Terra-Solar-Quelle

Horizontal ground heat exchangers (HGHX) lead to a higher efficiency of heat pumps than air heat exchangers and have a lower installation effort compared to borehole heat exchangers. However, due to their high site area demand, HGHX are still less attractive if compared to other heat pump sources. In cooperation with tewag GmbH and the Bundesverband Wärmepumpe (German Federal Association of Heat Pump Industry) the combination of HGHX and solar thermal collectors is going to be investigated at ISFH. The currently running project, which is funded by the German Federal Ministry for Economic Affairs and Energy, aims to minimize the site area required for HGHX while the system’s efficiency will be maintained, in order to increase the attractiveness of HGHX for single- and multi-family houses. Unlike borehole heat exchangers, HGHX have less restrictions on the fluid inlet temperature. Thus, the latent heat of the surrounding soil may be used as a reservoir, which can effectively be charged by solar thermal energy. First investigations indicate that a space reduction of at least 50% compared to conventionally dimensioned systems seems to be possible. This subject will therefore be investigated using different types of solar thermal collectors and system schemes. First of all, a new HGHX model will be developed and validated at the experimental facility of ISFH. This model will, in contrast to existing models, include the dynamic behavior of the fluid volume and HGHX edge effects. Subsequently, system simulations in TRNSYS as well as experimental investigations are supposed to identify the limits of space reduction for HGHX. Finally, simplified design rules will be released in order to enable the design of solar regenerated HGHX. Final workshop: “Ground heat exchangers and solar collectors as optimized bivalent source for highly efficient heat pump systems” on 28.02.2018