They may be facing extinction in the electric-transport revolution, but one benefit of cars with internal combustion engines is that they are easy and quick to refuel, so travelling a long way in one is rarely a problem. Not so for their successors. In the absence of universal standards, electric cars come with a variety of charging systems and different sorts of cables and sockets. Extended journeys therefore need careful planning to make sure that the battery is fully charged at the start and that compatible fast-charging stations are available en route.

在電力交通工具革命中,內燃機驅動型汽車可能正面臨被淘汰的命運,但它的一個優點是補充燃料方便快捷,所以駕駛一輛汽車長途旅行沒什么問題。但后繼汽車不是這樣,在缺少通用標準的情況下,電動汽車使用各種充電系統,電纜和插座也各不相同。因此,長途旅行需要周密的計劃,出發前確保電池滿電,途中有兼容的快速充電樁可用。

It would be much more convenient if electric cars could be recharged wirelessly. Some electric toothbrushes and other small devices, such as mobile phones, can already be topped up in this way using a process called electromagnetic induction. This employs an alternating mains current flowing through a coil to create a varying magnetic field, which then generates another current in a second coil placed alongside it according to principles elucidated in the 19th century by Michael Faraday. The device containing the second coil then converts the transmitted power into direct current, which is used to recharge a battery.

如果電動汽車可以無線充電就方便多了。有些電動牙刷和手機等小型設備已利用電磁感應原理實現了無線充電。根據19世紀邁克·法拉第闡明的原理,讓交流電流經一個線圈產生交變磁場,鄰近的次級線圈可產生另一股電流,包含次級線圈的設備再將傳輸的電能轉化為直流電,從而為電池充電。

As users of electric toothbrushes and phones will know, device and charger must be both close to each other and precisely aligned for this process to work. That is tricky to achieve with an electric car, which sits above the ground and requires higher levels of energy transfer.

電動牙刷和手機用戶都知道,設備和充電器必須相互靠近和對齊,該充電原理才能奏效。這對電動汽車來說很難實現,因為它位于地面,需要傳輸的電能較大。


WiTricity is working with a number of carmakers and sold its first commercial system in 2018 to bmw, which fits it to some of its 530e hybrid cars. Alex Gruzen, WiTricity’s boss, expects further developments soon. He says the arrangement can transmit power from the grid to the car’s battery with an efficiency of up to 93%, which is similar to that achieved by a plug-in system. Nor does a car’s receiving coil have to be positioned directly above the charging pad on the ground—a useful feature of resonating coils being that they do not have to be so closely aligned to transmit power.

WiTricity正在與多家汽車制造商合作,2018年將首款商用系統出售給了寶馬公司,后者在部分530e混合動力車上使用了該裝置。WiTricity公司總裁亞歷克斯·格魯澤期待不久將有更大的進展。他表示該裝置能使電網向汽車電池輸送電能的效率達到93%,接近插電式充電裝置的效率。汽車的接收線圈不必放置在地面充電墊的正上方,這種線圈共振特性很有用,因為兩者不必對齊就能傳輸電能。

As to how much power can be transferred, and how quickly, this is a question of cost and design. For most uses at home, a wireless charger of 11 kilowatts might suffice. That would provide around 50km of range per hour of charging and cost around $2,000, says Mr Gruzen. At this price, he says, a wireless system would be competitive with plug-in home-charging units.

至于能傳輸多少電能,傳輸的速度有多快,這涉及到成本和設計問題。對于多數家用場景來說,11千瓦的無線充電裝置夠用了。格魯澤先生表示,每充電一小時能讓汽車行駛約50公里,成本約2000美元。相比插電式家用充電裝置,無線充電裝置的這個價位是有競爭力的。

Another advantage of wireless recharging is what Mr Gruzen calls “power snacking”. This is topping up the battery when a car is stationary for a short time. The company provides systems to recharge taxis in this way while they wait in line, and to do the same for electric buses at bus stops. It is also possible to charge vehicles while they are on the move. That might make sense in places where vehicles often queue up, such as at airports, but Mr Gruzen does not think digging up motorways to install a charging lane is a realistic proposition.

無線充電的另一個優勢是格魯澤先生所說的“電力快餐”,在汽車短暫停駛時為電池充滿電。該公司提供的裝置能以該方式為排隊的出租車充電,為??吭诠卉囌镜碾妱庸卉嚦潆?,甚至為行駛中的汽車充電,對于汽車經常排隊的場所可能派上用場,比如機場。但格魯澤先生認為,設法在高速公路上布置充電車道的設想不現實。

Other companies are producing wireless-recharging systems which use various forms of magnetic-resonance induction. So far these are mostly for commercial vehicles, though such systems are bound to encourage the spread of the technology to cars as well. Momentum Dynamics, a Pennsylvanian firm, for instance, announced in March a deal to supply wireless rechargers to GreenPower Motor Company, a producer of electric shuttle buses.

其他企業正在生產無線充電裝置,它們采用各種磁共振感應方式。目前大部分被用于商用車輛,但這種裝置必將推動該技術在乘用車上的普及。例如:美國賓夕法尼亞州一家名為Momentum Dynamics的公司在3月份公布一筆交易,向電動區間車制造商GreenPower Motor Company供應無線充電裝置。

Wireless recharging of electric trucks is also coming. In February, a team led by Omer Onar at the Oak Ridge National Laboratory, in Tennessee, demonstrated a 20 kilowatt set-up that thus takes three hours to recharge the 60-kilowatt-hour battery pack in a hybrid ups delivery truck. The team have also developed a 120 kilowatt fast-charger, which Dr Onar says would be capable of wirelessly charging electric cars at a similar rate to a Tesla Supercharger, one of the fastest plug-in systems available.

電動貨車的無線充電時代也即將到來。由美國田納西州橡樹嶺國家實驗室的奧默·奧納帶領的團隊演示了一種20千瓦的充電裝置,它為一臺UPS混合動力貨運車的60千瓦時蓄電池組充滿電耗費3個小時。該團隊還研發出一種120千瓦的快充裝置,為電動汽車無線充電的速度堪比特斯拉的超級充電樁,后者是現有充電速度最快的插電式充電裝置之一。

Crucially, as did not happen for plug-in vehicles, standards are being developed that should, at least in theory, permit any suitably equipped electric vehicle to use any wireless charger. China recently ratified a set of national criteria similar to those being developed and promoted by industry groups in the West, including WiTricity. As China has been one of the countries most forcefully pushing the electrification of vehicles, its clout in the marketplace might ensure that most companies, foreign ones included, keep to the standards it has set.

至關重要的是,該行業正在研究相關標準,至少從理論上允許一切配置得當的電動汽車使用所有的無線充電裝置,這是插電式電動汽車所不具備的。中國最近通過了一系列國家標準,類似于西方行業團體研究和推廣的標準,包括WiTricity公司。由于中國是最大力度推動汽車電氣化的國家之一,其市場影響力可能會確保包括外企在內的多數企業遵守中國制定的標準。