Optimal Installation of Heat Pumps in Large District Heating Networks

Power-to-heat technology represents a promising solution for the decarbonization of the energy sector. The installation of large-scale heat pumps within district heating systems is widely recognized to be a cost-effective and competitive way to provide flexibility to the electric system, enhancing the use of intermittent renewable energy sources. The goal of this paper is to show how the economic and environmental benefits provided by the installation of a large-scale heat pump in existing district heating systems vary according to the installation location in different scenarios. To do that, an integrated methodology is developed. This includes a physical model of the thermo-fluid dynamic of the district heating network and a detailed modeling of the heat pump. To compare the different positions and also the different operating conditions, an approach based on exergy analysis is adopted. Moreover, a specific control strategy of the mass-flow rate is analyzed to further reduce greenhouse gas emissions. The application to a real large-scale district heating network shows that reductions in CO2 emissions of almost 4% can be obtained by installing a single heat pump of about 4 MWe (over a total thermal load of about 305 MWt), while this positive effect can be reduced by up to 63% if placing the heat pump at non-optimal locations.

Automated summary

This paper aims to demonstrate how the economic and environmental benefits of installing a large-scale heat pump in existing district heating systems vary in different scenarios. It presents an integrated methodology that includes a physical model of the district heating network and a detailed modeling of the heat pump, using exergy analysis to compare different positions and operating conditions. A specific control strategy for the mass-flow rate is also analyzed to reduce greenhouse gas emissions. Results applied to a real district heating network show that installing a 4 MWe heat pump can reduce CO2 emissions by almost 4% (over a total thermal load of about 305 MWt), but this effect can be significantly reduced if the heat pump is placed in non-optimal locations.