Electric bus picks up passengers… and energy

Electric bus picks up passengers… and energy

By Dominic Thiffault

April 08, 2013

Last November, Utah State University in partnership with WAVE™, a U.S. based technology spin off, showcased the first electric bus with Wireless Power Transfer (WPT) technology in North America. Three months later, Bombardier Transport announced a partnership with the German City of Mannheim and the Karlsruhe Institute of Technology for the 2014 rollout of this technology within the public transit system.

The application of WPT technology on electric buses mixes an understanding of Nikola Tesla’s principle of induction with advanced engineering. The technology itself is more than a hundred years old, as Bosnian-born American scientist and investor, Nikola Tesla (1856-1943), understood and conducted a series of experiments in 1888 involving electromagnetic radiation, a process called “electric resonance” by today’s engineers. That process consists of applying a vibratory action on an object (in this case an electronic receiver) in which this object reaches its highest absorption rate; this in turn produces power.

The induction-charged buses are equipped with batteries capable of taking 50kW of charge at 90 percent efficiency – that is to say, with only 10 percent electric losses from the grid to the battery. In comparison, a plug-in electrical distribution system is only 70-74 percent efficient, which is one of the reasons the technology is attractive to investors and governments. Other reasons for preferring induction-charging to overhead wires are: greater reliability and safety due to removing of the risk of electrocution, and the need to constantly maintain and move parts of the cables. It is also aesthetically pleasing to not having visible wiring.

The size of the batteries mounted on conventional (hybrid or not) electric vehicles, their cost-effectiveness, and the time needed to fully recharge are some issues that are overcome in this case. Instead of charging big batteries overnight before a route, smaller batteries free up the interior space and reduce the charging time, therefore reducing the costs of operation.

Induction plates, or pads, must be added to bus stops as well as under the vehicle. When the bus leaves the maintenance station, batteries are already fully charged. Then, whenever the bus stops to pick up passengers, batteries are topped off over a 10-inch air gap with a maximum misalignment of up to 6 inches, making it relatively easy for the driver to hit the charging zone. Here once again, as with the plug-in electrical charging systems, greenhouse gas emissions reduction depends on how the electricity is being generated at the grid. The technology however makes it advantageous in that respect compared with their diesel and hybrid counterparts.

Bombardier Transport will test the 40-foot electric buses in Montreal in 2013 under harsh winter conditions in partnership with Hydro-Quebec and an undisclosed bus manufacturer. In 2014, buses will be introduced on a transit route in Mannheim, Germany. An overall testing period of five-years is currently planned before the WPT technology can be considered commercially viable for transit systems.

(Icon photo courtesy of WAVE Inc)

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