Solar modules from Trina Solar, Canadian Solar, and Felicity Solar were tested in a prototype of a photovoltaic-thermal collector that uses excess heat from the PV elements to heat water. The system uses a thermally insulated helical coil heat exchanger to recover panel heat and a solenoid valve to allow water recirculation when the temperature below the PV module rises significantly.

Researchers from the Dschang University, in Cameroon, have tested the solar modules of three Chinese manufacturers – Trina Solar, Canadian Solar, and Felicity Solar – in water-based photovoltaic-thermal collectors.

In the proposed system configuration, the heat produced by the photovoltaic panel is recovered via a thermally insulated helical coil heat exchanger and used to heat the water. A south-oriented system with a tilt angle of six degrees was built with monocrystalline solar modules from Canadian Solar (305W), Trinasolar (305W), and Felicity Solar (250W).

The installation also utilizes a solenoid valve to allow water recirculation when the temperature below the PV module rises significantly. “The temperature below the modules and the system, is managed by a microcontroller that switches the different interfaces and two knobs that allow the adjustment of different temperature ranges,” the scientists explained, noting that the solenoid valve is turned on and the cold water circulates through the coil, passing via a water trap when the module temperature exceeds 59 degrees Celsius. The heat exchanger below the panel was thermally insulated with polyurethane foam and an aluminum sheet behind the insulation.

The system was tested on the second level of the building housing the local company Solaring, under the climatic conditions of the city of Bafoussam, in the western region of Cameroon. Temperature sensors were used to measure the various temperatures of the hybrid system as well as the water temperature at the outlet of the exchanger. Current and voltage sensors were used to assess the performance of the PV modules. The measurements were taken over four days at intervals of five minutes.

The scientists found that the PV/T system with the modules from Canadian Solar obtained the best overall efficiency, at 57.59%. With average irradiation of 877W/m2, these modules achieved an average power conversion efficiency of 16.8%, an average water thermal photovoltaic electric efficiency of 18.89%, a 12.3% growth in power yield, an average water thermal photovoltaic thermal efficiency of 38.7%, and an average hot water temperature of 41 degrees Celsius.

For comparison, the module from Trina achieved an average power conversion efficiency of 16.0%, an average water thermal photovoltaic electric efficiency of 18.42%, an 11.8% growth in power yield, an average water thermal photovoltaic thermal efficiency of 39.1%, and an average hot water temperature of 41.5 degrees Celsius.

The panel from Felicity Solar achieved the poorest performance, with an average power conversion efficiency of 15.8%, an average water thermal photovoltaic electric efficiency of 17.02%, an 11.0% growth in power yield, an average water thermal photovoltaic thermal efficiency of 38.7%, and an average hot water temperature of 41 degrees Celsius.

“This approach allowed us to recover some of the electrical power of the modules lost as heat while determining the amount of hot water that can be produced by a PV module,” the scientists concluded. “The prototype [that was] realized and experimented [on] also allowed us to note that the electrical performances of PV/T water systems also vary according to the type and brand of solar module chosen.”

The results of the tests can be found in the paper “Experimental study on the electrical and thermal characteristics of a hybrid photovoltaic/thermal water solar collector model using photovoltaic solar modules of different brands,” which was recently published in Energy Conversion and Management: X.