Editing Energy storage (section)

=== Grid electricity and power stations ===
{{Main|Grid energy storage|Battery storage power station}}

==== Renewable energy ====
[[File:Abengoa Solar (7336087392).jpg|thumbnail| Construction of the Salt Tanks which provide efficient [[thermal energy storage]]<ref>Wright, matthew; Hearps, Patrick; et al. [http://media.bze.org.au/ZCA2020_Stationary_Energy_Report_v1.pdf Australian Sustainable Energy: Zero Carbon Australia Stationary Energy Plan] {{Webarchive|url=https://web.archive.org/web/20151124173114/http://media.bze.org.au/ZCA2020_Stationary_Energy_Report_v1.pdf |date=November 24, 2015 }}, Energy Research Institute, [[University of Melbourne]], October 2010, p. 33. Retrieved from BeyondZeroEmissions.org website.</ref> so that electricity can be generated after the sun goes down, and output can be scheduled to meet demand.<ref>[http://www.renewableenergyfocus.com/view/3272/innovation-in-concentrating-thermal-solar-power-csp/ Innovation in Concentrating Thermal Solar Power (CSP)] {{Webarchive|url=https://web.archive.org/web/20150924090041/http://www.renewableenergyfocus.com/view/3272/innovation-in-concentrating-thermal-solar-power-csp/ |date=September 24, 2015 }}, RenewableEnergyFocus.com website.</ref> The 280 MW [[Solana Generating Station]] is designed to provide six hours of storage. This allows the plant to generate about 38% of its rated capacity over the course of a year.<ref>{{cite web|url=http://blogs.phoenixnewtimes.com/valleyfever/2013/10/solana_10_facts_you_didnt_know.php|title=Solana: 10 Facts You Didn't Know About the Concentrated Solar Power Plant Near Gila Bend|author=Ray Stern|work=Phoenix New Times|access-date=December 6, 2015|archive-date=October 11, 2013|archive-url=https://web.archive.org/web/20131011235507/http://blogs.phoenixnewtimes.com/valleyfever/2013/10/solana_10_facts_you_didnt_know.php|url-status=dead}}</ref>]]

[[File:Andasol 3.jpg|thumb|right| The 150 MW [[Andasol solar power station]] in [[Renewable energy in Spain|Spain]] is a [[parabolic trough]] [[solar thermal]] power plant that stores energy in [[Thermal energy storage#Molten salt technology|tanks of molten salt]] so that it can continue generating electricity when the sun is not shining.<ref name="Cartlidge" />]]

The largest source and the greatest store of renewable energy is provided by hydroelectric dams. A large reservoir behind a dam can store enough water to average the annual flow of a river between dry and wet seasons, and a very large reservoir can store enough water to average the flow of a river between dry and wet years. While a hydroelectric dam does not directly store energy from intermittent sources, it does balance the grid by lowering its output and retaining its water when power is generated by solar or wind. If wind or solar generation exceeds the region's hydroelectric capacity, then some additional source of energy is needed.

Many [[renewable energy]] sources (notably solar and wind) produce [[variable renewable energy|variable power]].<ref name="NYTimes-2010.07.28" /> Storage systems can level out the imbalances between supply and demand that this causes. Electricity must be used as it is generated or converted immediately into storable forms.<ref name="Ingebretsen-Johansen" />

The main method of electrical grid storage is [[pumped-storage hydroelectricity]]. Areas of the world such as Norway, Wales, Japan and the US have used elevated geographic features for [[reservoir]]s, using electrically powered pumps to fill them. When needed, the water passes through generators and converts the gravitational potential of the falling water into electricity.<ref name="NYTimes-2010.07.28" /> Pumped storage in Norway, which gets almost all its electricity from hydro, has currently a capacity of 1.4 GW but since the total installed capacity is nearly 32 GW and 75% of that is regulable, it can be expanded significantly.<ref>[https://www.hydropower.org/country-profiles/norway "Norway statistics – International Hydropower Association"] {{Webarchive|url=https://web.archive.org/web/20180914022911/https://www.hydropower.org/country-profiles/norway |date=September 14, 2018 }}. Retrieved on September 13, 2018.</ref>

Some forms of storage that produce electricity include pumped-storage [[hydroelectric dams]], [[Rechargeable battery|rechargeable batteries]], [[thermal energy storage|thermal storage]] including [[Molten salt heat storage|molten salts]] which can efficiently store and release very large quantities of heat energy,<ref name="NYTimes-2014.04.21" /> and [[compressed air energy storage]], [[Flywheel energy storage|flywheels]], [[cryogenic energy storage|cryogenic systems]] and [[superconducting magnetic energy storage|superconducting magnetic coils]].

Surplus power can also be converted into [[power to gas|methane]] ([[Sabatier process]]) with stockage in the natural gas network.<ref name="Schmid" /><ref name="NégaWatt" />

In 2011, the [[Bonneville Power Administration]] in the [[northwestern United States]] created an experimental program to absorb excess wind and hydro power generated at night or during stormy periods that are accompanied by high winds. Under central control, home appliances absorb surplus energy by heating ceramic bricks in [[Storage heater|special space heaters]] to hundreds of degrees and by boosting the temperature of modified [[Storage water heater|hot water heater tanks]]. After charging, the appliances provide home heating and hot water as needed. The experimental system was created as a result of a severe 2010 storm that overproduced renewable energy to the extent that all conventional power sources were shut down, or in the case of a nuclear power plant, reduced to its lowest possible operating level, leaving a large area running almost completely on renewable energy.<ref name="NYTimes-2011.11.05" /><ref name="NYTimes-2010.07.07" />

Another advanced method used at the former [[the Solar Project|Solar Two project]] in the United States and the [[Gemasolar Thermosolar Plant|Solar Tres Power Tower]] in Spain uses [[Thermal energy storage#Molten salt technology|molten salt]] to store thermal energy captured from the sun and then convert it and dispatch it as electrical power. The system pumps molten salt through a tower or other special conduits to be heated by the sun. Insulated tanks store the solution. Electricity is produced by turning water to steam that is fed to [[turbine]]s.

Since the early 21st century batteries have been applied to utility scale load-leveling and [[Utility frequency|frequency regulation]] capabilities.<ref name="NYTimes-2010.07.28" />

In [[vehicle-to-grid]] storage, electric vehicles that are plugged into the energy grid can deliver stored electrical energy from their batteries into the grid when needed.