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Thermal energy storage

As thermal energy accounts for more than half of the global final energy demands, thermal energy storage (TES) is unequivocally a key element in today’s energy systems to fulfill climate targets.

Starting from the age-old TES practices in water and ice, TES has progressed today into many energy systems. TES offers benefits in balancing the time and location mismatch between thermal supplies and demands, allowing peak shaving and load shifting while improving energy efficiency and reducing emissions. TES also enables flexible sector coupling via the storage of intermittent renewable electricity with power-to-heat and power-to-cold adaptation. TES is achieved in sensible TES, latent TES (with phase change materials- PCMs) and thermochemical TES (with thermochemical heat storage materials - TCMs), and can be designed for short-term (daily), medium-term (weekly) or long-term (seasonal) storage. There are countless TES systems and applications in commercial use today (led by water and ice, but also with underground TES (with bedrock and/or groundwater), PCM and TCM examples). Regardless, there still is a myriad of aspects requiring research and development (R&D) concerning TES materials, heat exchanger components and systems, to be able to exploit the full potential of TES.

TES research at the Division of Applied Thermodynamics and Refrigeration (ETT) has a long history. The division’s key TES research areas comprise underground (i.e., geothermal) TES (UTES), latent TES with PCMs and also thermochemical TES with TCMs. UTES entails sensible TES in the subsurface, involving borehole TES (BTES), aquifer TES (ATES), and cavern TES (CTES). These systems offer the possibility of seasonally storing large capacities of heat for a relatively low price, and are natural solutions in the Swedish thermal energy systems, with a significant interest in R&D. Modelling the heat transfer of UTES systems, coupled with experimental validation through lab tests and long term full-scale monitoring, is among the ETT division’s core competencies. The division is also dedicated to R&D on latent TES and thermochemical TES, driven by their competitive advantages in e.g. compactness, temperature versatility and temperature regulation capabilities, to elevate their technology readiness levels (TRLs). Here, the design and characterization of new PCMs and TCMs and their property enhancements, as well as the design of heat exchangers, reactors and compact TES system solutions are all embedded in the R&D agenda.

The research conducted in this area cover: 

  • Underground TES (Geothermal TES)
  • Latent TES (with PCMs)
  • Thermochemical TES (with TCMs)


Projects related to thermal energy storage (TES) during the last ten years have been investigating:

Novel tool and guidelines for designing ground source heat pumps (GSHPs) in densely populated areas

Long-term performance measurement of GSHP systems serving commercial, institutional and multi-family buildings

Page responsible:Oxana Samoteeva
Belongs to: Energy Technology
Last changed: Sep 20, 2021
Distributed Cold Storages in District Cooling
Integrating Latent Heat Storage into Residential Heating Systems
Simulation of temperature distribution in borehole thermal storages supported by fiber optic temperature measurements (completed)
Solar energy and ground source heat pumps for Swedish multi-family housing (completed)
Neutrons for Heat Storage, NHS, (completed)
4D Monitoring of BTES (completed)
Aquifer Thermal Energy Storage (completed)
Deep Borehole Heat Exchanger (completed)
Combined Heat and Power plants in combination with borehole thermal energy storage (completed)
Improved borehole technology for Geothermal Heat Pumps development (completed)
Compact Minichannel Latent Energy Storage for Air Related Cold Storage Applications
Building heating solutions in China
Toward Sustainable (Fossil-free) Heating System in Small Residential Buildings