On the opportunity to integrate absorption heat pumps in substations of district energy networks

Abstract

This article aims to study the opportunity to integrate absorption heat pumps (AHP) in substations of district heating networks (DHN). Three different operating modes of the AHP are proposed to match the varying building needs throughout the year from the heat provided by the DHN. The upgrade mode allows to increase locally the temperature of the DHN to cover high temperature needs with low temperature DHN. The cooling mode allows to cool down buildings from DHN heat in summer. And the heating mode allows to improve the heat transfer from the DHN to the building. To compare the performance reached with several absorbent/refrigerant couples, a steady state model was developed to simulate the AHP in DHN substations in typical operating conditions for the three operating modes considered. The results of the simulations confirm the thermodynamic opportunity to use AHP in DHN substations and the opportunity to switch between the operating modes during the day or the year to improve the profitability of the system. However, this study showed that attention should be paid to crystallization risks. Regarding the performance and the crystallization occurrence, couples using ammonia as refrigerant should be preferred to ones using water.