Researchers at Razi University in Iran have investigated how the geometry of copper cooling tubes affects the electrical and thermal performance of photovoltaic-thermal (PVT) collectors. They aimed to determine whether wavy tubes could improve heat extraction and boost overall system efficiency compared with conventional straight tubes. To this end, they experimentally assessed three tube configurations at different water flow rates.

“This study presents an experimental investigation into the performance of a water-cooled PVT system integrated with wavy copper channels, aiming to quantify the impact of channel geometry and flow rate on thermal and electrical efficiencies,” the researchers said. “Notably, unlike many small-scale studies, this research is conducted on a commercially representative PV module.”

The researchers built a water-cooled PVT collector using a 180 W PV module measuring 68 cm × 148 cm, with an aluminum absorber plate attached to its rear side. They fabricated three copper-tube cooling assemblies: one with straight tubes and two with mechanically bent wavy tubes featuring pitches of 200 mm and 300 mm, respectively, and a wave height of 50 mm. They used silicone thermal paste to improve thermal contact between the tubes and the absorber plate, while copper strips and thermally conductive adhesive secured the assemblies.

The team conducted outdoor tests in Kermanshah, western Iran, in May 2025, under an average ambient temperature of 27 C and solar irradiance of 1,038 W/m2. Each configuration was tested at water flow rates ranging from 200 mL/min to 800 mL/min, with the inlet water temperature maintained at 20 C.

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