The benefits of energy storage systems have been summarised by The Renewable Energy Association (Energy Storage in the UK: An Overview second edition):
• Energy storage can enable the integration of more renewables (especially solar and wind) in the energy mix;
• Storage technologies can decrease the need to invest in new conventional generation capacity, resulting in financial savings and reduced emissions especially from electricity generation;
• They can also provide system stability during electricity outages by supplying energy at these times and reducing the financial costs of power outages;
• Utilisation of storage means fewer and cheaper electricity transmission and distribution system upgrades are required; and
• Storage technologies can reduce the usage of fossil fuels, enabling a greener energy supply mix.
The battery system will operate in two modes to address two areas of the electricity system. The first is to provide support to the national electricity system by providing ‘response services’. These are services which act quickly to signals from the grid system operator to either charge or discharge power into the grid to respond to imbalances between generation and load. Because these imbalances are generally small, the battery very rarely operates at full power and most of the time it is in standby mode ready to react. This is the battery’s default state.
The second mode that the battery will operate in is energy trading. This means that the battery will charge or discharge in response to price signals in the electricity trading markets. Typically, when there is an abundance of energy in the market from renewable generators (wind and solar for example) then the price will typically be low.
Conversely, if there is a shortage of power then the price will be high. The battery will operate to charge up with abundant (cheap) renewable electricity and discharge later in the day when the power price is higher, typically during the late afternoon peak