About Heat Pump water heater

About Eco Cute

Eco Cute is a heat pump water heater using aerothermal energy to heat water for domestic, commercial and industrial use. Eco-Cute is combination of “eco” from economy and ecology and kyuto, the Japanese word for hot water supply (pronounced like “cute”).Chlorofluorocarbon used as refrigerant in air conditioners are not able to efficiently produce high temperatures required for hot water supply. Using CO2 as refrigerant has solved this bottleneck.
Compressed CO2 up to 100 barometric pressures reaches supercritical state, a state somewhere between a gas and a liquid. CO2 in this state can be easily heated up to much higher temperatures, enabling heating water over 90°C, necessary for hot water supply. Then, in 1998, Central Research Institute of Electric Power Industry of Japan, DENSO CORPORATION, and Tokyo Electric Power Company (TEPCO) started joint development of the world's first natural refrigerant heat pump water heater. Eco Cute was introduced to the Japanese market in 2001.
The largest advantage of Eco Cute is that "it does not burn fuel." "The common sense of burning fuel to boil water" has become completely outdated. Instead of burning, necessary heat is taken in from the "air." Accordingly, no CO2 is emitted, as contrasted to a burning process.
A small amount of CO2 is emitted at the time of power generation to obtain marginal power required for pumping up heat from the air. But, the amount of CO2 emission is much less than a combustion type water heater.
A combustion type water heater is unable to take in energy more than the amount put in. On the other hand, Eco Cute has improved its efficiency to COP = 5.1 in the recent model from COP = 3.5 of the initial model. Even taking into account of 40% of power generation efficiency, it produces heat greater than the energy put in a power station. Its primary energy consumption is much less than combustion type water heater.
As a result, in case of Eco Cute with COP = 4, it releases some 65% less CO2, compared with conventional water heaters. Reduction in CO2 emission totals 0.8 ton a year per household in Japan.

One-third of total household energy consumption of Japan is for hot water supply. Currently, combustion type water heaters have a majority market share. If efficient Eco Cute spreads, significant energy-saving and reduction of CO2 emissions would be possible. Residential sector accounts for 15% of total energy consumption in Japan. If all home water heaters are replaced by Eco Cute of COP = 4, 25 million tons of CO2 emissions, or some 2% of the total, could be reduced a year in Japan.

Heat pumps, as well as PV or Solar water heater, utilize Solar energy.