Combining solar collectos with an air heat pump for domestic hot water and space heating by Erik Svantesson

Today there are still single family houses with direct electric heating systems, even though this is an expensive and inefficient way of heating a house. It is common to install an air-to-air heat pump that requires less electricity to produce the same amount of heat as a direct electricity heating system. These heat pumps do not produce any energy for domestic hot water since the water is heated via separate hot water storage. To cut the cost of water heating a solar collector system could be installed that covers the heating need during the summer. If it was possible to change the construction of the heat pump so it could heat the water as well, this would eliminate all need for direct electric heating. A simulation model of a heat pump used for both domestic hot water and space heating was built using TRNSYS software. The heat pump was modelled in such a way that heat is directed either for indoor space heating, or to a heat exchanger in the hot water tank. In this thesis, a single family house using approximately 17 300 kWh during a year for heating was modelled, which is close to the Swedish average. The simulation results indicates that if the heating system is changed from direct electricity to an air heat pump that produces both indoor space heating and domestic hot water, without using a hydronic heat delivery system and combined with solar collectors, it is possible to save 76.6-79.5% of the electricity used for heating. Such a system would have a seasonal coefficient of performance between 4.28 and 4.89. This investment in a heating system would have a simple pay-back time of 2.3 to 8.8 years.