Researchers: Light-rail flywheel system could save energy, money

Using flywheel technology to reuse the braking energy of light-rail trains in Edmonton, Alberta, could result in a 31 percent increase in energy savings, according to researchers at the University of Alberta.

Mechanical engineering professors Pierre Mertiny and Marc Secanell examined the possibility of using flywheel technology to store energy created when light-rail trains in Edmonton decelerate and stop. The trains feature dynamic braking, which uses traction motors on the vehicles' wheels.

Flywheels are disks that rotate and increase rotational speed as they're fed electricity. The rotational energy can then be turned back into electrical energy when needed.

Conventional systems send the braking electric power to resistors on the train, which convert the electrical energy to heat that's released into the air. A flywheel system would take that electrical energy and store it as mechanical energy, which could then be converted back to electrical energy when the train is ready to move again, according to a press release issued by the University of Alberta.

Mertiny and Secanell also found that using flywheel technology would result in an 11 percent reduction in costs.

"The flywheel is an old technology, but that’s partly what makes it so sensible," Mertiny said. "Fundamentally, it's a really simple technology. We already have everything we need."

The city of Hannover, Germany, currently is testing flywheel technology for its light-rail system, Mertiny said. The city has banks of flywheels at each station to capture and reuse the electricity generated as trains pull into the station.