This theme focuses on reactive energy storage in porous materials. An important application is the built environment. This is responsible for about 40% of energy consumption and 33% of CO2 emissions within Europe. In order to achieve a balance between supply and demand of electricity, small-scale energy storage systems should be developed for applications “behind the meter”. Here, a surplus of electricity is converted into thermal energy by means of high-efficiency heat pumps, which is stored in compact buffer systems: the heat battery. These storage systems will be based on composite thermochemical porous materials. Another storage mechanism is formed by porous capacitors saturated with salt water. By discharging this again at a lower salt content, a circuit process is created that produces energy (“blue energy”). Because there will be a huge market in Europe in the field of energy storage, it is of the utmost importance to now combine the existing expertise from UU and TU/e within the DARCY CENTER, in order to develop the required strength within this theme, to continue to play a pioneering role and to further develop this.