Thermal and electrical gain from Photovoltaic Trombe wall: analysis and modification

Photovoltaic Trombe wall (PVTW) realizes solar photovoltaic conversion besides solar thermal conversion for building consumption by applying photovoltaic cells on the cover glazing of Trombe wall. The annual solar usage by PVTW is thereby increased compared with Trombe wall since the electrical generating is year around in addition to space heating in winter. However, the amount of solar heat gain for space heating from PVTW is found less than conventional Trombe wall because more solar heat is dissipated to the environment from the PV glazing. Hence structural modification is proposed in this work by adhering PV cells on an intermedia absorbing plate instead of glazing in order to reduce the thermal loss in winter. Numerical model to simulate the operation of PVTW is established based on previous experiment results. The effect of structural modification on the thermal field in PVTW is analyzed by the numerical method. The corresponding structural and thermal effects on the characteristics of solar photovoltaic conversion by PV module in PVTW are studied. The calculation results reveal that the modification greatly improves the thermal output for space heating in winter, but also reduces electrical output due to higher operation temperature of PV cells. Hence the assessment of overall energy output considering both electrical and thermal gain from PVTWs is conducted. The assessment with respect to climate condition, such as solar irradiance in different regions and different seasons is performed and analysed. The optimal structural parameters, such as channel depth and PV coverage ratio are suggested based on the assessment. The modification of PVTW by covering PV cells on an absorbing plate with air-flow channel behind is recommended for the building in cold climate region having long-period heating season. But the PVTW with PV cells on the glazing is recommended for the building that prefers electrical gain year around.