The EcoCute (エコキュート, ekokyūto) is an energy-efficient electric Air source heat pump, only for water heating and supply system, not use for air conditioning or alike, that uses heat extracted from the air to heat water for domestic, industrial and commercial use. Instead of the more conventional ammonia or haloalkane gases, EcoCute uses supercritical carbon dioxide as a refrigerant. The technology offers a means of energy conservation and reduces the emission of greenhouse gas. It is a registered trademark of Kansai Electric Power Company.[1]
The name of the EcoCute comes from the Japanese phrase Shizen Reibai Hīto Ponpu Kyūtō-ki (自然冷媒ヒートポンプ給湯機), which literally means "natural refrigerant heat pump water heater". [2] Eco is a contraction of either ecology or economical and Cute is a near homonym to kyūtō (給湯); literally "supply hot water". [3]
In Japan in 1998, water heating (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.[4] 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 machines, and sales of domestic units increased 130–150% each year between 2001 and 2005.[5]
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.[6][7] 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.[3] [8]
An EcoCute machine or system consists of a heat pump and hot water storage unit. The sealed components are serially connected with refrigerant CO2 gas in circulation.[9][3]
Refrigerant carbon dioxide (CO2) is numbered or coded as R-744 by ASHRAE standard 34. The EcoCute can derive two to five unit ratio of COP (Coefficient Of Performance) to heated hot water energy from outdoor air with single unit input of electrical energy, resulting in reduced CO2 emissions compared to water heating via electricity or natural gas.[14] The COP value changes on temperature of outside air and water feed in.[15] To produce 90 °C hot water, an EcoCute consumes 75% less electricity than an electric water heater, and costs 80% less than heating water by natural gas in Japan.[16] Also, by reducing use of fossil fuels, the EcoCute results 50% reduction in CO2 emissions.[17]
Not considering upstream losses of input source energy, as one example reference value, 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.[16]