Combined photovoltaic and solar thermal systems for facade integration and building insulation

Abstract

Most photovoltaic (PV) facades are built as curtain facades in front of thermally insulated buildings, with air ducts in between. This causes additional costs for support structure and installation, while heat dissipation from the solar cells is often not optimal. Measurements carried out are facing both concerns: integration of a thermal insulating layer (which meets the latest German heat-preserving regulation, WSV 95) into the PV facade, plus additional cooling by active ventilation or water flow. Active ventilation at conventional curtain PV facades allows a reduction of cell operating temperatures of 18 K, resulting in an 8% increase in electrical energy output at an airspeed of about 2 m/s. Cell temperatures increase by 20.7 K at thermal insulating PV facade elements (TIPVE) without cooling, which causes a 9.3% loss of electrical yield, but installation costs can be reduced by 20% (all related to a conventional PV curtain plus a heat-insulating facade at a building). HYTIPVE, a hybrid thermal insulating PV facade element combined with a water cooling system, which could also serve for heating up water, lowers the operating cell temperature by 20 K and increases electrical yield by 9% (compared with conventional curtain PV facades). Further economic investigations of such a HYTIPVE, including its operational costs and substitution effect, related to the electrical and thermal yield, are in progress.