PSI WP1 Work Summary – District Heating in Zurich (District) and Helsinki
Publish date: 26/05/2026
Farah Alsafadi from Paul Scherrer Institut summarizes the WP1 work focusing on use cases of district heating, specifically in Zurich, Zurich District and Helsinki, analyzing various factors for successful implementation.
District heating networks play a crucial role in decarbonizing the heating sector, especially in cold regions with high heat demand. They offer more efficient heating compared to decentralized heating systems. Decarbonizing the heat generation source is essential to achieve the goal of reducing carbon emissions from heating systems. The utilization of nuclear heat has great potential in achieving that. In Switzerland, district heating has been supplied using heat extracted from the Beznau nuclear power plant, which has delivered approximately 170 gigawatt-hours (GWh) of thermal energy per year since the 1980s. More recently, dedicated nuclear heat production has emerged as a promising low-carbon option for district heating. The low temperature district heating reactor (LDR-50), a Finnish heat only nuclear reactor is designed to produce 50 MWth of heat for district heating applications, represents a recent development in this field. In this work, we performed a study on the feasibility and viability of utilizing a heat-only reactor for district heating in two different climate zones: Switzerland and Finland. The assessment of feasibility and viability of district heating in a given region are evaluated based on the local heat demand density. Three regions were compared (1) Zurich, (2) Helsinki, and (3) Zurich district (city).
(1) A comparison of annual heat demand density in Zurich, Helsinki, and Zurich district.
Nuclear heat has been utilized for district heating since 1980s in Switzerland, and it offers a great potential for decarbonizing heat supply within district heating networks. The analysis in this study extrapolated the data available from Beznau to a case with heat-only reactor for producing nuclear heat. The analysis aimed to assess the feasibility of deploying district heating in different climate zones using heat-only reactors. The results showed that the feasibility of district heating networks is governed by the heat demand, population density, and winters temperatures and durations. At district level in Zurich and Helsinki, the required heat demand density threshold is reached, while expanding to include sparsely populated areas, as in the full Canton of Zurich, reduces the feasibility due to the reduced heat
demand density.
Colder climates such as Finland increases the annual heat demand density per person, while higher population density as observed in Zurich district can compensate for lower individual demand. As a result, similar or higher heat demand densities can be achieved with smaller heat demand per person when population density is sufficiently high. A generalized reactor thermal power analysis was also performed to compare the population served with nuclear heat as a function of reactor thermal power in both Finland and Switzerland. The results showed that in Switzerland, more people could be served than in Finland under the same reactor power conditions, due to the colder winters in Finland.
The utilization of nuclear heat can significantly reduce fossil fuel consumption and hence reduce CO₂ emissions. However, when using heat-only reactors, efficiency of the reactor is affected by the seasonal demand variation which requires further assessment of the economic viability and considering diverting the heat for different applications in summer.
(2) Normalized monthly heat demand comparison between data from Finnish Energy and REFUNA.
For more information, do not hesitate to reach out to:
Farah Alsafadi