Editing Distributed generation (section)

== Technologies ==

Distributed energy resource ('''DER''') systems are small-scale power generation or storage technologies (typically in the range of 1&nbsp;kW to 10,000&nbsp;kW)<ref name=nrel-using-der>{{cite web
 |title=Using Distributed Energy Resources
 |url=http://www.nrel.gov/docs/fy02osti/31570.pdf
 |website=nrel.gov
 |publisher=NREL
 |access-date=8 September 2014
 |archive-url=https://web.archive.org/web/20140908085049/http://www.nrel.gov/docs/fy02osti/31570.pdf
 |archive-date=8 September 2014
 |page=1
 |year=2002
 |url-status=dead
}}</ref> used to provide an alternative to or an enhancement of the traditional electric power system. DER systems typically are characterized by high initial [[capital cost]]s per kilowatt.<ref>http://www.NREL.gov [http://www.nrel.gov/docs/fy02osti/32459.pdf Distributed Energy Resources Interconnection Systems: Technology Review and Research Needs], 2002</ref> DER systems also serve as storage device and are often called ''Distributed energy storage systems'' (DESS).<ref name="smartgrid-gov-lexicon" />

DER systems may include the following devices/technologies:
* [[Combined heat power]] (CHP),<ref>{{Cite journal|last1=Du|first1=R.|last2=Robertson|first2=P.|date=2017|title=Cost Effective Grid-Connected Inverter for a Micro Combined Heat and Power System|journal=IEEE Transactions on Industrial Electronics|volume=64|issue=7|pages=5360–5367|doi=10.1109/TIE.2017.2677340|s2cid=1042325|issn=0278-0046|url=https://www.repository.cam.ac.uk/handle/1810/263361}}</ref> also known as ''cogeneration'' or ''trigeneration''
* [[Fuel cells]]
* [[Hybrid renewable energy system|Hybrid power systems]] ([[Solar hybrid power systems|solar hybrid]] and [[Wind hybrid power systems|wind hybrid]] systems)
* [[MicroCHP|Micro combined heat and power]] (MicroCHP)
* [[Microturbines]]
* [[Photovoltaic system]]s (typically [[rooftop solar PV]])
* [[Reciprocating engines]]
* Small wind power systems
* [[Stirling engine]]s
* or a combination of the above. For example, hybrid [[photovoltaic]], CHP and [[Battery (electricity)|battery]] systems can provide full electric power for single family residences without extreme storage expenses.<ref>Kunal K. Shah, Aishwarya S. Mundada, Joshua M. Pearce. [https://www.academia.edu/14674492/Performance_of_U.S._hybrid_distributed_energy_systems_Solar_photovoltaic_battery_and_combined_heat_and_power Performance of U.S. hybrid distributed energy systems: Solar photovoltaic, battery and combined heat and power.] ''Energy Conversion and Management'' '''105''', pp. 71–80 (2015).</ref>

=== Cogeneration ===

Distributed [[cogeneration]] sources use steam turbines, natural gas-fired [[fuel cell]]s, [[microturbine]]s or [[reciprocating engine]]s<ref>[http://www.clarke-energy.com/chp-cogeneration/ Gas engine cogeneration], http://www.clarke-energy.com, retrieved 9.12.2013</ref> to turn generators. The hot exhaust is then used for space or [[water heating]], or to drive an [[absorptive chiller]]<ref>{{cite web|url=http://www.buderus.de/Ueber_uns/Presse/Fachpresse/Anlagen_zur_Kraft_Waerme_Kopplung/Heiss_auf_kalt-2119341.html|title=Heiß auf kalt|access-date=15 May 2015|archive-date=18 May 2015|archive-url=https://web.archive.org/web/20150518102403/http://www.buderus.de/Ueber_uns/Presse/Fachpresse/Anlagen_zur_Kraft_Waerme_Kopplung/Heiss_auf_kalt-2119341.html|url-status=dead}}</ref><ref>[http://www.clarke-energy.com/gas-engines/trigeneration/ Trigeneration with gas engines], http://www.clarke-energy.com, retrieved 9.12.2013</ref> for cooling such as [[air-conditioning]]. In addition to natural gas-based schemes, distributed energy projects can also include other renewable or low carbon fuels including biofuels, [[biogas]], [[landfill gas]], [[sewage gas]], [[coal bed methane]], [[syngas]] and [[associated petroleum gas]].<ref>[http://www.clarke-energy.com/gas-engines/ Gas engine applications], [http://www.clarke-energy.com], retrieved 9 December 2013</ref>

Delta-ee consultants stated in 2013 that with 64% of global sales, the fuel cell [[micro combined heat and power]] passed the conventional systems in sales in 2012.<ref>{{cite report|url = http://www.fuelcelltoday.com/media/1889744/fct_review_2013.pdf |title= The fuel cell industry review 2013|publisher = FuelCellToday.com|archiveurl = https://web.archive.org/web/20131007223834/http://www.fuelcelltoday.com/media/1889744/fct_review_2013.pdf|archivedate = 7 October 2013}}</ref> 20.000 units were sold in [[Japan]] in 2012 overall within the Ene Farm project. With a [[Service life|Lifetime]] of around 60,000 hours for [[proton-exchange membrane fuel cell|PEM fuel cell]] units, which shut down at night, this equates to an estimated lifetime of between ten and fifteen years.<ref name="fuelcelltoday.com">{{cite web|url=http://www.fuelcelltoday.com/analysis/analyst-views/2013/13-02-27-latest-developments-in-the-ene-farm-scheme|title=Latest Developments in the Ene-Farm Scheme|access-date=15 May 2015}}</ref> For a price of $22,600 before installation.<ref>{{cite web|url=http://panasonic.co.jp/corp/news/official.data/data.dir/2013/01/en130117-5/en130117-5.html |title=Launch of New 'Ene-Farm' Home Fuel Cell Product More Affordable and Easier to Install – Headquarters News – Panasonic Newsroom Global|access-date=15 May 2015}}</ref> For 2013 a state subsidy for 50,000 units is in place.<ref name="fuelcelltoday.com"/>

In addition, [[molten carbonate fuel cell]] and [[solid oxide fuel cell]]s using natural gas, such as the ones from [[FuelCell Energy]] and the [[Bloom energy server]], or waste-to-energy processes such as the Gate 5 Energy System are used as a distributed energy resource.

=== Solar power ===
{{Further|Photovoltaic system}}

[[Photovoltaics]], by far the most important solar technology for distributed generation of [[solar power]], uses [[solar cell]]s assembled into [[solar panel]]s to convert sunlight into electricity. It is a [[growth of photovoltaics|fast-growing]] technology doubling its worldwide installed capacity every couple of years. [[PV system]]s range from distributed, residential, and commercial [[Rooftop photovoltaic power station|rooftop]] or [[Building-integrated photovoltaics|building integrated]] installations, to large, centralized utility-scale [[photovoltaic power station]]s.

The predominant PV technology is [[crystalline silicon]], while [[thin-film solar cell]] technology accounts for about 10 percent of global photovoltaic deployment.<ref name="Fraunhofer-PR-2014">
{{cite web |date=28 July 2014 |title=Photovoltaics Report |url=http://www.ise.fraunhofer.de/en/downloads-englisch/pdf-files-englisch/photovoltaics-report-slides.pdf |url-status=live |archive-url=https://web.archive.org/web/20140809192020/http://www.ise.fraunhofer.de/en/downloads-englisch/pdf-files-englisch/photovoltaics-report-slides.pdf |archive-date=9 August 2014 |access-date=31 August 2014 |publisher=Fraunhofer ISE |pages=18–19}}
</ref> In recent years, PV technology has improved its sunlight to electricity [[Solar cell efficiency|conversion efficiency]], reduced the installation [[Price per watt|cost per watt]] as well as its [[energy payback time]] (EPBT) and [[levelised cost of electricity]] (LCOE), and has reached [[grid parity]] in at least 19 different markets in 2014.<ref>
{{cite web
 |last1=Parkinson
 |first1=Giles
 |title=Deutsche Bank predicts second solar "gold-rush"
 |url=http://reneweconomy.com.au/2014/deutsche-bank-predicts-second-solar-gold-rush-40084
 |work=REnewEconomy
 |access-date=14 September 2014
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 |archive-date=28 June 2014
 |date=7 January 2014
 |url-status=dead
}}</ref>

As most [[renewable energy]] sources and unlike coal and nuclear, solar PV is variable and non-[[Dispatchable generation|dispatchable]], but has no fuel costs, operating pollution, as well as greatly reduced mining-safety and operating-safety issues. It produces peak power around local noon each day and its [[capacity factor]] is around 20 percent.<ref>https://www.academia.edu, Janet Marsdon [https://www.academia.edu/446324/Distributed_Generation_Systems_A_New_Paradigm_for_Sustainable_Energy Distributed Generation Systems:A New Paradigm for Sustainable Energy]</ref>

=== Wind power ===
{{Main|Wind power}}

[[Wind turbine]]s can be distributed energy resources or they can be built at utility scale. These have low maintenance and low pollution, but distributed wind unlike utility-scale wind has much higher costs than other sources of energy.<ref>{{Cite web|title = NREL: Energy Analysis – Distributed Generation Energy Technology Capital Costs|url = http://www.nrel.gov/analysis/tech_cost_dg.html|website = nrel.gov|access-date = 2015-10-31}}</ref> As with solar, wind energy is variable and non-dispatchable. Wind towers and generators have substantial insurable liabilities caused by high winds, but good operating safety. Distributed generation from [[wind hybrid power systems]] combines wind power with other DER systems. One such example is the integration of wind turbines into [[solar hybrid power systems]], as wind tends to complement solar because the peak operating times for each system occur at different times of the day and year.

=== Hydro power ===
{{Main|Small hydro|Wave power}}

Hydroelectricity is the most widely used form of renewable energy and its potential has already been explored to a large extent or is compromised due to issues such as environmental impacts on fisheries, and increased demand for recreational access. However, using modern 21st century technology, such as [[wave power]], can make large amounts of new hydropower capacity available, with minor environmental impact.

Modular and scalable ''Next generation kinetic energy turbines'' can be deployed in arrays to serve the needs on a residential, commercial, industrial, municipal or even regional scale. ''Microhydro kinetic generators'' neither require dams nor impoundments, as they utilize the kinetic energy of water motion, either waves or flow. No construction is needed on the shoreline or sea bed, which minimizes environmental impacts to habitats and simplifies the permitting process. Such power generation also has minimal environmental impact and non-traditional microhydro applications can be tethered to existing construction such as docks, piers, bridge abutments, or similar structures.<ref>https://www.academia.edu, Janet Marsdon [https://www.academia.edu/446324/Distributed_Generation_Systems_A_New_Paradigm_for_Sustainable_Energy Distributed Generation Systems:A New Paradigm for Sustainable Energy], pp. 8, 9</ref>

=== Waste-to-energy ===
{{Main|Waste-to-energy|Waste-to-energy plant}}

Municipal solid waste (MSW) and natural waste, such as sewage sludge, [[food waste]] and animal manure will decompose and discharge methane-containing gas that can be collected and used as fuel in gas turbines or micro turbines to produce electricity as a distributed energy resource. Additionally, a California-based company, Gate 5 Energy Partners, Inc. has developed a process that transforms natural waste materials, such as sewage sludge, into biofuel that can be combusted to power a steam turbine that produces power. This power can be used in lieu of grid-power at the waste source (such as a treatment plant, farm or dairy).

=== 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
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