維修工(gong)人手持監測(ce)工(gong)具檢查并修理汽車空調(diao)系統。(Shutterstock)
目(mu)前,美國(guo)銷售(shou)的95%的新車(che)都使用(yong)R-1234yf制冷劑。(Chemours)
密歇根州(zhou)的研究人員對雨水進行了測試(shi),以找出TFA在(zai)當(dang)地環(huan)境中的聚集位置和方式(shi)。(The Ecology Center)
最近,一個(ge)環保組(zu)織聯盟對密歇(xie)根州雨水中被廣泛(fan)使用的(de)PFAS進行了調查,并于 2024 年 8 月報告說,三個(ge)取(qu)樣(yang)點中的(de)兩個(ge)TFA占(zhan)比最大,第三個(ge)取(qu)樣(yang)點中占(zhan)比靠前。(The Ecology Center)
大(da)眾ID.4可(ke)配備使(shi)用R-744制冷(leng)劑(ji)(也稱為二氧化碳(tan))的熱泵。(大(da)眾)
幾(ji)乎所有在美國市場上出售的汽(qi)車均使(shi)用了四氟丙烯(R-1234yf)制冷(leng)劑,但歐盟目(mu)前(qian)正在醞釀(niang)關于該制冷(leng)劑的禁令,同時行(xing)業也在研究(jiu)諸如(ru)二氧化碳和丙烷等替代制冷(leng)劑。
據(ju)R-1234yf的(de)制造(zao)商科慕公(gong)司(Chemours)稱(cheng),自(zi)R-1234yf取(qu)代(dai)(dai)已被(bei)廣(guang)泛使(shi)用(yong)的(de)四氟乙(yi)烷(R-134a)以(yi)來(lai),其(qi)使(shi)用(yong)量大(da)幅增長,且目前已用(yong)于美(mei)國市場95%的(de)新(xin)車中。據(ju)估計,全(quan)球道路上(shang)約2.2億輛(liang)汽車正在使(shi)用(yong)R-1234yf。被(bei)淘(tao)汰的(de)R-134a自(zi)上(shang)世紀90年代(dai)(dai)開始廣(guang)泛應用(yong)于汽車和卡車中,但美(mei)國環境保護署(EPA)的(de)數據(ju)顯示,這種氣體冷卻劑(ji)存(cun)在一個問題,即“其(qi)全(quan)球增溫潛勢(shi)(GWP)高達二(er)氧化碳的(de)1430倍。”
EPA研究了(le)(le)二氧化碳作為制冷劑替代方(fang)案(an)的(de)可行(xing)性,并得到(dao)了(le)(le)積極的(de)結論(lun)。該環保機構表(biao)示其仍在“繼(ji)續評估(gu)適用于機動(dong)車空調領域中的(de)新(xin)型制冷劑替代方(fang)案(an)。”
環保組織并(bing)未因此消除對(dui)三氟(fu)乙酸(suan)累積的擔(dan)憂(you)。密歇根州安娜堡生態中心的研究總監Jeff Gearhart在(zai)(zai)接受SAE采(cai)訪時質疑(yi)道:“既然(ran)汽(qi)車制造商有能力識別出引發公眾擔(dan)憂(you)的新興化學物質,那(nei)么他們當初(chu)為(wei)何還要使(shi)用R-1234yf呢?汽(qi)車制造商的選擇導致我(wo)們在(zai)(zai)還未識別出其(qi)潛(qian)在(zai)(zai)風險時,就(jiu)使(shi)三氟(fu)乙酸(suan)成為(wei)了全球性污染物。”
旨在(zai)推(tui)動制(zhi)(zhi)冷行業清潔化(hua)的(de)全球性組織ATMOsphere的(de)資深編(bian)輯Michael Garry表示:“二氧化(hua)碳被視為[R-1234yf](尤(you)其在(zai)電動車熱泵領域)最具替(ti)代潛(qian)力的(de)天然制(zhi)(zhi)冷劑。丙烷也被視為一種天然制(zhi)(zhi)冷劑替(ti)代方(fang)案,但(dan)在(zai)該領域中的(de)關注度較低。”
歐洲汽車(che)制(zhi)造商協會(The European Automobile Manufacturers’ Association)在(zai)2023年發(fa)(fa)布(bu)的一份(fen)報告中指出,將R-1234yf系統替換(huan)為(使用(yong)二氧化(hua)碳的)R-744系統會導致每臺(tai)汽車(che)的空調成本上漲300歐元(yuan)(334.73美元(yuan))。該報告稱:“更換(huan)制(zhi)冷劑(ji)意味著歐盟汽車(che)制(zhi)造商每年的制(zhi)造成本將增加17億歐元(yuan)(18.9億美元(yuan)),從(cong)而導致其在(zai)全球市場上失去競(jing)爭力。”報告還預測,更換(huan)制(zhi)冷劑(ji)將引發(fa)(fa)零部(bu)件短缺的問題(ti)。
According to its manufacturer, Chemours, use of R-1234yf has grown so much since the refrigerant replaced the long-established R-134a that it’s now used in 95% of new cars sold in the U.S. An estimated 220 million cars on global roads are also using it. The problem with R-134a, which came in cars and trucks in the 1990s, is that it’s a gas with “a global warming potential (GWP) that is 1,430 times that of CO2,” according to the EPA.
Since 2017, EU legislation has banned the use of any refrigerant in new vehicles with a GWP higher than 150. That rule doomed R-134a but opened the door for R-1234yf, which has a GWP of only four. The EU is currently revisiting R-1234yf emissions rules and may ban the substance in a few years. In the U.S., the EPA stands by its use.
Fighting over refrigerants is nothing new. In 2015, the European Commission took Germany to the Court of Justice because it was allowing automakers to use banned refrigerants. At the time, Daimler argued that R-1234yf could cause fires in front-end collisions, but the EU said, “these concerns were not shared by any other car manufacturer.” Chemours describes R-1234yf as “a thoroughly tested, mildly flammable refrigerant” and referenced an approval the European Commission gave in 2014 after a scientific review. Mercedes-Benz is now in favor of the newer refrigerant and said it has“ implemented a comprehensive safety concept to mitigate the potential risk of fire” on cars fitted with R-1234yf, spokesperson Pascal Becker told SAE Media.
But does R-1234yf also pose serious health problems when it degrades into the environment? Chemours defended its product vigorously to SAE Media, claiming that it “delivers a 99% reduction in global warming potential versus the incumbent refrigerant [R-134a], advancing global climate targets without compromising performance.” But concerns remain.
A 2021 study from the University of Bristol found that both R-134a and R-1234yf result in emissions of organic trifluoroacetic acid (TFA), but the latter is much worse in that regard. The study found that changing from one chemical to the other caused a “33-fold increase of the global burden of TFA, from an annual value of 65 tons formed from the 2015 emissions of 134a to a value of 2,200 tons formed from an equivalent emission of 1234yf.”
Chemours said that TFA is “more than 95% naturally occurring” and comes from“ a variety of manmade sources, including agriculture and pharmaceutical.” The company also said, “numerous independent studies conducted over the past two decades have concluded that TFA from manmade sources does not pose a risk to the environment or human health.” Chemours can point to a 2022 UN Environmental Programme report that found that produced TFA is distributed globally and evenly distributed. “This is unlikely to present a risk to humans or the environment in these locations, but changes in concentration in surface water (or soil) would respond rapidly to releases. Monitoring of the environment for residues of TFA would provide an early warning if trends in concentration indicate rapid increases,” the organization wrote.
The UN report confirmed that TFA has a very long life but did not sound a warning. “Because of its lack of reactivity, TFA salts are persistent in the environment, and estimates of half-life are uncertain but could be in the range of centuries or millennia,” the report said. “This persistence is not a major concern because it does not react with biomolecules. TFA and its salts are easily excreted by animals and do not bioaccumulate in food chains. Salts of TFA have low toxicity to animals and plants.”
Where the EPA stands
The EPA has taken a similar position, telling SAE Media that TFA “does not interact with biological molecules and, due to its high solubility in water, it does not bioaccumulate. It is unlikely to cause adverse effects in terrestrial and aquatic organisms.” The agency says that the TFA concentrations “that would be formed, even under high assumptions of use, would still be far below the threshold for causing adverse effects.”
As an alternative, the EPA has studied CO2 as a refrigerant and found it “acceptable.” EPA is also “continuing to evaluate new alternatives for [the] motor vehicle air-conditioning sector,” the environmental agency said.
Environmental groups are not convinced they should stop worrying about accumulating TFA. “The question is why the auto companies, with all of their ability to identify emerging chemicals of concern, were using R-1234yf in the first place?” Jeff Gearhart, research director at the Ecology Center in Ann Arbor, Michigan, told SAE Media. “This is yet another missed opportunity to identify a hazard before it becomes a global pollutant.”
The New Jersey Department of Health and Senior Services describes TFA as a “corrosive chemical,” exposure to which “can severely irritate and burn the skin and eyes with possible eye damage,” and cause “coughing, wheezing and/or shortness of breath.” And the German consulting and engineering firm Refolution Industriekälte GmbH said in 2021 that “TFA in drinking water can potentially damage the liver and have other impacts, for example, on the hormone system.”
The EPA declared R-134a “unacceptable” for new vehicles as of model year 2021 but has not taken any action against R-1234yf and does not classify it as an environmentally persistent per- and polyfluorinated substance (PFAS) chemical. A study from consulting firm Ducker Carlisle, however, said that “many OEMs and thermal-management suppliers anticipate that the EU will implement a regulation banning R-1234yf by 2030.” A proposal that would include it on a list of banned chemicals is under review at the European Chemical Agency, the report said.
The EPA did not respond to SAE Media inquiries on this subject. A 2023 petition to the European Parliament proposed banning R-1234yf and replacing it with carbon dioxide (CO2). The agency said this year that it was considering restricting the use of R-1234yf.
The auto industry is already investigating alternatives to R-1234yf. Dana Nicgorski, director of engineering at Bosch with responsibility for thermal management, told SAE Media that “the definition of what constitutes a PFAS is not standard in the world, and the European definition covers a whole lot more chemicals. Absent an EPA ban, some companies might adopt natural alternatives voluntarily.”
Bosch is studying CO2 and propane as future refrigerants. “Air conditioning and heat pumps are moving toward propane, and we think automotive will move next,” Nicgorski said. He added that propane is “thermodynamically superior” and systems using it will likely “cost a bit less than a system using 1234yf, with fewer components.” That latter point might blunt auto industry concerns, but the switchover is likely to be costly. Propane is a climate issue when burned but does not have a high GWP when released as a gas. Leaks might still be an issue, but Nicgorski said today’s hermetically sealed air conditioning units are not emitters like belt-driven systems.
At the ATMOsphere conference on refrigerant alternatives in Berlin in September 2024, Stefan Elbel, the head of TU Berlin’s department of heat transfer and heat conversion, said, “Time will tell which one is the better option, propane or CO2. From an environmental standpoint, though, you could say it doesn’t matter as both are great options.”
The EPA doesn’t necessarily agree, writing, “Hydrocarbon refrigerants, such as propane, are highly flammable and are not acceptable alternatives for motor vehicle air conditioners under the Clean Air Act and the EPA’s Significant New Alternatives Policy (SNAP) Program. The use of these refrigerants…can result in fire or explosion, possibly causing injury and property damage. It may also void your car’s warranty.”
Alternatives already available
Volkswagen Group started offering CO2-based, PFAS-free heat pumps in the ID.3 and ID.4 in 2020, as well as on the Audi Q4 etron. Ford’s electric Explorer, built on VW’s MEB platform, also has an optional CO2 heat pump. Ford has said that it sees propane, code name R290, as the best refrigerant for next-generation thermal architectures.
Michael Garry, editor at large for ATMOsphere, a global market accelerator with a mission to clean up cooling, said, “The natural refrigerant that is most slated to replace [R-1234yf] (particularly in electric vehicle heat pumps) is CO2. Propane is also discussed as a natural option but has gotten less traction in the field so far.”
The Alliance for Automotive Innovation, which represents over 20 automakers, declined to comment on a potential European ban on R-1234yf. Instead, it referred us to a letter it sent to Minnesota’s Pollution Control Agency in 2023 when the state was considering PFAS legislation. “Banning use of the refrigerant now currently used in our vehicles, as the Minnesota PFAS law might do, would…result in OEMs having to significantly redesign and re-engineer our recently revamped mobile air-conditioning systems and vehicles, possibly even with the need to retrofit older vehicles,” the Alliance said. “The definition of PFAS needs to be revised to exempt these substances.”
If TFA is officially labeled PFAS, it would run afoul of states that have enacted PFAS bans. California has one of the country’s strictest bans, but it was Maine that became the first U.S. state to ban the sale of products containing intentionally added PFAS and is scheduled to start addressing refrigerants in 2040.
Heidi Pickard, a postdoctoral fellow in the School of Engineering and Applied Sciences at Harvard who has studied TFAs, said, “Many of the [refrigerants] that are currently used…can degrade into short-chain PFAS like TFA, which is accumulating in the environment. Europe is pushing for the ban of PFAS as a class, but it’s unclear if this will include TFA.”
The European Automobile Manufacturers’ Association said in a 2023 report that switching from R-1234yf to an R-744 system (which uses CO2) would add 300 euros ($334.73) to the cost of making each car with air-conditioning. “This would mean a 1.7-billion-euro [$1.89 billion] increase per year for the vehicle manufacturers in the EU and loss of competitiveness on [the] worldwide market,” the report said. It also predicted parts shortages as a result of the change.
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