Wireless charging technology is almost ready for the big stage. Qualcomm has demonstrated its Halo system in various vehicles, including the Drayson B12/69 electric race car. Evatran’s Plugless aftermarket system is now commercially available for the Volt and the LEAF, and a Model S-compatible version is coming soon. Several major automakers have indicated that they’re working on offering wireless charging for future EVs.
For the home charging market, the main benefit of wireless charging is convenience – but that doesn’t mean it won’t be a popular option. “Never underestimate the laziness of the American consumer,” one equipment vendor told us. In public or workplace charging applications, wireless offers the additional benefits of reducing the clutter of cables, as well as wear and tear and vandalism risks.
The killer app for wireless charging, however, is likely to be the fast-growing field of electrified public transit. Here the benefits of wireless are so great, and so easy to quantify, that some industry players see it as almost a practical necessity.
Battery-electric buses offer a cleaner and quieter ride, and can save transit authorities huge sums of money over their lifetimes. However, they suffer from the same drawbacks as all EVs: limited range and high up-front cost. Incorporating en route charging into an electrified bus route can address both of these challenges.
Being able to partially charge at a short stop along the route increases the effective range of a bus, and/or allows the battery pack to be smaller, saving on the purchase price of each vehicle. While wireless is not the only way to perform en route charging, it’s arguably the best for several reasons.
When the market for electric transit buses really starts to roll, a Utah company called WAVE (Wireless Advanced Vehicle Electrification) is poised for massive growth. WAVE was spun out from Utah State University in 2011, and grew into the commercial phase a couple of years ago.
Utah State’s Energy Dynamics Laboratory has been studying wireless charging for some time. In 2013 it demonstrated the Aggie Bus, a 20-passenger bus powered with a 20-25 kW stationary wireless charger, with efficiency greater than 90%. Since then, WAVE has doubled the power of its system to 50 kW, while maintaining a similar efficiency level (for comparison, a typical wired connection might achieve efficiency of 92-95%).
The WAVE system uses a charging pad that lies flush with the pavement and is sturdy enough to be run over all day without damage. Another pad is mounted on the vehicle’s undercarriage 7 to 8 inches above.
WAVE CEO Michael Masquelier explained to Charged why he believes his company’s system is the best option for en route charging. Some existing e-buses use an overhead catenary for charging, but Masquelier considers wireless far superior for several reasons.
The WAVE system is designed to be unobtrusive – at the en route charging site, the only visible component is a small interface box that houses circuitry between the pad and the grid connection. With the next-generation system, this box will be placed underground, for a completely invisible infrastructure.
An overhead catenary, on the other hand, can’t be hidden. “You’re always going to have some sort of mechanical movement over the bus, which tends to be not only an eyesore, but could be a safety hazard, or could get in the way of fire equipment,” Masquelier points out. In fact, in some municipalities, fire marshals have specifically said they would not allow overhead chargers, because of the fire and safety risks.
As for conductive chargers, Masquelier doesn’t consider them to be feasible at all in an en route transit application. “Drivers are not trained or in some cases allowed by a union to plug in to chargers, and cables that would be on the ground or even on a hook pose a tripping or high-voltage hazard.” It’s also plain that a cable that might need to be plugged in and unplugged dozens of times per day would require a fair amount of ongoing maintenance, to say nothing of the depredations of vandals and copper thieves.
WAVE currently has systems in operation in several cities, and Masquelier told Charged that he expects to have at least 20 systems up and running later this year. “We’re in a position now where we can produce the systems very quickly.”
The company has demonstrated “multiple OEM integration and interoperability.” Its system is currently in operation with several vehicle types, from a 30-foot trolley to 40-foot buses, with different battery pack voltages, from different OEMs. It now has systems running with buses made by BYD and Gillig, as well as Complete Coach Works (profiled in our last issue), which sells remanufactured buses with electric powertrains. Masquelier says WAVE has “a good working relationship” with Proterra, and sees a strong possibility of working with it in the future.
The WAVE system is easily adapted to buses from different manufacturers. The onboard components take up little space, and can be used in different vehicles with only minor modifications. The same in-ground charging pad is used for all vehicles, so it would be no problem for a transit company to operate different types of buses on the same route.
WAVE is a fully automated system that requires minimal or zero driver intervention. It can automatically detect pad alignment and initiate charging. There’s also a safety procedure that’s implemented in both software and hardware. “If for some reason the driver were to pull away, or the bus were to roll back, the system would automatically and safely shut down,” says Masquelier.
WAVE offers an option to incorporate stationary storage into the charging station, although it has yet to deploy this commercially. Storage is not necessary for operation of the system, which can pull 480-volt, 3-phase power directly from the grid. However, in places where there are utility demand charges, the company is seeing increasing interest in stationary storage, which would allow power to be drawn from a battery during the day.
So far, WAVE has sold its system only for transit vehicles, but is “vigorously exploring opportunities in other markets.” The system is designed to be scalable and adaptable to many different vehicle types. Masquelier sees opportunities in off-road and industrial markets, port vehicles, forklifts and urban delivery vans.
So far, WAVE seems to have little competition in the wireless transit charging market. Masquelier told us that nobody else has a commercial system deployed in the US. Competitors in Europe include Bombardier and the German firm IPT Technology, whose IPT Charge system is operating in a fleet of 23 electric buses in Turin, Italy. Both of these firms’ systems use bus-mounted pads that have to lower toward the street with mechanical actuation. To the best of Masquelier’s knowledge, none of the OEMs in the transit sector are working on their own wireless systems.
At least one transit agency has said that the WAVE system is what sealed the deal to go electric. En route charging roughly doubles the range of a bus – or on the other hand, it can allow an operator to serve the same route with a smaller battery pack, saving big on both cost and weight. “That’s been our business model all along,” says Masquelier. “Without us, the clients wouldn’t be able to have those buses operate on an entire daily route – they would have had to buy an additional bus, or buy a bus with a larger battery pack.”
Masquelier wouldn’t tell us exactly what a WAVE system costs, but he says that it easily pays for itself even at this early stage of commercialization. “The cost of our system is much less than the additional cost of batteries to extend range. Not to mention the additional weight added to the vehicle.”
WAVE is also researching dynamic wireless charging (charging vehicles while in motion), but Masquelier thinks a commercial deployment would be several years in the future. “It comes down to the market. I think the cost of the infrastructure is going to be significantly higher for a dynamic system, and the real market has yet to be defined that can deal with that cost structure. I think first we’ll see some pre-commercial deployments to prove the concept, and once people become more aware of it, they’ll figure out if there’s a place it makes sense cost-wise.”
This article originally appeared in Charged Issue 24 – March/April 2016. Subscribe now.