Listen and read 31: Wirelessly charging electric cars - Thấm Tâm Vy

Nội dung text: Listen and read 31: Wirelessly charging electric cars - Thấm Tâm Vy

1. LISTEN AND READ 31 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 WIRELESSLY CHARGING ELECTRIC CARS 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 It’s time to cut the cord that achieved by a plug-in system. Nor does a car’s receiving coil have to be positioned Wireless vehicle-charging is starting to look promising 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. THEY MAY BE facing extinction in the electric-transport revolution, but one benefit As to how much power can be transferred, and how quickly, this is a question of cost of cars with internal combustion engines is that they are easy and quick to refuel, so and design. For most uses at home, a wireless charger of 11 kilowatts might suffice. travelling a long way in one is rarely a problem. Not so for their successors. In the That would provide around 50km of range per hour of charging and cost around $2,000, absence of universal standards, electric cars come with a variety of charging systems says Mr Gruzen. At this price, he says, a wireless system would be competitive with and different sorts of cables and sockets. Extended journeys therefore need careful plug-in home-charging units. planning to make sure that the battery is fully charged at the start and that compatible Another advantage of wireless recharging is what Mr Gruzen calls “power snacking”. fast-charging stations are available en route. This is topping up the battery when a car is stationary for a short time. The company It would be much more convenient if electric cars could be recharged wirelessly. Some provides systems to recharge taxis in this way while they wait in line, and to do the electric toothbrushes and other small devices, such as mobile phones, can already be same for electric buses at bus stops. It is also possible to charge vehicles while they are topped up in this way using a process on the move. That might make sense in places where vehicles often queue up, such as at called electromagnetic induction. This airports, but Mr Gruzen does not think digging up motorways to install a charging lane employs an alternating mains current is a realistic proposition. flowing through a coil to create a varying Other companies are producing wireless-recharging systems which use various forms magnetic field, which then generates of magnetic-resonance induction. So far these are mostly for commercial vehicles, another current in a second coil placed though such systems are bound to encourage the spread of the technology to cars as alongside it according to principles well. Momentum Dynamics, a Pennsylvanian firm, for instance, announced in March a elucidated in the 19th century by Michael deal to supply wireless rechargers to GreenPower Motor Company, a producer of Faraday. The device containing the second electric shuttle buses. coil then converts the transmitted power into Wireless recharging of electric trucks is also coming. In February, a team led by Omer direct current, which is used to recharge a Onar at the Oak Ridge National Laboratory, in Tennessee, demonstrated a 20 kilowatt battery. set-up that thus takes three hours to recharge the 60-kilowatt-hour battery pack in a As users of electric toothbrushes and hybrid ups delivery truck. The team have also developed a 120 kilowatt fast-charger, phones will know, device and charger must which Dr Onar says would be capable of wirelessly charging electric cars at a similar be both close to each other and precisely rate to a Tesla Supercharger, one of the fastest plug-in systems available. Crucially, as aligned for this process to work. That is did not happen for plug-in vehicles, standards are being developed that should, at least tricky to achieve with an electric car, which sits above the ground and requires higher in theory, permit any suitably equipped electric vehicle to use any wireless charger. levels of energy transfer. These problems are being overcome with advances like that China recently ratified a set of national criteria similar to those being developed and made by WiTricity, a firm based near Boston, Massachusetts. promoted by industry groups in the West, including WiTricity. As China has been one This company was founded in 2007 to commercialise the work of Marin Soljaốiổ and of the countries most forcefully pushing the electrification of vehicles, its clout in the his colleagues at the Massachusetts Institute of Technology. Dr Soljaốiổ knew, in marketplace might ensure that most companies, foreign ones included, keep to the theory, that by having the transmitting and receiving coils resonate at the same standards it has set. [The Economist 16.5.2020 US] frequency it should be possible to transfer greater amounts of energy over longer Notes: distances, and he sought to turn that knowledge to practical account. In one experiment, - en route: [< French} = on the way he and his colleagues sent enough power over a two-metre gap to illuminate a 60 watt - topped up : increased the level slightly - elucidate: to explain something difficult by providing information (= clarify) bulb. They also did safety tests and found that transmission of this power could be done - digging up: finding hidden information by careful searching without harming people in the vicinity. - magnetic-resonance induction: cảm ứng cộng hưởng từ - clout: the authority to influence people's decision Thẩm Tõm Vy, 16.05.2020 LISTEN AND READ 31