Distributed generation: Difference between revisions

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Conventional [[power station]]s, such as [[coal]]-fired, [[combined cycle|gas]], and [[nuclear power]]ed plants, as well as [[hydroelectric]] dams and large-scale [[photovoltaic power station|solar power station]]s, are centralized and often require electric energy to be [[Electric power transmission|transmitted]] over long distances. By contrast, DER systems are decentralized, modular, and more flexible technologies that are located close to the load they serve, albeit having capacities of only 10 [[megawatt]]s (MW) or less. These systems can comprise multiple generation and storage components; in this instance, they are referred to as [[hybrid power]] systems.<ref>{{cite web|url=https://www.atulhost.com/empowering-the-future-with-distributed-energy-resources|title=Empowering the future with distributed energy resources|year=2023}}</ref>

DER systems typically use [[renewable energy]] sources, including [[small hydro]], [[biomass]], [[biogas]], [[solar power]], [[wind power]], and [[geothermal power]], and increasingly play an important role for the [[electric power distribution]] system. A grid-connected device for [[Grid energy storage|electricity storage]] can also be classified as a DER system and is often called a '''distributed energy storage system''' ('''DESS''').<ref>{{cite journal |last1=Nadeem |first1=Talha Bin |last2=Siddiqui |first2=Mubashir |last3=Khalid |first3=Muhammad |last4=Asif |first4=Muhammad |title=Distributed energy systems: A review of classification, technologies, applications, and policies |journal=Energy Strategy Reviews |date=2023 |volume=48 |pagesarticle-number=101096 |doi=10.1016/j.esr.2023.101096 |doi-access=free|bibcode=2023EneSR..4801096N }}</ref> By means of an interface, DER systems can be managed and coordinated within a [[smart grid]]. Distributed generation and storage enables the collection of energy from many sources and may lower environmental impacts{{Citation needed|date=November 2024|reason=small diesel generators can be very polluting}} and improve the security of supply.<ref>{{Cite news |last=Koshiw |first=Isobel |date=2024-04-08 |title=Russia changes tack on targeting Ukraine's energy plants |url=https://www.ft.com/content/18882abd-6277-4aae-bc43-f3e5fa786445 |access-date=2024-11-29 |work=Financial Times|___location=London}}</ref>

One of the major issues with the integration of the DER such as solar power, wind power, etc. is the uncertain nature of such electricity resources. This uncertainty can cause a few problems in the distribution system: (i) it makes the supply-demand relationships extremely complex, and requires complicated optimization tools to balance the network, and (ii) it puts higher pressure on the transmission network,<ref>{{Cite journal|last1=Mohammadi Fathabad|first1=Abolhassan|last2=Cheng|first2=Jianqiang|last3=Pan|first3=Kai|last4=Qiu|first4=Feng|date=2020|title=Data-driven Planning for Renewable Distributed Generation in Distribution Systems|url=https://ieeexplore.ieee.org/document/9112707|journal=IEEE Transactions on Power Systems|volume=35|issue=6|pages=4357–4368|doi=10.1109/TPWRS.2020.3001235|s2cid=225734643|issn=1558-0679|hdl=10397/89857|hdl-access=free|url-access=subscription}}</ref> and (iii) it may cause reverse power flow from the distribution system to transmission system.<ref>{{Cite journal|last1=De Carne|first1=Giovanni|last2=Buticchi|first2=Giampaolo|last3=Zou|first3=Zhixiang|last4=Liserre|first4=Marco|date=July 2018|title=Reverse Power Flow Control in a ST-Fed Distribution Grid|journal=IEEE Transactions on Smart Grid|volume=9|issue=4|pages=3811–3819|doi=10.1109/TSG.2017.2651147|bibcode=2018ITSG....9.3811D |s2cid=49354817|issn=1949-3061|url=https://nbn-resolving.org/urn:nbn:de:gbv:8-publ-14890}}</ref>

[[Microgrid]]s are modern, localized, small-scale grids,<ref>{{Cite book|last1=Saleh|first1=M.|last2=Esa|first2=Y.|last3=Mhandi|first3=Y.|last4=Brandauer|first4=W.|last5=Mohamed|first5=A.|title=2016 IEEE Industry Applications Society Annual Meeting |chapter=Design and implementation of CCNY DC microgrid testbed |date=October 2016|pages=1–7|doi=10.1109/IAS.2016.7731870|isbn=978-1-4799-8397-1|s2cid=16464909|chapter-url=https://academicworks.cuny.edu/cgi/viewcontent.cgi?article=1722&context=cc_pubs}}</ref><ref>{{Cite book|last1=Saleh|first1=M. S.|last2=Althaibani|first2=A.|last3=Esa|first3=Y.|last4=Mhandi|first4=Y.|last5=Mohamed|first5=A. A.|title=2015 International Conference on Smart Grid and Clean Energy Technologies (ICSGCE) |chapter=Impact of clustering microgrids on their stability and resilience during blackouts |date=October 2015|pages=195–200|doi=10.1109/ICSGCE.2015.7454295|isbn=978-1-4673-8732-3|s2cid=25664994|chapter-url=https://academicworks.cuny.edu/cgi/viewcontent.cgi?article=1623&context=cc_pubs}}</ref> contrary to the traditional, centralized [[electricity grid]] (macrogrid). Microgrids can disconnect from the centralized grid and operate autonomously, strengthen grid resilience, and help mitigate grid disturbances. They are typically low-voltage AC grids, often use [[diesel generator]]s, and are installed by the community they serve. Microgrids increasingly employ a mixture of different distributed energy resources, such as [[solar hybrid power systems]], which significantly reduce the amount of carbon emitted.

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{{ISBN|1-118-02901-1}}, pages v-x</ref> As a result, [[smart grid]] functions, [[virtual power plant]]s<ref>[https://www.researchgate.net/publication/270821401_Decision_Making_Tool_for_Virtual_Power_Plants_Considering_Midterm_Bilateral_Contracts/ Decision Making Tool for Virtual Power Plants Considering Midterm Bilateral Contracts]</ref><ref>[https://www.researchgate.net/publication/279849005_The_Design_of_a_Risk-hedging_Tool_for_Virtual_Power_Plants_via_Robust_Optimization_Approach/ The Design of a Risk-hedging Tool for Virtual Power Plants via Robust Optimization Approach]</ref><ref>[https://www.researchgate.net/publication/296307377_A_Medium-Term_Coalition-Forming_Model_of_Heterogeneous_DERs_for_a_Commercial_Virtual_Power_Plant/ A Medium-Term Coalition-Forming Model of Heterogeneous DERs for a Commercial Virtual Power Plant]</ref> and [[grid energy storage]] such as [[power to gas]] stations are added to the grid. Conflicts occur between utilities and resource managing organizations.<ref>{{cite web |last1=Bandyk |first1=Matthew |title=Propelling the transition: The battle for control of virtual power plants is just beginning |url=https://www.utilitydive.com/news/propelling-the-transition-the-battle-for-control-of-virtual-power-plants-i/581875/ |website=Utility Dive |archive-url=https://web.archive.org/web/20200819022737/https://www.utilitydive.com/news/propelling-the-transition-the-battle-for-control-of-virtual-power-plants-i/581875/ |archive-date=19 August 2020 |date=18 August 2020 |url-status=live}}</ref>

Each distributed generation resource has its own integration issues. Solar PV and wind power both have intermittent and unpredictable generation, so they create many stability issues for voltage and frequency. These voltage issues affect mechanical grid equipment, such as load tap changers, which respond too often and wear out much more quickly than utilities anticipated.<ref>{{cite journal|last1=Agalgaonkar|first1=Y.P. |display-authors=etal |title=Distribution Voltage Control Considering the Impact of PV Generation on Tap Changers and Autonomous Regulators|journal=IEEE Transactions on Power Systems|date=16 September 2013|volume=29|issue=1|pages=182–192|doi=10.1109/TPWRS.2013.2279721|hdl=10044/1/12201 |s2cid=16686085 |hdl-access=free}}</ref> Also, without any form of energy storage during times of high solar generation, companies must rapidly increase generation around the time of sunset to compensate for the loss of solar generation. This high ramp rate produces what the industry terms the ''[[duck curve]]'' that is a major concern for grid operators in the future.<ref>{{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|access-date=29 April 2015}}</ref> Storage can fix these issues if it can be implemented. Flywheels have shown to provide excellent frequency regulation.<ref>{{cite book|last1=Lazarewicz|first1=Matthew |last2=Rojas|first2=Alex |title=IEEE Power Engineering Society General Meeting, 2004 |chapter=Grid frequency regulation by recycling electrical energy in flywheels |journal=Power Engineering Society General Meeting|volume=2|date=10 June 2004|pages=2038–2042 |doi=10.1109/PES.2004.1373235|isbn=0-7803-8465-2|s2cid=20032334 }}</ref> Also, flywheels are highly cyclable compared to batteries, meaning they maintain the same energy and power after a significant amount of cycles( on the order of 10,000 cycles).<ref>{{cite web |title=Flywheels |url=http://energystorage.org/energy-storage/technologies/flywheels |publisher=Energy Storage Association |access-date= |archive-date=21 November 2017 |archive-url=https://web.archive.org/web/20171121013319/http://energystorage.org/energy-storage/technologies/flywheels |url-status=dead }}</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>{{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|access-date=29 April 2015}}</ref> However, cost is a major limiting factor for energy storage as each technique is prohibitively expensive to produce at scale and comparatively not energy dense compared to liquid fossil fuels.

Finally, another method of aiding in integration is in the use of [[intelligent hybrid inverter|intelligent inverter]]s that have the capability to also store the energy when there is more energy production than consumption.<ref>{{cite web|title=Smart Grid, Smart Inverters for a Smart Energy Future|url=https://www.nrel.gov/state-local-tribal/blog/posts/smart-grid-smart-inverters-for-a-smart-energy-future.html |publisher=National Renewable Energy Labortatory }}</ref>

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{{Main|Microgrid}}

A ''microgrid'' is a localized grouping of electricity generation, energy storage, and loads that normally operates connected to a traditional centralized grid ([[electrical grid|macrogrid]]). This single [[point of common coupling]] with the macrogrid can be disconnected. The microgrid can then function autonomously.<ref>Stan Mark Kaplan, Fred Sissine, (ed.) ''Smart grid: modernizing electric power transmission and distribution...'' The Capitol Net Inc, 2009, {{ISBN|1-58733-162-4}}, page 217</ref> Generation and loads in a microgrid are usually interconnected at low voltage and it can operate in DC, AC, or the combination of both. From the point of view of the grid operator, a connected microgrid can be controlled as if it were one entity.

Microgrid generation resources can include stationary batteries, fuel cells, solar, wind, or other energy sources. The multiple dispersed generation sources and ability to isolate the microgrid from a larger network would provide highly reliable electric power. Produced heat from generation sources such as microturbines could be used for local process heating or space heating, allowing flexible trade off between the needs for heat and electric power.