Grid energy storage

These systems help balance supply and demand by storing excess electricity from variable renewables such as solar and inflexible sources like nuclear power, releasing it when needed.

Demand response can shift load to other times and interconnections between regions can balance out fluctuations in renewables production.

Energy derived from solar and wind sources varies with the weather on time scales ranging from less than a second to weeks or longer.

Nuclear power is less flexible than fossil fuels, meaning it cannot easily match the variations in demand.

[5] Electricity storage is one of the three key ways to replace flexibility from fossil fuels in the grid.

[6] Energy storage has a large set of roles in the electricity grid and can therefore provide many different services.

On the generation side, it can help with the integration of variable renewable energy, storing it when there is an oversupply of wind and solar and electricity prices are low.

On the generation side, storage can smooth out the variations in production, for instance for solar and wind.

On the consumption side, storage can help to improve the quality of the delivered electricity in less stable grids.

Additionally, storage can ensure there is sufficient capacity to meet peak demand within the electricity grid.

In the 21st century, interest in storage surged due to the rise of sustainable energy sources, which are often weather-dependent.

In comparison with EVs, grid batteries require less energy density, meaning that more emphasis can be put on costs, the ability to charge and discharge often and lifespan.

[19] The electric vehicle fleet has a large overall battery capacity, which can potentially be used for grid energy storage.

[26] Flow batteries have the advantages of low capital cost for charge-discharge duration over 4 h, and of long durability (many years).

[29] Storage in supercapacitors works well for applications where a lot of power is needed for short amount of time.

[34] Green hydrogen is produced from the electrolysis of water and converted back into electricity in an internal combustion engine, or a fuel cell, with a round-trip efficiency of roughly 41%.

Underground storage is easiest in salt caverns, but only a certain number of places have suitable geology.

Tank storage is usually done at between one and ten times atmospheric pressure and at a temperature of −30 °C (−22 °F), in liquid form.

[43] As of 2023[update], pumped-storage hydroelectricity (PSH) was the largest form of grid energy storage globally, with an installed capacity of 181 GW, surpassing the combined capacity of utility-scale and behind-the-meter battery storage, which totaled approximately 88 GW.

[45] The system has an efficiency rate of 75% to 85% and can quickly respond to changes in demand, typically within seconds to minutes.

[46] While traditional PSH systems require specific geographical conditions, alternative designs have been proposed.

These include using deep salt caverns or constructing hollow structures on the seabed, where the ocean serves as the upper reservoir.

[45] However, PSH construction is often expensive, time-consuming, and can have significant environmental and social impacts on nearby communities.

As well as energy generation, they often play a role in flood defense and protection of ecosystems, recreation, and they supply water for irrigation.

This can be achieved inside old mine shafts[50] or in specially constructed towers where heavy weights are winched up to store energy and allowed a controlled descent to release it.

This can be provided by a low-carbon source, or in the case of advanced CAES, by reusing the heat that is released when air is compressed.

The energy in a CSP system can for instance be stored in molten salts or in a solid medium such as sand.

[4] There are four categories of services which provide economic value for storage: those related to power quality (such as frequency regulation), reliability (ensuring peak demand can be met), better use of assets in the system (e.g. avoiding transmission investments) and arbitrage (exploiting price differences over time).

When the share of variable renewables climbs to 80%, medium-duration storage (between 4 and 16 hours, for instance compressed air) is needed.

[78] Typically, electricity prices vary most between day and night, which means that storage up to 8 hours has relatively high potential for profit.