Master's Thesis Moritz Jaeger


Computer-aided development of dimensioning strategies for air-to-water heat pumps in the building stock

Approach for improved design strategies for air-to-water heat pumps Copyright: EBC Development approach for improved design strategies for air-to-water heat pumps in building stock.

The air-to-water heat pump is a key technology to successfully reach the energetical and ecological goals of the german government. To fully exploit the saving potential of heat pumps regarding primary energy the integration of the entire energy system into the building stock has to be improved. Therefore it is necessary to develop strategies for dimensioning and operation matching the energy consumption behavior of the specific building. Based on dynamic building simulations and statistical methods a new dimensioning technique for air-to-water heat pumps is developed. Dynamic boundary conditions have a huge impact on the building’s heat load. Highly dynamic behavior, as opposed to normative heat load calculations, caused by the impact of weather and user dependent behavior can be observed utilizing dynamic building simulations. Field studies of air-to-water heat pumps in building stock show discrepancies between normative calculated Seasonal Coefficients of Performance and measured values. Dynamic user behavior, faulty assembly and the overdimensioning of the heating system in many hours of operation during the heating period are reasons for those discrepancies. Cluster analysis to find concise regions with high operating hours is used to analyse the dynamic heat load curves in order to use these regions for dimensioning of the heat pump. A hybrid approach of on-off control and variable-speed control in order to minimize the energy consumption of compressor cycling and long operation hours of the evaporator fan. An optimization of the compressor is simulated by increasing the quality grade at the centroids of the clusters. The developed dimensioning strategy increases the Seasonal Coefficient of Performance by 35.9% which leads to a primary energy saving of 26.4% and an annual saving in operational costs of 875€ in comparison to normative dimensioning. 6.3% savings in primary energy can be achieved in contrast to a conventional condensing boiler. For mathematical optimization of the entire energy systems new operation strategies for air-to-water heat pumps in building stock have to be developed. Suitable objective functions of the optimization are the minimization of primary energy consumption and the overall costs of the heating system.