While quick charging technology installed at strategic points along a planned route might be a good fit for inner city buses, it's not going to be of much use to electric vehicles that stop infrequently. Volvo sees our future long-haul trucks and buses drawing the juice they need from the road itself, making large onboard batteries a thing of the past.

In addition to making a commitment that will see each new generation of diesel engine be more efficient than the last, Volvo is also actively engaged in EV research and development. As a member of a large research project, along with the Swedish Transport Administration, Vattenfall, Alstom, other vehicle manufacturers and suppliers, and several universities, the company is looking at ways to supply constant power to long-haul vehicles from an external source.

You could just fill up the precious cargo space of trucks and buses with enough batteries to make a long, non-stop journey, but where would you put the goods or passengers? Volvo, however, has something else in mind.

Along with power generation and transport firm Alstom, the company has constructed a 400 meter (1,312 ft) -long track at a facility in Hällered near Gothenburg, to test a truck fitted with a special collector that draws its power from rails installed into the surface of the road. It's an adaptation of technology that's been successfully used to supply electricity to trams in several cities around the world since 2003, and could help reduce an electric vehicle's dependence on big battery banks.

The two power rails/lines run along the road's entire length. One is a positive pole, and the other is used to return the current. The lines are sectioned so that live current is only delivered to a collector mounted at the rear of, or under, the truck if an appropriate signal is detected. As an additional safety measure, the current flows only when the vehicle is moving at speeds greater than 60 km/h (37 mph).

"The vehicle is equipped with a radio emitter, which the road segments can sense," explains Volvo's Per-Martin Johnansson. "If an electric vehicle passes a road segment with a proper encrypted signal, then the road will energize the segments that sense the vehicle."

The truck being used as a test bed for the project is a standard Volvo FH12 tractor sporting a diesel engine. There's no electric motor installed at the moment. When the collector comes into contact with the power lines, 750 V of direct current is delivered and routed to a water-cooled heating element, that has a similar power requirement to an electrically-driven truck. The collector has been designed to track the power rails, even when the vehicle is not directly over the middle of the contact lines.

The present phase of the project, which is supported by the Swedish Energy Agency, is set to come to a close soon, but Volvo is already discussing the next logical step. This will see the installation of an electric motor in the truck to determine how it fares on the test track. Johansson confirmed that other project members are working on various electricity delivery methods, including induction charging.

Elsewhere, companies like Siemens are looking into power delivery using overhead cables, but Volvo suggests that its development may prove a more attractive proposition.

"From what we have seen so far, overhead lines are a more expensive solution than the what we are testing right now," says Johansson. "Overhead lines have the additional drawback that they cannot be used by cars. The visual impact is also less appealing compared to a technology located in the road. But we're not ruling out a solution that uses overhead lines. The research in the coming years will hopefully show what will be best for society."

While technical development of the current collector, electric motor and necessary control systems continues, the research project is also considering how best to implement and maintain a deployed system. At the moment, this system is managed locally using smart sensors, but there is scope for remote operation and monitoring, and it's reported capable of providing much more power, if needed. There's also a possibility that the technology could be adapted to deliver AC in the future.

It's also likely that the power lines will be built into existing roads, rather than requesting the construction of new roads. The first vehicles to use such a system could well be hybrids rather than full EVs, to help guard against short power interruptions. Then there's the small matter of working out how much drivers will be charged to use such a system, and the subsequent setting up of payment models.

Source: Volvo