Electric Road System technologies

There are two technologies for Electric Road Systems (ERS): conductive and inductive, and the energy can be supplied from three different directions: from the top, sideways and from below.

Electric road technology can be described according to two different principles, either according to how the energy is transferred or from which side of the vehicle the energy is transferred. The picture below gives you an overview of the combinations.

Conductive ERS

Conductive ERS technology allows the power to be transmitted through direct contact between an overhead line or a rail and a receiver. It is used by, for example, trams, trains and trolley buses which have an overhead contact line in the air above the vehicle and the receiver mounted on top of the roof of the vehicle. The method is found in applications both from the top, from the side and from the bottom (picture).

Pros: A contact line or contact rail is quite inexpensive to create and can transmit high electrical powers.

Cons: A contact rail in the road is a potential electric safety hazard, it can be slippery and road maintenance requires more effort.

Inductive ERS

Inductive ERS technology use induction principles to transfer electricity wirelessly to moving vehicles, which means that no mechanical contact is required. Instead, high frequency magnetic fields are used. The “transmitter” is placed under the road (inductive technology is only used from below), and a “receiver” is located under the vehicle. To be able to transfer large amounts of energy, for example to be able to drive a truck on a road, the size of the “transmitter” and “receiver” need to be large. To charge the truck, the receiver needs to be about one meter wide and several meters long. The technology is basically the same is as used to charge an electric toothbrush or heat a pan on an induction stove top in the kitchen.

Pros: No physical connection is needed between the vehicle and the road and the “transmitter” can be hidden in the tarmac.

Cons: Large areas are required to transmit sufficient power to drive heavy trucks, for example. Magnetic leakage fields can be a health hazard.