Analys av kombinationen frånluftsvärmepump och fjärrvärme : En fallstudie i två flerbostadshus med olika tekniklösningar

Sammanfattning: In Sweden, district heating is the most common way to heat apartment buildings and premises. It is most common for properties to use district heating as the only heating source, but there are now trends in which more and more properties combine district heating with another energy source such as an exhaust air heat pump or geothermal heating. This report is a case study on how an exhaust air heat pump can be combined with district heating in an apartment building compared to if the house uses only district heating for heating. The background to the study is that Gävle Energi AB wants to investigate the return temperature to the district heating network from a facility that has an exhaust air heat pump and district heating in combination compared to a normal facility that only has district heating. The focus of this thesis is on investigating two structurally identical properties in Gävle with two different ventilation systems and heating systems. The first property, Property 1, has an exhaust and supply air ventilation system with a heat exchanger and only district heating for heating. The other property, Property 2, has a mechanical exhaust air ventilation system with exhaust air heat pump and district heating in combination. The method used during the analysis has been a compilation of collected data from Gävle Energi AB and of own measurements with a measurement period of one week. The analysis compares two different heating systems based on three different factors, energy use (kWh), supply and return temperature to the district heating network (°C) and operating costs (SEK/Year). Results show that, Property 2 (exhaust air heat pump in combination with district heating) has 31% lower district heating use on average. However, electricity uses for the property increased by 20%. The total energy use for property 2 was thus reduced by 15%. The reduction in energy use in Property 2 corresponds to a reduction in operating costs of 5.4%.However, the operating cost of Property 2 does not include the investment in the heat pump or the maintenance cost. Both the investment in the district heating center and the maintenance cost are included in the district heating price. COP calculated varying between 1.8 and 3.8. COP measured varied between 2.2 and 3.8. COP value for Property 2 was 3 on average for both COP measured, and COP calculated.   District heating in combination with an exhaust air heat pump gives a higher return temperature than district heating alone, the difference was about 10 °C during the measurement carried out for a week in April 2022. The difference was also verified by the volume-weighted return temperature, which was calculated to be 1.0 °C higher. The conclusion is that an exhaust air heat pump in combination with district heating seems to have a lower operating cost resp district heating and mechanical supply and exhaust air with heat recovery ventilation for the user in the studied types of building, but it also creates an elevated return temperature in the district heating network. Environmentally, an exhaust air heat pump together with district heating can be positive if electricity is produced from renewable energy sources with low carbon dioxide emissions, such as solar energy and wind power, but consideration must be given to system effects in the district heating network, such as how the production of electricity is affected, this varies between different district heating systems.