Heat storage potential for the state of Berlin (Christidis et al. 2025)

The transformation of Berlin’s heating sector is crucial to achieving the climate targets of the Berlin Energy and Climate Protection Act. The heating sector is responsible for 47% of CO2 emissions and the heating planning prescribed by 2026 is intended to show the way to a climate-neutral heating supply for Berlin by 2045. Seasonal heat storage can play an important role in this by reducing the discrepancy between the heat surplus in summer and the higher heat demand in winter and reducing dependence on fossil fuels.

The project is investigating the role of heat storage systems for Berlin’s heat supply, in particular for the district heating network and neighbourhood heating networks. Long-term heat storage systems increase the share of renewable energies and waste heat by storing surplus heat to cover winter demand. Calculations for the interconnected grid show that long-term heat storage systems with a storage capacity of up to 1,200 GWh could fully utilise a forecast output of 700 MW from renewable energies and waste heat. This would increase the share of renewable heat from 49.5 % to 61 %.

Heat storage systems are currently hardly economically feasible for neighbourhood networks without subsidies, but could become more profitable with rising energy prices and subsidies. Particularly in combination with heat pumps and electric heaters, heat storage systems can contribute to reducing the heat generation costs. The availability of space in Berlin is low due to competing uses. A lack of space is a major obstacle for tank and underground heat storage systems in existing neighbourhoods. There are fewer problems with underground aquifer heat reservoirs. Here, uncertainties in the in authorisation law complicate implementation. There is a need to identify potential areas and clarify the legal framework.

Calculations in the project show that heat storage facilities are a central component of the heat transition in Berlin, as they contribute to climate neutrality, reduce heat generation costs and increase the flexibility of the energy system. Six measures were developed to promote the use of heat storage systems in Berlin, including the optimisation of administrative processes and the sharpening of the legal framework.
legal framework. In the long term, heat storage systems should become part of Berlin’s district and local heating networks in order to relieve the strain on electricity grids and make the energy supply more sustainable and flexible.

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