Merits Heat Battery Tested

Merits heat battery

The thermal energy can be stored with a high density while limiting the energy losses to the ambient

Since May 2016, the Merits prototype of a compact rechargeable heat battery is tested. The test will take the whole summer. 

The battery is developed including high energy density thermochemical materials that can supply required heating, cooling and domestic hot water for a dwelling with up to 100% renewable energy sources (e.g. the sun) throughout the year.

The 300 Liter stainless steel buffer store, has been successfully installed in the MERITS Field Test Demonstrator (FTD). This central element of the FTD has the important function of de-coupling thermal energy supply from demand.

Thermal heat battery on solar

The sensible store is charged primarily by Solar Thermal panels, and supplies this energy when required to the demand side technologies for Domestic Hot Water, Space Heating and Cooling.

  • Initial tests including thermal imaging have been completed on the subsystem in Lleida Spain, to establish and take actions to minimise heat loss from the installed buffer and pipework.
  • Tests were also performed to integrate control of the buffer’s back up immersion heater into the overall FTD control system.
  • Over the coming months the long term seasonal storage units – the Thermochemical modules –will be installed in the FTD, and will transfer energy to and from the STSV.

PCM Sub-system potential

Phase-changing materials (PCM) offer the option to store thermal heat in a compact way by exploiting a change in a materials state.

A common example of this is cold storage using ice where the heat required during the melting process of a given quantity of ice is sufficient to raise the temperature of the same amount of water by 80 degC.

In contrast to a high change in temperature when using sensible heat storage, latent heat during a phase change does not implies a significant temperature change. Hence, the thermal energy can be stored with a high density while limiting the energy losses to the ambient.


Merits goals

This EU Merits battery project is carried out by universities, SMEs and industries from all over Europe.

The key development issues are:

  1. the delivery of heat on different dedicated temperature levels for heating, cooling and domestic hot water
  2. the tailoring to the requirements of individual dwellings
  3. the design and development of a dedicated solar collector
  4. the integrated design for the different components and enhanced thermo-chemical materials, including the control system

Furthermore, the project includes the development of business models and market strategies to foster market take-up before 2020.

Seasonal storage

Seasonal storage of heat produced during summer for usage in winter is a step forward to gain independence on non-renewable energy sources. For short storage times an easy and cheap way of storing heat is in water boilers. For seasonal storage, however, the loss of heat has to be minimalized and the storage density has to be improved.

More info
Ir. C.L.G. (Christophe) Hoegaerts


This film item deals with the successful testing of the Field Test Demonstration container housing the thermochemical storage modules, and coincides with the latest General Board meeting, held in April in Warsaw, Poland. The importance of the successful testing of the storage modules and the complete MERITS system for heating, cooling and domestic hot water generation is highlighted. Watch the video.

Stay informed about this new heat battery for homes and buildings on


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