Modelling of an exhaust air heat pump used for heating and domestic hot water production

Exhaust heat pump is a promising solution to heat and ventilate a building with a high energy efficiency, and a competitive investment cost. The authors presented in 2015 laboratory test results about an exhaust heat pump and showed a COP of 4.4 for the conditions A22W35. A simple annual extrapolation of the results showed a similar primary energy consumption than the conventional balanced ventilation system combined with an outside air heat pump. However, the authors presented in 2018 the performance of the same machine integrated in a demonstration building in Belgium. Due to the ultra-low heating capacity (1500 W), the measured overall COP of the system was 2.18. In order to increase the heating capacity of the system, this paper presents a semi-empirical model of the heat pump to study the impact of the design of the different elements of the machine on the performance.