Development of a photovoltaic thermal facade system

A photovoltaic thermal (PVT) collector is made of a photovoltaic (PV) module and a solar thermal collector and thereby delivers electrical and thermal energy at the same time. These systems can contribute significantly to the renewable energy supply of residential, public, and commercial buildings. This paper gives insight into the development of a facade-integrated PVT system within the research project PVT Fassade. Thermal simulations evaluated useful operating conditions and efficiency-decreasing factors. Thus, 10 kg/(hm²) and 60 kg/(hm²) were identified as lower and upper limits for the mass flow and the losses by the internal heat transfer resistance of a 3.5 mm air layer between the PV module and the heat exchanger were determined to 35 % and 48 % for 10 and 60 kg/(hm²). These findings and structural, aesthetical, and general building law requirements were taken into consideration for the design of the facade-integrated PVT system. The functionality and feasibility of the developed system is shown through a constructed prototype facade where an intensive monitoring of the thermal and electrical performance of the PVT system is conducted. The performance of the PVT facade collector is described on the basis of an exemplary day of this monitoring. On this day, an area-specific thermal yield of 4.13 kWh/m² with a temperature spread of up to 10.7 K is reached. At the same time, the thin film PV modules of the PVT system achieve an electrical yield increase of 2.5 % compared to a reference PV facade system.