Editing Energy storage (section)

== Applications ==

=== Mills ===
The classic application before the [[Industrial Revolution]] was the control of waterways to drive water mills for processing grain or powering machinery. Complex systems of [[reservoir]]s and [[dam]]s were constructed to store and release water (and the [[potential energy]] it contained) when required.<ref>{{cite book|url=https://archive.org/details/encyclopediaofte10newy/page/1400/mode/2up|title=Encyclopedia of technology and applied sciences.|date=2000|publisher=Marshall Cavendish|isbn=076147126X|volume=10|location=New York|page=1401|quote=Simple waterwheels were used in the Balkans of Europe in 100 B.C.E for powering flour mills. Elaborate Irrigation systems had been built in Egypt and Mesopotamia a thousand years before that, and it is very likely that these systems contained simple waterwheels. Waterwheels powered by a stream running underneath were common in the Roman Empire during the third and fourth centuries C.E. After the fall of the Western Roman Empire, water technology advanced further in the Middle East than in Europe, but waterwheels were commonly used to harness water as a source of power in Europe during the Middle Ages. The Doomsday Book of 1086 C.E. lists 5624 water powered mills in the southern half of England. The designs of more efficient waterwheels were brought back to Europe from the Middle East by the Crusaders and were used for grinding grain and for powering furnace bellows.|access-date=31 December 2020}}</ref>

=== Homes ===
{{Main|Home energy storage}}

Home energy storage is expected to become increasingly common given the growing importance of distributed generation of renewable energies (especially photovoltaics) and the important share of energy consumption in buildings.<ref name="Silva-Hendrick" /> To exceed a self-sufficiency of 40% in a household equipped with photovoltaics, energy storage is needed.<ref name="Silva-Hendrick" /> Multiple manufacturers produce rechargeable battery systems for storing energy, generally to hold surplus energy from home solar or wind generation. Today, for home energy storage, Li-ion batteries are preferable to lead-acid ones given their similar cost but much better performance.<ref>{{Cite journal|last1=de Oliveira e Silva|first1=Guilherme|last2=Hendrick|first2=Patrick|date=June 1, 2017|title=Photovoltaic self-sufficiency of Belgian households using lithium-ion batteries, and its impact on the grid|journal=Applied Energy|volume=195|pages=786–799|doi=10.1016/j.apenergy.2017.03.112|bibcode=2017ApEn..195..786D |url=https://www.sciencedirect.com/science/article/pii/S0306261917303495|url-access=registration}}</ref>

[[Tesla Motors]] produces two models of the [[Tesla Powerwall]]. One is a 10 kWh weekly cycle version for backup applications and the other is a 7 kWh version for daily cycle applications.<ref name="businessinsider">{{cite news |first=Matthew |last=Debord |url=http://www.businessinsider.com/here-comes-teslas-missing-piece-battery-announcement-2015-4 |title=Elon Musk's big announcement: it's called 'Tesla Energy' |work=[[Business Insider]] |date=May 1, 2015 |access-date=June 11, 2015 |archive-date=May 5, 2015 |archive-url=https://web.archive.org/web/20150505021205/http://www.businessinsider.com/here-comes-teslas-missing-piece-battery-announcement-2015-4 |url-status=live }}</ref> In 2016, a limited version of the Tesla Powerpack 2 cost $398(US)/kWh to store electricity worth 12.5 cents/kWh (US average grid price) making a positive [[Tesla Powerwall#Return on investment calculations|return on investment]] doubtful unless electricity prices are higher than 30 cents/kWh.<ref name="Price-Powerpack-2016">{{cite news|url= https://electrek.co/2016/11/14/tesla-powerpack-2-price/|title= Tesla slashes price of the Powerpack system by another 10% with new generation|date= May 15, 2017|work= Electrek|access-date= November 14, 2016|archive-date= November 14, 2016|archive-url= https://web.archive.org/web/20161114235216/https://electrek.co/2016/11/14/tesla-powerpack-2-price/|url-status= live|last1= Lambert|first1= Fred}}</ref>

RoseWater Energy produces two models of the "Energy & Storage System", the HUB 120<ref>{{Cite web|url=https://www.svconline.com/the-wire/rosewater-energy-group-debut-hub-120-cedia-2017-409670/409670|title=RoseWater Energy Group to Debut HUB 120 at CEDIA 2017|date=August 29, 2017|access-date=June 5, 2019|archive-url=https://web.archive.org/web/20190605152235/https://www.svconline.com/the-wire/rosewater-energy-group-debut-hub-120-cedia-2017-409670/409670|archive-date=June 5, 2019|url-status=dead}}</ref> and SB20.<ref>{{Cite web|url=https://rosewaterenergy.com/products/|title=Rosewater Energy – Products|access-date=June 5, 2019|archive-date=June 5, 2019|archive-url=https://web.archive.org/web/20190605152514/https://rosewaterenergy.com/products/|url-status=live}}</ref> Both versions provide 28.8 kWh of output, enabling it to run larger houses or light commercial premises, and protecting custom installations. The system provides five key elements into one system, including providing a clean 60&nbsp;Hz Sine wave, zero transfer time, industrial-grade surge protection, renewable energy grid sell-back (optional), and battery backup.<ref>{{Cite web|url=https://www.commercialintegrator.com/ci/rosewater_energy_the_cleanest_greenest_60k_power_supply_ever/|title=RoseWater Energy: The Cleanest, Greenest $60K Power Supply Ever|date=October 19, 2015|website=Commercial Integrator|access-date=June 5, 2019|archive-date=June 5, 2019|archive-url=https://web.archive.org/web/20190605152220/https://www.commercialintegrator.com/ci/rosewater_energy_the_cleanest_greenest_60k_power_supply_ever/|url-status=live}}</ref><ref>{{Cite web|url=https://www.cepro.com/cep/how_rosewaters_giant_home_battery_is_different_from_teslas/|title=How RoseWater's Giant Home Battery is Different from Tesla's|date=October 19, 2015|website=CEPRO|access-date=July 12, 2021|archive-date=July 12, 2021|archive-url=https://web.archive.org/web/20210712003902/https://www.cepro.com/cep/how_rosewaters_giant_home_battery_is_different_from_teslas/|url-status=live}}</ref>

[[Enphase Energy]] announced an integrated system that allows home users to store, monitor and manage electricity. The system stores 1.2 kWh of energy and 275W/500W power output.<ref>{{Cite web|title = Enphase plug-and-play solar energy storage system to begin pilot program|url = http://www.gizmag.com/enphase-ac-battery-for-pv-storage/39990|website = gizmag.com|access-date = December 20, 2015|date = October 29, 2015|last = Delacey|first = Lynda|archive-date = December 22, 2015|archive-url = https://web.archive.org/web/20151222234650/http://www.gizmag.com/enphase-ac-battery-for-pv-storage/39990/|url-status = live}}</ref>

Storing wind or solar energy using [[thermal energy storage]] though less flexible, is considerably cheaper than batteries. A simple 52-gallon electric water heater can store roughly 12 kWh of energy for supplementing hot water or space heating.<ref>{{cite web|url=http://www.popsci.com/need-high-power-home-battery-use-your-water-heater|title=Your Water Heater Can Become A High-Power Home Battery|website=popsci.com|date=April 7, 2016 |access-date=May 16, 2017|archive-date=May 5, 2017|archive-url=https://web.archive.org/web/20170505233536/http://www.popsci.com/need-high-power-home-battery-use-your-water-heater|url-status=live}}</ref>

For purely financial purposes in areas where [[net metering]] is available, home generated electricity may be sold to the grid through a [[grid-tie inverter]] without the use of batteries for storage.

=== 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.

=== Air conditioning ===
{{Main|Ice storage air conditioning}}

[[Thermal energy storage]] (TES) can be used for [[air conditioning]].<ref name="Calmac" /> It is most widely used for cooling single large buildings and/or groups of smaller buildings. Commercial air conditioning systems are the biggest contributors to peak electrical loads. In 2009, thermal storage was used in over 3,300 buildings in over 35 countries. It works by chilling material at night and using the chilled material for cooling during the hotter daytime periods.<ref name="NYTimes-2014.04.21" />

The most popular technique is [[Thermal energy storage#Air conditioning|ice storage]], which requires less space than water and is cheaper than fuel cells or flywheels. In this application, a standard chiller runs at night to produce an ice pile. Water circulates through the pile during the day to chill water that would normally be the chiller's daytime output.

A partial storage system minimizes capital investment by running the chillers nearly 24 hours a day. At night, they produce ice for storage and during the day they chill water. Water circulating through the melting ice augments the production of chilled water. Such a system makes ice for 16 to 18 hours a day and melts ice for six hours a day. Capital expenditures are reduced because the chillers can be just 40% – 50% of the size needed for a conventional, no-storage design. Storage sufficient to store half a day's available heat is usually adequate.

A full storage system shuts off the chillers during peak load hours. Capital costs are higher, as such a system requires larger chillers and a larger ice storage system.

This ice is produced when electrical utility rates are lower.<ref name="DistributedEnergy.com" /> Off-peak cooling systems can lower energy costs. The U.S. [[Green Building Council]] has developed the [[Leadership in Energy and Environmental Design]] (LEED) program to encourage the design of reduced-environmental impact buildings. Off-peak cooling may help toward LEED Certification.<ref>Air-Conditioning, Heating and Refrigeration Institute, Fundamentals of HVAC/R, Page 1263</ref>

Thermal storage for heating is less common than for cooling. An example of thermal storage is storing solar heat to be used for heating at night.

Latent heat can also be stored in technical [[Phase-change material|phase change materials]] (PCMs). These can be encapsulated in wall and ceiling panels, to moderate room temperatures.

=== Transport ===
Liquid [[hydrocarbon fuel]]s are the most commonly used forms of energy storage for use in [[transportation]], followed by a growing use of [[Battery Electric Vehicles]] and [[Hybrid Electric Vehicle]]s. Other energy carriers such as [[hydrogen]] can be used to avoid producing greenhouse gases.

Public transport systems like trams and trolleybuses require electricity, but due to their variability in movement, a steady supply of electricity via renewable energy is challenging. [[Photovoltaic]] systems installed on the roofs of buildings can be used to power public transportation systems during periods in which there is increased demand for electricity and access to other forms of energy are not readily available.<ref>{{cite journal |last1=Bartłomiejczyk |first1=Mikołaj |title=Potential Application of Solar Energy Systems for Electrified Urban Transportation Systems |journal=Energies |date=2018 |volume=11 |issue=4 |page=1 |doi=10.3390/en11040954 |doi-access=free }}</ref> Upcoming transitions in the transportation system also include e.g. ferries and airplanes, where electric power supply is investigated as an interesting alternative.<ref>{{Cite journal|last1=Brelje|first1=Benjamin J.|last2=Martins|first2=Joaquim R.R.A.|date=January 2019|title=Electric, hybrid, and turboelectric fixed-wing aircraft: A review of concepts, models, and design approaches |journal=Progress in Aerospace Sciences|language=en|volume=104|pages=1–19|doi=10.1016/j.paerosci.2018.06.004|bibcode=2019PrAeS.104....1B|doi-access=free}}</ref>

=== Electronics ===
Capacitors are widely used in [[electronic circuit]]s for blocking [[direct current]] while allowing [[alternating current]] to pass. In [[analog filter]] networks, they smooth the output of [[power supply|power supplies]]. In [[LC circuit|resonant circuit]]s they tune [[radio]]s to particular [[frequency|frequencies]]. In [[electric power transmission]] systems they stabilize voltage and power flow.<ref name="Bird" />