In high-temperature TES, energy is stored at temperatures ranging from 100°C to above 500°C. High-temperature technologies can be used for short- or long-term storage, similar to low-temperature technologies, and they can also be categorised as sensible, latent and thermochemical storage of heat and cooling (Table 6.4).
In sensible Thermal Energy Storage (TES), energy is stored by changing the temperature of the storage material. The amount of heat stored is proportional to the density, specific heat, and volume of the storage material, as well as the variation of its temperature.
Latent thermal energy storage systems using phase change materials are highly thought for such applications due to their high energy density as compared to their sensible heat counterparts. This review, therefore, gives a summary of major factors that need to be assessed before an integration of the latent thermal energy system is undertaken.
One issue with latent thermal energy storage is the low thermal conductivity of the phase change materials, which limits the power that can be extracted from the energy storage system. To improve the thermal conductivity of some paraffins, various methods have been used, including the addition of metallic fillers, metal matrix structures, finned tubes, and aluminum shavings.
Sensible, latent, and thermochemical energy storages for different temperatures ranges are investigated with a current special focus on sensible and latent thermal energy storages. Thermochemical heat storage is a technology under development with potentially high-energy densities.
In contrast to potential energy storage, such as pumped hydro or compressed air, thermal energy storage systems utilize either the thermochemical reactions, sensible or latent heat capacity of materials to provide a heating or cooling resource, which can be replenished as required.