Photovoltaic solar-thermal (PVT) combipanels

Photovoltaic solar cells convert sunlight into electricity at a conversion efficiency of 5 to 15%, implying that the remaining 85 to 95% of the energy is, in principle, available in the form of heat. In a PVT combi-panel the aim is to collect as much as possible of this heat. One of the initial bottlenecks in the development of PVT combi-panels was the lack of optical and thermal models describing the behavior of various PVT combi-panel designs under operational conditions. In our group, the required thermal models have been developed, enabling both the selection and further optimization of PVT combi-panel designs. These models have provided important insights into the possibilities and limitations of PVT combi-panels. The absorption in the solar cells largely determines the thermal efficiency of a PVT combi-panel. Optical models for the absorption in various types of solar cells have therefore recently been developed in our group as well. These models have provided detailed insight into the precise mechanisms determining absorption in solar cells. This insight enables the design of solar cells with an absorption factor almost equal to that of a black plate, as used in a conventional thermal collector.