Design Framework and Laboratory Experiments for Slinky-Loop Type Ground Source Heat Exchangers and Integration of Novel Heat Pump Designs for Retrofitting Projects

Abstract

Slinky-loop collectors, spiral heat exchangers and earth baskets are interesting for using geothermal technologies in retrofitting projects, particularly when drilling of vertical borehole heat exchangers is not possible. However, up to now no engineering design tools or field capacity tests exist for these systems, leading to a low employment of these systems. Within the H2020-project GeoFit we develop calculation tools and test protocols for geothermal designers, based on comprehensive laboratory experiments as well as dynamic simulations of the heat transfer to test the performance of different slinky-loop type ground source heat exchangers (GHEX) under different conditions in a climate chamber. The data of these experiments and simulations will then be used to develop an engineering tool for these types of collectors. The work on the GHEX design will go hand in hand with the development of suitable heat pumps for selected retrofitting cases. One system under development is a gas-fired hybrid adsorption/compressor heat pump suitable for size-reduced GHEX compared to pure compressor heat pump systems. The second concept is an electrically driven system based on an advanced electrical driven heat pump cycle which is optimized to utilize a maximum of renewable thermal energy from the GHEX.