Integration of Latent Thermal Storage with Heat Pumps: Challenges and Future Developments

This paper explores the integration of latent thermal energy storage (LTES) systems with heat pumps (HPs), a promising solution for increasing energy efficiency and flexibility in heating and cooling applications. Despite the growing commercial availability of LTES technologies, they are often sold as standalone products, requiring on-site integration with HPs. This lack of system-level co-design frequently results in suboptimal performance, including reduced efficiency, operational instability, and hardware failures. The preliminary studies presented in this work—focused on coupling commercially available LTES units with both domestic hot water (DHW) propane heat pump systems and propane HP/air conditioning (AC) setups—demonstrate the critical technical challenges involved. Key issues include mismatched component sizing, inadequate thermal exchange performance, and frequent cycling of compressors, all of which underline the importance of integrated design. These initial investigations have clearly shown the necessity for a holistic, application-specific approach to LTES–HP system design. In response, this research has laid the groundwork for a newly launched European project that addresses these integration challenges directly. The project focuses on the co-design and prototyping of integrated LTES–HP systems, their real-world installation for data collection, and the eventual commercialization of fully integrated solutions tailored for residential climate control applications.