Assessment of heat pumps for district heating applications

Heat pumps will be a major player in the future energy system for their ability to efficiently extract heat from a source at lower temperature and provide it at higher temperature using electrical work. If coupled with a heat storage tank, the system can store heat and provide it at the point in time when the electricity price is more favorable.
In this study, we present a model of the heat pump energy performance using the coefficient of performance (COP) and the Lorentz efficiency. The latter gives an indication of the offset of the actual COP from the theoretical COP. We then compare different refrigerants performance to find out which one provide the best performance for district heating application. Finally, we study the cost-optimal operation of a heat pump with and without a thermal storage tank.
Results show that ammonia is a better candidate in terms of performance compared to other selected refrigerants. The performance analysis shows that the heat pump has a better Lorentz efficiency for lower COPs. Finally, we show that coupling the heat pump to a thermal storage tank can reduce the electricity cost of operation.