Montreal Protocol
I The 28th Meeting of the Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer (MOP 28) held in Kigali, Rwanda, in October 2016 adopted an amendment to the Montreal Protocol that obligates the parties to phase down their use of hydrofluorocarbons (HFCs). As an international treaty to protect the ozone layer, the Montreal Protocol up to this point has prohibited the use of chlorofluorocarbons (CFCs) and other substances with ozone depletion potential (ODP). By committing countries to reducing their use of greenhouse gases as a way to combat global warming, the Kigali Amendment represents a breakthrough.
As a result of this amendment, countries are obligated to reduce their use of HFC refrigerants with high global warming potential (GWP). For example, developed countries such as Japan are obligated to reduce their HFC consumption by 70% in 2029 and 85% in 2036, compared with average HFC production and consumption in 2011–2013 + the hydrochlorofluorocarbon (HCFC) baseline × 15%. All countries must shift away from using high-GWP refrigerants in order to fulfill their commitments.
Shift to Low-GWP Refrigerants
The current mainstream air conditioner refrigerant in use is R410A (HFC), but it has a high GWP of 2,088. The HFC R32 (GWP of 675) has become widely used as a replacement. However, R32 is a mildly flammable gas (ASHRAE classification of A2L), so it carries high safety risks in large-size equipment and particular applications such as supermarkets.
Refrigerants for refrigeration, setting aside applications such as those using ammonia that require handling by certified service providers, have shifted from using R22 (nonflammable HCFC) to R404A in equipment such as small-and midsized display cases, but R404A’s high GWP of 3,922 is a problem.
Honeywell and Chemours
Honeywell and Chemours are two refrigerant manufacturers leading the development of alternative low- GWP refrigerants. Let’s first take a look at their latest developments.
As we reported in the April 2019 issue of JARN (, in June 2018 U.S.-based Honeywell announced Solstice N41 (ASHRAE provisional number R466A) with a GWP of 733 as a nonflammable alternative refrigerant to R410A. However, although Honeywell had initially announced that R466A would be available in mid-2019, it only just received its A1, non-flammable, non-toxic designation from ASHRAE in November 2019. It took a year and a half until then for various original equipment manufacturers (OEMs) and component manufacturers to conduct their tests and evaluate the results.
Among the OEMs, following Toshiba Carrier’s announcement at the 2018 Kobe Symposium that R466A was a ‘promising’ alternative refrigerant for R410A, China-based Midea indicated its intention to adopt the new refrigerant in its air conditioners. Sanhua, a China-based component manufacturer known for its four-way valves, also evaluated R466A positively. However, as of January 2020, R466A was still not generally available in the market, perhaps due to unresolved issues with manufacturing costs or other roadblocks.
Meanwhile, Chemours is recommending its XP41 (R463A) refrigerant in the Opteon series as a replacement for R410A and R404A. R463A is a nonflammable hydrofluoroolefin (HFO) blend with a GWP of 1,377. Chemours’ R463A has been tested by Mitsubishi Electric, which is using it in a condensing unit for refrigeration released in 2019.
Table 1 shows the standard low-GWP alternative refrigerants and their applications and brand names.
In addition to these, a number of other refrigerants are also being proposed. For example, Chemours has presented other next-generation refrigerants to replace currently used refrigerants. It has said, for example, that nonflammable XP10 (ASHRAE number R513A) in its Opteon series is suitable to replace R134a.
Other Manufacturers
Daikin, in addition to R407H, is suggesting use of
R407I (GWP of 1,337, nonflammable) and R468A (GWP of 146, mildly flammable),
which is still under development. Daikin is in the process of obtaining ASHRAE
designation for R468A.
AGC’s AMOLEA 1224yd has almost zero ODP and a GWP of less than 1, giving it minimal impact on the global environment. In terms of refrigerant performance, it offers excellent energy efficiency, high thermal, and chemical stability, and has little effect on metals, resins, or elastomers.
AGC is proposing R1224yd as the best refrigerant option for centrifugal chillers, binary cycle power plants, and exhaust-heat-recovery heat pumps among other applications.
As this shows, a range of alternative refrigerants are under development, and currently equipment manufacturers and users are field testing the refrigerants together with refrigerant manufacturers and making improvements to their equipment while trying to determine which refrigerant is the best option for the application.
Retrofitting Existing Equipment
Convenience store chains Seven-Eleven, Lawson, and
others have many franchise stores in Japan. For example, Seven-Eleven Japan has
contracts with approximately 21,000 stores throughout Japan. Almost all of
these stores have switched their refrigeration equipment from using R22 to
R404A or R410A. The Seven-Eleven headquarters now has a plan to shift this
equipment to R448A refrigerant, and has begun this shift at some stores. Lawson
has also begun retrofitting refrigeration equipment to low-GWP refrigerants.
Existing refrigerants have been criticized for their high GWP and harmful
effects on the global environment, and their use is gradually being restricted.
In Japan for example, the price of R404A has skyrocketed and it has become more
difficult to obtain after production restrictions went into effect in 2019.
Manufacturers of equipment such as reach-in display cases are gradually
shifting the refrigerant they use from R404A to R448A or R449A. R448A is a
nonflammable blend of five refrigerants (R32, R125, R134a, R1234yf, R1234ze)
with a GWP of 1,387. Compared with R404A, it offers higher energy efficiency
and therefore running cost benefits.
Toshiba Carrier, Hitachi Group, and others have released products that use
R448A refrigerant.
Mitsubishi Electric is using Chemours’ XP41 (R463A) refrigerant in
refrigeration equipment that uses R410A, which it displayed at FOOMA JAPAN 2019
held in Tokyo last July.
R463A is a blend of the five refrigerants R32, R125, R134a, R1234yf, and R744
(CO2). It is nonflammable with a GWP of 1,377 and has high energy
content similar to R410A.
Daikin was an early adopter of mildly flammable R32 as a replacement for R410A.
It has allowed open access to its R32 patents and has been highly successful in
getting R32 adopted in Japan, other parts of Asia, and Europe.
Daikin is also proposing non-flammable R407H refrigerant and conducting tests
using it in converted display cases in Japan, the United States, and Europe.
Which will become the leading next-generation refrigerants?
A
variety of refrigerants have been announced, but which ones will become the
leading players in the coming years?
For air conditioner applications, will it be R466A or R463A?
For refrigeration applications, will it be R448A or R463A (or R468A under
development by Daikin)?
For large chiller applications, will it be R1233zd(E), R1234ze(E) or R1224yd?
Other than chemical refrigerants, there are also natural refrigerants, and
research is also being conducted on their safe use. In Japan, Japan Society of
Refrigerating and Air Conditioning Engineers (JSRAE) and the Japan
Refrigeration and Air Conditioning Industry Association (JRAIA) committees have
begun risk assessments on using highly flammable R290 (propane) as refrigerant.
Currently in Japan, mildly flammable R32 has become the leading refrigerant
used in residential and commercial air conditioners, and R32 is becoming
commonly used in air conditioners in Europe as well. However, R32 has a GWP of
675 and is mildly flammable. In the future, development of refrigerants with
lower GWP, for example less than 150, will be needed.
| 出典: | eJARN |
【記事冒頭の抄訳】
エアコン用として現在主流の冷媒はR 410Aだが、その地球温暖化係数（GWP）は2088と高い。その代替としてGWPが675のR 32が現在広く使用されるようになってきた。しかし、R 32は微燃性（ASHRAE安全等級A2L）の冷媒であり、大型機器やスーパーマーケットなど特定の場所で使用される機器への使用は安全性において高いリスクが伴う。冷凍・冷蔵機器用冷媒は、アンモニアのように取扱いに有資格者を必要とする用途は別として、小型から中型のショーケースの場合不燃性のR 22からR 404Aへシフトしているが、R 404AはGWPが3922と高いのが難点である。
英文記事にある冷媒メーカによる代替冷媒の開発状況の一部を下表にまとめた。
