Buildings have lower exergy demand than their energy demand. Heat pumps can exploit this potential. Their COP greatly increases for a reduced temperature difference between evaporator and condenser. Given a low-temperature heating emission system, the performance of the heat pumps can be maintained high throughout the year, even in cold climates, if a ground storage system or a ground heat source is present. The interactions between building, heat pump, circulation pumps and source systems are complex. The performance of ground-coupled heat pumps is commonly measured in terms of COP, but the mere energy analysis might be misleading in finding potential for further optimization. Instead, the concept of exergy has been chosen since it yields the thermodynamic value of its associated energy flow.

In this paper exergy has been applied to practical study cases, involving ground-coupled heat pumps, to give a better understanding on such systems and explore the potential for improving them. Dynamic simulations of the buildings have been done with IDA and the storage has been modeled by means of MATLAB.