Dunkelflaute

Unlike a typical anticyclone, dunkelflauten are associated not with clear skies, but with very dense cloud cover (0.7–0.9), consisting of stratus, stratocumulus, and fog.{{sfn|Li|Basu|Watson|Russchenberg|2021|p=7}} {{As of|2022}} there is no agreed quantitative definition of dunkelflaute.{{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}} Li et al. define it as wind and solar both below 20% of capacity during a particular 60-minute period. 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 or 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),{{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|pages=111927|doi=10.1016/j.rser.2021.111927|last1=Ohba |first1=Masamichi |last2=Kanno |first2=Yuki |last3=Nohara |first3=Daisuke |s2cid=245067748 }} while the latter is caused by arrivals of south-coast cyclones.{{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 |pages=113188 |doi=10.1016/j.rser.2023.113188 |last1=Ohba |first1=Masamichi |last2=Kanno |first2=Yuki |last3=Shigeru |first3=Bando }}

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.{{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 }}{{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|pages=113188|doi=10.1016/j.rser.2023.113188|last1=Ohba |first1=Masamichi |last2=Kanno |first2=Yuki |last3=Shigeru |first3=Bando }} 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.{{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}} To ensure power during such periods flexible energy sources may be used, energy may be imported, and demand may be adjusted.{{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}}{{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}}

For alternative energy sources, countries use fossil fuels (coal, oil and natural gas), hydroelectricity or nuclear power and, less often, energy storage to prevent power outages.{{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}}{{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}}{{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}}{{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|pages=106771|issn=1040-6190|doi=10.1016/j.tej.2020.106771|s2cid=218966955 }} Long-term solutions include designing electricity markets to incentivise clean power which is available when needed. 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.{{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}}

By analogy with hydrological droughts, 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}}

• Duck curve
• Variable renewable energy

{{reflist|30em}}

• {{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|ref=|access-date=2024-12-14|date=2024|publisher=DIW Berlin}}
• {{cite arXiv |first1=Martin| last1= Kittel |first2= Wolf-Peter|last2= Schill|arxiv=2402.06758|title=Measuring the Dunkelflaute: How (not) to analyze variable renewable energy shortage|date=2024}}
• {{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|last=Sahoo|first=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|url=https://ieeexplore.ieee.org/ielx7/6287639/10005208/10121760.pdf|access-date=2024-12-14}}
• {{cite report|last=Somani|first=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|url=https://www.osti.gov/biblio/2349123|access-date=2024-12-14}}

Category:Electric power generation

Category:Anticyclones