Editing Wind power (section)

=== Variability ===

{{Main|Variable renewable energy}}
{{Further|Grid balancing}}

[[File: Toro de osborne.jpg|thumb|Wind turbines are typically installed in windy locations. In the image, wind power [[Wind power in Spain|generators in Spain]], near an [[Osborne bull]].]]
[[File:Roscoe Wind Farm in West Texas.jpg|thumb|right|[[Roscoe Wind Farm]]: an onshore wind farm in [[West Texas]] near [[Roscoe, Texas|Roscoe]]]]

Wind power is variable, and during low wind periods, it may need to be replaced by other power sources. Transmission networks presently cope with outages of other generation plants and daily changes in electrical demand, but the variability of [[intermittent power source]]s such as wind power is more frequent than those of conventional power generation plants which, when scheduled to be operating, may be able to deliver their nameplate capacity around 95% of the time.

Electric power generated from wind power can be highly variable at several different timescales: hourly, daily, or seasonally. Annual variation also exists but is not as significant.{{Citation needed|date=November 2021}} Because instantaneous electrical generation and consumption must remain in balance to maintain grid stability, this variability can present substantial challenges to incorporating large amounts of wind power into a grid system. Intermittency and the non-[[Intermittent power sources#Terminology|dispatchable]] nature of wind energy production can raise costs for regulation, incremental [[operating reserve]], and (at high penetration levels) could require an increase in the already existing [[energy demand management]], [[load shedding]], storage solutions, or system interconnection with [[high voltage direct current|HVDC]] cables.

Fluctuations in load and allowance for the failure of large fossil-fuel generating units require operating reserve capacity, which can be increased to compensate for the variability of wind generation.

[[Battery storage power station|Utility-scale batteries]] are often used to balance hourly and shorter timescale variation,<ref>{{Cite web|last=Katz|first=Cheryl|title=The batteries that could make fossil fuels obsolete|url=https://www.bbc.com/future/article/20201217-renewable-power-the-worlds-largest-battery|access-date=2021-11-23|website=www.bbc.com|date=18 December 2020 |language=en|archive-date=11 January 2021|archive-url=https://web.archive.org/web/20210111075439/https://www.bbc.com/future/article/20201217-renewable-power-the-worlds-largest-battery|url-status=live}}</ref><ref>{{Cite web|date=2021-01-14|title=Report: An additional 20GWh of battery storage could significantly reduce wind power curtailment in UK|url=https://www.renewableenergyworld.com/storage/report-an-additional-20gwh-of-battery-storage-could-significantly-reduce-wind-power-curtailment-in-uk/|access-date=2021-11-23|website=Renewable Energy World|language=en-US|archive-date=26 February 2021|archive-url=https://web.archive.org/web/20210226223141/https://www.renewableenergyworld.com/storage/report-an-additional-20gwh-of-battery-storage-could-significantly-reduce-wind-power-curtailment-in-uk/|url-status=live}}</ref> but [[Vehicle-to-grid|car batteries]] may gain ground from the mid-2020s.<ref>{{Cite web|title=Answers to the UK's wind energy storage issues are emerging – NS Energy|date=9 September 2021 |url=https://www.nsenergybusiness.com/features/wind-energy-storage-in-the-uk-is-posing-problems-but-long-term-solutions-are-emerging/|access-date=2021-11-23|language=en-US|archive-date=10 September 2021|archive-url=https://web.archive.org/web/20210910082016/https://www.nsenergybusiness.com/features/wind-energy-storage-in-the-uk-is-posing-problems-but-long-term-solutions-are-emerging/|url-status=live}}</ref> Wind power advocates argue that periods of low wind can be dealt with by simply restarting existing power stations that have been held in readiness, or interlinking with HVDC.<ref name="Czisch-Giebel">[http://www.risoe.dk/rispubl/reports/ris-r-1608_186-195.pdf Realisable Scenarios for a Future Electricity Supply based 100% on Renewable Energies] {{webarchive|url=https://web.archive.org/web/20140701230913/http://www.risoe.dk/rispubl/reports/ris-r-1608_186-195.pdf |date=1 July 2014}} Gregor Czisch, University of Kassel, Germany and Gregor Giebel, Risø National Laboratory, Technical University of Denmark</ref>

The combination of diversifying variable renewables by type and location, forecasting their variation, and integrating them with dispatchable renewables, flexible fueled generators, and demand response can create a power system that has the potential to meet power supply needs reliably. Integrating ever-higher levels of renewables is being successfully demonstrated in the real world.<ref>{{Cite web |title=Annual variable renewable energy share and corresponding system integration phase in selected countries/regions, 2018 – Charts – Data & Statistics |url=https://www.iea.org/data-and-statistics/charts/annual-variable-renewable-energy-share-and-corresponding-system-integration-phase-in-selected-countries-regions-2018 |access-date=2023-01-20 |website=IEA |language=en-GB}}</ref>

[[File: Seasonal cycle of capacity factors for wind and photovoltaics in Europe under idealized assumptions.png|thumb|Seasonal cycle of capacity factors for wind and photovoltaics in Europe under idealized assumptions. The figure illustrates the balancing effects of wind and solar energy at the seasonal scale (Kaspar et al., 2019).<ref name="balancing-europe" />]]
[[Solar power]] tends to be complementary to wind.<ref name=windsun>Wood, Shelby (21 January 2008) [http://blog.oregonlive.com/pdxgreen/2008/01/wind_sun_join_forces_at_washin.html Wind + sun join forces at Washington power plant] {{Webarchive|url=https://web.archive.org/web/20120118135025/http://blog.oregonlive.com/pdxgreen/2008/01/wind_sun_join_forces_at_washin.html |date=18 January 2012 }}. ''The Oregonian''.</ref><ref name=smallWindSystems>{{cite web |url=http://www.seco.cpa.state.tx.us/re/wind/smallwind.php |title=Small Wind Systems |publisher=Seco.cpa.state.tx.us |access-date=29 August 2010 |archive-url=https://web.archive.org/web/20121023190904/http://www.seco.cpa.state.tx.us/re/wind/smallwind.php |archive-date=23 October 2012 |url-status=dead}}</ref> On daily to weekly timescales, [[high-pressure area]]s tend to bring clear skies and low surface winds, whereas [[low-pressure area]]s tend to be windier and cloudier. On seasonal timescales, solar energy peaks in summer, whereas in many areas wind energy is lower in summer and higher in winter.{{efn-ua|1=[[Wind power in California|California]] is an exception}}<ref name="cleveland_water_crib">{{cite web |url = http://www.development.cuyahogacounty.us/pdf_development/en-US/ExeSum_WindResrc_CleveWtrCribMntr_Reprt.pdf |title = Lake Erie Wind Resource Report, Cleveland Water Crib Monitoring Site, Two-Year Report Executive Summary |publisher = Green Energy Ohio |date = 10 January 2008 |access-date = 27 November 2008 |archive-url = https://web.archive.org/web/20081217063550/http://www.development.cuyahogacounty.us/pdf_development/en-US/ExeSum_WindResrc_CleveWtrCribMntr_Reprt.pdf |archive-date = 17 December 2008 |url-status=dead |df = dmy-all}} This study measured up to four times as much average wind power during winter as in summer for the test site.</ref> Thus the seasonal variation of wind and solar power tend to cancel each other somewhat.<ref name="balancing-europe">Kaspar, F., Borsche, M., Pfeifroth, U., Trentmann, J., Drücke, J., and Becker, P.: A climatological assessment of balancing effects and shortfall risks of photovoltaics and wind energy in Germany and Europe, Adv. Sci. Res., 16, 119–128, https://doi.org/10.5194/asr-16-119-2019 {{Webarchive|url=https://web.archive.org/web/20211124094345/https://asr.copernicus.org/articles/16/119/2019/ |date=24 November 2021 }}, 2019</ref> [[Wind hybrid power systems]] are becoming more popular.<ref>{{Cite web|date=2021-11-23|title=Turkish Cengiz evaluates expansion of its giant hybrid power plant|url=https://balkangreenenergynews.com/turkish-cengiz-evaluates-expansion-of-its-giant-hybrid-power-plant/|access-date=2021-11-24|website=Balkan Green Energy News|language=en-US}}</ref>