Editing Renewable energy (section)

=== Intermittency ===
{{Main|Variable renewable energy}}
[[File:20240706 Energy storage - renewable energy - battery - 100 ms.gif |thumb |Energy from sunlight or other renewable energy is converted to potential energy for storage in devices such as electric batteries. The stored potential energy is later converted to electricity that is added to the power grid, even when the original energy source is not available.]]
[[File:Renewables need flexible backup not baseload.png |thumb |Estimated power demand over a week in May 2012 and May 2020, Germany, showing the variability in solar and wind power both day-to-day and month-to-month.]]
The two most important forms of renewable energy, solar and wind, are ''intermittent energy sources'': they are not available constantly, resulting in lower [[capacity factor]]s. In contrast, [[Fossil fuel power station|fossil fuel power plants]], nuclear power plants and hydropower are usually able to produce precisely the amount of energy an [[Electrical grid|electricity grid]] requires at a given time. Solar energy can only be captured during the day, and ideally in cloudless conditions. Wind power generation can vary significantly not only day-to-day, but even month-to-month.<ref>{{Cite book |last=Wan |first=Y. H. |url=https://www.nrel.gov/docs/fy12osti/53637.pdf |title=Long-term wind power variability |date=January 2012 |publisher=[[National Renewable Energy Laboratory]] |language=en}}</ref> This poses a challenge when transitioning away from fossil fuels: energy demand will often be higher or lower than what renewables can provide.<ref name="Olauson 16175">{{Cite journal |last1=Olauson |first1=Jon |last2=Ayob |first2=Mohd Nasir |last3=Bergkvist |first3=Mikael |last4=Carpman |first4=Nicole |last5=Castellucci |first5=Valeria |last6=Goude |first6=Anders |last7=Lingfors |first7=David |last8=Waters |first8=Rafael |last9=Widén |first9=Joakim |date=December 2016 |title=Net load variability in Nordic countries with a highly or fully renewable power system |url=http://www.nature.com/articles/nenergy2016175 |url-status=live |journal=Nature Energy |volume=1 |issue=12 |pages=16175 |doi=10.1038/nenergy.2016.175 |bibcode=2016NatEn...116175O |issn=2058-7546 |s2cid=113848337 |archive-url=https://web.archive.org/web/20211004082439/https://www.nature.com/articles/nenergy2016175 |archive-date=4 October 2021 |access-date=4 October 2021}}</ref>

In the medium-term, this variability may require keeping some [[gas-fired power plant]]s or other [[dispatchable generation]] on standby<ref>{{Cite web |last=Swartz |first=Kristi E. |date=2021-12-08 |title=Can U.S. phase out natural gas? Lessons from the Southeast |url=https://www.eenews.net/articles/can-u-s-phase-out-natural-gas-lessons-from-the-southeast/ |access-date=2022-05-02 |website=E&E News |language=en-US}}</ref><ref>{{Cite web |title=Climate change: phase out gas power by 2035, say businesses including Nestle, Thames Water, Co-op |url=https://news.sky.com/story/climate-change-phase-out-gas-power-by-2035-say-businesses-including-nestle-thames-water-co-op-12415528 |access-date=2022-05-02 |website=Sky News |language=en}}</ref> until there is enough energy storage, [[demand response]], grid improvement, or [[Base load|base load power]] from non-intermittent sources. In the long-term, [[energy storage]] is an important way of dealing with intermittency.<ref>{{Cite web |last=Roberts |first=David |date=2018-11-30 |title=Clean energy technologies threaten to overwhelm the grid. Here's how it can adapt. |url=https://www.vox.com/energy-and-environment/2018/11/30/17868620/renewable-energy-power-grid-architecture |access-date=2024-04-20 |website=Vox |language=en}}</ref> Using diversified renewable energy sources and [[smart grid]]s can also help flatten supply and demand.<ref>{{Cite news |title=AI and other tricks are bringing power lines into the 21st century |url=https://www.economist.com/business/2024/05/05/ai-and-other-tricks-are-bringing-power-lines-into-the-21st-century |access-date=2024-05-12 |newspaper=The Economist |issn=0013-0613}}</ref>

Sector coupling of the power generation sector with other sectors may increase flexibility: for example the transport sector can be coupled by charging electric vehicles and sending electricity from [[Vehicle-to-grid|vehicle to grid]].<ref>{{Cite journal |last1=Ramsebner |first1=Jasmine |last2=Haas |first2=Reinhard |last3=Ajanovic |first3=Amela |last4=Wietschel |first4=Martin |date=July 2021 |title=The sector coupling concept: A critical review |url=https://onlinelibrary.wiley.com/doi/10.1002/wene.396 |journal=WIREs Energy and Environment |language=en |volume=10 |issue=4 |bibcode=2021WIREE..10E.396R |doi=10.1002/wene.396 |issn=2041-8396 |s2cid=234026069}}</ref> Similarly the industry sector can be coupled by hydrogen produced by electrolysis,<ref>{{Cite web |title=4 questions on sector coupling |url=https://www.wartsila.com/insights/article/4-questions-on-sector-coupling |access-date=2022-05-15 |website=Wartsila.com |language=en}}</ref> and the buildings sector by thermal energy storage for space heating and cooling.<ref>{{Cite web |date=2021-12-16 |title=Intelligent, flexible Sector Coupling in cities can double the potential for Wind and Solar |url=https://energypost.eu/intelligent-flexible-sector-coupling-in-cities-can-double-the-potential-for-wind-and-solar/ |access-date=2022-05-15 |website=Energy Post |language=en-GB |archive-date=27 May 2022 |archive-url=https://web.archive.org/web/20220527191915/https://energypost.eu/intelligent-flexible-sector-coupling-in-cities-can-double-the-potential-for-wind-and-solar/ |url-status=dead }}</ref>

Building overcapacity for wind and solar generation can help ensure sufficient electricity production even during poor weather. In optimal weather, it may be necessary to curtail energy generation if it is not possible to use or store excess electricity.<ref>{{Cite book |last=IEA |author-link=International Energy Agency |url=https://www.iea.org/reports/world-energy-outlook-2020 |title=World Energy Outlook 2020 |publisher=International Energy Agency |year=2020 |isbn=978-92-64-44923-7 |page=109 |archive-url=https://web.archive.org/web/20210822044327/https://www.iea.org/reports/world-energy-outlook-2020 |archive-date=22 August 2021 |url-status=live}}</ref>

==== Electrical energy storage ====
{{main|Energy storage|Grid energy storage}}

Electrical energy storage is a collection of methods used to store electrical energy. Electrical energy is stored during times when production (especially from intermittent sources such as [[wind power]], [[tidal power]], [[solar power]]) exceeds consumption, and returned to the [[power grid|grid]] when production falls below consumption. [[Pumped-storage hydroelectricity]] accounts for more than 85% of all [[Grid energy storage|grid power storage]].<ref>{{Cite web |date=30 June 2021 |title=Hydropower Special Market Report – Analysis |url=https://www.iea.org/reports/hydropower-special-market-report |access-date=2022-01-31 |website=IEA}}</ref> Batteries are increasingly being deployed for storage<ref>{{Cite web |date=2022-05-05 |title=What role is large-scale battery storage playing on the grid today? |url=https://www.energy-storage.news/what-role-is-large-scale-battery-storage-playing-on-the-grid-today/ |access-date=2022-05-09 |website=Energy Storage News |language=en-US}}</ref> and grid [[ancillary services]]<ref>{{Cite book |last1=Zhou |first1=Chen |title=2021 2nd International Conference on Artificial Intelligence and Information Systems |last2=Liu |first2=Rao |last3=Ba |first3=Yu |last4=Wang |first4=Haixia |last5=Ju |first5=Rongbin |last6=Song |first6=Minggang |last7=Zou |first7=Nan |last8=Li |first8=Weidong |date=2021-05-28 |publisher=Association for Computing Machinery |isbn=978-1-4503-9020-0 |series=ICAIIS 2021 |location=New York, NY, USA |pages=1–6 |chapter=Study on the optimization of the day-ahead addition space for large-scale energy storage participation in auxiliary services |doi=10.1145/3469213.3471362 |chapter-url=https://doi.org/10.1145/3469213.3471362 |s2cid=237206056}}</ref> and for domestic storage.<ref>{{Cite web |last=Heilweil |first=Rebecca |date=2022-05-05 |title=These batteries work from home |url=https://www.vox.com/recode/23057167/home-battery-tesla-powerwall-biden |access-date=2022-05-09 |website=[[Vox (website)|Vox]] |language=en}}</ref> [[Green hydrogen]] is a more economical means of long-term renewable energy storage, in terms of [[capital expenditure]]s compared to pumped hydroelectric or batteries.<ref>{{Cite journal |last1=Schrotenboer |first1=Albert H. |last2=Veenstra |first2=Arjen A.T. |last3=uit het Broek |first3=Michiel A.J. |last4=Ursavas |first4=Evrim |date=October 2022 |title=A Green Hydrogen Energy System: Optimal control strategies for integrated hydrogen storage and power generation with wind energy |url=https://pure.rug.nl/ws/portalfiles/portal/230184233/1_s2.0_S1364032122006323_main.pdf |journal=Renewable and Sustainable Energy Reviews |language=en |volume=168 |pages=112744 |doi=10.1016/j.rser.2022.112744 |arxiv=2108.00530 |bibcode=2022RSERv.16812744S |s2cid=250941369}}</ref><ref>{{Cite news |last=Lipták |first=Béla |date=January 24, 2022 |title=Hydrogen is key to sustainable green energy |url=https://www.controlglobal.com/home/article/11288951/hydrogen-is-key-to-sustainable-green-energy |access-date=February 12, 2023 |work=Control}}</ref>

==== Energy supply security ====
Two main renewable energy sources - solar power and wind power - are usually deployed in [[distributed generation]] architecture, which offers specific benefits and comes with specific risks.<ref>{{Cite journal |last1=Gordon |first1=Samuel |last2=McGarry |first2=Connor |last3=Bell |first3=Keith |date=2022 |title=The growth of distributed generation and associated challenges: A Great Britain case study |journal=IET Renewable Power Generation |language=en |volume=16 |issue=9 |pages=1827–1840 |doi=10.1049/rpg2.12416 |issn=1752-1424|doi-access=free |bibcode=2022IRPG...16.1827G }}</ref> Notable risks are associated with centralisation of 90% of the supply chains in a single country (China) in the photovoltaic sector.<ref>{{Cite web |last=O’Sullivan |first=Alexander Lipke, Janka Oertel, Daniel |date=2024-05-29 |title=Trust and trade-offs: How to manage Europe's green technology dependence on China |url=https://ecfr.eu/publication/trust-and-trade-offs-how-to-manage-europes-green-technology-dependence-on-china/ |access-date=2024-12-12 |website=ECFR |language=en-GB}}</ref> Mass-scale installation of photovoltaic [[Power inverter|power inverters]] with remote control, [[Vulnerability (computer security)|security vulnerabilities]] and [[Web shell|backdoors]] results in cyberattacks that can disable generation from millions of physically decentralised panels, resulting in disappearance of hundreds of gigawatts of installed power from the grid in one moment.<ref>{{Cite news |date=2024-12-12 |title=Hacking Rooftop Solar Is a Way to Break Europe's Power Grid |url=https://www.bloomberg.com/news/articles/2024-12-12/europe-s-power-grid-vulnerable-to-hackers-exploiting-rooftop-solar-panels |access-date=2024-12-12 |work=Bloomberg.com |language=en}}</ref><ref>{{Cite web |date=2024-08-19 |title=The gigantic and unregulated power plants in the cloud |url=https://berthub.eu/articles/posts/the-gigantic-unregulated-power-plants-in-the-cloud/ |access-date=2024-12-12 |website=Bert Hubert's writings}}</ref> Similar attacks have targeted wind power farms through vulnerabilities in their remote control and monitoring systems.<ref>{{Cite web |last=Tam |first=Kimberly |date=2024-09-05 |title=How cyberattacks on offshore wind farms could create huge problems |url=https://theconversation.com/how-cyberattacks-on-offshore-wind-farms-could-create-huge-problems-238165 |access-date=2024-12-12 |website=The Conversation |language=en-US}}</ref> The European [[Cyber-security regulation|NIS2 directive]] partially responds to these challenges by extending the scope of cybersecurity regulations to the energy generation market.<ref>{{Cite web |date=2024-07-12 |title=SolarPower Europe calls for stronger cybersecurity measures |url=https://www.pv-magazine.com/2024/07/12/solarpower-europe-calls-for-stronger-cybersecurity-measures/ |access-date=2024-12-12 |website=pv magazine International |language=en-US}}</ref>