{{Short description|Long period of gloomy calm weather}} {{italic title}} {{use dmy dates |date=February 2023}} [[File:Dunkelflaute-Germany-2023.svg|thumb|upright=1.4|A ''dunkelflaute'' of three days in Germany 2023 (wind in light blue and solar in yellow)]] In the [[renewable energy]] sector, a '''''dunkelflaute''''' ({{IPA|de|ˈdʊŋkəlˌflaʊtə|lang|De-Dunkelflaute.ogg}}, {{Literal translation|dark doldrums|dark wind lull}}, plural ''dunkelflauten'')<ref name="gap">{{Cite web|date=2021-05-24|title=When the wind goes, gas fills in the gap {{!}} Q1 2021 Quarterly Report |work=Electric Insights|url=https://reports.electricinsights.co.uk/q1-2021/when-the-wind-goes-gas-fills-in-the-gap/|access-date=2021-06-29|language=en-GB}}</ref> is a period of time in which little or no energy can be generated with [[wind power|wind]] and [[solar power]], because there is neither wind nor sunlight.<ref>{{Cite web |work=en-former.com |title=Dark doldrums: When wind and sun take a break|url=https://www.en-former.com/en/dark-doldrums-when-wind-and-sun-take-a-break/ |date=31 July 2018 |access-date=2021-05-27}}</ref><ref>{{Cite journal |date=2020-06-01 |title=Investigating the economics of the power sector under high penetration of variable renewable energies |url=https://www.sciencedirect.com/science/article/abs/pii/S0306261919316435 |journal=Applied Energy |language=en |volume=267 |article-number=113956 |doi=10.1016/j.apenergy.2019.113956 |issn=0306-2619 |last1=Matsuo |first1=Yuhji |last2=Endo |first2=Seiya |last3=Nagatomi |first3=Yu |last4=Shibata |first4=Yoshiaki |last5=Komiyama |first5=Ryoichi |last6=Fujii |first6=Yasumasa |bibcode=2020ApEn..26713956M |s2cid=216301290 |url-access=subscription }}</ref><ref>{{Cite journal |date=2021-12-08 |title=Climatology of dark doldrums in Japan|url=https://www.sciencedirect.com/science/article/pii/S1364032121011928 |journal=Renewable and Sustainable Energy Reviews |language=en |volume=155 |article-number=111927 |doi=10.1016/j.rser.2021.111927 |last1=Ohba |first1=Masamichi |last2=Kanno |first2=Yuki |last3=Nohara |first3=Daisuke |s2cid=245067748 |url-access=subscription }}</ref> In [[meteorology]], this is known as '''anticyclonic gloom'''.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=2}}
== Meteorology == [[File:Ulmen und Eschenhain (Altmannsdorf) - 14.JPG|thumb|A cloudy and foggy January evening in Austria, one hour before sunset]] Unlike a typical [[anticyclone]], ''dunkelflauten'' are associated not with clear skies, but with very dense [[cloud cover]] (0.7–0.9), consisting of [[Stratus cloud|stratus]], [[Stratocumulus cloud|stratocumulus]], and fog.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=7}} {{As of|2022}} there is no agreed quantitative definition of ''dunkelflaute''.<ref>{{Cite web |title=Was ist die Dunkelflaute? {{!}} Definition |url=https://www.next-kraftwerke.de/wissen/dunkelflaute |language=de |trans-title=What are the Dark Doldrums? |access-date=2022-12-13 |website=next-kraftwerke.de}}</ref> Li et al. define it as wind and solar both below 20% of [[capacity factor|capacity]] during a particular 60-minute period.<ref name="LiBasu2020" /> High [[albedo]] of low-level stratocumulus clouds in particular{{snd}}sometimes the [[cloud base]] height is just 400 meters{{snd}}can reduce [[solar irradiation]] by half.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=7}}
In the north of Europe, ''dunkelflauten'' originate from a static high-pressure system that causes an extremely weak wind combined with [[overcast]] weather with [[stratus cloud|stratus]] or [[Stratocumulus cloud|stratocumulus]] clouds.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=6}} There are 2–10 ''dunkelflaute'' events per year.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=11}} Most of these events occur from October to February; typically 50 to 150 hours per year, a single event usually lasts up to 24 hours.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=1}}{{fv|date=October 2024}}
In Japan, on the other hand, ''dunkelflauten'' are seen in summer and winter. The former is caused by stationary fronts in early summer and autumn rainy seasons (called Baiu and Akisame, respectively),<ref>{{Cite journal|date=2021-12-08|title=Climatology of dark doldrums in Japan|url=https://www.sciencedirect.com/science/article/pii/S1364032121011928|journal=Renewable and Sustainable Energy Reviews|language=en|volume=155|article-number=111927|doi=10.1016/j.rser.2021.111927|last1=Ohba |first1=Masamichi |last2=Kanno |first2=Yuki |last3=Nohara |first3=Daisuke |s2cid=245067748 |url-access=subscription}}</ref> while the latter is caused by arrivals of south-coast cyclones.<ref>{{Cite journal |date=2023-01-21|title=Effects of meteorological and climatological factors on extremely high residual load and possible future changes |url=https://www.sciencedirect.com/science/article/pii/S1364032123000448|journal=Renewable and Sustainable Energy Reviews |language=en |volume=175 |article-number=113188 |doi=10.1016/j.rser.2023.113188 |last1=Ohba |first1=Masamichi |last2=Kanno |first2=Yuki |last3=Shigeru |first3=Bando |bibcode=2023RSERv.17513188O |url-access=subscription }}</ref>
== Renewable energy effects == These periods are a big issue in energy infrastructure if a significant amount of electricity is generated by [[variable renewable energy]] (VRE) sources, mainly solar and wind power.<ref>{{Cite web|title=What happens with German renewables in the dead of winter?|website=[[Deutsche Welle]] |url=https://www.dw.com/en/what-happens-with-german-renewables-in-the-dead-of-winter/a-37462540 |url-status=live |first=Tamsin |last=Walker |date=8 February 2017 |archive-url=https://web.archive.org/web/20170209102347/https://www.dw.com/en/what-happens-with-german-renewables-in-the-dead-of-winter/a-37462540 |access-date=2021-05-28|archive-date=9 February 2017 }}</ref><ref name="gap"/><ref>{{Cite journal|date=2023-01-21|title=Effects of meteorological and climatological factors on extremely high residual load and possible future changes|url=https://www.sciencedirect.com/science/article/pii/S1364032123000448|journal=Renewable and Sustainable Energy Reviews|language=en|volume=175|article-number=113188|doi=10.1016/j.rser.2023.113188|last1=Ohba |first1=Masamichi |last2=Kanno |first2=Yuki |last3=Shigeru |first3=Bando |bibcode=2023RSERv.17513188O |url-access=subscription}}</ref> ''Dunkelflauten'' can occur simultaneously over a very large region, but are less correlated between geographically distant regions, so multi-national power grid schemes can be helpful.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=9}} Events that last more than two days over most of Europe happen about once every five years.<ref>{{Cite web |date=2022-12-13 |title=Can Europe survive the dreaded dunkelflaute? |first=Tim |last=McDonnell |url=https://qz.com/can-europe-survive-the-dreaded-dunkelflaute-1849886529 |access-date=2023-02-01 |website=Quartz |language=en}}</ref> To ensure power during such periods flexible energy sources may be used, [[Interconnector|energy may be imported]], and [[Energy demand management|demand may be adjusted]].<ref>{{Cite report|title=Modelling 2050: Electricity System Analysis|url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/943714/Modelling-2050-Electricity-System-Analysis.pdf |date=December 2020 |access-date=12 December 2023 |publisher=[[Department for Business, Energy and Industrial Strategy]]}}</ref><ref name="push">{{Cite news |date=2022-12-13 |title=The dreaded Dunkelflaute is no reason to slow UK's energy push |work=Financial Times |url=https://www.ft.com/content/93d61f33-b1f9-4791-a9f8-37d826bd68af |access-date=2022-12-13}}</ref>
For alternative energy sources, countries use fossil fuels ([[coal]], [[oil]] and [[methane gas|natural gas]]), [[hydroelectricity]] or [[nuclear power]] and, less often, [[energy storage]] to prevent [[power outage]]s.<ref name="KosowskiDiercks2021">{{cite journal |last1=Kosowski |first1=Kai |last2=Diercks |first2=Frank |year=2021 |title=Quo Vadis, Grid Stability? |url=https://kernd.de/wp-content/uploads/2023/08/Article-atw-2021-2-Quo-vadis-Grid-Stability-Kosowski-Diercks.pdf |journal=Atw |volume=66 |issue=2 |pages=16–26 |issn=1431-5254}}</ref><ref>{{cite web|last=Ernst|first=Damien|title=Big infrastructures for fighting climate change|url=https://orbi.uliege.be/bitstream/2268/243620/1/Ernst-EIB.pdf| website=Université de Liège}}</ref><ref name="LiBasu2020">{{cite journal|last1=Li|first1=Bowen|last2=Basu|first2=Sukanta|last3=Watson|first3=Simon J.|last4=Russchenberg|first4=Herman W. J.|title=Mesoscale modeling of a "Dunkelflaute" event|journal=Wind Energy|volume=24|issue=1|year=2020|pages=5–23|issn=1095-4244|doi=10.1002/we.2554|doi-access=free}}</ref><ref name="AbbottCohen2020">{{cite journal|last1=Abbott|first1=Malcolm|last2=Cohen|first2=Bruce|title=Issues associated with the possible contribution of battery energy storage in ensuring a stable electricity system|journal=The Electricity Journal|volume=33|issue=6|year=2020|article-number=106771|issn=1040-6190|doi=10.1016/j.tej.2020.106771|bibcode=2020ElecJ..3306771A |s2cid=218966955 }}</ref> Long-term solutions include designing [[Electricity market|electricity markets]] to incentivise clean power which is available when needed.<ref name="push"/> A group of countries is following on from [[Mission Innovation]] to work together to solve the problem in a clean, low-carbon way by 2030, including looking into [[carbon capture and storage]] and the [[hydrogen economy]] as possible parts of the solution.<ref>{{Cite news |first=Roger |last=Harrabin |date=2021-06-02|title=Major project aims to clear clean energy hurdle|language=en-GB|work=BBC News|url=https://www.bbc.com/news/science-environment-57313991|access-date=2021-06-03}}</ref>
=== Droughts === By analogy with hydrological [[drought]]s, long used in planning for [[hydroelectricity]], the researchers of the future VRE-intensive power grids in the 2020s started using the term '''variable renewable energy drought''' ('''VRE drought''' or simply '''power drought''') that is nearly synonymous to the dunkelflaute.{{sfn|Kittel|Roth|Schill|2024|pp=1,5}}{{sfn|Sahoo|Timmann|2023|p=49691}} Unlike the dunkelflaute, the drought can be a series of isolated adverse events, the most severe effects are forecasted are of this series type, and the planning for [[resource adequacy]] thus should span multiple years.{{sfn|Kittel|Roth|Schill|2024|p=14}} Kittel et al. indicate the years 1996–1997 as particularly bad example of the VRE drought, they call for an additional EU-wide energy storage of 50 to 170 [[TWh]] (on top of current projections) to accommodate a series of events of this magnitude.{{sfn|Kittel|Roth|Schill|2024|pp=9,14}}
== See also == * [[Duck curve]] *[[Variable renewable energy]]
== References == {{reflist|30em}}
== Sources == * {{cite web|first1=Martin| last1= Kittel |first2= Alexander |last2=Roth |first3= Wolf-Peter|last3= Schill|title=Variable renewable energy droughts ("Dunkelflauten") and power sector implications |url=https://www.diw.de/documents/vortragsdokumente/220/diw_01.c.901323.de/v_2024_kittel_dunkelflauten_enerday.pdf|access-date=2024-12-14|date=2024|publisher=[[DIW Berlin]]}} * {{cite journal |first1=Martin| last1= Kittel |first2= Wolf-Peter|last2= Schill|arxiv=2402.06758|title=Measuring the Dunkelflaute: How (Not) to analyze variable renewable energy shortage| journal= Environmental Research: Energy |date=2024| volume= 1 | issue= 3 | page= 035007 | doi= 10.1088/2753-3751/ad6dfc | bibcode= 2024EREne...135007K }} * {{cite journal | last1 = Li | first1 = Bowen | last2 = Basu | first2 = Sukanta | last3 = Watson | first3 = Simon J. | last4 = Russchenberg | first4 = Herman W. J. | title = A Brief Climatology of Dunkelflaute Events over and Surrounding the North and Baltic Sea Areas | journal = Energies | date = 11 October 2021 | volume = 14 | issue = 20 | page = 6508 | eissn = 1996-1073 | doi = 10.3390/en14206508 | pmid = | url = https://pure.tudelft.nl/ws/portalfiles/portal/100313934/energies_14_06508.pdf| doi-access = free }} * {{cite journal|last1=Sahoo|first1=Subrat|last2=Timmann|first2=Pascal|title=Energy Storage Technologies for Modern Power Systems: A Detailed Analysis of Functionalities, Potentials, and Impacts|journal=IEEE Access|volume=11|date=2023|issn=2169-3536|doi=10.1109/ACCESS.2023.3274504|doi-access=free|pages=49689–49729|bibcode=2023IEEEA..1149689S |url=https://ieeexplore.ieee.org/ielx7/6287639/10005208/10121760.pdf|access-date=2024-12-14}} * {{cite report|last1=Somani|first1=Abhishek |last2=Barrett|first2=Emily|last3=Zhou|first3=Zhi|last4=Chan |first4=Gavin|last5=Middleton|first5=Luke|last6=Tarel|first6=Guillaume|last7=Campbell |first7=Allison|last8=Botterud|first8=Audun |last9=Bhatnagar|first9=Dhruv|last10=Beckitt|first10=Alex|last11=O'Reilley|first11=Christopher|last12=Zhu|first12=Yanyan|last13=Sun|first13=Xueqing|title=An Assessment of Resource Drought Events as Indicators for Long-Duration Energy Storage Needs|date=2024-05-01|doi=10.2172/2349123|doi-access=free|osti=2349123 }}
[[Category:Electric power generation]] [[Category:Anticyclones]]