EcoCute (Japan)

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Domestic EcoCute outdoor unit (front) and hot water storage tank (back)

The EcoCute (エコキュート, ekokyūto) is an energy-efficient, type of air source heat pump and only for water heating with holding storage tank as the single hot water supply system, not use for air conditioning or alike. EcoCute uses heat extracted from the air to heat water for domestic, industrial and commercial use. Instead of the more conventional ammonia or pollutant 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. EcoCute is used mostly in Japan.

Etymology[edit]

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". [1] Eco is a contraction of either ecology or economical and Cute is a near homonym to kyūtō (給湯); literally "supply hot water". [2] It is a registered trademark of Kansai Electric Power Company.[3]

Features and demand[edit]

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.[2] [8]

History[edit]

See also: Air source heat pump § History

Fusanosuke Kuhara, founder of Hitachi, Ltd., made air conditioner for his own home use using compressed CO2 as refrigerant in 1917.[9] Thomas Midgley Jr. discovered dichlorodifluoromethane, a chlorinated fluorocarbon (CFC) known as freon in 1930. CFCs rapidly replaced traditional refrigerant substances, including CO2 (which proved hard to compress for domestic use([10]), for use in heat pumps and refrigerators. From the 1980s, CFCs began to lose favor as refrigerant when their damaging effects on the ozone layer were discovered. Two alternative types of refrigrant, hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs), also lost favor when they were identified as greenhouse gases. HCFCs were found to be more damaging to the ozone layer than originally thought. The Vienna Convention for the Protection of the Ozone Layer, the Montreal Protocol and the Kyoto Protocol call for the complete abandonment of such refrigerant by 2030.

In 1989, international concern about the effects of chlorofluorocarbons and hydrochlorofluorocarbons on the ozone layer, scientist Gustav Lorentzen and SINTEF patented a method for using CO2 as 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.[10]

Denso in collaboration with Gustav Lorentzen, developed an automobile air conditioner using CO2 as refrigerant in 1993. They demonstrated the invention at the June 1998 International Institute of Refrigeration/Gustav Lorentzen Conference.[11] After the conference, CRIEPI and TEPCO approached Denso about developing 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.

The first commercial domestic EcoCute was marketed in Japan by Corona Corporation [ja] in May 2001, and several manufacturers sold there this year, and nine manufacturers were awarded by Minister of Economy, Trade and Industry,[1] cumulative total 300 thousand units in 2001 (fiscal year, April to March), 1.74 million units by 2008, and 9.01 million units by August 2023.[12][13]

EcoCute machine basics[edit]

An EcoCute machine or system consists of a heat pump unit and hot water storage unit.

The following is to describe functional steps in heat pump unit. The sealed components of heat pump unit are serially connected with refrigerant CO2 gas in circulation. [2] Heat pump unit is installed in outside of house or building, but in cold district unit to be installed inside.
  1. At the first stage, first heat exchanger (air to refrigerant) collects heat from the air outside then move it’s heat to the refrigerant as energy transfer. Air flow is usually obtained using a centrifugal fan; in cold areas with ambient temperatures around −20 to −25 °C an auxiliary fan heater is attached.
  2. A gas compressor is used to increase the temperature of the gaseous CO2 refrigerant to hot around 100 °C under pressure of 10M Pa via adiabatic compression. The carbon dioxide becomes a supercritical fluid.[2]Several types of compressors can be used, including dual layer cylindrical compressors, scroll compressors, and dual stage rotary compressors.[14]
  3. At the third stage, second or another heat exchanger (refrigerant to water) transfers energy from the hot refrigerant into water to produce hot water. Cool water from storage tank unit here is feed into heat pump unit and changed to hot water through heat exchanger then return to feed out to storage tank unit. Water temperatures around 50 °C and up are suitable at this stage.[15][16][17]
  4. Finally, ejector or expansion valvesreduce pressure on the refrigerant, letting it cool refrigerant CO2 gas via adiabatic expansion and revert to CO2 gas from supercritical fluid, then circulation back to the first stage.[2]
The following is to describe cool/hot water flow via heat exchanger component of heat pump unit and water storage unit. Large hot water storage tank unit with volume range from 180L[18] to 560L[19][20][21] and installed in outside, but in cold district, tank to be installed inside to keep hot water from cold air outside. The storage tank has two inputs and two outputs. Named here, A Cool water input, B Cool water output, C Hot water input and D Hot water output for explanation purpose for to/from tank basis.
  1. At lower part of tank, named here, A Cool water input from tap water into tank, and B Cool water output to second heat exchanger (refrigerant to water, the third stage of pump unit description above) via pipe.　
  2. B Cool water output from tank to heat pump, heat exchanger (refrigerant to water, the third stage above), and C Hot water input from heat pump to tank, each component is serially connected via pipe. Cool water changed to hot water in this stage.
  3. Hot water output from heat pump unit to tank, is also hot water input into tank. Note that cool water is input and output at lower part of tank, and hot water is also input and output at upper part of tank. The single tank stores both cool and hot temperature of water, cool water in lower part and hot water in upper part. In Relative density, cool water is heavier and hot water is lighter in weight so that each cool/hot water kept lower and upper part and not mixed nor be tepid/lukewarm water.
  4. D Hot water output from tank to feed to final stage as user's usage hot water such as bathing, kitchen, underfloor heating and others.

JIS published revised JIS C 9220：2018, 90 pages standard document in 2018, from initial version JIS C 9220：2011, that states with titled Residential heat pump water heaters and use refrigerant CO2 or Hydrofluorocarbons (HFCs) with hot water storage tank unit as the single system.[22]

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.[23] The COP value changes on temperature of outside air and water feed in.[24] 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.[25] Also, by reducing use of fossil fuels, the EcoCute results 50% reduction in CO2 emissions.[26]

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.[25]

Market response[edit]

Married couple in Gunma had been felt insomnia, headache, dizziness, nausea etc. health hazards caused possible low frequency sound, operation sound and vibration of EcoCute since Feb. 2009 by husband and May by wife. Couple claimed to Consumer Affairs Agency for inspection and survey in 2012, and litigation to the house next door who own EcoCute. Conclusion of trial is reconciliation with approx. 2.7 million Japanese yen include health hazards and replacement of brand new EcoCute system, all fee covered by its mfg. and owners house builder in Nov. 2013. Consumer Affairs Agency reported technical details in Dec. 2014. Yotaro Hatamura (ja:畑村洋太郎), chairman of the committee in Consumer Affairs Agency asked manufacturers to make efforts to reduce the risk of health hazards from EcoCute on 19, Dec. 2014.[27]

See also[edit]

References[edit]

  1. ^ a b "Fiscal year 2001, 12th Energy Conservation Award of Minister of Economy, Trade and Industry" (in Japanese). The Energy Conservation Center, Japan (ECCJ). Archived from the original on 2002-10-20. Retrieved 2008-07-10.(in Japanese) The Energy Conservation Center, Japan (ECCJ) (in Japanese) Fiscal year 2001 (Heisei 13), 12th Energy Conservation Award from Ministry of Economy, Trade and Industry. 5 companies with product named EcoCute and other 4 not named but conforming EcoCute requirement and performance, total 9 companies awarded, marked with "*" (*Denso, *CORONA, *Mitsubishi Electric, *Sekisui Chemical, *四変テック Archived 2024-03-02 at the Wayback Machine, *キューヘン Archived 2024-03-02 at the Wayback Machine, *Former 日立空調システム Archived 2024-04-01 at the Wayback Machine, *Tokyo Electric Power Company, *Central Research Institute of Electric Power Industry).
  2. ^ a b c d e "Making hot water by CO2" (in Japanese). Central Research Institute of Electrical Power Industry. Archived from the original on 2009-08-10. Retrieved 2008-07-10. Archive indicates: Go to page 1-3, by bottom right selector ← Back [1] [2] [3] Next → Page 1: Naming. Page 2: illustrated EcoCute compositions and function. Page 3 shows, 2nd sentence from bottom in 2nd paragraph indicates 5.2 million (*3) unit diffusion by 2010. Back to page 2, top left illustration is detail of EcoCute closed refrigerant loop circuit, from left, the heat of outside air is taken into (pumping into) refrigerant gas CO2 via evaporation type heat exchanger (Electricity fan used for smooth air flow in/out for outdoor unit with negligible electricity cost in this stage). This is first stage in four stages. Step forward next stage in clockwise, compressor (electricity is mostly consumed here) compressing gas CO2 to higher heat temperature. Heated up CO2 circulates to another heat exchanger, hot refrigerant CO2 to hot water, then step to expansion valve (no electricity) and refrigerant back to gas CO2 as last stage, then step back to first stage. Noted that as EcoCute principle (<エコキュートの原理>), CO2 is state of matter of supercritical between compressor – heat exchanger (producing hot water) – expansion valve in sealed manner circulation.
  3. ^ Report of Patents application trend on Heating and cooling by natural refrigerant Archived 2006-12-08 at the Wayback Machine Trademark No. 4575216 – Japan, third line 10. from bottom on page 3/24, May 15, 2003, Japan Patent Office (in Japanese)
  4. ^ 2.2 (2) Yearly home energy consumption by usage category Archived 2007-06-11 at the Wayback Machine Bar graph: Section (2) Energy consumption by purpose of usage per household、bottom, year '98 ((2) 世帯当たり用途別エネルギー消費量) The Energy Conservation Center, Japan (ECCJ) (in Japanese)
  5. ^ TOKUGIKON (特許庁技術懇話会) Archived 2005-05-12 at the Wayback Machine, Organized current and retired officers, with Japan Patent Office, technical discussion association (特許庁技術懇話会) since 1934 (in Japanese). Archive indicates: First page with page number 122: Context/content line 10-11. EcoCute put on market in 2001, approx. 450 types produced by 26 Mfg. as of now/today (2005.1.28. shown at bottom line, this pdf file/document issued date) and 130 – 150% annual increased in 2001–2005. (エコキュートは、2 0 0 1年に発売されて以来年成長率 1 3 0〜1 5 0%と好調な売れ行きを見せており、今では2 6 社から約4 5 0種類の製品が販売されています)
  6. ^ EcoCute demand surges in Europe Archived 2008-10-19 at the Wayback Machine, European Heat pump network
  7. ^ Heat pumps offer huge potential Archived 2009-08-13 at the Wayback Machine, IEA Conference
  8. ^ 26 pages of the plan for energy saving and CO2 emission reduction: Archived 2024-03-02 at the Wayback Machine Page 16/26, the second block from left of bottom layer frame: Promote CO2 refrigerant heat pump for hot water supply 5.2 million unit by 2010. (CO2冷媒ヒートポンプ給湯器の普及台数<約520万台>) Official issue from Kantei (in Japanese)
  9. ^ Fusanosuke Kuhara used CO2 gas compressed Cryocooler in 1917. Archived 2022-07-10 at the Wayback Machine 2nd Page numbered 28, right side line 3-6. Fusanosuke Kuhara attached CO2 gas compressed Cryocooler with approx. 6,400kcal/h in his home in 1917. In Japanese: 冷凍機が冷房用として使用されたのは1917年久原房之助が神戸の私邸に約6400kcal/h炭酸ガス圧縮機を取り付け、室内を冷やしたのが最初といわれています.
  10. ^ a b The rediscovery of CO2 Archived 2007-10-07 at the Wayback Machine SHECCO
  11. ^ Natural Working Fluids '98, IIR – Gustav Lorentzen Conference: CiNii Archived 2024-02-27 at the Wayback Machine
  12. ^ EcoCute: number of units , cumulative transition, shipments, 9.01 million by August 2023Archived 2024-02-28 at the Wayback Machine Archived: Bar graph describes: EcoCute, number of units in transition, cumulative shipments (エコキュート累積出荷台数の推移), Horizontal axis represents year (Japanese fiscal year Apr.-Mar.) 2001–2021. Vertical axis depicts shipment units in Myriad 10,000 units. 1.74 million by 2008 and 8.06 million by 2021 for example. Heat Pump & Thermal Storage Technology center of Japan (HPTCJ)
  13. ^ Announcement Archived 2004-06-09 at the Wayback Machine, CORONA Corp., Japanese edition: コロナ (in Japanese) Page 2, section 2. Growth Strategy (コロナの成長戦略): World first household use EcoCute developed, shipment and on sale in 2001 (2001年に世界で初めて家庭用「エコキュート」」の開発に成功し、発売以来)
  14. ^ Cooling System Composed with Rolling Piston Type 2-Stage CO2 Compressor Archived 2006-02-19 at the Wayback Machine, Sanyo
  15. ^ Output of hot water supply temperature is preference of individual or family user, and EcoCute manufacture set temperature range by model for market, not industrial specific value.
  16. ^ EcoCuteArchived 2005-11-07 at the Wayback Machine, Japan Patent Office Society (in Japanese). Page 127, 2005.1.28. no.236 tokugikon, Fig 7 Heat pump configuration illustration: At top right, Output of hot water is possible to rise up to 90 °C. Under the condition of outside air temperature -10 °C, EcoCute can produce 90 °C hot water that could not obtain by chlorofluorocarbon refrigerant (5 °C water inlet at bottom right). Website is organized current and retired officers from Japan Patent Office technical discussion association (特許庁技術懇話会) since 1934. Accessed on 2024-02-06.
  17. ^ Referenced web site (in Japanese) of Sakaguchi Boiler ServiceArchived 2023-06-06 at the Wayback Machine, sakabo.com (in Japanese) Referenced web site of Sakaguchi Boiler Service in Kumamoto, Japan (坂口ボイラーサービス). Recommending temperature setting is boiling the hot water tank to be 65 to 80 °C, hot water supply is recommended to 50 to 60 °C then mixed with cool water suitable for human body. Avoid growth range of legionella in 20 to 45 °C, also under 40 °C tend to make the trouble on thermostatic mixing valve with hot and cool water. Temperature more than 90 °C is wasting heat energy and cost of electric cost. Accessed on 2024-02-06.
  18. ^ Kakaku.com Japanese site: 180L, Archived 2024-05-17 at the Wayback Machine
  19. ^ Kakaku.com Japanese site: 560L, Archived 2024-05-17 at the Wayback Machine
  20. ^ Image of heat pump unit and storage tank
  21. ^ Kakaku.com site pick up, in May 2024, five mfg. out of listed 17 for household market and 21 for business, as of 27 April 2024, according to EcoCute Japanese language version EcoCute#manufacture (ja: エコキュート#メーカー). Daikin, Mitsubishi Electric, Panasonic, Hitachi and Corona Corporation [ja] are compared price and other specifications. Tank storage volume searched range of 180L to 560L
  22. ^ JIS C 9220 2018 revised JIS std. (written in Japanese language) for JIS C 9220：2018 in 2018, from C9220 : 2011, Archived 2023-11-28 at the Wayback Machine, titled Residential heat pump water heaters (家庭用ヒートポンプ給湯機), next page of (3), covering range (1 適用範囲), apply to machine use Refrigerant (CO2) or Hydrofluorocarbons (HFCs) (二酸化炭素（CO2）又はハイドロフルオロカーボン(HFC)を冷媒として用いたもの), this JIS C 9220 2018 states required heat pump, water heater and hot water storage tank within as single machine system. As the standard does not mention wording trademark of EcoCute in English nor Japanese.
    Before JIS C 9220：2011, JARAIA (The Japan Refrigeration and Air Conditioning Industry Association) site JARAIA , Archived 2022-06-26 at the Wayback Machine, statement from JARAIA is: Home use heat pump and hot water supply machine (家庭用ヒートポンプ給湯機（エコキュート）had been standards JRA 4050 based indication to be started as JIS C 9220 of 2011 (Heisei 23) (In Japanese: 家庭用ヒートポンプ給湯機(エコキュート)…JRA 4050…平成23年2月…JIS C 9220制定されJIS C 9220の表示が始まります).
  23. ^ Japan Atomic Energy Relations Organization JAERO (ja:日本原子力文化財団) Archived 2023-10-05 at the Wayback Machine (in Japanese) Energy Encyclopedia (エネ百科), website supported by JAERO, describing: Mechanism of CO2 refrigerant heat pump, titled EcoCute (エコキュート), for hot water supply Electric energy (1) + Outdoor air energy (2 or more) = Obtained hot water energy (3 or more) (CO₂冷媒ヒートポンプ給湯器のしくみ): Three frames from left are Heat pump unit (ヒートポンプユニット), Hot water storage unit (貯湯ユニット) and House part. Within Heat pump unit, closed loop in circulation manner, operates to transfer Outdoor air energy (2 or more) (大気熱2以上) into the refrigerant CO2 through Air Heat Exchanger (空気熱交換器) via fan, then follow in clockwise, the refrigerant compressed by compressor (圧縮機/コンプレッサー) operates under applied Electric energy (1) (電気エネルギー1). Next step, heat energy transition into cool water and warm up to hot water (水加熱) through Heat Exchanger (熱交換器), then flow proceed down to Expansion Valve (膨張弁), the refrigerant CO2 back to Air Heat Exchanger (空気熱交換器), as total refrigerant CO2 cycle (CO2冷媒サイクル). The device, at bottom right in Heat pump unit frame, is cool/hot water circulate pump (ポンプ) feed in to Hot water storage unit. At this stage, 1 + (2 or more) = (3 or more) energy transition realized. Cool/hot water tank store obtained energy of more than 3 (得られる給湯エネルギー3以上). Top right is the temperature adjustment valve (温調弁) to maintain suitable temperature of storage hot water and to supply for household use for kitchen (キッチン), washroom (洗面所), bath (お風呂), underfloor heating (床暖房). Cool water supplied into Hot water storage unit at bottom right.
  24. ^ Website for example; EcoCute consideration of relation on electric cost and outside air temperature (エコキュート: 電気代と気温の関係に関する考察) Archived 2021-04-12 at the Wayback Machine (in Japanese) Table shows COP value of four mfg.'s EcoCute and these average with outside air temperature (left most column), next to right, feed in water temp., COP value of Mitsubishi (三菱), CORONA (コロナ), Daikin (ダイキン), Panasonic (formerly 松下) and average, right most column is measured season with top line air 7 °C (気温) in warmer/high temp. winter (冬季高温), middle line 16 °C rated Japanese temp.; Average temperature in Japan (定格), bottom line 25 °C in summer (夏季). Top line shows; Warm winter air temp. 7 °C, water temp. 9 °C, Average COP 3.32, for look at example. Fig.1 (COP vs. Temp. diagram (COP 0 – 6 vs. temp. 0-30 °C) indicates temp. between 0 and 16 °C; presents COP 2 to 5 in linear, and over 16 to 25 °; COP is saturated to 5. Line colour; Blue line=Mitsubishi, Pink=CORONA, Green=Daikin, Red=Panasonic
  25. ^ a b Feature of industrial use Ecocute Archived 2008-06-10 at the Wayback Machine, www.itomic.co.jp (in Japanese) Archive indicates: Information from Nihon Itomic Co., Ltd. Archived 2024-02-18 at the Wayback Machine for their EcoCute: EcoCute effectively heat up water to 90 °C. First bar chart shows comparison of COP of, from top, Itomic industrial EcoCute COP:4.0, electric heather COP:1.0, gas boiler COP:0.88. Itomic industrial EcoCute having marginal tolerance from COP 4.0 to 3.8 as specification value on delivery from factory. Chart also implicates four COP:1 machines brings the same thermal energy of hot water in volume of one COP:4 machine does. Ratio is (COP:4 – COP:1) / COP:4=0.75 so that EcoCute consume 75% less than COP:1 electric kW. Second bar chart shows CO2 emission comparison: EcoCute:50% is half compared to town gas or city gas burning boiler type 100%.
  26. ^ Research and development of EcoCute Archived 2005-09-24 at the Wayback Machine CRIEPI (in Japanese) Archive indicates: Titled – Development of home appliance hot water supply by refrigerant CO2. In 2/2 page, last two sentences in area inside the bold line: EcoCute reduce primary energy 30% and CO2 emission 50% compared to water heating by town gas or city gas burning boiler type. There points well evaluated and awarded with prizes, on Energy Conservation Award (省エネルギー大賞) by Minister of Economy, Trade and Industry, and from other organizations in 2001–2002.
  27. ^ Referring Japanese site, Yomiuri Shimbun Archived 2014-12-19 at the Wayback Machine dated on 19, Dec. 2014: Possible reason of health hazards with low frequency of EcoCute is claimed to Consumer Affairs Agency by married couple in Gunma Pref.(ｴｺｷｭｰﾄの音、健康被害原因の可能性) and chairman of the committe 畑村洋太郎 asked
    Consumer Affairs Agency report: Married couple in Gunma pref. had been felt insomnia, headache, dizziness, nausea etc. since Feb. 2009 by husband and May by wife. Couple claimed, in Oct. 2012(平成24年10月), to Consumer Affairs Agency for inspection and survey. The report issued in 19, Dec. 2014 (平成26年12月19日), that health hazards caused possible low frequency sound, operation sound and vibration of heat pump hot water supply machine, (家庭用 ヒートポンプ給湯機) (not use trade term EcoCute on government documents), that heat pump hot water supply machine is installed in the house next door, 2 Metre distance from couple’s house as high residential density. 17, June 2016(平成 28) Erratum (Errata sheets)
    Nikkei site 18, Nov. 2013 Nikkei site Archived 2013-11-21 at the Wayback Machine report it resulted that settlement in litigation between couple and EcoCute owner EcoCute suspension of operation, and litigation with approx. 2.7 million Japanese yen, and reached to reconciliation include health hazards, and replacement of EcoCute system by mfg. and owners house builder on 18, Nov. 2013. EcoCute should stop in that year and replacement by other mfg. ‘s EcoCute. All fee to be covered by EcoCute mfg. and owners house builder (who seems recommended EcoCute).
    Note for yearly sequence: In 2009: Couple felt health hazards, in 2012 Couple claimed to Agency, in 2013 settlement in litigation, in 2014 Yomiuri and Agency reported.

External links[edit]

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