有人說，聚變能“是一種未來的能源來源，并且取之不盡、用之不竭”，很多人對此加以抨擊。似乎燃料電池車也受到了類似質(zhì)疑，因?yàn)檫@種車似乎非常神奇，能將儲存的氫氣和大氣中的氧氣轉(zhuǎn)化為動能，用于個人交通，且排出的副產(chǎn)品僅為水。但在過去的幾十年中，這種車都是可望而不可即的。
一些環(huán)保主義者就曾指責(zé)小布什政府，稱其支持汽車燃料電池是在偷梁換柱，真正的目的是繼續(xù)使用化石燃料，因?yàn)樗麄冋J(rèn)為，用燃料電池為汽車提供能源并不現(xiàn)實(shí)。
但事實(shí)上，汽車制造商為了滿足加州的零排放要求，已開始逐漸推出燃料電池汽車。所有車都是手工制造的，只能租賃使用，并且限量上市。燃料電池的技術(shù)障礙已得到攻克，但下一步的實(shí)施工作卻極具挑戰(zhàn)性，因?yàn)槿剂想姵仄嚨某杀靖甙?，而且在極低溫度方面的難題仍未解決。
“到2020年，我們預(yù)計(jì)燃料電池汽車的產(chǎn)量可以破萬，”燃料電池和氫能源協(xié)會（Fuel Cell and Hydrogen Energy Association）主席Morry Markowitz表示。“很多主流汽車制造商已斥資數(shù)十億美元發(fā)展這項(xiàng)技術(shù)，現(xiàn)在汽車展廳里也展示了一些燃料電池汽車，”他說。“這充分說明這些公司的決心和燃料電池技術(shù)的未來。”
“我們面臨的主要挑戰(zhàn)是如何擴(kuò)大規(guī)模，包括基礎(chǔ)設(shè)施建設(shè)和汽車量產(chǎn)，” 美國國家可再生能源實(shí)驗(yàn)室（National Renewable Energy Lab）燃料電池小組主管Bryan Pivovar表示。過去，基礎(chǔ)科學(xué)的突破性進(jìn)展較少，阻礙了燃料電池汽車的實(shí)際應(yīng)用，但如今這些障礙已得到攻克，他說。“現(xiàn)在，我們已經(jīng)取得了長足進(jìn)步，實(shí)現(xiàn)量產(chǎn)不再遙遠(yuǎn)。”
現(xiàn)在，量產(chǎn)化道路越來越明確，這是前所未有的。在2015年東京車展上，本田發(fā)布了下一代Clarity燃料電池汽車，這款車將于2016年3月開始面向日本客戶租售。在開場致辭中，本田總裁兼CEO Takahiro Hachigo表示，量產(chǎn)化征程艱難而漫長。
“約13年前，也就是2002年12月，秉持面向未來的理念，本田成為全球首個實(shí)現(xiàn)終極清潔汽車——燃料電池汽車實(shí)際應(yīng)用的汽車制造商，”Hachigo表示。“自那時起，本田一直致力于提升旗下燃料電池汽車的性能，包括車輛在寒冷區(qū)域的行駛性能，這是非常有挑戰(zhàn)性的。”
豐田展示了新款FCV Plus概念車和雷克薩斯LF-FC。FCV Plus是一款別具一格、吸引眼球的概念車，搭載了輪轂電機(jī)；LF-FC則展示了下一代雷克薩斯LS旗艦轎車的設(shè)計(jì)風(fēng)格，該車型很可能會配置燃料電池動力總成。
現(xiàn)代推出了一款燃料電池動力版途勝跨界SUV，公司官網(wǎng)上的里程計(jì)數(shù)器顯示，旗下燃料電池汽車的累積行駛里程已超過75萬英里。
寶馬在東京車展上表示，寶馬首輛燃料電池汽車很可能是一款大尺寸轎車，將于2020年以后上市。屆時，寶馬與豐田的氫氣研發(fā)合作伙伴關(guān)系（始于2013年）也將結(jié)束。寶馬正在研發(fā)一種工藝，在極端低溫下壓縮氫氣，從而提高存儲量。為此，寶馬采用了豐田研發(fā)的燃料電池堆。寶馬表示，其燃料電池汽車的續(xù)航里程將高于豐田的Mirai。豐田稱，Mirai的續(xù)航里程可達(dá)435英里（700 km）。
目前，豐田Mirai已經(jīng)與少數(shù)加州顧客見面，這是一款專門的FCV車型，外形獨(dú)特，彰顯了車內(nèi)的可替代燃料動力總成系統(tǒng)。燃料電池汽車市場方興未艾，市場也必須明確客戶更傾向于專門的燃料電池車型，還是現(xiàn)行熱門車型的燃料電池改裝版。NREL的Pivovar認(rèn)為，豐田選擇推出專門的FCV是正確的做法。
“我認(rèn)為這是正確的做法，之前這種策略就非常成功，”他說。他也提到，作為首批投入混動車市場的車型，普銳斯獲得了巨大成功。
日本正在斥巨資發(fā)展燃料電池技術(shù)和氫基礎(chǔ)設(shè)施，并將其納入國家政策，目的是打造一個 “氫能社會”，使用零排放燃料為家庭和車輛供能。
合作走向成功
本田與通用建立了研發(fā)合作關(guān)系，打造了一個燃料電池產(chǎn)品系列，從2008年的雪佛蘭Equinox FCV到2011年的第一代本田FCX Clarity，再到2016年的新款第二代Clarity FCV，最后是2020年之前將推出的采用了合作研發(fā)的燃料電池系統(tǒng)的車型。兩家公司將其稱為“第三代”燃料電池。
與FCX Clarity相比，新款Clarity FCV使用的燃料電池體積減小了33%，功率供應(yīng)卻提高了60%。此外，一個里程碑式的進(jìn)步是，與常規(guī)發(fā)動機(jī)類似，新Clarity的整個電池系統(tǒng)置于車輛發(fā)動機(jī)罩下方，大小合適。后座也因此更為寬敞，可以乘坐三人。所以新車型可乘坐五人，而非老車型的四人。
Pivovar表示，雖然本田已率先將燃料電池汽車交付給客戶，但在燃料電池專業(yè)知識方面，以年專利申請量和掌握的關(guān)鍵技術(shù)衡量，通用仍舊是行業(yè)領(lǐng)先者。早在20世紀(jì)60年代，通用就成功生產(chǎn)了首輛FCV。
但豐田在奮起直追。因此，這兩家公司的合作相當(dāng)合適。通用汽車燃料電池業(yè)務(wù)執(zhí)行總監(jiān)Charlie Freese表示，一款燃料電池汽車的量產(chǎn)定型意味著資源將不再用于提升、改良產(chǎn)品，或削減燃料電池系統(tǒng)成本，而是用于解決汽車生產(chǎn)的實(shí)際問題。
通過合作，本田可以審慎打造Clarity FCV，并學(xué)習(xí)生產(chǎn)經(jīng)驗(yàn)；而通用的工程師則可以專注于研發(fā)第三代燃料電池，公司2020年即將推出的新車型將搭載這款電池。
“我們與本田有合作，現(xiàn)在本田已經(jīng)鎖定了一個已經(jīng)推出的量產(chǎn)項(xiàng)目，”Freese表示。“他們可以繼續(xù)重點(diǎn)發(fā)展這個項(xiàng)目，而我們則可以重點(diǎn)研發(fā)新技術(shù)。”
通用自2011年開始與美國海軍研究人員合作，為一款無人潛水裝置（UUV）——機(jī)器人迷你潛水艇，設(shè)計(jì)燃料電池電源。自此，公司的質(zhì)子交換膜（PEM）燃料電池有了新的發(fā)展模式。與通用118 Equinox FCV測試車輛相似，這款UUV由一個自動燃料電池堆提供動力。潛水時，UUV的燃料電池可以通過一個復(fù)雜的閉環(huán)氧氣存儲系統(tǒng)“呼吸”（具體可見http://articles.sae.org/13909/）。
目前，燃料電池技術(shù)已經(jīng)攻克最大難題。Clarity的燃料電池可以完整契合到發(fā)動機(jī)蓋下的位置，因此，繼續(xù)花費(fèi)資源縮小電池尺寸并不會帶來任何明顯受益。
同樣地，鉑的使用量也已成功削減，降至與內(nèi)燃機(jī)的催化轉(zhuǎn)換器相當(dāng)?shù)幕鶞?zhǔn)水平。通用的Equinox燃料電池使用了80 gm（2.8 oz）鉑，2011 款Clarity FCV用了30 gm（1.05 oz）。Pivovar表示，催化轉(zhuǎn)換器一般會用10 gm（.35 oz）鉑。
他說，催化劑其實(shí)無需這么多鉑，但是，為了保證使用壽命和安全性，汽車制造商往往會謹(jǐn)慎地額外多加幾克放進(jìn)催化劑。
通用表示，新款Clarity FCV使用的鉑不到12 gm（.42 oz），有利于節(jié)約稀有金屬。
下一步：量產(chǎn)
這意味著Freese的通用團(tuán)隊(duì)將繼續(xù)致力于通過設(shè)計(jì)降低量產(chǎn)成本?？尚写胧┲皇呛喕囅到y(tǒng)。Clarity的燃料電池系統(tǒng)搭載了兩個圓柱形的氫氣罐，因?yàn)槔硐氲那蛐卧O(shè)計(jì)會占用乘坐空間，必須修改。
兩個圓柱形的氫氣罐替代了單個球形設(shè)計(jì)，因此可以將其置于汽車底板下，但這需要更精密、更昂貴的組裝，并且需要更多的氣門和生產(chǎn)線，這也額外增加了成本。
更好的解決方案是，使用新的氫氣罐，而無需做成圓柱形或球形，單罐裝載足量氫氣，以便滿足300到400英里（482-643 km）的行駛里程。汽車行業(yè)的工程師們正在竭力攻克這個技術(shù)難題。
“常規(guī)的汽車塑料油罐可以塑造成任何形狀。”Freese告訴《汽車工程雜志》，“我們希望燃料電池汽車的儲氫罐也能實(shí)現(xiàn)這一點(diǎn)。”
一位參與項(xiàng)目的知情人士表示，豐田過去一直與壓力油罐專業(yè)公司——量子技術(shù)（Quantum Technologies）合作研發(fā)一種新型高壓儲氫方案，但后來豐田叫停了合作項(xiàng)目，開始進(jìn)行內(nèi)部研發(fā)。
成本削減面臨一大問題，即以產(chǎn)業(yè)標(biāo)準(zhǔn)衡量，F(xiàn)CV的量產(chǎn)數(shù)量較小。雖然本田和通用均已開始銷售燃料電池汽車，但該車型市場在2020年前不會走向成熟。但是，即便在整車相對小規(guī)模量產(chǎn)的情況下，一些部件可以大規(guī)模量產(chǎn)，實(shí)現(xiàn)規(guī)模經(jīng)濟(jì)效益，因?yàn)樗熊囆投紩褂眠@些部件。
Freese指出，每個電池的氣體擴(kuò)散需要330層碳紙。因此，如果汽車年產(chǎn)量可達(dá)1萬，就能創(chuàng)造330萬層的碳紙需求。
此外，部件生產(chǎn)也可以受益于大規(guī)模量產(chǎn)。盡管一些部件只適用于燃料電池汽車，但它們與高產(chǎn)量內(nèi)燃機(jī)汽車中使用的部件十分類似。例如，燃料電池中使用的壓縮機(jī)與渦輪增壓機(jī)類似，可以受益于渦輪的大規(guī)模量產(chǎn)。
“可以借用的知識有很多，”他說。“這和噴油器的情況一樣。噴油器的要求各有不同，但FCV需要的噴射設(shè)備和壓縮天然氣汽車的噴油器不會有很大區(qū)別。因此，傳統(tǒng)汽車行業(yè)對FCV的噴射設(shè)備并非完全陌生。”
Freese指出，通用與本田合作還有另一個好處，就是可以向獲得這些部件的供應(yīng)。
“有時候，能提供我們需要的部件的供應(yīng)商屈指可數(shù)，”他表示。“我們有一些共同的供應(yīng)商，也有一些各自分別合作的供應(yīng)商。因此，通過合作，我們不僅能收獲不同的觀點(diǎn)，還能接觸到其他的供應(yīng)商。”
目前，燃料電池車仍處于低產(chǎn)量和手工生產(chǎn)階段。汽車制造商們致力于實(shí)現(xiàn)FCV的大規(guī)模量產(chǎn)，并降低價格，目的是吸引更多消費(fèi)者，并幫助汽車制造商扭虧為盈。
“為了發(fā)展FCV，汽車制造商們都承受了一定虧損，”Pivovar表示。“但從技術(shù)層面來看，毋庸置疑，燃料電池汽車已經(jīng)成為現(xiàn)實(shí)。”
也許，聚變能就是未來的希望。
作者：Dan Carney
來源：SAE《汽車工程雜志》
翻譯：SAE上海辦公室
Fuel cell futures no longer a dream
The knock on fusion power is that “It is the energy source of the future, and it always will be.” It has seemed like the same criticism could be levied against fuel cell vehicles, as their seemingly magical ability to turn stored hydrogen and atmospheric oxygen into motive power for personal transportation — with only water as a by-product emission —has remained tantalizingly out of reach for decades.
Indeed, some environmentalists charged that the George W. Bush administration’s support for automotive fuel cells was a cynical play to perpetuate fossil fuel consumption, because, they insisted, fuel cells weren’t a realistic automotive power source.
But the truth is, as manufacturers begin to dribble out hand-built, lease-only, limited-market fuel cell cars to meet California’s zero-emission requirements, the technical obstacles to fuel cells have been overcome. What remains is some challenging crossing of ‘t’s and dotting of ‘i’s, because exorbitant costs and challenges like freezing temperatures have been left in fuel cells’ rear-view mirror.
“We are looking at fuel cell vehicle production to exceed tens of thousands by 2020,” predicts Morry Markowitz, president of the Fuel Cell and Hydrogen Energy Association. “Some of the leading manufacturers have spent billions of dollars and products are now reaching showrooms,” he said. “That speaks volumes to the commitment these companies have and the future of this technology."
“The major challenge we’re facing is the scale-up, both for the infrastructure and for the mass production of vehicles,” stated Bryan Pivovar, Fuel Cell Group Manager for the National Renewable Energy Lab. While breakthroughs in basic science used to stand in the way of practical fuel cell vehicles, those obstacles have been overcome, he said. “Now, we’re to the point where we’re pretty close and incremental advances might be sufficient.”
The march toward production is proceeding with a certainty unseen previously. At the 2015 Tokyo Motor Show, Honda introduced its next-generation Clarity Fuel Cell car that it will begin leasing to Japanese customers in March, 2016. In his introductory remarks at the show, Honda President and CEO Takahiro Hachigo acknowledged that the road to production has been a long one.
“Approximately 13 years ago, in December 2002, Honda opened the door to the future by becoming the world’s first automaker to put the ultimate clean car, a fuel cell vehicle, into practical use,” Hachigo said. “Since then, Honda has been advancing and improving the performance of its fuel cell vehicles, including success in making it possible to drive a fuel cell vehicle in areas with cold climates, which was thought to be difficult.”
Toyota showed the far-out FCV Plus concept and the Lexus LF-FC. The FCV-Plus is an ambitious, eye-catching concept with in-wheel electric motors, while the LF-FC is a design study hinting at the next iteration of the Lexus LS flagship sedan, but shown with a potentially optional fuel cell drivetrain.
Hyundai offers a fuel cell-powered version of its Tucson crossover SUV, with a mileage counter on the company’s web site showing more than 750,000 miles of fuel cell travel so far in its vehicles.
BMW said at Tokyo that its first fuel-cell vehicle would likely be a larger-sized sedan which would go on the market after 2020, when its hydrogen development partnership with Toyota (launched in 2013) concludes. In the partnership BMW is developing a process to compress hydrogen at ultra-low temperatures to increase its storage volume, using a fuel cell stack developed by Toyota. BMW officials claim that their FCV will have greater range than the 435 mi (700 km) claimed by Toyota for its Mirai.
The Mirai, now reaching a few California customers, is a dedicated model with its own unique styling to underscore its alternative powertrain. The nascent fuel cell market will have to determine whether customers prefer specific fuel cell models or if they are happier with fuel cell versions of existing popular vehicles. NREL's Pivovar thinks Toyota is on the right track with a dedicated FCV.
“I think it is the correct approach and it has worked for them before,” he said, noting the popularity of Prius’s success as a pioneer in the hybrid-electric market.
Japan is investing heavily in fuel-cell technology and hydrogen infrastructure as part of a national policy to foster a 'hydrogen society' where the zero-emission fuel would power homes and vehicles.
Partnering for success
Honda’s development partnership with General Motors lets the two companies create a fuel cell product arc, starting with the Chevrolet Equinox FCVs of 2008, continuing through the Generation-1 2011 Honda FCX Clarity, the new Generation-2 2016 Clarity FCV and onward to vehicles using a jointly developed fuel cell system by 2020. The companies label this their “Generation-3” fuel cell.
The fuel cell in the Clarity FCV is 33% smaller and makes 60% more power than that in the FCX Clarity. A key milestone is that the entire system now fits under the car’s hood like a conventional powerplant, leaving space in the rear seat for three passengers, so the new car carries five people instead of the old car’s four.
Though Honda is the company that has been putting fuel cell vehicles in customers’ hands, GM remains the industry leader in fuel cell know-how, as measured by the number of patents filed each year and the critical technologies it commands, according to Pivovar. GM built its first FCV in the 1960s.
Toyota, however, has been catching up, so GM’s partnership with Honda is a good match. That’s because freezing a fuel cell specification for production means that resources are no longer used to improve, refine and reduce the cost of the fuel cell system and instead get focused on the practical matter of building the cars, according to Charlie Freese, GM’s Executive Director of Fuel Cell Activities.
With this partnership, Honda can take care of building Clarity FCVs and learning production lessons, while GM engineers toil on the Gen 3 fuel cell the companies will use in their 2020 products.
“By teaming up with Honda, Honda was already locked in on a production program they are rolling out,” said Freese. “They are able to remain focused on that while we remain focused on this next generation technology.”
GM's development of proton-exchange membrane (PEM) fuel cells took on a new dimension in 2011, when the automaker began working with U.S. Navyresearchers to develop a fuel-cell power unit for an unmanned undersea vehicle—essentially a robotic mini-submarine. The UUV is powered by an automotive fuel-cell stack similar to those used GM's fleet of 118 Equinox FCV test vehicles. When submerged the UUV's fuel cell “breathes” through a sophisticated closed-loop oxygen storage system (see http://articles.sae.org/13909/).
Today’s fuel cells have already conquered the most significant issues. The Clarity’s fuel cell fits entirely under the car’s hood, so spending additional resources to shrink the size of the next iteration wouldn’t provide any discernible benefit.
Similarly, the amount of platinum used has already been successfully reduced to nearly the benchmark level of that used in the catalytic converters for internal combustion engines. GM’s Equinox fuel cells used 80 gm (2.8 oz) of platinum and the 2011 Clarity FCV used 30 gm (1.05 oz). Catalytic converters typically use 10 gm (.35 oz), according to Pivovar.
Catalysts can work with less than that, but for the sake of longevity and to provide a margin of safety, manufacturers tend to err on the side of caution by using an extra couple grams in their catalysts, he said.
So with the new Clarity FCV using less than 12 gm (.42 oz), according to the company, the precious metals battle is also nearly won.
Next stop: mass production
That means that Freese’s GM team is focused on designing to reduce the cost of manufacturing in volume. One thing they can do is to simplify the cars’ systems. The Clarity Fuel Cell has a pair of cylindrical hydrogen tanks because the ideal design, a sphere, would intrude unacceptably on passenger space.
Using a pair of cylinders in place of a single sphere lets the tanks fit under the car’s floor, but it requires more complex and costly assembly and adds valves and lines that contribute additional cost.
A better solution would be a new tank that doesn't have the packaging compromises of a cylinder or sphere, and holds enough hydrogen in a single tank to provide the requisite 300-400 mi (482-643 km) driving range. The industry’s engineers are scrambling to solve this technical challenge.
“Conventional vehicles have a plastic tank molded to any shape available,” Freese told Automotive Engineering. “That would be the thing you’d aspire to get closest to.”
Toyota had been working with pressure-tank specialists Quantum Technologies on a new high-pressure hydrogen storage solution, but the automaker brought development back in house, said a source involved with the program.
A big challenge to cost reduction is that production volumes will be low by industry standards, even with both Honda and GM selling cars, because the market for the cars will still be immature in 2020. But even with relatively low-unit production, it is possible for some components to enjoy high enough volumes to exploit economies of scale because many of them are used in each car.
With 330 layers of carbon paper for gas diffusion in the cell, it creates the opportunity for 3.3 million of those layers in a production year of 10,000 cars, Freese pointed out.
Another area where there is the potential to benefit from production scale is in the production of components that, while they are unique to fuel cell vehicles, are similar to those used in high-volume internal combustion vehicles. For example, the compressors used in fuel cells are similar to turbochargers, and so they may be able to benefit from the higher production volumes of turbos, Freese said.
“There is a lot of knowledge that can be brought over,” he said. “It is the same thing on injectors. There are unique requirements, but it is not unlike other injectors that inject gaseous fuels like CNG. So they are not entirely foreign to the rest of the industry.”
The supply base that can provide these components is another area Freese points to as a benefit of GM’s joint effort with Honda.
“In some cases there are not a lot of suppliers out there who can do the things we need,” he explained. “We were working with some of the same suppliers but some were different. So we not only get exposure to other ideas, we also got exposure to other supply base players.”
As automakers find the path from today’s low-volume, hand-built production to more affordable mass-produced fuel cell vehicles, the cars will be able to attract customers and manufacturers can stop losing money on them.
“Everybody loses money on the way through just to get us to a better place,” Pivovar reflected. “From a technological perspective, it is clear: fuel cell vehicles are here.”
Maybe fusion is next.
Author: Dan Carney
Source: SAE Automotive Engineering Magazine
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