Polymer Collectors with Temperature Control - Thermosyphon Valve Development and System Integration
Abstract
The goal of several projects in Europe is to develop and design collectors made out of polymers. A main boundary condition for such polymer collectors is the possibility to use as cheap as possible polymer material, which can typically withstand temperatures only up to about 95°C. Therefore solutions for limiting the temperatures during stagnation are looked for. One possible solution is a collector with integrated thermosiphon cooling, which limits the temperature during stagnation, but also allows the design of a collector with highest possible efficiency during operation. Based on this collector type also solar domestic hot water systems (SDHW) and solar combisystems (SCS) as well can be developed and operated under different boundary conditions in a new way. In a single family house a solar combisystem with overheat controlled polymer collector in combination with building mass activation can achieve a solar fraction which is comparable with conventional high performing flat plate collector systems coupled only to a water storage. In solar domestic hot water systems a polymer collector system with thermosiphon cooling can avoid stagnation periods, which allows restarting at any time also after a high insulation period during noon. This gives the potential to reduce the disadvantage of reduced efficiency during operation by longer operation periods in comparison to standard flat plat collectors.