Editing Energy storage (section)

==== Solid mass gravitational {{anchor|Gravitational_potential_energy_storage}} ====
{{Main|Gravity battery}}
Changing the altitude of solid masses can store or release energy via an elevating system driven by an electric motor/generator. Studies suggest energy can begin to be released with as little as 1 second warning, making the method a useful supplemental feed into an electricity grid to balance load surges.<ref>{{cite news|last1=Fraser|first1=Douglas|title=Edinburgh company generates electricity from gravity|publisher=BBC News|date=October 22, 2019|url=https://www.bbc.com/news/uk-scotland-scotland-business-50146801|access-date=14 January 2020|archive-date=July 28, 2020|archive-url=https://web.archive.org/web/20200728083135/https://www.bbc.com/news/uk-scotland-scotland-business-50146801|url-status=live}}</ref>

Efficiencies can be as high as 85% recovery of stored energy.<ref name="quartz" />

This can be achieved by siting the masses inside old vertical mine shafts or in specially constructed towers where the heavy weights are [[winch]]ed up to store energy and allowed a controlled descent to release it. At 2020 a prototype vertical store is being built in Edinburgh, Scotland<ref>{{Cite web|last=Gourley|first=Perry|date=31 August 2020|title=Edinburgh firm behind incredible gravity energy storage project hails milestone|url=https://www.edinburghnews.scotsman.com/business/edinburgh-firm-behind-incredible-gravity-energy-storage-project-hails-milestone-2955863|access-date=2020-09-01|website=The Scotsman|language=en|archive-date=September 2, 2020|archive-url=https://web.archive.org/web/20200902003909/https://www.edinburghnews.scotsman.com/business/edinburgh-firm-behind-incredible-gravity-energy-storage-project-hails-milestone-2955863|url-status=live}}</ref>

Potential energy storage or gravity energy storage was under active development in 2013 in association with the [[California Independent System Operator]].<ref name="Economist-2012.03.03" /><ref name="Bloomberg-2012.09.06" /><ref name="Kernan" /> It examined the movement of earth-filled [[Hopper car|hopper rail cars]] driven by [[electric locomotive]]s from lower to higher elevations.<ref name="Scientific American-2014.03.25" />

Other proposed methods include:-

* using rails,<ref name="Scientific American-2014.03.25" /><ref>{{cite magazine |author=David Z. Morris |date=May 22, 2016 |title=Energy-Storing Train Gets Nevada Approval |url=http://fortune.com/2016/05/22/energy-storing-train-nevada/ |magazine=Fortune |access-date=August 20, 2018 |archive-date=August 20, 2018 |archive-url=https://web.archive.org/web/20180820140850/http://fortune.com/2016/05/22/energy-storing-train-nevada/ |url-status=live }}</ref> cranes,<ref name="quartz">{{cite news |title=Stacking concrete blocks is a surprisingly efficient way to store energy |author=Akshat Rathi |date=August 18, 2018 |url=https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy/ |work=Quartz |access-date=August 20, 2018 |archive-date=December 3, 2020 |archive-url=https://web.archive.org/web/20201203050354/https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy/ |url-status=live }}</ref> or elevators<ref>{{Cite web |date=2022-05-31 |title=Lift Energy Storage System: Turning skyscrapers into gravity batteries |url=https://newatlas.com/energy/lift-energy-skyscraper-batteries/ |access-date=2022-05-31 |website=New Atlas |language=en-US}}</ref> to move weights up and down;
* using high-altitude solar-powered balloon platforms supporting winches to raise and lower solid masses slung underneath them,<ref>{{cite web | title=StratoSolar gravity energy storage | url=http://www.stratosolar.com/gravity-energy-storage.html | access-date=August 20, 2018 | archive-date=August 20, 2018 | archive-url=https://web.archive.org/web/20180820110224/http://www.stratosolar.com/gravity-energy-storage.html | url-status=live }}</ref> 
* using winches supported by an ocean barge to take advantage of a 4&nbsp;km (13,000&nbsp;ft) elevation difference between the sea surface and the seabed,<ref>{{cite web |last1=Choi |first1=Annette |title=Simple Physics Solutions to Storing Renewable Energy |url=https://www.pbs.org/wgbh/nova/article/storing-renewable-energy/ |website=[[Nova (American TV program)|NOVA]] |publisher=[[PBS]] |date=May 24, 2017 |access-date=29 August 2019 |archive-date=August 29, 2019 |archive-url=https://web.archive.org/web/20190829141630/https://www.pbs.org/wgbh/nova/article/storing-renewable-energy/ |url-status=live }}</ref>

[[File:Fernwärmespeicher Theiss.jpg|thumb|District heating accumulation tower from Theiss near [[Krems an der Donau]] in [[Lower Austria]] with a thermal capacity of 2 GWh]]