The EcoCute is an energy efficient heat pump that uses both electricity and heat extracted from the air to heat water for domestic use. Instead of the more conventional ammonia or haloalkane gases, EcoCute uses carbon dioxide as a refrigerant. The technology offers a means of energy conservation and reduces the emission of greenhouse gas.


The formal name of the nihongo| EcoCute|自然冷媒ヒートポンプ式電気給湯機|Sizen reibai hīto ponpu shiki denki kyūtō ki literally means "natural refrigerant heat pump type electricity water heating supply machine". [ [ Fiscal year 2001, 12th Energy conservation award] by Minister of Economy, Trade and Industry (Japan), jp icon ] Eco is a contraction of either Ecology or Economical and nihongo|Cute also means |給湯|kyūtō; literally "supply hot water." Make hot water by CO2, initiative in the world jp icon]


Modern chemical refrigeration techniques developed after the proposal of the Carnot cycle in 1824. Jacob Perkins invented an ice-making machine that used ether in 1843, and Edmond Carré built a refrigerator that used water and sulfuric acid in 1850. In 1870, the first ice-making machine in Japan was experimentally made and installed in the Tokyo University laboratory of Fukuzawa Yukichi to cool him down during a period of illness. Fusanosuke Kuhara, founder of Hitachi, Ltd., made for his own home use an air conditioner using compressed CO2 as a refrigerant.

In 1930 Thomas Midgley discovered dichlorodifluoromethane, a chlorinated fluorocarbon (CFC) known as Freon. CFCs rapidly replaced traditional refrigerant substances, including CO2 (which proved hard to compress for domestic use [ The rediscovery of CO2] SHECCO] ), for use in heat pumps and refrigerators. But from the 1980s CFCs began to lose favor as refrigerant when their damaging effects on the ozone layer were discovered. An alternative type of refrigerant, Hydro fluoro compounds (HFC), also lost favour when they were identified as greenhouse gases. The Vienna Convention for the Protection of the Ozone Layer, the Montreal Protocol and the Kyoto Protocol call for the complete abandonment of such refrigerants by 2030.

In 1989, amid international concern about the effects of chlorofluorocarbons (CFC and HFC) on the ozone layer, scientist Gustav Lorentzen and SINTEF patented a method for using CO2 as a refrigerant in heating and cooling. Further research into CO2 refrigeration was then conducted at Shecco (Sustainable Heating and Cooling with CO2) in Brussels, Belgium, leading to increasing use of CO2 refrigerant technology in Europe.

In 1993 the Japanese company Denso, in collaboration with Gustav Lorentzen, developed an automobile air conditioner using CO2 as a refrigerant. They demonstrated the invention at the June 1998 International Institute of Refrigeration/Gustav Lorentzen Conference. [ Technology of Car air conditioner blooms as EcoCute,] Denso jp icon] [ [ Concerns and Solutions for CO2 Air Conditioning Systemsfor Compact Vehicles,] Denso Corporation, 15 April, 2004, Mobile Air Conditioning Summit 2004, Washington, D.C] [ [ Concerns of C02 Air Conditioning System for Compact Vehicles] , Denso Corporation, "References: at bottom": Natural working fluids ’98 (IIR Gustav Lorentzen Conference on Natural Working Fluids, Oslo, Norway,1998] . After the conference Denso were approached by CRIEPI (Central Research Institute of Electric Power Industry) and TEPCO (The Tokyo Electric Power Company) to develop a prototype air conditioner using natural refrigerant materials instead of Freon. Together they produced 30 prototype EcoCute units for a year-long experimental installation at locations throughout Japan, from the cold climate of Hokkaidō to hotter Okinawa. After this successful feasibility study, Denso obtained a patent to compress CO2 refrigerant for use in a heat pump from SINTEF in September 2000. [ EcoCute] , Japan Patent Office Society jp icon]

The first commercial domestic EcoCute was marketed in Japan by CORONA Corp. in May 2001, and several manufacturers sold one million units there by 25 May, 2007. [ [ Over 1 million EcoCute units sold in Japan on 25 May, 2007] Federation of Electric Power Companies jp icon] [ [ Announcement,] CORONA Corp., Japanese edition: コロナ jp icon]

Features and demand

In Japan in 1998, water heating (nihongo| Kyuto |給湯|kyūtō) accounted for 33.8% of typical domestic energy consumption, with air conditioner and kerosene heater heating accounting for another 26.9% and cooling by air conditioner another 2.3%. Most of the remaining 37% was spent on electrical home appliances, a field where 21st century innovations in energy conservation began to make considerable energy savings. [ [ 2.2 (2) Yearly home energy consumption by usage category] The Energy Conservation Center, Japan (ECCJ) jp icon] [ What is EcoCute] TEPCO jp icon] This left hot water supply as the most difficult area for energy conservation, leaving a gap in the market for the EcoCute. By January 2005, 26 Japanese companies were producing more than 450 models of EcoCute machine, and sales of domestic units increased 130-150% each year between 2001 and 2005.

Denso first introduced the EcoCute outside Japan at the COP9 Milan, Italy on December, 9, 2003. From 2007, Denso began concentrating on marketing the EcoCute in the EU. [ [ EcoCute demand surges in Europe,] European Heat pump network] [ [ Heat pumps offer huge potential] , IEA Conference] . In Japan, the Japanese government incorporated the EcoCute into its CO2 reduction program under the Kyoto Protocol, mandating the installation of 5.2 million units in commercial and domestic properties by 2010. [ [ Page 16/24, CO2 reduction plan, Popularlizing high efficiency hot water supply machine,] Kantei jp icon] .

EcoCute machine basics

An EcoCute machine or system consists of a heat pump and hot water storage unit. The components are serially concatenated with sealing refrigerant CO2 gas in circulation.
# At the first stage, a heat exchanger collects heat from the air outside to use as energy for the refrigerant. Air flow is usually obtained using a centrifugal fan; in cold areas with ambient temperatures around -20 to -25 an fan heater is attached.
# A gas compressor is used to heat the gas CO2 refrigerant to around 100℃ under pressure of 10MPa via adiabatic compression. The carbon dioxide becomes a supercritical fluid. [ [ Section2. Seeking supercritical fluid of CO2] Denso jp icon] [ [ EcoCute structure] Panasonic jp icon] . Several types of compressor can be used, including dual layer cylindrical compressors, scroll compressors, and dual stage rotary compressors [ [ Cooling System Composed with Rolling Piston Type 2-Stage CO2 Compressor] , Sanyo]
# At the second stage a heat exchanger transfers energy from the hot refrigerant into water to produce hot water. Water temperatures around 5℃ and up are suitable at this stage.
# Finally, ejector or expansion valves reduce pressure on the refrigerant, letting it cool via adiabatic expansion and revert to CO2 gas.

The EcoCute derives two units of energy from ambient air temperature for every unit of electrical power it requires. Each of these one unit plus two cost free units produces more than three units of hot water energy, resulting in reduced CO2 emissions compared to water heating via electricity or town gas. To produce 90℃ hot water, an EcoCute consumes 66% less energy than an electric water heater, and costs 80% less than heating water via town gas in Japan. [ [ Section 6, Denso's assumption,] Denso jp icon] . Also, by reducing use of fossil fuels, the EcoCute results in more than 50% reductions in CO2 emissions [ [ Research and development of EcoCute] CRIEPI jp icon]

The EcoCute's COP is 3.8 in industrial use, while electric power water heating is 1.0, and gas boiler is 0.88 including pilot light loss. [ [ Feature of industrial use Ecocute] , jp icon]


nihongo|EcoCute|エコキュート|ekokyūto is a registered trademark (No. 4575216 - Japan) [ [ Patents application on Heating and cooling by natural refrigerant] page 3/24 bottom, note No.10, May 15, 2003, Japan Patent Office jp icon] of Kansai Electric Power Company, but the term is also used generically to refer to water heaters designed for energy conservation or greenhouse gas emission reduction.

See also

* Transcritical cycle
* Supercritical fluid
* Gustav Lorentzen (scientist)
* R-744
* Heat exchanger
* The Cool War


External links

* [ Everything R744]
* [ Sustainable Heating and Cooling with CO2]
* [ High-efficient EcoCute models launched] , - 2008-02-01
* [ Research on Performance Evaluation of Heat Pump Water Heaters] , EcoCute 24/31 page;Prize List:(4), Mar.2002, EPA Climate Protection Award & 25/31 page Ecocute history, CRIEPI
* cite web
title=DENSO Earns 2002 Climate Protection Award From U.S. Environmental Protection Agency

* [ TEPCO'S 'Eco Cute' the World's First CO2 Heat Pump Water Heater for Residential Use]
* [ Technology and Market Development of Heat Pump Water Heaters in Japan] , IEA, Heat Pump Centre (HPC)
* [ Demand-side management] ,
*cite news | url = | title = DENSO Develops World's First CO2 Car Air Conditioner | publisher = The Auto Channel | date = 2002-12-04 | accessdate = 2008-07-19

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