Cogeneration 763555 226021855 2008-07-16T14:02:07Z Cgingold 2013997 Quick-adding category "Residential heating" (using [[WP:HOTCAT|HotCat]]) {{portal|Energy}} {{see also|Energy recycling}}{{otheruses|CHP}} '''Cogeneration''' (also '''combined heat and power''', '''CHP''') is the use of a [[heat engine]] or a [[power station]] to simultaneously generate both [[electricity]] and useful [[heat]]. Conventional power plants emit the heat created as a by-product of [[electricity generation]] into the environment through [[cooling tower]]s, [[flue gas]], or by other means. CHP or a bottoming cycle captures the by-product heat for domestic or industrial [[heating]] purposes, either very close to the plant, or &mdash;especially in [[Scandinavia]] and eastern [[Europe]]&mdash;for distribution through pipes to [[district heating|heat local housing]]. In the [[United States]], [[Con Edison]] produces 30 billion pounds of steam each year through its seven cogeneration plants (which boil water to 1,000[[°F]]/538[[°C]] before pumping it to 100,000 buildings in [[Manhattan]]&mdash;the biggest commercial steam system in the world.<ref>{{cite web | last = | first = | authorlink = | coauthors = | title =Newsroom: Steam | work = | publisher =ConEdison | date = | url =http://www.coned.com/newsroom/energysystems_steam.asp | format = | doi = | accessdate =2007-07-20}}</ref><ref> {{cite web | last =Bevelhymer | first =Carl | authorlink = | coauthors = | title =Steam | work = | publisher =Gotham Gazette | date =[[2003-11-10]] | url =http://www.gothamgazette.com/article/issueoftheweek/20031110/200/674 | format = | doi = | accessdate =2007-07-20}}</ref> By-product heat at moderate temperatures (212-356°F/100-180°C) can also be used in [[Gas-absorption refrigerator|absorption chillers]] for cooling. A plant producing electricity, heat and cold is sometimes called '''[[trigeneration]]''' or more generally: '''polygeneration''' plant. Cogeneration is a [[thermal efficiency|thermodynamically efficient]] use of [[fuel]]. In separate production of electricity some energy must be rejected as [[waste heat]], but in cogeneration this [[thermal energy]] is put to good use. ==Overview== [[Image:Masnedø power station.jpg|300px|thumb|right|[[Masnedø]] CHP power station in [[Denmark]]. This station burns straw as fuel. The adjacent greenhouses are heated by [[district heating]] from the plant.]] Thermal power plants (including those that use [[uranium|fissile elements]] or burn [[coal]], [[petroleum]], or [[natural gas]]), and [[heat engine]]s in general, do not convert all of their available energy into electricity. In most heat engines, a bit more than half is wasted as excess heat (see: [[Second law of thermodynamics]]). By capturing the excess heat, CHP uses heat that would be wasted in a conventional [[power plant]], potentially reaching an [[thermal efficiency|efficiency]] of up to 89%, compared with 55%<ref>{{cite web |url=http://www.coolkeeraghesb.co.uk/about/index.htm |title=Coolkeeragh ESB & the Environment}}</ref> for the best conventional plants. This means that less fuel needs to be consumed to produce the same amount of useful energy. Also, less pollution is produced for a given economic benefit. Some tri-cycle plants have utilized a [[combined cycle]] in which several thermodynamic cycles produced electricity, and then a heating system was used as a condenser of the power plant's [[bottoming cycle]]. For example, the RU-25 [[MHD generator]] in [[Moscow]] heated a boiler for a conventional steam powerplant, whose condensate was then used for space heat. A more modern system might use a [[gas turbine]] powered by [[natural gas]], whose exhaust powers a steam plant, whose condensate provides heat. Tri-cycle plants can have thermal efficiencies above 80%. An exact match between the heat and electricity needs rarely exists. A CHP plant can either meet the need for heat (''heat driven operation'') or be run as a [[power plant]] with some use of its waste heat. CHP is most efficient when the heat can be used on site or very close to it. Overall efficiency is reduced when the heat must be transported over longer distances. This requires heavily insulated pipes, which are expensive and inefficient; whereas electricity can be transmitted along a comparatively simple wire, and over much longer distances for the same energy loss. A car engine becomes a CHP plant in winter, when the reject heat is useful for warming the interior of the vehicle. This example illustrates the point that deployment of CHP depends on heat uses in the vicinity of the heat engine. Cogeneration plants are commonly found in [[district heating]] systems of big towns, hospitals, prisons, oil refineries, paper mills, wastewater treatment plants, thermal [[enhanced oil recovery]] wells and industrial plants with large heating needs. Thermally [[enhanced oil recovery]] (TEOR) plants often produce a substantial amount of excess electricity. After generating electricity, these plants pump leftover steam into heavy oil wells so that the oil will flow more easily, increasing production. TEOR cogeneration plants in [[Kern County, California]] produce so much electricity that it cannot all be used locally and is transmitted to [[Los Angeles]]{{Fact|date=February 2007}}. == Types of plants == Topping cycle plants primarily produce electricity from a steam turbine. The exhausted steam is then condensed, and the low temperature heat released from this condensation is utilised for e.g. [[district heating]]. [[Bottoming cycle]] plants produce high temperature heat for industrial processes, then a waste heat recovery boiler feeds an electrical plant. Bottoming cycle plants are only used when the industrial process requires very high temperatures, such as furnaces for glass and metal manufacturing, so they are less common. Large cogeneration systems provide heating water and power for an industrial site or an entire town. Common CHP plant types are: * [[Gas turbine]] CHP plants using the waste heat in the flue gas of gas turbines * [[Combined cycle]] power plants adapted for CHP * [[Steam turbine]] CHP plants that use the heating system as the [[steam]] condenser for the steam turbine. * [[Molten-carbonate fuel cell]]s have a hot exhaust, very suitable for heating. Smaller cogeneration units may use a [[reciprocating engine]] or [[Stirling engine]]. The heat is removed from the exhaust and the radiator. These systems are popular in small sizes because small gas and diesel engines are less expensive than small gas- or oil-fired steam-electric plants. Some cogeneration plants are fired by [[biomass]] <ref>[http://www.opet-chp.net/download/wp3/iisalmifinland.pdf Microsoft Word - Case_Iisalmi.doc<!-- Bot generated title -->]</ref>, or industrial and [[municipal waste]] (see [[incineration]]). === MicroCHP === [[MicroCHP|"Micro cogeneration"]] is a so called [[Distributed Energy Resource|distributed energy resource]] (DER). the installation is usually less than 5 kWe in a house or small business[http://www.cogen.org/about/workinggroup_microcogeneration.htm]. Instead of burning fuel to merely heat space or water, some of the energy is converted to electricity in addition to heat. This electricity can be used within the home or business, or (if permitted by the grid management) sold back into the electric power grid. === MiniCHP === [[MiniCHP|"Mini cogeneration"]] is a so called [[Distributed Energy Resource|distributed energy resource]] (DER). the installation is usually more than 5 kWe and less than 500 kWe in a building or medium sized business [http://www.schmitt-enertec.com]. Current (2007) Micro- andMiniCHP installations use five different technologies: [[microturbines]], [[internal combustion]] engines, [[stirling engine]]s, closed cycle [[steam engine]]s and [[fuel cell]]s. ==History== Perhaps the first modern use of energy recycling was done by [[Thomas Edison]]. His 1882 Pearl Street Station, the world’s first commercial power plant, was a combined heat and power plant, producing both electricity and thermal energy while using waste heat to warm neighboring buildings.<ref>{{web cite|url=http://www.cogeneration.net/ThomasEdisonsCogenPlant.htm|title=World’s First Commercial Power Plant Was a Cogeneration Plant|work=[[Cogeneration Technologies]]}}</ref> Recycling allowed Edison’s plant to achieve approximately 50 percent efficiency. By the early 1900s, regulations emerged to promote rural electrification through the construction of centralized plants managed by regional utilities. These regulations not only promoted electrification throughout the countryside, but they also discouraged decentralized power generation, such as cogeneration. They even went so far as to make it illegal for non-utilities to sell power.<ref>{{web cite|url= http://www.senate.gov/~finance/hearings/testimony/2007test/052407testsc.pdf |title=Testimony of Sean Casten before Senate subcommittee on Energy, Natural Resources, and Infrastructure, 5/27/07|}}</ref> By 1978, Congress recognized that efficiency at central power plants had stagnated and sought to encourage improved efficiency with the [[Public Utility Regulatory Policies Act]] (PURPA), which encouraged utilities to buy power from other energy producers. Cogeneration plants proliferated, soon producing about 8 percent of all energy in the U.S.<ref>{{web cite|url= http://www.localpower.org|title=World Survey of Decentralized Energy, 5/06|}}</ref> However, the bill left implementation and enforcement up to individual states, resulting in little or nothing being done in many parts of the country. In 2008 Tom Casten, chairman of the company Recycled Energy Development, said that "''We think we could make about 19 to 20 percent of U.S. electricity with heat that is currently thrown away by industry.''"<ref name=npr2008may22/> Outside the U.S., energy recycling is more common. Denmark is probably the most active energy recycler, obtaining about 55% of its energy from cogeneration and waste heat recovery. Other large countries, including Germany, Russia, and India, also obtain a much higher share of their energy from decentralized sources.<ref>{{web cite|url= http://www.localpower.org|title=World Survey of Decentralized Energy, 5/06|}}</ref><ref name=npr2008may22>[http://www.npr.org/templates/story/story.php?storyId=90714692 'Recycling' Energy Seen Saving Companies Money]. By David Schaper. May 22, 2008. [[Morning Edition]]. [[National Public Radio]].</ref> <!-- commenting out removed image ==Diagram== Here is a typical isometric representation: [http://en.wikipedia.org/wiki/Image:Cogen_iso1.jpg] --> == See also == *[[Biogas powerplant#Plant types|Biogas Powerplant]] *[[Decentralized energy]] (more general term that encompasses CHP) *[[Distributed generation|Distributed Generation]] (more general term that encompasses CHP) *[[Geothermal power in Iceland]] *[[New York City steam system]] *Proposed [[oil phase-out in Sweden]] *[[Trigeneration]] (using waste heat for cooling during the summer) *[[District heating]] *[[Organic Rankine Cycle]] ==References== {{reflist}} == External links == * [http://www.howardhallfarm.com/freewatt.html Information about the Climate Energy Warm Air Freewatt Cogeneration System] * [http://a257.g.akamaitech.net/7/257/2422/01jan20061800/edocket.access.gpo.gov/2006/E6-1096.htm Energy Policy Act of 2005 - sec. 1817 "Study of Cogeneration"] * CHP in Finland: ** [http://www.opet-chp.net/download/wp3/iisalmifinland.pdf High cogeneration performance by innovative steam turbine for biomass-fired CHP plant in Iisalmi, Finland] (URL accessed on 30 March 2006) * CHP in Belgium : **[http://www.labothap.ulg.ac.be/cmsms/Staff/QuoilinS/TFE_SQ010607.pdf Experimental study and modeling of a low temperature Rankine Cycle for small scale cogeneration] * UK micro CHP schemes: ** [http://www.defra.gov.uk/environment/climatechange/uk/energy/chp/ CHP at DEFRA] ** BBC News: [http://news.bbc.co.uk/2/hi/programmes/working_lunch/3231549.stm Power from the people] ** [http://cogen.mit.edu/powermit/ M.I.T. algae reactor] * Associations: ** [http://www.uschpa.org/ U.S. Combined Heat and Power Association] ** [http://www.cogen.org/ COGEN Europe The European Association for the Promotion of Cogeneration] ** [http://www.localpower.org/ The World Alliance for Decentralized Energy] [[Category:Power station technology]] [[Category:Electricity distribution]] [[Category:Electric power]] [[Category:Sustainable technologies]] [[Category:Sustainable energy]] [[Category:Energy efficiency]] [[Category:Residential heating]] [[bg:Когенерация]] [[ca:Cogeneració]] [[cs:Kogenerace]] [[de:Kraft-Wärme-Kopplung]] [[et:Koostootmine]] [[es:Cogeneración]] [[eu:Baterako sorkuntza]] [[fr:Cogénération]] [[gl:Coxeración]] [[it:Cogenerazione]] [[nl:Warmtekrachtkoppeling]] [[ja:コジェネレーション]] [[pl:Elektrociepłownia]] [[ru:Теплоэлектроцентраль]] [[sl:Soproizvodnja toplote in električne energije]] [[sr:Kogeneracija]] [[sv:Kraftvärmeverk]]