At TreeHugger we've reported with great interest on the schemes to have electric vehicles charge wirelessly via underground electricity induction, chronicling efforts to make e-car re-charging easy, and on-the-go (and also make range anxiety disappear!).
The two e-buses in Mannheim's upcoming trial are made in Switzerland and will run on existing city bus routes. They will recharge via 'invisible' inductive technology called Primove, installed below road surfaces.
Induction works by having conductors (in Primove's case, rods of varying lengths under the asphalt) that create a magnetic field. The fields generate electricity when another conductor (the vehicle) is placed in the field. The generated electricity is picked up by an undercarriage unit and routed to the battery.
Direct contact between the vehicle and the charging system isn't required, and because it's below the asphalt surface, wireless induction charging is water and weatherproof. Charging can happen while a vehicle is stopped or simply moving over the top of the induction surface. At other times, the system is inactive, and Primove says its induction rods don't interfere with cell phones or pacemakers.
Inductive charging's down side is its low efficiency rates, but both Primove and Whytheville, Va.-based Plugless Power are talking of the 'high-power' and 'efficiency' of their wireless systems - Plugless says its system will delivery 3.3 KW of power. Instead of induction rods running underneath the asphalt, Plugless makes charging buttons to be installed in parking spots, allowing e-cars and buses to simply roll up to charge. In March 2013 Plugless received a grant from the Department of Energy that will help it put conductors into Chevy Volts and Nissan Leaf e-cars.