Distributed generation

Local wind generator, Spain, 2010

Distributed energy, also district or decentralized en-ergy is generated or stored by a variety of small, grid-connected devices referred to as distributed energy re-sources (DER) or distributed energy resource systems.Conventional power stations, such as coal-fired, gas andnuclear powered plants, as well as hydroelectric dams andlarge-scale solar power stations, are centralized and oftenrequire electricity to be transmitted over long distances.By contrast, DER systems are decentralized, modularand more flexible technologies, that are located close tothe load they serve, albeit having capacities of only 10megawatts (MW) or less.DER systems typically use renewable energy sources, in-cluding, but not limited to, small hydro, biomass, biogas,solar power, wind power, geothermal power and increas-ingly play an important role for the electric power dis-tribution system. A grid-connected device for electricitystorage can also be classified as a DER system, and is of-ten called a distributed energy storage system (DESS).By means of an interface, DER systems can be managedand coordinated within a smart grid. Distributed genera-tion and storage enables collection of energy from manysources and may lower environmental impacts and im-

prove security of supply.

1 Economies of scale

Historically, central plants have been an integral part ofthe electric grid, in which large generating facilities arespecifically located either close to resources or other-wise located far from populated load centers. These,in turn, supply the traditional transmission and distribu-tion (T&D) grid that distributes bulk power to load cen-ters and from there to consumers. These were developedwhen the costs of transporting fuel and integrating gen-erating technologies into populated areas far exceededthe cost of developing T&D facilities and tariffs. Centralplants are usually designed to take advantage of availableeconomies of scale in a site-specific manner, and are builtas “one-off,” custom projects.These economies of scale began to fail in the late 1960sand, by the start of the 21st century, Central Plants couldarguably no longer deliver competitively cheap and re-liable electricity to more remote customers through thegrid, because the plants had come to cost less than thegrid and had become so reliable that nearly all power fail-ures originated in the grid. Thus, the grid had becomethe main driver of remote customers’ power costs andpower quality problems, which becamemore acute as dig-ital equipment required extremely reliable electricity.[1][2]Efficiency gains no longer come from increasing generat-ing capacity, but from smaller units located closer to sitesof demand.[3][4]

For example, coal power plants are built away fromcities to prevent their heavy air pollution from affect-ing the populace. In addition, such plants are often builtnear collieries to minimize the cost of transporting coal.Hydroelectric plants are by their nature limited to oper-ating at sites with sufficient water flow.Low pollution is a crucial advantage of combined cycleplants that burn natural gas. The low pollution permitsthe plants to be near enough to a city to provide districtheating and cooling.Distributed energy resources are mass-produced, small,and less site-specific. Their development arose out of:

1. concerns over perceived externalized costs of centralplant generation, particularly environmental con-cerns,

1

2 2 TYPES OF DER SYSTEMS

2. the increasing age, deterioration, and capacity con-straints upon T&D for bulk power;

3. the increasing relative economy of mass productionof smaller appliances over heavy manufacturing oflarger units and on-site construction;

4. Along with higher relative prices for energy, higheroverall complexity and total costs for regulatoryoversight, tariff administration, and metering andbilling.

Capital markets have come to realize that right-sized re-sources, for individual customers, distribution substa-tions, or microgrids, are able to offer important butlittle-known economic advantages over central plants.Smaller units offered greater economies from mass-production than big ones could gain through unit size.These increased value—due to improvements in financialrisk, engineering flexibility, security, and environmentalquality—of these resources can often more than offsettheir apparent cost disadvantages.[5] DG, vis-à-vis centralplants, must be justified on a life-cycle basis.[6] Unfortu-nately, many of the direct, and virtually all of the indirect,benefits of DG are not captured within traditional utilitycash-flow accounting.[1]

While the levelized generation cost of distributed gener-ation (DG) is more expensive than conventional sourceson a kWh basis, this does not consider negative aspectsof conventional fuels. The additional premium for DGis rapidly declining as demand increases and technologyprogresses, and sufficient and reliable demand may bringeconomies of scale, innovation, competition, and moreflexible financing, that could make DG clean energy partof a more diversified future.Distributed generation reduces the amount of energy lostin transmitting electricity because the electricity is gener-ated very near where it is used, perhaps even in the samebuilding. This also reduces the size and number of powerlines that must be constructed.Typical DER systems in a feed-in tariff (FIT) schemehave low maintenance, low pollution and high efficien-cies. In the past, these traits required dedicated operatingengineers and large complex plants to reduce pollution.However, modern embedded systems can provide thesetraits with automated operation and renewables, such assunlight, wind and geothermal. This reduces the size ofpower plant that can show a profit.

1.1 Grid parity

Grid parity occurs when an alternative energy source cangenerate electricity at a levelized cost (LCOE) that is lessthan or equal to the end consumer’s retail price. Reach-ing grid parity is considered to be the point at which anenergy source becomes a contender for widespread devel-opment without subsidies or government support. Since

the 2010s, grid parity for solar and wind has become areality in a growing number of markets, including Aus-tralia, several European countries, and some states in theU.S.[7]

2 Types of DER systems

Distributed energy resource (DER) systems are small-scale power generation or storage technologies (typicallyin the range of 1 kW to 10,000 kW)[8] used to provide analternative to or an enhancement of the traditional elec-tric power system. DER systems typically are charac-terized by high initial capital costs per kilowatt.[9] DERsystems also serve as storage device and are often calledDistributed energy storage systems (DESS).[10]

2.1 Cogeneration

Distributed cogeneration sources use steam turbines, nat-ural gas-fired fuel cells, microturbines or reciprocatingengines[11] to turn generators. The hot exhaust is thenused for space or water heating, or to drive an absorptivechiller [12][13] for cooling such as air-conditioning. In ad-dition to natural gas-based schemes, distributed energyprojects can also include other renewable or low car-bon fuels including biofuels, biogas, landfill gas, sewagegas, coal bed methane, syngas and associated petroleumgas.[14]

Delta-ee consultants stated in 2013 that with 64% ofglobal sales the fuel cell micro combined heat and powerpassed the conventional systems in sales in 2012.[15]20.000 units where sold in Japan in 2012 overall withinthe Ene Farm project. With a Lifetime of around 60,000hours. For PEM fuel cell units, which shut down atnight, this equates to an estimated lifetime of betweenten and fifteen years.[16] For a price of $22,600 beforeinstallation.[17] For 2013 a state subsidy for 50,000 unitsis in place.[16]

In addition, molten carbonate fuel cell and solid oxide fuelcells using natural gas, such as the ones from FuelCellEnergy and the Bloom energy server, or waste-to-energyprocesses such as the Gate 5 Energy System are used asa distributed energy resource.

2.2 Solar power

Photovoltaics, by far the most important solar technol-ogy for distributed generation of solar power, uses solarcells assembled into solar panels to convert sunlight intoelectricity. It is a fast-growing technology doubling itsworldwide installed capacity every couple of years. PVsystems range from distributed, residential and commer-cial rooftop or building integrated installations, to large,centralized utility-scale photovoltaic power stations.

2.5 Waste-to-energy 3

The predominant PV technology is crystalline silicon,while thin-film solar cell technology accounts for about10 percent of global photovoltaic deployment.[18]:18,19 Inrecent years, PV technology has improved its sunlight toelectricity conversion efficiency, reduced the installationcost per watt as well as its energy payback time (EPBT)and levelised cost of electricity (LCOE), and has reachedgrid parity in at least 19 different markets in 2014.[19]

As most renewable energy sources and unlike coal andnuclear, solar PV is variable and non-dispatchable, buthas no fuel costs, operating pollution, mining-safety oroperating-safety issues. It produces peak power aroundlocal noon each day and its capacity factor is around 20percent.[20]

2.3 Wind power

Another source is small wind turbines. These have lowmaintenance, and low pollution, however as with solar,wind energy is variable and non-dispatchable. Construc-tion costs are higher ($0.80/W, 2007) per watt than largepower plants, except in very windy areas. Wind tow-ers and generators have substantial insurable liabilitiescaused by high winds, but good operating safety. In someareas of the US there may also be Property Tax costs in-volved with wind turbines that are not offset by incen-tives or accelerated depreciation.[21] Wind also tends tocomplement solar. Days without sun tend to be windy,and vice versa. Many distributed generation sites com-bine wind power and solar power such as Slippery RockUniversity, which can be monitored online.

2.4 Hydro power

Main articles: Small hydro and Wave power

Hydroelectricity is the most widely used form of renew-able energy and its potential has already been explored toa large extend or is compromised due to issues such as en-vironmental impacts on fisheries, and increased demandfor recreational access. However, using modern 21st cen-tury technology, such as wave power, can make largeamounts of new hydropower capacity available, with mi-nor environmental impact.Modular and scalable Next generation kinetic energy tur-bines can be deployed in arrays to serve the needs ona residential, commercial, industrial, municipal or evenregional scale. Microhydro kinetic generators neither re-quire dams nor impoundments, as they utilize the kineticenergy of water motion, either waves or flow. No con-struction is needed on the shoreline or sea bed, whichminimizes environmental impacts to habitats and simpli-fies the permitting process. Such power generation alsohas minimal environmental impact and non-traditionalmicrohydro applications can be tethered to existing con-

struction such as docks, piers, bridge abutments, or simi-lar structures.[22]

2.5 Waste-to-energy

Municipal solid waste (MSW) and natural waste, suchas sewage sludge, food waste and animal manure willdecompose and discharge methane-containing gas thatcan be collected and used as fuel in gas turbines or mi-cro turbines to produce electricity as a distributed en-ergy resource. Additionally, a California-based com-pany, Gate 5 Energy Partners, Inc. has developed aprocess that transforms natural waste materials, such assewage sludge, into biofuel that can be combusted topower a steam turbine that produces power. This powercan be used in lieu of grid-power at the waste source (suchas a treatment plant, farm or dairy).

2.6 Energy storage

Main article: Grid energy storage

A distributed energy resource is not limited to the gener-ation of electricity but may also include a device to storedistributed energy (DE).[10] Distributed energy storagesystems (DESS) applications include several types ofbattery, pumped hydro, compressed air, and thermal en-ergy storage.[23]:42

Flywheels

An advanced flywheel energy storage (FES) stores theelectricity generated from distributed ressources in theform of angular kinetic energy by accelerating a rotor(flywheel) to a very high speed of about 20,000 to over50,000 rpm in a vacuum enclosure. Flywheels can re-spond quickly as they store and feed back electricity intothe grid in a matter of minutes.[24][25]

Vehicle-to-grid

Future generations of electric vehicles may have the abil-ity to deliver power from the battery in a vehicle-to-gridinto the grid when needed.[26] An electric vehicle networkhas the potential to serve as a DESS.[23]:44

PV storage

Common battery technologies used in today’s PV sys-tems include, the valve regulated lead-acid battery (lead–acid battery), nickel–cadmium and lithium-ion batteries.Compared to the other types, lead-acid batteries have ashorter lifetime and lower energy density. However, dueto their high reliability, low self discharge as well as lowinvestment and maintenance costs, they are currently the

4 6 MODES OF POWER GENERATION

predominant technology used in small-scale, residentialPV systems, as lithium-ion batteries are still being devel-oped and about 3.5 times as expensive as lead-acid bat-teries. Furthermore, as storage devices for PV systemsare used stationary, the lower energy and power densityand therefore higher weight of lead-acid batteries are notas critical as for electric vehicles.[27]:4,9

Other rechargeable batteries that are considered fordistributed PV systems include, sodium–sulfur andvanadium redox batteries, two prominent types of amolten salt and a flow battery, respectively.[27]:4

3 Integration with the grid

For reasons of reliability, distributed generation re-sources would be interconnected to the same transmis-sion grid as central stations. Various technical and eco-nomic issues occur in the integration of these resourcesinto a grid. Technical problems arise in the areas of powerquality, voltage stability, harmonics, reliability, protec-tion, and control.[28] Behavior of protective devices onthe grid must be examined for all combinations of dis-tributed and central station generation.[29] A large scaledeployment of distributed generation may affect grid-wide functions such as frequency control and allocationof reserves.[30] As a result smart grid functions, virtualpower plants and grid energy storage such as power togas stations are added to the grid.

4 Cost factors

Cogenerators are also more expensive per watt than cen-tral generators. They find favor because most buildingsalready burn fuels, and the cogeneration can extract morevalue from the fuel . Local production has no electricitytransportation losses on long distance power lines or en-ergy losses from the Joule effect in transformers where ingeneral 8-15% of the energy is lost[31] (see also cost ofelectricity by source).Some larger installations utilize combined cycle genera-tion. Usually this consists of a gas turbine whose exhaustboils water for a steam turbine in a Rankine cycle. Thecondenser of the steam cycle provides the heat for spaceheating or an absorptive chiller. Combined cycle plantswith cogeneration have the highest known thermal effi-ciencies, often exceeding 85%.In countries with high pressure gas distribution, small tur-bines can be used to bring the gas pressure to domesticlevels whilst extracting useful energy. If the UK wereto implement this countrywide an additional 2-4 GWewould become available. (Note that the energy is alreadybeing generated elsewhere to provide the high initial gaspressure - this method simply distributes the energy via adifferent route.)

5 Microgrid

Picture of a local microgrid, the Sendai Microgrid, located onthe campus of Tohoku Fukushi University in Sendai City in theTohoku district in Japan

A microgrid is a localized grouping of electricity gener-ation, energy storage, and loads that normally operatesconnected to a traditional centralized grid (macrogrid).This single point of common coupling with the macro-grid can be disconnected. The microgrid can then func-tion autonomously.[32] Generation and loads in a micro-grid are usually interconnected at low voltage. From thepoint of view of the grid operator, a connected microgridcan be controlled as if it were one entity.Microgrid generation resources can include fuel cells,wind, solar, or other energy sources. The multiple dis-persed generation sources and ability to isolate the micro-grid from a larger network would provide highly reliableelectric power. Produced heat from generation sourcessuch as microturbines could be used for local processheating or space heating, allowing flexible trade off be-tween the needs for heat and electric power.Micro-grids were proposed in the wake of the July 2012India blackout:[33]

• Small micro-grids covering 30–50 km radius[33]

• Small power stations of 5–10 MW to serve themicro-grids

• Generate power locally to reduce dependence onlong distance transmission lines and cut transmissionlosses.

GTMResearch forecastsmicrogrid capacity in theUnitedStates will exceed 1.8 gigawatts by 2018.[34]

6 Modes of power generation

DER systems may include the following de-vices/technologies:

5

• Combined heat power (CHP)

• Fuel cells

• Micro combined heat and power (MicroCHP)

• Microturbines

• Photovoltaic Systems

• Reciprocating engines

• Small Wind power systems

• Stirling engines

• Trigeneration

7 Communication in DER systems• IEC 61850−7-420 is under development as a partof IEC 61850 standards, which deals with the com-plete object models as required for DER systems.It uses communication services mapped to MMS asper IEC 61850-8-1 standard.

• OPC is also used for the communication betweendifferent entities of DER system.

8 Legal requirements for dis-tributed generation

In 2010 Colorado enacted a law requiring that by 2020that 3% of the power generated in Colorado utilize dis-tributed generation of some sort.[35][36]

9 See also• Autonomous building

• Demand response

• Energy harvesting

• Electric power transmission

• Electricity generation

• Electricity market

• Electricity retailing

• Energy demand management

• Future energy development

• Green power superhighway

• Grid-tied electrical system

• Hydrogen station

• IEEE 1547 Standard for Interconnecting Dis-tributed Resources with Electric Power Systems

• Islanding

• Microgeneration

• Net metering

• Relative cost of electricity generated by differentsources

• Renewable energy development

• Smart meter

• Smart power grid

• Solar Guerrilla

• Stand-alone power system

• Sustainable community energy system

• Trigeneration

• World Alliance for Decentralized Energy

10 References[1] DOE; The Potential Benefits of Distributed Generation

and Rate-Related Issues that May Impede Their Expan-sion; 2007.

[2] Lovins; Small Is Profitable: The Hidden Economic Bene-fits of Making Electrical Resources the Right Size; RockyMountain Institute, 2002.

[3] Takahashi, et al; Policy Options to Support DistributedResources; U. of Del., Ctr. for Energy & Env. Policy;2005.

[4] Hirsch; 1989; cited in DOE, 2007.

[5] Lovins; Small Is Profitable: The Hidden Economic Bene-fits of Making Electrical Resources the Right Size; RockyMountain Institute; 2002

[6] Michigan (Citation pending)

[7] McFarland, Matt (25 March 2014). “Grid parity:Why electric utilities should struggle to sleep at night”.http://www.washingtonpost.com/''. Washingtonpost.com.Archived from the original on 14 September 2014. Re-trieved 14 September 2014.

[8] “Using Distributed Energy Resources”. http://www.nrel.gov''. NREL. 2002. p. 1. Archived from the original on 8September 2014. Retrieved 8 September 2014.

[9] www.NREL.gov Distributed Energy Resources Inter-connection Systems: Technology Review and ResearchNeeds, 2002

6 12 EXTERNAL LINKS

[10] www.smartgrid.gov Lexicon Distributed Energy Re-source

[11] Gas engine cogeneration, www.clarke-energy.com, re-trieved 9.12.2013

[12] Cogeneration with absorptive chiller

[13] Trigeneration with gas engines, www.clarke-energy.com,retrieved 9.12.2013

[14] Gas engine applications, www.clarke-energy.com, re-trieved 9th December 2013

[15] The fuel cell industry review 2013

[16] Latest developments in the Ene-Farm scheme

[17] Launch of new 'Ene-Farm' home fuel cell product moreaffordable and easier to install

[18] “Photovoltaics Report”. Fraunhofer ISE. 28 July 2014.Archived from the original on 31 August 2014. Retrieved31 August 2014.

[19] Parkinson, Giles (7 January 2014). “Deutsche Bank pre-dicts second solar “gold-rush”". http://reneweconomy.com.au/''. REnewEconomy. Archived from the original on14 September 2014. Retrieved 14 September 2014.

[20] www.academia.edu, Janet Marsdon Distributed Genera-tion Systems:A New Paradigm for Sustainable Energy

[21] Retrieved on 20 October 2010

[22] www.academia.edu, Janet Marsdon Distributed Genera-tion Systems:ANewParadigm for Sustainable Energy, pp.8, 9

[23] www.NREL.gov - The Role of Energy Storage with Re-newable Electricity Generation

[24] Castelvecchi, Davide (May 19, 2007). “Spinning intocontrol: High-tech reincarnations of an ancient way ofstoring energy”. Science News 171 (20): 312–313.doi:10.1002/scin.2007.5591712010.

[25] Willis, Ben (23 July 2014). “Canada’s first grid storagesystem launches in Ontario”. http://storage.pv-tech.org/''.pv-tech.org. Archived from the original on 12 September2014. Retrieved 12 September 2014.

[26] How electric vehicles are a part of distributed generation

[27] ETH Zürich, Harvard University The Economic Viabil-ity of Battery Storage for Residential Solar PhotovoltaicSystems - A Review and a Simulation Model Joern Hopp-mann, Jonas Volland, Tobias S. Schmidt, Volker H. Hoff-mann, July 2014

[28] Tomoiagă, B.; Chindriş, M.; Sumper, A.; Sudria-Andreu,A.; Villafafila-Robles, R. Pareto Optimal Reconfigurationof Power Distribution Systems Using a Genetic AlgorithmBased on NSGA-II. Energies 2013, 6, 1439-1455.

[29] P. Mazidi, G. N. Sreenivas; Reliability Assessment of ADistributed Generation Connected Distribution System; In-ternational Journal of Power System Operation and En-ergy Management(IJPSOEM), Nov. 2011

[30] Math H. Bollen, Fainan Hassan Integration of DistributedGeneration in the Power System, JohnWiley & Sons, 2011ISBN 1-118-02901-1, pages v-x

[31] How big are Power line losses?

[32] Stan Mark Kaplan, Fred Sissine, (ed.) Smart grid: mod-ernizing electric power transmission and distribution... TheCapitol Net Inc, 2009, ISBN 1-58733-162-4, page 217

[33]

[34] http://www.greentechmedia.com/articles/read/US-Microgrid-Capacity-Will-Exceed-1.8-GW-by-2018

[35] “Going Solar Is Harder Than It Looks, a Valley Finds”article by Kirk Johnson in The New York Times June 3,2010

[36] “Colorado Increases Renewables Requirements” blog byKate Galbraith on NYTimes.Com March 22, 2010

11 Further reading

• Brass, J. N.; Carley, S.; MacLean, L. M.; Bald-win, E. (2012). “Power for Development: A Reviewof Distributed Generation Projects in the Develop-ing World”. Annual Review of Environment andResources 37: 107. doi:10.1146/annurev-environ-051112-111930.

• Gies, Erica. Making the Consumer an Active Par-ticipant in the Grid, The New York Times, November29, 2010. Discusses distributed generation and theU.S. Federal Energy Regulatory Commission.

• Pahl, Greg (2012). Power from the people : how toorganize, finance, and launch local energy projects.Santa Rosa, Calif: Post Carbon Institute. ISBN9781603584098.

12 External links

• The UK District Energy Association - advocatingthe construction of locally distributed energy net-works

• Decentralized Power as Part of Local and RegionalPlans

• IEEE P1547 Draft Standard for InterconnectingDistributed Resources with Electric Power Systems

• World Alliance for Decentralized Energy

• The iDEaS project by University of Southampton onDecentralised Energy

• Biofuels and gas pressure energy recovery

7

• Microgrids projects and DER Optimization Modelat Berkeley Lab

• DERlab

• Center for Energy and innovative Technologies

• Decentralized Power System (DPS) in Pakistan

8 13 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

13 Text and image sources, contributors, and licenses

13.1 Text• Distributed generation Source: http://en.wikipedia.org/wiki/Distributed%20generation?oldid=638998801Contributors: Rmhermen, RayVan De Walker, Heron, Hephaestos, Patrick, Michael Hardy, Fred Bauder, Nixdorf, Zanimum, Cameron Dewe, Tiles, Mac, Glenn, Reddi,Silpol, Omegatron, Phoebe, Philopp, UtherSRG, Casito, Alan Liefting, Akadruid, Tweenk, Bobblewik, Beland, Biffa, BioPizza, Discospin-ster, Scott.graham, El C, Duk, Vortexrealm, Elipongo, Kjkolb, Wtshymanski, Versageek, Gene Nygaard, Jefflundberg, Ultramarine, Bushy-tails, OwenX, Linas, Georgia guy, Armando, Mtaff, Pingswept, Cartman02au, Behun, Ellenmc, Seraphimblade, Vegaswikian, Alvin-cs,Chobot, Roboto de Ajvol, Postglock, Salsb, Helfire57, Tabby, Fsiler, Jonathan.s.kt, SmackBot, Hmains, MalafayaBot, DHN-bot, Chendy,Theanphibian, Mion, Beetstra, Wega14, Dl2000, Hu12, Britannica, CmdrObot, Rawling, Article editor, Cydebot, Teratornis, Thijs!bot,Cimbalom, Gralo, Imotorhead, LachlanA, RobotG, Harryzilber, Yeliseyev, RebelRobot, Geniac, Engineman, Juvepa2002, Beagel, DGG,KTo288, Skier Dude, Upaplc, Jorfer, STBotD, Benstrider, AeoniosHaplo, Jutulen, Onetoremember, Monkolosit, Thadius856AWB, Jjjbell,Mr gavin, SieBot, BotMultichill, 16hana, Happysailor, Jojalozzo, Nopetro, Cheapthrill, Trishashrum, Jaded-view, Sun Creator, Nukeless,Aitias, HarrivBOT, Shawis, DumZiBoT, Jordanp, Lenrpk, Addbot, Billyeager, CanadianLinuxUser, Couposanto, MrOllie, Tide rolls,Mscada, Luckas-bot, Yobot, Thameshead, AnomieBOT, Materialscientist, Wdl1961, GrouchoBot, Leeking337, Patrick.charpiat, Amazy,Joshschel, Francis E Williams, Nickanc, Harold51, Sricciar, TjBot, Essicajay, AManWithNoPlan, Demiurge1000, Kajsar, Helpsome,ClueBot NG, Satellizer, Snotbot, NathanResearch, Helpful Pixie Bot, BG19bot, Solarguy1, Wacb2000, Nicola.Manini, ChrisGualtieri,Mogism, Joeinwiki, Rfassbind, Epicgenius, McDKhan, Sdelson92653, Karenluo87, Btomoiaga and Anonymous: 114

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