Materials for chemical and electrochemical energy storage are key for a diverse range of applications, including batteries, hydrogen storage, sunlight conversion into fuels, and thermal energy storage.
1. Active materials for energy storage that require a certain structural and chemical flexibility, for instance, as intercalation compounds for hydrogen storage or as cathode materials. 2. Novel catalysts that combine high (electro-) chemical stability and selectivity. 3. Solid-state ionic conductors for batteries and fuel cells.
Improvement in the energy storage materials leading to high capacity, longer cycling life, improved safety issues and being reliable will accelerate the commercialization of some of these energy storage medium and their usage in other portable and automotive applications.
Traditionally, heat storage has been in the form of sensible heat, raising the temperature of a medium. Examples of such energy storage include hot water storage (hydro-accumulation), underground thermal energy storage (aquifer, borehole, cavern, ducts in soil, pit) , and rock filled storage (rock, pebble, gravel).
Table 2. Examples of current energy storage systems in operation or under development. Consists of two large reservoirs with 385 m difference in height, a power house and the tunnels that connect them. At high demand, water is passed through the tunnel at a rate of up to 852 m 3 /s to drive six generators .
The storage medium can be a naturally occurring structure or region (e.g., ground) or it can be artificially made using a container that prevents heat loss or gain from the surroundings (water tanks). There are three main thermal energy storage (TES) modes: sensible, latent and thermochemical.