PARIS – Wireless-induction charging of electric vehicles and plug-in hybrids is certain to become standard, one of America’s top researchers in power electronics says.

“We believe it’s not a matter of if but when wireless charging will be in all (electric) vehicles,” Laura Marino of the Oak Ridge National Laboratory tells several hundred engineers attending the recent Automotive Power Electronics conference here sponsored by the French automotive engineering society SIA.

Marino, deputy director for the Power Electronics and Electrical Power Systems Research Center, says Oak Ridge, working with auto makers and suppliers, has developed and tested technology that will pass 5kW of recharge across 10 ins. (25.4 cm) of air with more than 90% efficiency.

Inductive charging will win out because of convenience, says Marino. “Think of a mother of three children coming back from shopping with her arms full. It would not be surprising if she forgets to plug in her car.”

Inductive charging sends electricity wirelessly between two coils. One coil is in the car, the other in the infrastructure. It could be hidden in the floor of a garage or part of a mat rolled out on top of the concrete.

Ford and Chrysler both are working on inductive charging, she says, and researchers at Oak Ridge will retrofit some Nissan Leaf EVs to work with inductive charging to learn more.

Supplier Delphi has been showcasing its wireless-charging system that it hopes to make available with the next wave of EVs expected around 2015.

Meanwhile, Oak Ridge is working on ideas to reduce costs. “Two years ago, a project was presented using the internal windings of the motor as well as the switches in the inverter to accomplish the charging function,” Marino says.

“We were asked by OEMs if we could do this with a power-split architecture like Toyota uses. We built it up where we now have two motors and two inverters, so we can charge the battery through them. This year, we are elaborating on this project.”

In the future, charging points could be built into roads at stop signs, she says. Shorter term, a company that runs shuttle busses from Logan Airport in Boston to car-rental agencies will put the idea into action by embedding inductive chargers at the spaces where a bus waits for passengers, so it can recharge while it waits.

In Europe, where the industry has not yet agreed on a standard for plugs, Renault is investigating inductive charging for its next-generation electric vehicles.

Development of the EV industry “also relies on the cost of infrastructure,” says Patrick Bastard, director-advanced electronics and technologies at Renault. “We are working on new concepts.”

For Europe’s fast-charge standard, Renault is arguing for a system based on alternating current, which could lower the cost of building charging points. Some estimates find a direct-current fast-charge point would cost E50,000 ($70,000).

By having the electronics that convert alternating current into direct current for the battery located in the car, instead of the infrastructure, the infrastructure would be less-expensive.

The next-generation Renault EVs, already being planned for 2015-2020, could include inductive-charging capability, as well as whatever standard plug-and-socket Europe decides to adopt.

“We have been working on this topic for years now,” says Bastard. “For the third generation, we will introduce breakthroughs to get big cost reductions and offer the customer a big increase in efficiency. Induction would be a performance increase that we could offer. It could be a good, easy way of charging your car.”

The AC/DC battle over charging standards in Europe is a bit ironic, because alliance partners Renault and Nissan are on different sides of the debate. Nissan already has chosen the direct- current, fast-charge standard agreed upon by the Japanese electric and auto industries.

But AC/DC is not the only problem for a European standard. For conductive charging, there continues to be a debate over the shape of the socket.

That’s because some country building codes require shutters on the holes in the socket to prevent children from sticking things inside, while other countries don’t.

In addition, national electric grids follow several different standards for the nature of their electricity, although 240V is the standard across the continent.