Focus area of Eindhoven Institute for Renewable Energy Systems (EIRES)

Systems for Sustainable Heat

This focus area aims to support scientific discussion and collaborative research opportunities in the field of thermal energy storage with emphasis on development of new storage materials and systems.


The area focuses on storage concepts based on thermochemical materials (TCMs) and phase change materials (PCMs). The research aims for material design and characterization from molecular to reactor scale, integration into systems for heat storage and harvesting for domestic applications.

Of the total energy consumption in the built environment, more than 65% is used for low temperature space and domestic hot water heating. Due to the mismatch between consumption of thermal energy (heat) and production by renewable sources, thermal energy storage will be an indispensable element in futures energy system. Promising concepts for heat/cold storage are based on thermochemical materials (TCMs) and phase change materials (PCMs).

Concepts for Heat/Cold Storage

Promising concepts for heat/cold storage are based on thermochemical materials (TCMs) and phase change materials (PCMs). 

  • TCM-based storage works via reversible binding of molecules in the gas phase with a solid. The gas maybe water, ammonia, methanol, CO2, etc. The solid can be a crystalline material (i.e. a salt) incorporating gas molecules in its crystal lattice but can also be a nanoporous material (i.e. Zeolites or MOF’s) binding gas molecules to their internal surface. Energy is released when the gas binds with the solid. Energy is stored via the reverse reaction. TCM storage has two major advantages. First, TCM’s have high energy density on material level (> 1 GJ/m3). Secondly, the energy is stored loss free as long as the gas and the solid are stored separately. The major challenges for this technology are to improve the power output as solid-state reactions are slow and to guarantee cyclic stability.
  • PCM-based storage utilizes melting transitions. Heat is stored during the melting transition and recovered during solidification. PCM materials can be divided into inorganic (i.e. hydrated salt mixtures) or organic materials (i.e. wax, fatty acids, sugar alcohols). PCM storage is of great use for buffering temperatures as large amount of heat or stored/released during the melting/solidification transition. Challenges for this technology are the following. First, the power output has to be increased by heat conductive additives as heat transfer limits the process. Second, density differences between the solid and liquid phases lead to instabilities in the performance.

Iconic project: Thermal Battery

Approximately 25% of all energy consumption concerns heat. Whereas in the built environment temperatures below 100°C are most common, in industry there is a significant demand for temperature levels in the range of 800-1100°C. As TU/e will primarily focus on low temperature storage, the link with the built environment is adamant. Coupling the heat consumption by the build environment and low- and mid-T waste heat production by the industry might become feasible in case suitable storage materials become available. Thermal energy can be stored in three different ways: i) sensible heat/cold (water tank), ii) phase change materials (increasing the thermal mass) and iii) thermo-chemical materials (storing through a reversible chemical reactions during the sorption process). Advanced heat/cold storage typically takes place in porous structures consisting of novel materials with high energy densities so that relatively small reservoirs are sufficient. Focus is on the relation between stability, speed, reliability, non-corrosiveness, performance and costs of materials. The best storage capabilities will be obtained if not only the storage materials are optimized, but if also the entire system including building, heat exchangers, pumps and valves are modeled, designed and installed to function as a perfectly tuned thermal battery. Main topics covered by thermal heat storage include: development of new thermochemical materials (TCMs) and systems and harvesting for domestic applications with emphasis on stability, cyclability, efficient doping for enhanced conductivity, free of toxic byproducts, encapsulation for increased system performance and development of a lab-scale thermal battery demonstrator pilot.

Principal Scientists

Departments involved/ contributing to EIRES

The following departments are currently actively involved in the focus area on  Systems for Sustainable Heat. However, the aim is to involve more departments and research groups in the near future.

  • Applied Physics
  • Chemical Engineering and Chemistry
  • Mechanical Engineering
  • Built Environment

Related Research Groups

Here below we acknowledge the TU/e research groups which are already involved in the focus area Systems for Sustainable Heat of EIRES. We welcome all research groups interested in collaborating and contributing to the research focus of EIRES.

Current and planned collaborations

Current projects and collaborations where Principal Investigators (PI) are involved:

  • ESA project: ESA, Bari Univ, Chieti Univ, Design of hydrogen storage materials for a ground reservoirs.
  • Impulse project: Molecular Dynamics and multiscale simulations of composite and doped materials.
  • NWO - Mat4Heat: a collaboration of the TUE and Radboud University on materials for thermochemical materials.
  • H2020 projects CREATE and HEAT INSYDE: both projects aim for combining fundamental research on thermochemical energy storage and its demonstration in the built environment.
  • The TKI project deal with several aspects of a heat battery, ranging from materials improvement (power & stability) to designing components of an efficient heat battery.


EIRES | Focus Area: Systems for Sustainable Heat