Analysis of the feasibility, efficiency and cost-effectiveness of air-ground heat exchangers as a heat source for air/water heat pumps

The aim of the AMELi micro-project is to investigate the efficiency of air-ground heat exchangers as a heat source for an air/water heat pump in the context of soil properties and the climate in Germany.
Based on the exemplary air volume flow required for a heat pump, a parameter study is carried out taking into account the parameters of the air-ground heat exchanger (pipe length, number of pipes, diameter, distance between pipes and depth). For this purpose, dynamic simulations are carried out using TRNSYS software for hundreds of combinations of air-ground heat exchanger parameters. The thermal performance of the air-ground heat exchanger in combination with the air/water heat pump is evaluated based on the air-ground heat exchanger outlet temperature, the coefficient of performance of the heat pump and the heating capacity. Finally, an economic assessment is carried out to investigate the feasibility of an air-ground heat exchanger for Germany.

Result

Based on over 1.600 simulations, the thermal performance of the air-ground heat exchanger was evaluated for various parameter configurations, and it was shown that combining an air-ground heat exchanger with an air/water heat pump raises its source temperature, thereby increasing efficiency. However, the savings potential of the variants examined was more than offset by the consumption of the additional fans, which meant that operation was not feasible from an ecological and economic point of view. In addition, it was shown that very high costs for the installation of the air-ground heat exchanger are to be expected in Germany. There is high savings potential here through combination with construction measures that are necessary anyway. It should be noted, however, that some of the simulations had to be carried out under idealised conditions. Further practical investigations of the technologies are necessary in order to conclusively assess the economic feasibility of an air-ground heat exchanger in Germany and to improve the data available for the simulation study.

Publication

• 30th REGWA Energy Symposium 2023
  >> https://www.hochschule-stralsund.de/regwa/