, heat pumps, refrigerants, or TiO₂-based materials, but the experimentally resolved interaction between passive face thermal regulation, active refrigerant-based heat extraction, and seasonal refrigerant response within the same PV/T–HP platform,” the researchers said.

The experimental system combined a 1.0064 m² monocrystalline PV module rated at 150 W with a 120 W vapor-compression heat pump. A 1.30 m × 0.40 m roll-bond aluminum plate installed behind the PV module served as the heat pump’s evaporator, extracting heat from the panel. A water-cooled condenser recovered the heat to produce hot water.

The refrigerant circuit also included a compressor, filter-drier, sight glass, and capillary tube with an inner diameter of 0.787 mm and an outer diameter of 1.803 mm. The researchers tested the system with three refrigerants – R134a, ...