Wireless charging has magnetic appeal for EV buyers

Cabled EV charging systems have the jump, but electromagnetic wireless alternatives can complement and potentially overtake them

In the mid-1990s, PC maker Compaq published a full-page ad in major newspapers spruiking its new wireless power supply. Packed with jargon, trademarks and diagrams, it proved a convincing act until someone noticed it was April 1.

Turns out the ad wasn’t merely witty, but unwittingly prescient. Fifteen years on, you can find wireless charge mats for mobile phones, iPods and the like at any Dick Smith. They’re also found under some electric toothbrushes.

And now, with climate change, peak oil and legislators worldwide pushing auto makers and buyers alike towards battery electric vehicles, some of the industry’s biggest names are sinking serious dollars into putting similar technology in cars, garages and public parking spaces.

Nissan has been talking up wireless EV charging for a couple of years. The company’s first announcements came around the mid-2009 appearance of its production Leaf EV. At that time, despite the rising excitement about EVs in media and motor shows, research was flagging problems ahead, with Nissan’s UK study revealing 61 per cent of potential buyers were put off by the inconvenience of recharging (pictured). Announcements were common that makers were readying their EVs for high voltage rapid-charge cabled systems; Nissan took it a step further by announcing it was also working on wireless inductive systems.

Not much has changed in the consumer research. Indeed studies have turned up so much in the way of continued resistance to EVs that the term ‘range-anxiety’ has been absorbed into the industry lexicon.

This year, Toyota has announced a development deal with WiTricity, a company emanating from the research labs of the Massachusetts Institute of Technology (MIT), while BMW has done the same things with German electronics giant Siemens. It’s likely that in coming years we’ll hear more of names like Evatran, Momentum Dynamics and HaloIPT alongside Better Place, the company that’s consumed most of the media mindshare to date with its cabled charging and battery-swap systems.

This new gang – even the ones without Siemens’s and MIT’s brand power – is attracting plenty of attention and cash for an idea that potentially clears away many of the obstacles blocking the electric car’s path to acceptance. Evatran’s Plugless Power system, for example, is currently undergoing testing in Google’s fleet at the IT giant’s headquarters in Mountain View, California.


Charging issues the chief point of consumer resistance to EVs
Either of the two wireless technologies being investigated potentially provides a neat solution to a number of the problems slowing battery power’s headway into the global auto market. Those issues are well researched and documented: essentially, batteries are slower to fill up than petrol tanks, even using high-voltage rapid charging facilities, and faster to empty.

In day-to-day life terms, it translates into this: as things are, you spend all night charging up from a domestic plug in the carport, and you’re lucky to get more than 100 or 150 kilometres max out of it the next day. Lithium-ion technology is still early in its developmental arc, but progress is slow. Researchers estimate that as things are at present, a battery good for more than 200km would double the price of a mass-market vehicle.

Many a deal has been struck around the world working towards networks of wired charging points, but they have their problems. Not least, they’re vulnerable to vandalism and simultaneously liable to send an unfortunate vandal into orbit with a 415-volt whack. And even with rapid-charge facilities, it still takes far longer to fill a battery than the two or three minutes we’re used to at the petrol pump.

At any rate, drivers are not likely to be happy about leaving their car plugged into a charge point in a public place for an eight-hour working day – let alone overnight, when we consider inner city terrace suburbs where street parking is the norm and off-street parking is restricted to the plum end of the property market.


Wireless charging’s answer to problems with cabled systems
On paper at least, the advantages of wireless over cabled systems are manifold. Because wireless charging generates no heat there’s no fire risk, and because it works by magnetism rather than radiation, there’s no anxiety (at least yet...) about health risks. It uses no moving parts and no physical connections, dramatically reducing its maintenance costs – Rolls-Royce cited this as an important consideration in setting up its 102EX electric show car for it. And with the right economies of scale, it’s also prospectively easy and cost-effective to retrofit receiver units to vehicles.

The absence of physical connections and moving parts makes full automation easy, too. More so because it’s safe and economical to run the transmission units in always-on mode – they only use power during coupling time with a vehicle. Its automation potential also makes it easy to integrate data communications systems into it that extend to ‘smart’ payment and reporting systems.

At the way-out-there end of the development scale lies the potential to embed transmission infrastructure along stretches of road, allowing vehicles to charge on the move.

All that and there’s little transmission efficiency difference between wireless and cabled systems (efficiency here refers to the rate of power shrinkage between transmitter and receiver). Developers claim to have closed the efficiency gap considerably in just a couple of years. In early 2009, researchers at the Korea Advanced Institute of Science and Technology reported efficiency rates of up to 80 per cent transmitting across a 1cm gap from an embedded power line. Within a few months, the team was powering a bus at efficiency levels of up to 60 per cent across a 12 cm gap.

More recently, UK developer HaloIPT has claimed power losses of just 10 per cent, putting it on a par with most plug-in systems, and without their complex electronic circuitry. The company’s system is capable of coupling coils up to 400mm apart and up to 250mm off centre.

Momentum Dynamics, meanwhile, claims its technology charges a vehicle much faster off a 240V grid than a cabled system. It’s developed its receiver coils for retrofitting to a wide variety of vehicles with undersides up to 60cm above the road surface.


The downside
The main downside, as UK analyst Toby Procter pointed out in a recent article published by his firm, Trend Tracker, is that most of the technologies are yet to undergo real-world testing. And while hardware integration between send and receive coils is simple, transmitter installation costs could prove problematic. This is reflected in what Procter cites as a likely infrastructure scenario to emerge: one that opts for affordable cable-based systems in homes and other private charge points where plugs and wires present little problem, and wireless systems in public spaces.

The problem here is that local governments, most of whom operate on tight budgets, may take some persuading of its merits, given how much more work it takes to bury a wireless charging coil under a parking spot than erect a cabled stump next to it. If there’s a clear sell, it lies in the near-zero maintenance costs mitigating the up-front slug, but those selling the idea face entrenched competition from cable vendors who, with several years’ jump on them, are already well into rolling out their own networks.


Establishing standards
At this early stage in the development of a technology ultimately dependent for success on standardisation, most makers are still working with operating standards and protocols developed in-house and unique to their product.

“Each manufacturer has developed their own protocols, their own security subscription schemes and the units aren’t interoperable,” John Rosinski, spokesman for one such firm, Pennsylvania-based Momentum Dynamics, told Procter in a recent interview.

“So a car driver moving around a city or through an area might have to have several subscriptions.” So embryonic is the technology, Rosinski told Procter, that the US government hasn’t yet worked out which agency should be tasked with addressing it, let alone got to the nuts and bolts.

In the next phase, these manufacturers begin jockeying to have their solution implemented as the industry standard. Overseeing that process is SAE International, the engineering profession’s global peak body. Charged with the development and worldwide implementation of standards and guidelines for such matters, SAE launched a taskforce late in 2010 “to establish performance and safety limits for wireless power transfer for automotive applications while establishing a minimum interoperability requirement”, according to its statement announcing its convening. This involves a look in depth at the two wireless charging technologies in play – inductive and magnetic resonance – assessing the pros and cons of each and interoperability issues.

After setting to work early this year under the leadership of BMW executive Jesse Schneider, the team aims to come up with first draft guidelines by year’s end.  Schneider told media through SAE’s statement that field data requirements mean it will likely be 2012 or 2013 before a full balloted standard is finalised and published.


How does wireless charging work?
In a word, magnetically. Both technologies leverage the natural magnetic fields surrounding every object, which are strengthened under charge. Inductive coupling uses an electromagnetic field between two objects in close proximity as the medium for transferring energy between them. A charging station or mat beneath the vehicle sends energy to the vehicle receiving unit, which collects it and stories it in its batteries.

Magnetic resonance ‘strong coupling’ uses the oscillating nature of magnetic fields to pair objects on discovery of a common frequency. When they do, it’s possible for the transmitter coil to convert electrical energy into a magnetic field, transfer it into the orbit of the receiver coil, which converts it back to electricity and dispatches it to the battery.

Arguments continue over cost differences, but the wireless advocates are at a distinct disadvantage having to prove the efficacy of their technologies in the face of cabled system suppliers who have already won contracts and begun rolling out their networks. That said, the electric mobility industry is in its infancy, meaning it’s so dynamic and unpredictable that even each-way bets are fraught with risk. Among all the ideas being flung around, however, this one has a clear enough value proposition to guarantee it a place in the not too distant future.