Energy is found in a number of different forms including electrical, thermal (heat), chemical, nuclear, kinetic, radiant (e.g. light and x-rays), sound, elastic, magnetic and gravitational. Energy can be transferred usefully, stored or dissipated (wasted) but it cannot be created or destroyed.
What is energy storage?
Energy storage is the storage of potential energy to be used at a later time. Common examples of energy storage include batteries, thermal, pumped hydro and compression technologies.
Thermal storage (heat stores)
Thermal stores or heat stores are used on many district heating networks to help level peaks in hot water and heating demand. ‘Spare’ hot water is generated at a time of low demand and stored in an accumulator tank ready to be used later at a time of high demand. By levelling demand using a thermal store the heat generator (e.g. CHP or boiler) can be run more efficiently and ensures that it does not need to be ‘oversized’ in order to meet the occasional peak in demand.
Heat stores also enable electricity to be produced when it is most needed or when it is most profitable. An industrial site using combined heat and power can generate electricity for its production processes and simply store heat for use at a later time. In addition, heat stores can help balance the electricity grid. CHP units can be brought online efficiently within a matter of minutes, helping to balance peaks and troughs in overall power supply into the electricity network. This will become an increasingly important option as we increase the amount of intermittent renewable energy we use over coming decades.
Benefits of heat stores
Heat stores provide the following direct benefits:
- enabling CHP plant and other energy generation technologies to provide valuable ancillary support to electricity network, without loss of efficiency
- enabling CHP to generate electricity at the most commercially advantageous time, as determined by the electricity market, without loss of efficiency
- recovering energy from electricity that is generated in excess of system requirements, helping to balance the electricity system and maximising the value of ‘must-run’ electricity generators
- providing resilience and energy security to district heating networks
These in turn deliver a range of beneficial outcomes:
- much more efficient, reliable and responsive management of the overall supply of energy across the system as a whole
- higher levels of deployment of inflexible and intermittent power generators is made possible