Heat sources are categorized as natural (air, geothermal energy, water) and non-natural (industrial waste heat). Air, as a natural heat source, exhibits significant temperature fluctuations, while river water and sewage water show more stability. Understanding the characteristics of these heat sources is crucial for planning large-scale heat pump systems.
The Carnot-COP (Coefficient of Performance) is used to assess the theoretical efficiency of heat sources at a constant district heating temperature of 75 °C. Air, with its high daily temperature variation, shows a Carnot-COP between 5 and 9 in summer and 4 and 5 in winter. River water and sewage water, with minor temperature differences, exhibit more stable Carnot-COP values, ranging from 5 to 5.5 in winter and up to 6.5 in summer.
To account for varying heat demand, the Carnot-COP is weighted using the district generator, which provides a typical annual demand profile for district heating. The resulting Carnot-SCOP (Seasonal Coefficient of Performance) is calculated, considering the share of the annual heat demand for each quarter. Sewage water consistently shows the highest Carnot-SCOP, indicating its potential as the most efficient heat source throughout the year.
The study highlights the importance of considering temperature deviations and fluctuations when choosing a heat source for large-scale heat pumps. While maximal or minimal temperatures alone may not determine efficiency advantages, understanding the interactions between heat demand and source characteristics is crucial. The findings contribute to a better understanding of factors influencing large-scale heat pump efficiency, promoting their increased integration into district heating systems and facilitating a transition towards more sustainable heating solutions in Germany.
Sebastian Ostlender, Robin Kannengießer, Peter Kröning, Christian Vering, Dirk Müller, Germany
This text has been shortened by the HPC team
