Editing Energy storage (section)

==== Power-to-gas ====
[[File:World’s 1st Low-Emission Hybrid Battery Storage, Gas Turbine Peaker System.jpg|thumb|220px|right|The new technology helps reduce greenhouse gases and operating costs at two existing peaker plants in [[Norwalk, California|Norwalk]] and [[Rancho Cucamonga, California|Rancho Cucamonga]]. The 10-megawatt battery storage system, combined with the gas turbine, allows the peaker plant to more quickly respond to changing energy needs, thus increasing the reliability of the electrical grid.]]
{{Main|Power-to-gas}}

[[Power-to-gas]] is the conversion of [[electricity]] to a gaseous [[fuel]] such as [[hydrogen]] or [[methane]]. The three commercial methods use electricity to reduce [[water splitting|water]] into [[hydrogen]] and [[oxygen]] by means of [[electrolysis]].

In the first method, hydrogen is injected into the natural gas grid or is used for transportation. The second method is to combine the hydrogen with [[carbon dioxide]] to produce [[methane]] using a [[methanation]] reaction such as the [[Sabatier reaction]], or biological methanation, resulting in an extra energy conversion loss of 8%. The methane may then be fed into the natural gas grid. The third method uses the output gas of a [[wood gas generator]] or a [[biogas]] plant, after the [[biogas upgrader]] is mixed with the hydrogen from the electrolyzer, to upgrade the quality of the biogas.

===== Hydrogen =====
{{Main|Hydrogen storage}}
{{See also|Combined cycle hydrogen power plant|Hydrogen fuel cell power plant}}
The element [[hydrogen]] can be a form of stored energy. Hydrogen can produce electricity via a [[hydrogen fuel cell]].

At penetrations below 20% of the grid demand, renewables do not severely change the economics; but beyond about 20% of the total demand,<ref name="ZerrahnSchill2018"/> external storage becomes important. If these sources are used to make ionic hydrogen, they can be freely expanded. A 5-year community-based pilot program using [[wind turbine]]s and hydrogen generators began in 2007 in the remote community of [[Ramea, Newfoundland and Labrador]].<ref name="NaturalResourcesCan" /> A similar project began in 2004 on [[Utsira]], a small Norwegian island.

Energy losses involved in the [[hydrogen storage]] cycle come from the electrolysis of water, liquification or compression of the hydrogen and conversion to electricity.<ref name="PhysOrg.com-news-85074285" />

Hydrogen can also be produced from [[aluminum]] and [[water]] by stripping aluminum's naturally-occurring [[aluminum oxide]] barrier and introducing it to water. This method is beneficial because recycled aluminum cans can be used to generate hydrogen, however systems to harness this option have not been commercially developed and are much more complex than electrolysis systems.<ref name="Aluminum-Hydrogen" /> Common methods to strip the oxide layer include caustic catalysts such as [[sodium hydroxide]] and alloys with [[gallium]], [[Mercury (element)|mercury]] and other metals.<ref name="Woodall" />

[[Underground hydrogen storage]] is the practice of [[hydrogen storage]] in [[cave]]rns, [[salt dome]]s and depleted oil and gas fields.<ref name="Royal Society of Chemistry-a" /><ref name="Hyunder" /> Large quantities of gaseous hydrogen have been stored in caverns by [[Imperial Chemical Industries]] for many years without any difficulties.<ref name="Hyweb.de" /> The European Hyunder project indicated in 2013 that storage of wind and solar energy using underground hydrogen would require 85 caverns.<ref name="Hyunder.eu-b" />

Powerpaste is a [[magnesium]] and [[hydrogen]] -based fluid gel that releases hydrogen when reacting with [[water]]. It was [[invention|invented]], [[patent]]ed and is being developed by the ''Fraunhofer Institute for Manufacturing Technology and Advanced Materials'' (''IFAM'') of the [[Fraunhofer-Gesellschaft]].  Powerpaste is made by combining magnesium powder with hydrogen to form [[magnesium hydride]] in a process conducted at 350&nbsp;°C and five to six times [[atmospheric pressure]]. An [[ester]] and a [[Salt (chemistry)|metal salt]] are then added to make the finished product.  Fraunhofer states that they are building a production plant slated to start production in 2021, which will produce 4 tons of Powerpaste annually.<ref name="FraunhoferPowerpaste2021">{{cite press release
 |author       = <!--Not stated-->
 |title        = Hydrogen-powered drives for e-scooters
 |url          = https://www.fraunhofer.de/en/press/research-news/2021/february-2021/hydrogen-powered-drives-for-e-scooters.html
 |publisher    = [[Fraunhofer Society]]
 |date         = 2021-02-01
 |access-date  = 2021-02-22
 |archive-date = February 3, 2021
 |archive-url  = https://web.archive.org/web/20210203211045/https://www.fraunhofer.de/en/press/research-news/2021/february-2021/hydrogen-powered-drives-for-e-scooters.html
 |url-status   = live
}}</ref> Fraunhofer has patented their invention in the United States and [[European Union|EU]].<ref name="FraunhoferPowerpaste2019">{{cite tech report
|first= Lars
|last= Röntzsch
|first2= Marcus
|last2= Vogt
|title= White paper – PowerPaste for off-grid power supply
|number= 
|institution= [[Fraunhofer Society]]
|url= https://www.researchgate.net/publication/331929208_PowerPaste_for_off-grid_power_supply
|date= February 2019
|access-date= February 22, 2021
|archive-date= February 7, 2021
|archive-url= https://web.archive.org/web/20210207214925/https://www.researchgate.net/publication/331929208_PowerPaste_for_off-grid_power_supply
|url-status= live
}}</ref> Fraunhofer claims that Powerpaste is able to store hydrogen energy at 10 times the [[energy density]] of a [[Lithium-ion battery|lithium battery]] of a similar dimension and is safe and convenient for automotive situations.<ref name="FraunhoferPowerpaste2021"/>

===== Methane =====
{{Main|Substitute natural gas}}

[[Methane]] is the simplest hydrocarbon with the molecular formula CH<sub>4</sub>. Methane is more easily stored and transported than hydrogen. Storage and combustion infrastructure (pipelines, [[gas holder|gasometers]], power plants) are mature.

Synthetic natural gas ([[syngas]] or SNG) can be created in a multi-step process, starting with hydrogen and oxygen. Hydrogen is then reacted with [[carbon dioxide]] in a [[Sabatier reaction|Sabatier process]], producing methane and water. Methane can be stored and later used to produce electricity. The resulting water is recycled, reducing the need for water. In the electrolysis stage, oxygen is stored for methane combustion in a pure oxygen environment at an adjacent power plant, eliminating [[nitrogen oxide]]s.

Methane combustion produces carbon dioxide (CO<sub>2</sub>) and water. The carbon dioxide can be recycled to boost the Sabatier process and water can be recycled for further electrolysis. Methane production, storage and combustion recycles the reaction products.

The CO<sub>2</sub> has economic value as a component of an energy storage vector, not a cost as in [[carbon capture and storage]].