Intermittent energy source: Difference between revisions

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[[File:Abengoa Solar (7336087392).jpg|thumbnail| Construction of the Salt Tanks which provide efficient [[thermal energy storage]]<ref>Wright, matthew; Hearps, Patrick; et al. [http://media.bze.org.au/ZCA2020_Stationary_Energy_Report_v1.pdf Australian Sustainable Energy: Zero Carbon Australia Stationary Energy Plan], Energy Research Institute, [[University of Melbourne]], October 2010, p. 33. Retrieved from BeyondZeroEmissions.org website.</ref> so that output can be provided after the sun goes down, and output can be scheduled to meet demand requirements.<ref>[http://www.renewableenergyfocus.com/view/3272/innovation-in-concentrating-thermal-solar-power-csp/ Innovation in Concentrating Thermal Solar Power (CSP)], RenewableEnergyFocus.com website.</ref> The 280&nbsp;MW [[Solana Generating Station]] is designed to provide six hours of energy storage. This allows the plant to generate about 38 percent of its rated capacity over the course of a year.<ref>[http://blogs.phoenixnewtimes.com/valleyfever/2013/10/solana_10_facts_you_didnt_know.php Solana: 10 Facts You Didn't Know About the Concentrated Solar Power Plant Near Gila Bend]</ref>]]

An '''intermittent energy source''' is any source of [[energy]] that is not continuously available for conversion into [[electricity]] and outside direct control because the used [[primary energy]] cannot be stored. Intermittent energy sources may be predictable but cannot be [[dispatchable generation|dispatched]] to meet the demand of an electric power system.

The use of intermittent sources in an electric power system usually displaces storable primary energy that would otherwise be consumed by other [[power station]]s. Another option is to store electricity generated by non-dispatchable energy sources for later use when needed, e.g. in the form of [[pumped storage]], [[Compressed_air_energy_storageCompressed air energy storage|compressed air]] or in [[Battery (electricity)|batteries]]. A third option is the [[sector coupling]] e.g. by electrode heating for district heating schemes.

The use of small amounts of intermittent power has little effect on [[Electrical grid|grid]] operations. Using larger amounts of intermittent power may require upgrades or even a redesign of the grid infrastructure.<ref name='All_Island_Grid_Overview'>{{cite web |url=http://www.dcenr.gov.ie/NR/rdonlyres/E20F6E3D-8724-4E39-B315-0670B8C9841E/0/AllIslandGridStudyStudyOverviewJan08a2.pdf |title=All Island Grid Study |accessdate=2008-10-15 |date=January 2008 |pages=3–5, 15 |format=PDF |work=Department of Communications, Energy and Natural Resources |deadurl=yes |archiveurl=https://web.archive.org/web/20090318231419/http://www.dcenr.gov.ie/NR/rdonlyres/E20F6E3D-8724-4E39-B315-0670B8C9841E/0/AllIslandGridStudyStudyOverviewJan08a2.pdf |archivedate=2009-03-18 |df= }}</ref><ref name='CarbonDTI'>{{cite web|url=http://www.ensg.gov.uk/assets/ct_impact_of_re_final_report.pdf |archive-url=http://webarchive.nationalarchives.gov.uk/20100919181607/http://www.ensg.gov.uk/assets/ct_impact_of_re_final_report.pdf |dead-url=yes |archive-date=2010-09-19 |title=The Carbon Trust & DTI Renewables Network Impacts Study |accessdate=2009-04-22 |date = January 2004 |orig-year=commissioned June 2003 |format=PDF |work=Carbon Trust and UK Department of Trade and Industry }}</ref>

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===Complementary power sources and matching demand===

In the past electrical generation was mostly dispatchable and consumer demand led how much and when to dispatch power. The trend in adding intermittent sources such as wind, solar, and run-of-river hydro means the grid is beginning to be led by the intermittent supply. The use of intermittent sources relies on electric power grids that are carefully managed, for instance using highly dispatchable generation that is able to shut itself down whenever an intermittent source starts to generate power, and to successfully startup without warning when the intermittents stop generating.<ref>US Department of Energy: [https://www.energy.gov/sites/prod/files/2017/01/f34/Maintaining%20Reliability%20in%20the%20Modern%20Power%20System.pdf Maintaining Reliability in the Modern Power System], December 2016, p. 17</ref> Ideally the capacity of the intermittents would grow to be larger than consumer demand for periods of time, creating excess low price electricity to displace heating fuels or be converted to [[Energy storage|mechanical or chemical storage]] for later use.

The displaced dispatchable generation could be coal, natural gas, biomass, nuclear, geothermal or storage hydro. Rather than starting and stopping nuclear or geothermal it is cheaper to use them as constant [[base load]] power. Any power generated in excess of demand can displace heating fuels, be converted to storage or sold to another grid. Biofuels and conventional hydro can be saved for later when intermittents are not generating power. [[Fossil fuel phase-out|Alternatives to burning]] coal and natural gas which produce fewer [[greenhouse gas]]es may eventually make fossil fuels a [[stranded asset]] that is left in the ground. Highly integrated grids favor flexibility and performance over cost, resulting in more plants that operate for fewer hours and lower [[capacity factor]]s.<ref>Michael G. Richard: [https://www.treehugger.com/renewable-energy/death-capacity-factor-how-wind-solar-ultimately-win-game.html Death by 'capacity factor': Is this how wind and solar ultimately win the game?], 2015-10-06</ref>

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==Penetration==

Penetration refers to the proportion of ana [[primary energy]] (PE) source in an electric power system, expressed as a percentage.<ref name="ieawind.org"/> There are several methods of calculation yielding different penetrations. The penetration can be calculated either as:<ref name="ukerc2006tpa"/>

# the nominal capacity (installed power) of a PE source divided by the peak load within an electric power system; or