18 May 2017

P.2.1.4 Hybrid Heat Pumps in Combination with District Heating

In Sweden the two most common ways to heat a building is either by heat pumps or by district heating. In many facilities and multifamily houses with an installed heat pump there are many times, by historical reasons also a connection to district heating. The prices for both electricity and district heating often vary over time. For the building owner it would be cost efficient if he had the possibility to combine the two heating facilities and switch between the two systems in order to choose the one with the lowest operating cost for the moment. One step closer to such a solution is to develop a method on how to calculate and chose the most cost efficient combination of heat pump and district heating operation depending on the operating conditions at the moment.
The main object with the study have been to develop an algorithm to calculate when it is best according to price to use district heating and when to use a heat pump for facilities that have both district heating and heat pump installations. In addition, life cycle cost calculations (LCC) have been performed in order to evaluate the costs related to using double systems. The method developed is based on Swedish conditions and takes into account running costs for electricity and district heating as well as the heat pumps performance at current conditions such as outdoor temperature and the type of heating system. The method also differentiates between domestic hot water production and space heating operation.