Tallinn could buy buses with pantographs

Photo: Mihkel Maripuu

Contrary to the expectations that trolleybus lines will disappear, the construction of overhead power lines may speed up thanks to a German solution, which can make even trucks run under overhead wires.

Even Tallinn, having started to remove overhead wires, can now make U-turn provided Siemens, Germany’s leading electronics manufacturer, can convince the managers of public transport in the prospects of the novel idea.

Early in April Siemens will present to the Tallinna Linnatranspordi AS a solution suitable to public transport and cargo vehicles, which involves mounting overhead wires of the type used in electric railways over roads as well.

The novelty of the solution is in the fact that a vehicle fitted with a pantograph current collector can access the overhead contact line without stopping. “We are giving up on trolleybus lines because these are very troublesome: a local breakdown will take out the entire route and a trolleybus without power can suddenly block on a busy crossing,” said Enno Tamm, board chairman of Tallinna Linnatranspordi AS.

“The solution offered by Siemens would allow using the overhead wide on long straight stretches and near the terminals, charging the capacitors at the same time. But it would allow for more flexibility in complex junctions, which the vehicles could cross under their own power.”

The Kristiine junction is the biggest headache for Tallinn’s electric transport as main streets of several city districts cross there and an emergency stop of a trolleybus could paralyze all traffic.

Tallinn is preparing a tender for procuring electric buses currently considered the most environmentally friendly solution. But electric buses are inefficient because of their batteries. The batteries occupy up to ten percent of the space needed for passengers and the number of electric buses must be 1.5 times larger than that of hybrid buses due to the longer charging time.

Tallinn currently operates 44 first-generation hybrid buses, which consume one third less diesel fuel. The economy of diesel fuel compared with regular buses can reach 70 percent in second-generation hybrids.

Among Estonia’s neighbors, Sandviken in Sweden is testing the novel vehicles with pantographs – a two-kilometer test stretch of dynamic charging system is operated there jointly by Siemens and Scania, financed by the EU regional development fund. An overhead contact system similar to that of railway was built over a regular road. “This solution requires no law amendments,” said Jan Nylander, project manager of the E16 electric road.

Journalists taken to Sandviken with the European Commission’s support were shown a Scania tractor truck used on the test road, powered by a 254-kilowatt diesel engine, backed up by a 139-kilowatt electric motor. The 18 kWh battery on the vehicle provides enough power for 10 kilometers without the overhead contact line or the diesel engine. Using the pantograph raises the cost of the vehicle by some 10,000 euros.

Automatic control system reacted when the vehicle drove under the overhead wire without slowing down and independently raised the pantograph to working position. Leaving the overhead line was tested as well. The driver, who keeps the truck under the wire, can observe the pantograph through a skylight and on a special display. “Heavy rain can obscure the pantograph,” the driver pointed out a drawback of the solution.

The testers intend next to build a 100-kilometer electric road stretch starting from the Gävle port city; the cost of every kilometer would be 1-2 million euros. The pantograph-equipped truck would travel most of the road by receiving current from the overhead wire and would use batteries for the last mile.

“The electric road could be used first for regional traffic, but building a network covering Sweden, Denmark and Germany is likely,” Nylander said. “The enterprise will gather momentum if local enterprises considering environmentally friendly production an important sales argument will decide to use electric transport.”

Three test stretches are operated in Germany and one in the United States, all with Siemens’ participation. The innovation may start in future to obstruct the access of Estonian transport firms to the marker of countries building electric roads and local entrepreneurs are cautions about the new idea.

“The solution being tested in Sweden and Germany is suitable for predetermined routes and I can see no prospects for it in Estonia,” said Einar Vallbaum, president of the Association of Estonian International Road Carriers. A solution of the electric road type could be feasible on urban routes where buses could use the same overhead lines, he said.

Comment

New solutions will inevitably come – Dago Antov, professor of the Tallinn University of Technology

This solution seems good on the one hand, since the electric vehicle need not carry its power supply. Pictures of trucks with pantographs look funny, because we have grown used to trolleybuses and now we are dismantling the lines.

It is quite clear that electric transport will not develop rapidly as long as we do not have new and lighter batteries. These solutions will inevitably come, I am optimistic about that, but it will not happen within the next 20 years.