Many of the traditional industrial processes generate heat that is normally discharged into the atmosphere and yet could be reused. When such reuse cannot be carried out immediately, a storage system is needed to accumulate that heat until it can be used at another time. The challenge is to generate economically viable technologies for heat storage systems.

Generating an economically viable heat storage system requires that the materials that are part of that system be energy dense, compatible and very cheap. Steelworks slag is an ideal material, since it is a cost-free waste that is given a second life, revaluing it in a thermal storage system. CIC energiGUNE has developed a new thermal storage technology based on steel mill slag.