Power transformers as excess heat sources – a case study for Denmark

Abstract Large-scale heat pumps (HPs), biomass CHPs and excess heat (EH) from industry and data centres are promising district heating (DH) sources. Electricity and thus power transformers (PTs) will be an important part of the future energy system, which opens the possibility to use the thermal losses occurring in PTs for DH. The present paper analyses high voltage PTs in Denmark as DH sources. First, we employ a thermodynamic model of PTs to determine the EH they produce. Subsequently, we analyse thermodynamic properties of heat exchangers and HPs necessary to utilise EH for DH. Finally, we perform a GIS analysis to link the PTs with specific DH networks. From the theoretical amount of excess heat from power transformers (EHPT) available for DH of 0.28 TWh per year, 0.12 TWh or 0.5% of Danish DH demand can reach the consumers. 0.07-0.21 GWh can reach the consumers below the average DH price. The entire EHPT potential can be utilised through HPs, working with an average COP of 4. The sensitivity analysis showed that the EHPT can supply up to 2.26% of the Danish DH demand. Therefore, EHPT is a relatively small DH source on the national scale but could be an important local option.