Flexibility through thermal energy storage: cost-effective electrification of European district heating networks

Climate-neutral energy systems require flexibility to integrate variable renewable energy while meeting seasonal heat demand. We integrate tank thermal energy storage (TTES) and pit thermal energy storage (PTES) with dynamic self-discharge modelling in the European energy system model Enertile to address gaps in existing studies that rely on static efficiency assumptions. We analyse three main scenarios for 2050: (1) a baseline without thermal energy storage (TES), (2) a scenario with TTES, and (3) a scenario with PTES deployment. Our results show that TES enables deeper district heating electrification: Heat pump generation increases by 46%, hydrogen boilers are replaced, and biomass capacity is reduced by 51%. Contrary to static-efficiency studies that predict seasonal operation, PTES operates in monthly cycles and TTES in biweekly cycles. TES shifts Power-to-Heat electricity consumption to low electricity-cost periods, reduces curtailment, and decreases system costs. Overall, the results highlight TES as a highly valuable infrastructure for cost-efficient sector coupling in a climate-neutral European energy system.