View source for Duck curve

{{Short description|Graph showing the timing imbalance between peak demand and renewable electricity production}}
{{use dmy dates|date=December 2023}}
[[File:Duck Curve CA-ISO 2016-10-22.agr.png|thumb|upright=1.4|{{center|The Duck Curve}}<span style="color:blue;">'''Blue curve:'''</span> Demand for electrical power<br/><span style="color:orange;">'''Orange curve:'''</span> (the duck curve) supply of electrical power from [[dispatchable generation|dispatchable]] sources,<br/><span style="color:gray;">'''Gray curve:'''</span> supply of solar electrical power<br/>Data is for the State of California on October 22, 2016 (a Saturday),<ref name=":0">{{cite web|url=https://www.caiso.com/market/Pages/ReportsBulletins/DailyRenewablesWatch.aspx|title=California ISO - Renewables Reporting|website=www.caiso.com}}</ref> a day when the wind power output was low and steady throughout the day. <br/>The orange curve rises steeply from 17:00 to 18:00 as the sun sets, requiring about 5 gigawatt of generating capacity from dispatchable sources to come on line within one hour.]]

The '''duck curve''' is a graph of power production over the course of a day that shows the timing imbalance between [[peak demand]] and [[solar power]] generation. The graph resembles a sitting duck, and thus the term was created.<ref name="Azemena 2022 2747–2756">{{Cite journal |last=Azemena |first=Henri Joël |last2=Ayadi |first2=Ali |last3=Samet |first3=Ahmed |date=2022 |title=Explainable Artificial Intelligent as a solution approach to the Duck Curve problem |url=https://linkinghub.elsevier.com/retrieve/pii/S1877050922012224 |journal=Procedia Computer Science |language=en |volume=207 |pages=2747–2756 |doi=10.1016/j.procs.2022.09.333|doi-access=free }}</ref> Used in utility-scale [[electricity generation]], the term was coined in 2012 by the [[California Independent System Operator]].<ref>{{cite news|url=https://www.vox.com/energy-and-environment/2018/3/20/17128478/solar-duck-curve-nrel-researcher|title=Solar power's greatest challenge was discovered 10 years ago. It looks like a duck|last1=Roberts|first1=David|date=20 March 2018|work=[[Vox (website)|Vox]]|accessdate=20 March 2018}}</ref><ref>{{cite web |last1=Staple |first1=Gregory |title=California's Grid Geeks: Flattening the 'duck curve' |url=https://www.greenbiz.com/article/californias-grid-geeks-flattening-duck-curve |website=Green Biz |access-date=9 May 2021}}</ref>

== Solar power ==
In some energy markets, daily peak demand occurs after sunset, when [[solar power]] is no longer available. In locations where a substantial amount of solar electric capacity has been installed, the amount of power that must be generated from sources other than solar or wind displays a rapid increase around sunset and peaks in the mid-evening hours, producing a graph  that resembles the silhouette of a [[duck]].<ref name=":1">Paul Denholm, Matthew O'Connell, Gregory Brinkman, and Jennie Jorgenson. "[https://www.nrel.gov/docs/fy16osti/65023.pdf Overgeneration from Solar Energy in California: A Field Guide to the Duck Chart]" NREL/TP-6A20-65023. ''[[National Renewable Energy Laboratory]]'',  November 2015</ref><ref name=":2">{{cite web|url= http://insideenergy.org/2014/10/02/ie-questions-why-is-california-trying-to-behead-the-duck/ |title=IE Questions: Why Is California Trying To Behead The Duck? |first=Jordan |last=Wirfs-Brock |date=2 October 2014|work=Inside Energy  |accessdate= 29 October 2016}}</ref> [[Solar power in Hawaii|In Hawaii]], significant adoption of solar generation has led to the more pronounced curve known as the Nessie curve.<ref name=":3">{{cite web |url=http://theenergycollective.com/jeffstjohn/2188461/charting-hawaiis-spectacular-solar-growth |title=Charting Hawaii's Spectacular Solar Growth |accessdate=2015-02-04 |work=The Energy Collective |archive-date=3 July 2018 |archive-url=https://web.archive.org/web/20180703162327/http://theenergycollective.com/jeffstjohn/2188461/charting-hawaiis-spectacular-solar-growth |url-status=dead }}</ref><ref>{{cite web|url= https://www.greentechmedia.com/articles/read/hawaiis-solar-grid-landscape-and-the-nessie-curve |title=Hawaii's Solar-Grid Landscape and the 'Nessie Curve'|date=10 February 2014  |accessdate=10 January 2017}}</ref>

Without any form of [[energy storage]], after times of high solar generation, power companies must rapidly increase other forms of power generation around the time of sunset to compensate for the loss of solar generation, a major concern for grid operators where there is rapid [[growth of photovoltaics]].<ref name=":4">{{cite web|title=What the Duck Curve Tells Us About Managing A Green Grid|url= https://www.caiso.com/Documents/FlexibleResourcesHelpRenewables_FastFacts.pdf |website=caiso.com |publisher=California ISO|accessdate=29 April 2015}}</ref> Storage such as dammed hydropower can fix these issues if it can be implemented.<ref>{{Cite web |last=Wallach |first=Omri |date=2022-04-04 |title=The Solar Power Duck Curve Explained |url=https://elements.visualcapitalist.com/the-solar-power-duck-curve-explained/ |access-date=2022-12-28 |website=Elements by Visual Capitalist |language=en-US}}</ref> Short term use batteries, at a large enough scale of use, can help to flatten the duck curve and prevent generator use fluctuation and can help to maintain voltage profile.<ref name=ducks2fly>{{cite web|last1=Lazar|first1=Jim |title=Teaching the "Duck" to Fly|url=http://www.ripuc.ri.gov/eventsactions/docket/4443-EERMC-Presentation2_5-8-14.pdf |publisher=RAP|accessdate=29 April 2015}}</ref>

===Mitigation strategies===
Methods for coping with the rapid increase in demand at sunset reflected in the duck curve, which becomes more serious as the penetration of solar generation grows, include:<ref name=ducks2fly />
*Installing more [[dispatchable generation]]
*Orienting some solar collectors toward the west to maximize generation near sunset.<ref name=vorrath2020-08>{{cite web |last1=Vorrath |first1=Sophie |title=Solar tariffs reshaped to favour batteries, EVs, and west-facing panels |url=https://reneweconomy.com.au/solar-tariffs-reshaped-to-favour-batteries-evs-and-west-facing-panels-85015/ |website=RenewEconomy |language=en-AU |date=30 August 2020 |quote=even out the "solar duck curve". . install batteries and west-facing panels, which helps stretch solar generation into the afternoon-evening peak. }}</ref> 
*Energy storage<ref name=vorrath2020-08/> including:
**[[Pumped-storage hydroelectricity]]
**[[Battery storage power station]]s These can be colocated with solar power plants that are designed with DC capacity above their AC rating,<ref>{{cite web |url=https://qz.com/1950381/the-case-for-producing-way-more-solar-energy-than-we-need/ |title=It's time to start wasting solar energy |access-date=31 December 2020}}</ref> or at other suitable sites, including old fossil fuel plants so as to utilize their existing transmission infrastructure (e.g. the [[Moss Landing Power Plant]]).
**[[Solar thermal energy]] with [[thermal energy storage]]
**[[Ice storage air conditioning]]
**Use of batteries in electric vehicles for temporary storage ([[vehicle-to-grid]])<ref>{{cite web |last1=Pyper |first1=Julia |title=Electric Ridesharing Benefits the Grid, and EVgo Has the Data to Prove It |url=https://www.greentechmedia.com/articles/read/electric-ridesharing-benefit-the-grid-evgo |website=www.greentechmedia.com |archiveurl=https://web.archive.org/web/20201018043438/https://www.greentechmedia.com/articles/read/electric-ridesharing-benefit-the-grid-evgo |archivedate=18 October 2020 |date=9 May 2019 |quote=By charging up in the middle of the day, LDV fleets on EVgo's network also help to address the duck curve — where midday net load drops, driven by lots of solar flooding onto the grid |url-status=live}}</ref>
**[[Power-to-X]], storing surplus electricity production in chemical form, e.g. hydrogen
**[[Green hydrogen]] production from water during the peak hours of Solar production
*[[Energy demand management]], including:
**[[Time-of-use pricing]] (TOU) and [[real-time pricing]]
**[[Smart grid]] technology
**[[Electric power transmission]] from the west where the sun is shining to the east where the sun is low or set

A major challenge is deploying mitigating capacity at a rate that keeps up with the growth of solar energy production. The effects of the duck curve have happened faster than anticipated.<ref>{{cite web|url= https://www.greentechmedia.com/articles/read/the-california-duck-curve-is-real-and-bigger-than-expected |title=The California Duck Curve Is Real, and Bigger Than Expected|date=3 November 2016 |accessdate=10 January 2017}}</ref>

====Duck curve in California====
[[File:California average hourly electricity generation from natural gas, solar energy, and all other sources in selected months of 2020 (50705225643).png|thumb|upright=1.4|Sources of electricity generation in California in 2020. Because these graphs do not display energy demand, they are not Duck Curves themselves, but demonstrate daily and seasonal variation in power production. {{legend|05496c|Natural gas}} {{legend|be9203|Solar power}}]]
The California Independent System Operator (CAISO) has been monitoring and analyzing the Duck Curve and its future expectations for about a half a century now and their biggest finding is the growing gap between morning and evening hours prices relative to midday hours prices.<ref name=":0" /> According to their 2016 study, the U.S. Energy Information Administration, found that the wholesale energy market prices over the past six months during the 5&nbsp;pm to 8&nbsp;pm period (the "neck" of the duck) have increased to $60 per megawatt-hour, compared to about $35 per megawatt-hour in the same time frame in 2016.<ref name=":1" /> However, on the other side they have measured a drastic decrease in the midday prices, nearing $15 per megawatt-hour.<ref name=":1" />{{update inline|date=January 2022|reason=prices have changed since 2016}} These high peaks and deep valleys are only showing continued trends of going further apart making this Duck Curve even more prevalent as [[renewable energy]] production continues to grow.<ref name=":2" /><ref name="Azemena 2022 2747–2756"/><ref name="caiso2021a">{{cite web |title=2021 Summer Loads and Resources Assessment |url=http://www.caiso.com/Documents/2021-Summer-Loads-and-Resources-Assessment.pdf#search=Duck%20curve |publisher=California ISO |page=36 |date=23 May 2021 |quote=The growing amount of photovoltaic solar generation that is interconnected to the ISO grid continues to change the ISO’s net load profile and creates more challenges and uncertainty for ISO operations. The result is a constantly increasing ramping requirement, significantly more than what has been required from the generat ion fleet in the past, both upward and downward. Furthermore, solar generation does not provide significant power at the hours ending 19:00 to 21:00, which leads to reliance on gas and other non-solar generation after sunset. The continuing decline in dispatchable generation in the ISO as dispatchable units retire is beginning to challenge the ISO system’s ability to meet net peak demand after sunset and flexible capacity requirements. |url-status=live|archive-url=https://web.archive.org/web/20210512184733/http://www.caiso.com/Documents/2021-Summer-Loads-and-Resources-Assessment.pdf |archive-date=12 May 2021 }}</ref>

A crucial part of this curve comes from the '''net load''' ("the difference between expected load and anticipated electricity production from the range of renewable energy sources").<ref name=":1" /> In certain times of the year (namely Spring and Summer), the curves create a "belly" appearance in the midday that then drastically increases portraying an "arch" similar to the neck of a duck, consequently the name "The Duck Chart.<ref>{{Cite news|url=https://www.greentechmedia.com/articles/read/eia-charts-californias-real-and-growing-duck-curve |title=EIA Data Reveals California's Real and Growing Duck Curve|access-date=2017-12-01}}</ref>" This "neck" represents a ramp speed of between 10 and 17 GW in 3 hours (afternoon) in 2020 which has to be supplied by flexible generation.<ref name="caiso2021b">{{cite web |title=Final Flexible Capacity Needs Assessment for 2022 |url=http://www.caiso.com/InitiativeDocuments/Final2022FlexibleCapacityNeedsAssessment.pdf#search=Duck |publisher=California ISO |pages=9–10 |date=14 May 2021 |url-status=live|archive-url=https://web.archive.org/web/20220107005315/http://www.caiso.com/InitiativeDocuments/Final2022FlexibleCapacityNeedsAssessment.pdf |archive-date=7 January 2022 }}</ref> During the midday, large amounts of solar energy are created, which partially contributes to lower demand for additional electricity.<ref>{{Cite news|url=https://www.economist.com/news/briefing/21717365-wind-and-solar-energy-are-disrupting-century-old-model-providing-electricity-what-will |title=A world turned upside down|newspaper=The Economist|access-date=2017-12-01|language=en}}</ref> [[Curtailment (electricity)|Curtailment]] impacts the curve.<ref name="caiso2021b"/> Increasing battery storage can mitigate the issues of solar abundance during the day. When excess solar energy is stored during the day and used in the evening, the price disparity between inexpensive midday and expensive evening energy can be reduced. Enough total solar technology exists to power the world, but there is a current lack of infrastructure to store solar energy for later use.<ref name=":4" /> An oversupply of energy during low demand coupled with a lack of supply during high demand explains the large disparity between midday and evening energy prices. {{as of|2022}}, up to 6 GWh is shifted per day from low price to high price periods.<ref>{{cite web |last1=Murray |first1=Cameron |title=Battery storage load shifting up to 6GWh a day on CAISO grid; operator eyes SoC-linked prices |url=https://www.energy-storage.news/battery-storage-load-shifting-up-to-6gwh-a-day-on-caiso-grid-operator-eyes-soc-linked-prices/ |website=Energy Storage News |archive-url= https://web.archive.org/web/20220429203519/https://www.energy-storage.news/battery-storage-load-shifting-up-to-6gwh-a-day-on-caiso-grid-operator-eyes-soc-linked-prices/ |archive-date=29 April 2022 |date=13 April 2022 |url-status=live}}</ref>

== See also ==
* [[Dunkelflaute]]

==References==

{{reflist}}

==External links==
* [http://large.stanford.edu/courses/2015/ph240/burnett2/ Energy Storage and the California "Duck Curve"]

[[Category:Economics curves]]
[[Category:Electric power generation]]
[[Category:Solar energy]]