為了因應美國地區(qū)越來越嚴苛的公司平均燃料經(jīng)濟性（CAFE）相關(guān)政策，先期已在歐洲地區(qū)開始轉(zhuǎn)型的制冷劑行業(yè)也開始在美國地區(qū)加速轉(zhuǎn)型。具體來說，整個行業(yè)將轉(zhuǎn)而采用一種全球變暖潛能值（GWP）更低的制冷劑。汽車廠商可以通過提高車輛的燃料經(jīng)濟性獲得大量CO2積分，美國環(huán)保署(EPA)也有計劃逐步淘汰R-134a制冷劑。
根據(jù)EPA的新政策，2021年后，所有在美銷售的新車和輕質(zhì)卡車均不得再使用汽車行業(yè)常用的R-134a制冷劑。雖然這項政策僅限制汽車和輕質(zhì)卡車，但適用于中/重載卡車的類似條款也將在今年之內(nèi)出臺，因此到2021年，所有在美國境內(nèi)銷售的車輛可能均需更換制冷劑。不過，部分用于出口的車型仍可在2025年前使用R-134a系統(tǒng)。
與此同時，戴姆勒(Daimler)集團也最終同意在對制冷劑有特定政策要求的市場內(nèi)（比如美國），為旗下品牌梅賽德斯(Mercedes)車型搭配R-1234yf系統(tǒng)。不過，公司目前尚未公布任何日程。據(jù)悉，戴姆勒集團曾聲稱汽車行業(yè)用于替代R-134a系統(tǒng)的R-1234yf制冷劑存在一定消防安全隱患。為了解決這一問題，戴姆勒集團在旗下車型的發(fā)動機蓋下安裝了一款“滅火器”，可以直接向工程師認為存在起火隱患的部位噴射惰性氬氣滅火。這里的消防安全隱患主要是指，一些部件在工作時釋放的熱量可能足以點燃泄露的制冷劑。
由于低GWP潛能值的R-1234yf無法直接與R-134a系統(tǒng)兼容，因此R-134a可能并不會立刻退出歷史舞臺。R-1234yf的CAFE積分為：汽車13.8g/mi，卡車17.2 g/mi。（GWP是一種度量單位，意為全球變暖潛能值，世界各地的環(huán)境管理機構(gòu)可以用GWP描述單位氣體對全球變暖造成的影響。GWP是一個相對值，相當于單位質(zhì)量溫室氣體釋放的熱量與相同質(zhì)量CO2釋放熱量的比值。其中，CO2的GWP潛能值定義為1。）
由于采用低GWP潛能值的制冷劑可以獲得更多CAFE積分，菲亞特克萊斯勒汽車（FCA）自2014年開始進行制冷劑的改革。通用汽車旗下僅有凱迪拉克XTS采用了R-1234yf制冷劑，但公司將在今年年底前廣泛推廣R-1234yf系統(tǒng)。據(jù)報道，福特(Ford)將在今年4月開始進行制冷劑改革，第一款采用R-1234fy系統(tǒng)的車型為翼虎(Escape)，但目前尚無具體推廣的細節(jié)。目前而言，汽車廠商完全可以為同一裝配線上的不同汽車搭配不同的制冷劑，實現(xiàn)這一點并不困難。
保修報銷
據(jù)報道，目前R-1234yf的“零售價”每千克超過220美元，批發(fā)略有優(yōu)惠。網(wǎng)上也有各種R-1234yf的廣告，售價低至每千克160美元（未經(jīng)確認）。但無論如何，這仍比每千克售價通常僅要6.6美元的R-134a貴的多。
FCA所售的R-1234yf制冷劑按盎司計算，公司要求經(jīng)銷商僅向廠方申報額外使用的制冷劑（比如，維修結(jié)束后的制冷劑充裝、開始階段從汽車系統(tǒng)回收的少量制冷劑）。制冷劑回收/循環(huán)/充裝（簡稱RRR）設(shè)備的精度可達±1盎司，而且可以打印出額外使用的制冷劑劑量，經(jīng)銷商在向FCA報銷時，必須附上RRR設(shè)備打印的列表。
最近幾年，車輛所需的制冷劑用量正在不斷下降。目前，F(xiàn)CA公司R-1234yf制冷劑用量最少的車型為Alfa Romeo4C，僅為370克；最高的為克萊斯勒(Chrysler)300和道奇(Dodge)Charger，用量為709克；其余車型的用量多在454至510克之間。
FCA的低GWP潛能值制冷劑推廣相當順利。在最近舉行的移動空調(diào)協(xié)會（Mobile A/C Society，簡稱MACS）大會上，F(xiàn)CA中西部商業(yè)中心(Midwest Business Center)技術(shù)顧問Alan McAvoy向觀眾表示：“我們早在3年前就推出了采用R-1234yf系統(tǒng)的車型，目前已累計制造了超過200萬輛搭配R-1234yf的車輛。目前，針對制冷劑系統(tǒng)的維修服務(wù)主要局限在碰撞損傷和修復泄露等。”
雖然R-134a的性能與R-1234yf無異，但EPA平流層保護部(Stratospheric Protection Division)的Rebecca von dem Hagen在MACS大會上表示，任何修車廠如果試圖將R-1234yf系統(tǒng)改裝為R-134a系統(tǒng)，將面臨違反排放控制法規(guī)的風險。為了預防此類情況，車輛和制冷劑容器均需針對不同制冷劑，搭配專用的閥門配置。
R-744可以繼續(xù)使用
未來，EPA不會限制小罐R-1234yf制冷劑在DIY市場中的流通，但前提是這些罐子配備了自動閉合閥門，可以防止泄露。這項規(guī)定是基于加州針對R-134a的規(guī)定設(shè)定的，其中還包括每罐收取10美元押金的要求。
墨西哥化工(Mexichem)曾嘗試研制一種名為R-445a的混合制冷劑，用于替代R-1234yf系統(tǒng)，但目前已經(jīng)被叫停。同時，一系列與此相關(guān)的SAE標準修訂工作也停了下來。這種混合R-445a制冷劑內(nèi)含85%的R-1234ze（一種與R-1234yf同族的烯烴）、6%的二氧化碳，以及9%的R-134a。由于成分中含有將會在2021年禁用的R-134a，因此這種制冷劑是否受限于美國EPA的2021禁用規(guī)定，目前還尚無定論。
德國汽車生產(chǎn)商協(xié)會VDA的成員仍在繼續(xù)進行R-711 CO2制冷劑的合作研發(fā)。戴姆勒的工程師希望能將這種制冷劑用于部分2017款梅賽德斯E級和S級歐洲車型。目前，SAE為將這種制冷劑進入美國市場而制定的標準尚未重新開始生效。
在使用R-744制冷劑的車型開始在美銷售之前，EPA將可能需要針對 “所有制冷劑均不能排放，而必須回收（或銷毀）處理”的規(guī)定進行修改。這條規(guī)定也同時適用于R-1234yf，盡管這種制冷劑的GWP潛能值很低。CO2是一種自然物，而且非常便宜，因此強制回收CO2的規(guī)定存在一定的環(huán)保方面的爭議。這是由于“回收”這一行為本身就會產(chǎn)生排放，甚至可能超過制冷劑自身的熱效應（畢竟其GWP潛能值僅為1.0）。EPA已經(jīng)注意到這個問題，但目前尚未專門宣布頒發(fā)豁免條款的可能性。
與此同時，目前市場上尚無可以替換R-1234yf系統(tǒng)的低GWP制冷劑。戴姆勒曾經(jīng)強烈質(zhì)疑R-1234yf制冷劑的安全性，而且曾出示實驗視頻，展示輕度易燃的R-1234yf可能存在安全隱患。但這次，戴姆勒也別無他法。戴姆勒的測試曾引起了廣發(fā)爭議，因為也有汽車行業(yè)的其他成員表示，他們認為R-1234yf非常安全。
歐盟曾發(fā)出律師函，要求戴姆勒在“新型”汽車的設(shè)計中，遵守歐盟的低GWP規(guī)定。因此，戴姆勒最終同意使用R-1234yf系統(tǒng)，不過也同時搭配了上文提到的車載滅火器。
作者：Paul Weissler
來源：SAE《汽車工程雜志》
翻譯：SAE 上海辦公室
EPA's 2021 A/C refrigerant rules accelerate R-1234yf changeover
The industry transition to a low global-warming-potential (GWP) air conditioning refrigerant, already underway in Europe, moves into high gear in the U.S., as CAFE (Corporate Average Fuel Economy) regulations add incentives. Car manufacturers receive substantial CO2 credits that translate to more miles per gallon, and a newEPA phaseout schedule for R-134a has been adopted.
Per new EPA regulation, the long-used R-134a cannot be installed in new cars and light trucks built for domestic sale after 2021MY. Although this rule is limited to those vehicles, similar regulations for medium/heavy-duty trucks are coming this year, so the 2021 deadline may affect all domestic vehicles by that time. Some vehicles for export will still be able to use R-134a systems until 2025MY.
In the meantime, Daimler, which had charged that the alternative refrigerant R-1234yf posed potential fire safety dangers, has finally agreed to use R-1234yf systems in its Mercedes vehicles for markets where the refrigerant either is mandated or is effectively pressed for by regulatory bodies (as in the U.S.). However, no rollout schedule has been announced. Daimler will add an underhood "fire extinguisher"—an argon gas canister with spray lines directed at all parts that its engineers say might become hot enough for a leaking refrigerant to ignite.
Because low GWP R-1234yf cannot be retrofitted to R-134a systems, production of R-134a will continue indefinitely for service. The R-1234yf CAFE credits are 13.8 g/mi for cars, 17.2 g/mi for trucks. (GWP, a metric used by environmental regulatory agencies worldwide, is a measure of how much a given mass of a gas contributes to global warming. It is a relative scale which compares the amount of heat trapped by greenhouse gas to the amount of heat trapped in an equal mass of CO2. The GWP of CO2 is by definition 1.)
The value of storing CAFE credits for a low GWP refrigerant enticed Fiat Chrysler Automobiles (FCA) into beginning its changeover in 2014MY. General Motors has had just one entry in that period, the Cadillac XTS, but GM will be virtually across the board by the end of this year. Ford reportedly will begin its changeover in April with the Escape, but no details of its rollout are available. Sending vehicles with either refrigerant down the same assembly line is not a difficult process.
Warranty payments
The "street retail" price of R-1234yf—over $100 lb/ $220 kg has reportedly dropped slightly for volume buyers, and there are internet advertisements (of unknown validity) for as low as $72.50 lb ($160 kg). However, that's still much higher than the typical $3 lb/$6.60 kg for R-134a.
FCA's list price for R-1234yf is per ounce—because its dealers are instructed to bill the factory only for the additional amount (total refrigerant charge at the conclusion of the repair, less amount recovered from the vehicle system at the start). The recovery/recycle/recharge machines have a charge accuracy of ±1 oz and print out the amount added; the printout must be attached to a warranty claim.
Total refrigerant charges have been coming down in recent years, and those for FCA's R-1234yf systems are as low as 13 oz (370 g) on the Alfa Romeo 4C to a high of 25 oz (709 g) for the Chrysler 300 and Dodge Charger, with most in the 16-18-oz range (454-510 g).
FCA's launch of the low GWP refrigerant has gone very smoothly. At the recentMobile A/C Society (MACS) convention attended by Automotive Engineering, Alan McAvoy, technical advisor at the FCA Midwest Business Center, told the audience: "We currently have R-1234yf vehicles that have been on the road for over three years and have built over two million total. Service to this point is primarily limited to collision damage, plus a few with minor hose or fitting leakage."
Although R-134a will perform comparably to R-1234yf, EPA's Rebecca von dem Hagen, of the agency's Stratospheric Protection Division, told the MACS convention that a shop changing an R-1234yf system to R-134a would constitute the offense of tampering with an emissions control. Each refrigerant requires specific service valve fittings to discourage any attempt, both on the vehicle and the refrigerant containers.
R-744 work continues
EPA will allow sale of small cans of R-1234yf to the do-it-yourself market, provided the cans have self-closing valves to minimize venting. This is based on California's regulation for R-134a, which includes a $10/can deposit system.
An attempt by Mexichem to develop R-445a as a lower-cost blend refrigerant alternative to R-1234yf, has been put on hold. Work on a series of enabling SAE standards has stopped, too. The blend consists of 85% R-1234ze (an olefin in the same family as R-1234yf), 6% carbon dioxide and 9% R-134a, so whether it faced the 2021 deadline for R-134a is now moot.
Members of the VDA, the German automakers association, are continuing consortium development of R-744 (CO2) refrigerant. Daimler engineers hope for its 2017 introduction on some Mercedes E- and S-Class European models. As a result, the SAE program to develop enabling standards for a U.S. introduction has not been reactivated.
Before R-744 cars would be sold in America, EPA would be asked to modify its requirement that no refrigerants can be vented, so must be recycled (or destroyed)—a rule that includes R-1234yf despite its low GWP. CO2 is both natural and inexpensive, and any requirement to recycle it would be environmentally questionable. Emissions would be produced by the effort, perhaps in excess of the low GWP (just 1.0) of the refrigerant itself. EPA recognizes this issue but has not specifically announced it will address an exemption.
In the meantime, there is no market-ready low GWP alternative, hence the changeover to R-1234yf. Even Daimler, which has most strongly questioned its safety and famously showed videos of a laboratory test that demonstrated potential dangers from its mild flammability, has no choice at this time. The Daimler test indications were widely disputed, as others in the industry attested to R-1234yf safety.
The European Union has initiated lawsuits to force compliance by Daimler to EU's low- GWP rule for "new type" vehicles. So the automaker has finally agreed to use R-1234yf systems, but with the on-board argon fire-suppression system noted earlier.
Author: Paul Weissler
Source: SAE Automotive Engineering Magazine
由于價格昂貴，R-1234yf的銷售規(guī)格為一罐10磅，而R-134a的銷售規(guī)格為30磅。所有R-1234yf的容器上均有紅色警示，示意該物質(zhì)具有輕度易燃性。 
FCA經(jīng)銷商的制冷劑RRR設(shè)備可以打印出制冷劑的實際用量，用于保修報銷。圖左為一張RRR設(shè)備打印出來的樣表，由于使用了一輛沒有任何制冷劑的新車，因此本次充裝為“滿充”。
R-1234yf系統(tǒng)搭配了專用的閥門和蓋子，能夠阻止汽車行業(yè)擅用R-134a。對比而言，R-1234yf的GWP潛能值為4.0，而R-134a卻高達1430。