Editing Distributed generation (section)

=== Energy storage ===
{{Main|Grid energy storage}}

A distributed energy resource is not limited to the generation of electricity but may also include a device to store distributed energy (DE).<ref name="smartgrid-gov-lexicon">http://www.smartgrid.gov [https://www.smartgrid.gov/lexicon/6/letter_d Lexicon Distributed Energy Resource] {{Webarchive|url=https://web.archive.org/web/20171206030230/https://www.smartgrid.gov/ |date=6 December 2017 }}</ref> Distributed energy storage systems (DESS) applications include several types of battery, [[Pumped-storage hydroelectricity|pumped hydro]], [[Compressed air energy storage|compressed air]], and [[thermal energy storage]].<ref name="nrel-storage" />{{rp|42}} Access to energy storage for commercial applications is easily accessible through programs such as [[energy storage as a service]] (ESaaS).

==== PV storage ====
: Common [[rechargeable battery]] technologies used in today's PV systems include, the [[valve regulated lead-acid battery]] ([[lead–acid battery]]), [[nickel–cadmium battery|nickel–cadmium]] and [[lithium-ion batteries]]. Compared to the other types, lead-acid batteries have a shorter lifetime and lower energy density. However, due to their high reliability, low [[self-discharge]] (4–6% per year) as well as low investment and maintenance costs, they are currently the predominant technology used in small-scale, residential PV systems, as lithium-ion batteries are still being developed and about 3.5 times as expensive as lead-acid batteries. Furthermore, as storage devices for PV systems are stationary, the lower energy and power density and therefore higher weight of lead-acid batteries are not as critical as for [[electric vehicle]]s.<ref name=ethz-harvard>{{cite web |publisher=ETH Zürich, Harvard University |url=https://www.researchgate.net/publication/264239770 |title=The Economic Viability of Battery Storage for Residential Solar Photovoltaic Systems – A Review and a Simulation Model |author1=Joern Hoppmann |author2=Jonas Volland |author3=Tobias S. Schmidt |author4=Volker H. Hoffmann |date=July 2014 }}</ref>{{rp|4,9}}

: However, lithium-ion batteries, such as the [[Tesla Powerwall]], have the potential to replace lead-acid batteries in the near future, as they are being intensively developed and lower prices are expected due to economies of scale provided by large production facilities such as the [[Gigafactory 1]]. In addition, the Li-ion batteries of plug-in [[electric car]]s may serve as future storage devices, since most vehicles are parked an average of 95 percent of the time, their batteries could be used to let electricity flow from the car to the power lines and back. Other rechargeable batteries that are considered for distributed PV systems include, [[Sodium–sulfur battery|sodium–sulfur]] and [[Vanadium redox battery|vanadium redox]] batteries, two prominent types of a [[Molten salt battery|molten salt]] and a [[Flow battery|flow]] battery, respectively.<ref name=ethz-harvard />{{rp|4}}

==== Vehicle-to-grid ====

: Future generations of electric vehicles may have the ability to deliver power from the battery in a [[vehicle-to-grid]] into the grid when needed.<ref>{{cite web|url=http://www.energydsm.com/distributed-generation|title=Energy VPN Blog|access-date=15 May 2015|archive-url=https://web.archive.org/web/20120412020042/http://www.energydsm.com/distributed-generation|archive-date=12 April 2012|url-status=dead}}</ref> An [[electric vehicle network]] has the potential to serve as a DESS.<ref name="nrel-storage">http://www.NREL.gov [http://www.nrel.gov/docs/fy10osti/47187.pdf – The Role of Energy Storage with Renewable Electricity Generation]</ref>{{rp|44}}

==== Flywheels ====

: An advanced [[flywheel energy storage]] (FES) stores the electricity generated from distributed resources in the form of angular [[kinetic energy]] by accelerating a rotor ([[flywheel]]) to a very high speed of about 20,000 to over 50,000 rpm in a vacuum enclosure. Flywheels can respond quickly as they store and feed back electricity into the grid in a matter of seconds.<ref name="ScienceNews">{{Cite journal
| last1 = Castelvecchi
| first1 = Davide
| title = Spinning into control: High-tech reincarnations of an ancient way of storing energy
| doi = 10.1002/scin.2007.5591712010
| journal = Science News
| volume = 171
| issue = 20
| pages = 312–313
| date = 19 May 2007
| url = http://sciencewriter.org/flywheels-spinning-into-control/
| access-date = 12 September 2014
| archive-date = 6 June 2014
| archive-url = https://web.archive.org/web/20140606223717/http://sciencewriter.org/flywheels-spinning-into-control/
| url-status = dead
| url-access = subscription
}}</ref><ref>{{cite web
 |last1=Willis
 |first1=Ben
 |title=Canada's first grid storage system launches in Ontario
 |url=http://storage.pv-tech.org/news/canadas-first-grid-storage-system-launches-in-ontario
 |website=storage.pv-tech.org/
 |publisher=pv-tech.org
 |access-date=12 September 2014
 |archive-url=https://web.archive.org/web/20140831005958/http://storage.pv-tech.org/news/canadas-first-grid-storage-system-launches-in-ontario
 |archive-date=31 August 2014
 |date=23 July 2014
 |url-status=dead
}}</ref>