Decarbonisation potential of Switzerland’s building sector through thermal Nanogrids utilising surplus heat from neighbouring heat pumps

Space heating contributed around one third to Switzerland’s total heat consumption in 2023. Despite widespread integration of renewable energy systems, fossil systems are still dominant and contribute therefore strongly to the emissions. A fast implementable concept helping to reduce the activity of fossil systems is the thermal Nanogrid concept: small-scale local heating networks that interconnect heat-pump-heated and fossil-fuel-heated buildings to share surplus renewable heat. Using data from the federal register of buildings and dwellings combined with weather data and heating-demand modelling, clusters containing both buildings with heat pumps and fossil heating systems were determined using a clustering algorithm, imposing an upper bound of 30 m on the average inter-building distance. Within these clusters, potential thermal Nanogrids were identified as sets of buildings such that their entire heat demand can be covered by the pre-existing heat-pumps down to a given preselected threshold temperature. To this end, heating demand and heat pump capacity curves were estimated for all the buildings in a cluster. As heat pump power decreases and heat demand increases with lower ambient temperature, a lower threshold temperature results in smaller and fewer Nanogrids. . The results show that, in terms of fossil heat coverage relative to the required pipeline length, an optimal thermal Nanogrid configuration is achieved when the building selection criterion requires that all included buildings can be completely heated by the heat pump at outdoor temperatures of 4 °C and above. Under this condition, 85′223 potential thermal Nanogrids were identified across Switzerland, comprising 207′159 buildings. In this configuration, the existing heat-pump infrastructure could replace approximately 1.2 TWh of fossil-based heat demand, corresponding to an estimated 281 Mt of CO2 emission reductions and 5.7 % of the total residential fossil heating demand, under the assumption that all heat pumps operate entirely on renewable electricity. The analysis further reveals significant regional variation, with the highest potential concentrated in cantons with dense residential areas such as Zurich, Bern, and Aargau. These findings demonstrate that thermal Nanogrids could serve as an effective and complementary measure to accelerate building-sector decarbonisation.