| Abstract from DBPedia | Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time. Cogeneration is a more efficient use of fuel or heat, because otherwise-wasted heat from electricity generation is put to some productive use. Combined heat and power (CHP) plants recover otherwise wasted thermal energy for heating. This is also called combined heat and power district heating. Small CHP plants are an example of decentralized energy. By-product heat at moderate temperatures (100–180 °C, 212–356 °F) can also be used in absorption refrigerators for cooling. The supply of high-temperature heat first drives a gas or steam turbine-powered generator. The resulting low-temperature waste heat is then used for water or space heating. At smaller scales (typically below 1 MW), a gas engine or diesel engine may be used. Cogeneration is also common with geothermal power plants as they often produce relatively low grade heat. Binary cycles may be necessary to reach acceptable thermal efficiency for electricity generation at all. Cogeneration is less commonly employed in nuclear power plants as NIMBY and safety considerations have often kept them further from population centers than comparable chemical power plants and district heating is less efficient in lower population density areas due to transmission losses. Cogeneration was practiced in some of the earliest installations of electrical generation. Before central stations distributed power, industries generating their own power used exhaust steam for process heating. Large office and apartment buildings, hotels, and stores commonly generated their own power and used waste steam for building heat. Due to the high cost of early purchased power, these CHP operations continued for many years after utility electricity became available.コジェネレーション、またはコージェネレーション (cogeneration) 、英語では“combined heat and power”ともいわれ、内燃機関、外燃機関等の排熱を利用して動力・温熱・冷熱を取り出し、総合エネルギー効率を高めるエネルギー供給システムである。 略してコージェネ、コジェネとも呼ばれ、一般的には熱併給発電（ねつへいきゅうはつでん）または熱電併給（ねつでんへいきゅう）と訳されている。訳語から廃熱発電を用いるものと思われがちだが、給湯や蒸気吸収冷凍機で冷熱を製造するなど発電以外の運用もある。 日本においては、京都議定書の発効に伴い製造サイドとして電機メーカーやガス会社が、需要者サイドとしてイメージ向上の効果も狙うスーパーマーケットや大エネルギー消費者である大規模工場などで関心が高まっている。 コジェネレーションを発展させて二酸化炭素（CO2）も利用するようにしたトリジェネレーションがある。 (Source: http://dbpedia.org/resource/Cogeneration) |
