Low Temperature District Heating Consumer Unit with Micro Heat Pump for Domestic Hot Water Preparation

In this paper we present and analyse the feasibility of a district heating (DH) consumer unit with micro heat pump for domestic hot water (DHW) preparation in a low temperature (40 °C) DH network. We propose a micro booster heat pump of high efficiency (COP equal to 5,3) in a consumer DH unit in order to boost the temperature of the district heating water for heating the DHW.

The paper presents the main designs of the suggested system and different alternative micro booster heat pump concepts. Energy efficiency and thermodynamic performance of these concepts are calculated and compared. The results show that the proposed system has the highest efficiency. Furthermore, we compare thermodynamic and economic performance of the suggested heat pump-based concept with different solutions, using electric water heater.

The micro booster heat pump system has the highest annualised investment (390 EUR/year) and the lowest operation (320 EUR/year) expenditures. Electric heater-based concepts consume 5-14 times more electricity, which leads to relatively high annual operation costs (530-970 EUR/year); while investment costs are lower (326-76 EUR/year).

The suggested DHW heat pump-based system is cost-efficient for private consumers already today. Furthermore, application of the micro booster heat pump in low energy houses complies with the energy consumption requirements, set by the recent Danish Building Regulations. The use of electrical heater variants would exceed this limit.