From waste to heat: A spatio-temporal analysis of the surplus heat potential for Denmark’s district heating systems

Abstract. Unused energy is released into the environment from a number of sources, such as energy-intensive industries, whereas it could be used in district heating (DH) systems to make a significant contribution to decarbonising the heating sector. Despite its essential role, surplus heat (SH) is currently under-utilised and large amounts are wasted. Furthermore, there is a lack of detailed data in the literature on the sources that could potentially be captured. This paper examines the historical distribution of DH systems and their relationship with SH in Denmark, a country with very advanced DH. It also considers the potential for medium and low-temperature sources to be included alongside high-temperature industrial SH, which has been the dominant resource to date. Specifically, it utilises visual and statistical interpretation of the geospatial distribution of the utilised amounts of SH at municipal level. The analysis shows through classified choropleth mapping the dynamic temporal and spatial changes in the field, where the potentials depend on the availability of sources and their corresponding activities, but also shows that many municipalities with high and increasing DH shares could utilise SH from various sources that are not currently used such as in the food and beverages and retail and trade sector. Further potential from manufacturing and industrial activities could also be included, especially in the municipalities of the capital region, while significant low-temperature SH across the country would require a boost from heat pumps or upgrading of DH systems.