Air-source heat pump integration to support district heating decarbonization in Lithuanian climate

Abstract

Many district heating (DH) systems in Eastern Europe continue to rely heavily on fossil fuels and ageing biomass boilers, limiting operational efficiency and slowing progress toward climate targets. As these systems face growing decarbonization pressures, there is a clear need to identify feasible technological pathways that can reduce emissions while maintaining a reliable heat supply. This study examines the integration of air-source heat pumps (ASHPs) and thermal energy storage (TES) into DH networks as an effective strategy for reducing fossil fuel use and supporting long-term decarbonization. Conducted within the framework of the SET_HEAT project, the pre-feasibility assessment focuses on identifying an optimal technological solution by evaluating end-user needs, technical constraints, environmental compliance, system performance, and potential modernisation pathways. Techno-economic modelling performed using the energyPRO software was applied to assess a modernisation concept that integrates two air-source heat pump (ASHP) units with a hot-water TES tank. Designed to operate efficiently down to –10 °C, the ASHP sys-tem provides a low-emission, electricity-driven alternative to conventional heat generation, while the TES enables load shifting, peak reduction, and improved operational flexibility, particularly during periods of favourable electricity pricing or high renewable generation. The modelling results show that this hybrid ASHP–TES configuration can substantially reduce dependence on fossil fuels, cutting natural gas consumption by nearly half. Overall, the findings indicate that integrating ASHPs with TES is a technically viable and environmentally beneficial modernisation pathway that enhances system resilience and supports district heating decarbonization objectives.