Millions for new heat storage

The experimental setup for the zeolite storage system at AEE Intec. (Illustration: AEE INTEC)
The experimental setup for the zeolite storage system at AEE Intec. (Illustration: AEE INTEC)

A new research project by the European Union is funding the development of innovative heat storage systems with more than 4.7 million euros. The technologies are intended to help store solar heat generated during the summer inexpensively for use in the winter.

Storing heat is less expensive than storing electricity. One hears this quite often. Seasonal heat storage systems, however, are still a niche market. The main reason for this is that very large storage systems are necessary, which take up valuable space.

Chemical and latent heat storage systems could solve this problem because they offer considerably higher storage densities than water. A simple calculation demonstrates the difference: if water is used as the storage medium, a single-family house with good insulation values currently requires a 120-m³ heat storage tank.

The same amount of heat can be stored by a 60-m³ latent heat system, and a chemical system only requires 12 m³. Nevertheless, these technologies are still almost nonexistent on the market. In many cases, the costs of the storage media as well as entire systems need to be significantly reduced.

The COMTES research project, which is being led by AEE Intec from Austria, is now being tasked with developing these technologies further and demonstrating their ability to function. The project will focus on three technologies. Solid sorption storage, liquid sorption storage and latent heat storage are to be researched and improved.

The researchers are looking to use a zeolite material that stores solar heat when it loses humidity for the solid sorption storage systems. When the stored heat is needed in the winter, humid air is passed through the storage system. The sorption of water on the zeolites then releases the heat.

The liquid sorption storage that the project is researching uses a similar principle. It releases heat when sodium hydroxide is mixed with water vapour. In order to store heat in the system, water is vapourised by introducing heat from an external source. This type of storage system releases rather low temperatures, making it particularly suitable for low-temperature heating systems or in combination with heat pumps.

The third project will examine latent heat storage. This is also the only technology that can be found here and there on the market. The heat is stored in the phase transition of a salt from solid to liquid.

The research project has total funding of nearly 6.65 million euros at its disposal. The European Union is providing approximately 4.7 million euros of that total amount. The project includes partners from Denmark, Germany, Austria, Switzerland, and Northern Ireland.

Jan Gesthuizen

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