Cellcius, a spin-off start-up of the Dutch TU Eindhoven and TNO, developed and aims to commercialise a technology that uses solely water and salt to store residual industrial heat and making it available there where there is demand for it.

The technology is a low power-high capacity storage solution for relatively low temperatures (up to 150˚C/300˚F). For the heat storage, only salt, or rather, salt hydrate (a category of inorganic salts which contain one or multiple water molecules), and water are used, no toxic chemicals or rare metals are necessary.

The technology stores heat safely and loss-free for long periods of time. In addition, it can easily be transported. For example, residual heat from industry or data centres can be stored, then transported to use it to heat homes and offices.

So how does it work? If you add a little water to white salt grains, the mixture starts to sizzle, but it also releases heat as the salt crystals absorb the water. So that is how the heat is released. But the reverse is also possible. By adding heat, you evaporate the water, drying the salt and thus reducing the size of salt crystals. As long as no water reaches the salt, the heat is stored, completely loss-free.

The process can be repeated endlessly, one way or the other, thus creating a heat battery. If you apply this battery to all residual heat in the Netherlands alone (150 PetaJoule), nearly 3.5 million homes could be taken off the gas.

The first pilots have been launched at three locations in Europe, testing the heat battery technology in the residential environment. The first industrial application will be ready by the end of 2022.

Photos: TU/e / Vincent van den Hoogen