The second line of research within the framework CICe2020 has opened the door to the development of stationary storage technologies based on the application of oxygen (metal-air batteries) due to their high density of energy and, specially, their advantages from the environmental and resources utilization point of view, leading to the production of cathodes and the development of a harmless electrolyte. Studies have made significant progress in both the sodium-air combination and the zinc-air format.

As far as zinc-air is concerned, a system with very promising electrochemical properties has been developed. This progress has been a result of the optimization of formulations –anode and cathode- and the correct selection of materials. Compared to the most widely used lead acid technology in this field, the zinc-air alternative presents better environmental characteristics.

The third line of research within the electrochemical storage corresponds to the development of a new generation of flow batteries based on an aqueous organic electrolyte. In this sense, several organic active materials have been developed that can replace vanadium –the most widely used element in these types of batteries-. Moreover, work has been carried out in the joint development of the components of the power module, principally membranes and electrodes that can make possible the implementation of those organic materials. As a result, an electrolyte has been obtained that combines high energy densities without compromising its stability and opens the way for a new generation of flow batteries.

Advances in thermal storage

The fourth line of research of the Elkartek CICe2020 project has focused specifically on thermal storage technologies, based on the assumption that electricity generation and heating and cooling sectors play a very relevant role in the transformation towards a decarbonized economy.

The main challenge in this field has been the generation of a versatile system, with a lower cost and higher storage density, resulting in systems up to 3 times more compact than the conventional ones. These challenges have been addressed through the selection of Plastic Crystals as the basis for the development of the project. These materials are extremely energy dense and can be combined to adjust their working temperature to that required by the system. The solid-solid phase change materials and the development of new coverings also make it possible to dispense with heat exchangers, thus reducing costs.

After the work carried out, it has been possible to decipher the undercooling mechanisms of Plastic Crystals, as well as to reduce this effect and thus increasing their thermal conductivity, which allows to face with good prospects their practical applications. In fact, the work carried out in this field aims to open the door to a new generation of solid-solid phase change materials for thermal storage, which will contribute to the future development of new  thermal storage systems for domestic or industrial heat pumps, and in this way, advance in the electrification of heat. As a consequence, the volume of storage tanks and their investment costs will be drastically reduced.