Technology for the wireless charging of electric vehicles is due to be trialled in East London’s ‘Tech City’.
At the Seoul Climate Change Summit in 2009 the Mayor of London, Boris Johnson, announced plans to make London the ‘electric car capital of Europe’ by 2015 ― with 100,000 electric vehicles (EVs) on the city’s streets, served by 25,000 charging points.
Progress has been made with EVs, but the fact remains that only 588 EVs were registered in London since the 2009 announcement, giving a total of 2,313.
With regards to charging points, there are now 400 across London, with a target of 1,300 by next year ― the 25,000 marker quietly dropped.
In a statement in February this year, Murad Qureshi, chairman of the Environment Committee at the London Assembly, summed up the situation, saying that they must demonstrate ‘the charging network is adequate and fits with the way people will actually charge their vehicles’ and that ‘it is unclear at the moment whether it is delivering value for money given the sums already spent on it’.
The drive for a decent plug-in network should continue apace, but there is another way. It promises a completely invisible, but near ubiquitous, charging network that asks for little in the way of behaviour change from petrol vehicle owners ― and potentially allows charging while on the move.
Wireless charging is based on the principle of magnetic resonance coupling (see panel), which has been known about for more than 100 years.
Applied much more recently to EVs, it basically involves two active pads ― one on the underbelly of the car connected to the battery, and another mains one, usually embedded in the ground (see panel). An equipped car simply drives over the pad and charging can commence.
There are around 20 companies worldwide involved with the technology and one of the most prominent is Qualcomm Halo (formerly HaloIPT). The company draws on more than 10 years of research at Auckland University and has been working hard for the last few years ironing out practical issues such as efficiency losses involved in transferring energy past the air gap, tolerance of misalignment of the pads, and electromagnetic compatibility.
The trial around ‘Tech City’ will see charging plates installed at traffic lights, outside homes and on the streets
It has produced successful demonstrators, showing overall performance comparable to plug-in charging, in independent tests at Oxford Brookes University. There have also been some high-profile collaborations with Rolls-Royce Motor Cars ― which now offers inductive charging as an optional extra on its Phantom 102EX model ― and Drayson Racing, for its high-powered Le Mans EVs.
But where inductive wireless charging offers real benefits is not niche applications, but over the entire mass-market network. With the possibility of automatic verification and payment when parking up you can start to think about wireless charging in a different way to the existing plug-in network.
To this end, Halo was acquired by Qualcomm in 2011, a company that aims to transfer its experience of telecommunications and 3G networks to the automotive sector.
‘Engineering elegance is great, but mass consumer adoption should be the goal,’ said Andrew Gilbert, executive vice-president of European innovation at Qualcomm.
‘The thing we’ve found is when you make something wireless, you make it so much easier to use ― you very quickly get mass adoption, I’ve seen this on phones, internet access ― obviously that’s telecommunications, but I think the same model applies.’
Given the difficulty that the plug-in charging network has faced, this mass-market approach seems rather ambitious. The economy-of-scale argument is all very well, but any fundamental flaws in the concept and design will also be amplified across the network as a whole.
It is clearly something that Qualcomm Halo has acknowledged, as it is spearheading the largest trial of wireless inductive vehicle charging worldwide to date, involving 50 enabled vehicles driving around the streets of London.
The partners include Addison Lee, Chargemaster, the UK government, the Mayor of London’s office and Transport for London (TfL).
Centred around the burgeoning ‘Tech City’ area of East London, the trial will see charging plates installed in public and private spaces, including at traffic lights, outside homes, and on streets.
Onboard telemetry will provide continuous feedback regarding data such as battery performance, but there will be also be a strong qualitative aspect to the testing in conjunction with the local community and the individuals involved in the trial.
‘As humans, we’re very difficult to teach a new behaviour, but we can bend our behaviour a little bit; in this situation we all have to park our car so if we can use that time to also charge then we’re leveraging that behaviour,’ said Gilbert, who will oversee the trial.
‘What will happen is that when this becomes so easy that you use it at home and at work, maybe at the shops without thinking, people are going to get much less worried about the range and how it works ― and that could dramatically impact the success of electric vehicles.
“If you go wireless you get faster adoption and that drives down the cost point very quickly”
Andrew Gilbert, Qualcomm
’Inherent in this philosophy is a model of charging characterised by small, regular tops-up that keep the battery charge between 40-80 per cent ― which, according to the latest research, is the optimum level for lithium ion batteries to maximise their life cycle. Qualcomm also claims it could enable smaller batteries, reducing cost and weight.
The involvement of Addison Lee ― London’s largest minicab company, with more than 3,000 vehicles ― is an interesting one and something Dr Anthony Thompson, one of the founders of HaloIPT, has long seen potential in. ‘It’s difficult for drivers to be jumping out and plugging in… when you look at Paddington and Waterloo stations, they spend a lot of time cruising along the taxi rank for hundreds of metres and they could be picking up a charge all the way along,’ he said in an interview with The Engineer last year.
While it is unlikely to be tested in the upcoming trial, this dynamic charging of vehicles while on the move, is considered to be the ultimate goal of the technology.
Canadian manufacturer Bombardier is currently testing dynamic charging on fixed routes for buses and trams. The infrastructure challenge is much more acute for private vehicles on motorways, but a feasibility study by Stanford University suggests it is in theory possible.
Using mathematical simulations, the researchers found that a coil bent at a 90º angle and attached to a metal plate can transfer 10KW of electrical energy to an identical coil 6.5ft away.
Receiving coils attached to the bottom of the car would resonate as the vehicle speeds along, creating magnetic fields that transfer electricity to charge the battery.
That’s still some way in the future though, and arguably the biggest challenge for Qualcomm, and wireless charging networks in general, is a viable business model that will drive down the cost of the infrastructure. At present, retrofitting existing EVs with the capability for inductive charging costs around £3,000, while the charging pads themselves cost around £2,500.
‘Head to head, cable is always going to be cheaper to implement than wireless, because of the componentry involved,’ Gilbert said. ‘But when you look at economies of scale ― if you go wireless with anything, typically you get much quicker adoption and that drives down the cost point very quickly. By standardising this technology, so everybody is building to the same core specification, and by creating an environment where everybody on the product side can really be inventive about form factors and how they go about building it, that’s going to lead to a price reduction.’
Qualcomm Halo claims to have improved the efficiency of wireless charging
Any electrical current generates a magnetic field around itself, which travels at the same pace. If a conductor is placed within that field, its electrons will be dragged along ― generating a second electric current.
In the context of EVs, electrical power from the mains supply energises a lumped coil. Power is transferred by tuning the pick-up coil to the operating frequency of the primary coil with a series or parallel capacitor. A pick-up controller, which converts the induced high-frequency current into 250-400VDC, charges the car’s batteries.
The laws of physics state that the induced current will never flow as strongly as it does in the original conductor. However, Qualcomm Halo claims to have demonstrated a transfer efficiency of around 97 per cent across the air gap and 90 per cent for the DC/AC conversions.
‘There has been a lot of mythology around wireless charging being inefficient. Although we lose a couple of per cent from the road to the car, most high-frequency plug-in chargers have a similar loss through AC-DC conversion and back again,’ said Dr Anthony Thompson.
There are, however, still a few safety concerns with implementing the technology in the real world. ‘We’re going to have to have a solution to things getting underneath the vehicle, whether it’s metal heating up or cats going to sleep, we have to make sure we can deal with these corner cases,’ said Andrew Gilbert.