Breakthroughs in inductive power transfer are promising to transform the prospects for electric buses. In July 2011, the Utah State University (USU) Research Foundation demonstrated a 90% electrical transfer efficiency of 5kW over an air gap of 10 inches. The breakthrough made inductive power transfer viable for buses, potentially minimising pollution in urban centres and saving costs.
Since then, USU and its spin-off company WAVE, funded by a $2.7 million grant from the US Federal Transport Authority, have unveiled the Aggie Bus. This electric bus charges through induction, topping up its batteries from a charge plate in the ground whenever it collects passengers. It works regardless of weather conditions and even if the bus isn’t lined up perfectly with the charge plate at the bus stop, offering the same reliability as current public transit bus options, including diesel and compressed natural gas buses. It also holds out the prospect of electric buses being able to run all day – something that isn’t possible with overnight charging.
Petra Beitl, Marketing Director at Liberty Cars, which also develops more efficient charging systems for electric buses, says that, despite high upfront costs, the technology should save money over the vehicle’s lifespan. Kate Peterson, Marketing and Business Development Specialist at USU, agrees. “After initial investment has been paid back, long-term maintenance and cost estimates would be equivalent to about 40 cents per gallon. The technology is infrastructure intensive. [The charge plates have to be installed in the roads.] After we put in the first commercial system, we will have a better idea on exact price; initial costs for wireless charging systems are higher than traditional liquid fuel. But lifecycle costs can be lower because the operating expenditure of electric vehicles is so much cheaper than liquid fuels, particularly in Europe”, Peterson continues.
It saves on battery costs, too. “Charging wirelessly allows electric vehicles to use drastically reduced battery sizes”, says James May, Vice President of Business and Product Development, WAVE. By comparison, he adds, standard systems use batteries that are “prohibitively large, heavy, and expensive”.
The standards body SAE International is developing a standard specifically for conductive charging, which, says May, should help ensure that wireless systems will be “more inclusive than proprietary”. – Giles Crosse
Photos: Donna Barry / Utah State University