????8. 燃料電池

????經(jīng)濟(jì)實(shí)惠的氫動(dòng)力燃料電池對整整一代研究人員來說就像傳說中在遠(yuǎn)方閃耀的金山（El Dorado）一樣，是一個(gè)充滿誘惑力的目標(biāo)。氫氣之所以這么吸引人，是因?yàn)樗茉趪鴥?nèi)生產(chǎn)，而且燃燒清潔，同時(shí)燃料電池汽車的能效要比汽油車高兩到三倍。妨礙它推廣的主要因素是電池生產(chǎn)成本較高，加注氫氣的站點(diǎn)也太少。結(jié)果，現(xiàn)在汽車廠商正在測試小型燃料電池車車隊(duì)，但這類車還無法投放普通消費(fèi)者市場。目前兩款有名的車型正在接受極限測試：一個(gè)是本田FCX Clarity，另一個(gè)是2012款梅賽德斯奔馳F-Cell（見上圖），這輛車每公斤氫氣（大概相當(dāng)于一加侖汽油）可行駛52英里。

????8. Fuel cells

????Like a fictional El Dorado glimmering in the distance, affordable hydrogen-powered fuel cells have been an elusive goal for a generation of researchers. Hydrogen is appealing because it can be produced domestically and burns cleanly, and fuel cell vehicles are two or three times more efficient than gasoline-powered ones. What's held them back has been the cost of building the cells themselves and a network of fueling stations to distribute the hydrogen. As a result, small fleets of FCVs are being tested by manufacturers, but no fuel cell vehicles have reached the consumer market. Two notable models in limited tests: the Honda FCX Clarity, and the 2012 Mercedes-Benz F-cell (above), which gets 52 miles per kg of hydrogen (roughly equivalent to a gallon of gasoline).