UAlberta engineers look to old technology for light rail transit project

A flywheel is a disk, known as a rotor, that rotates and increases its rotational speed as it is fed electricity. This rotational energy can then be turned back into electrical energy whenever it is needed. It is an old traditional technology that has the potential for serious cost and energy savings when it comes to transit train operators.

UAlberta mechanical engineering professors Marc Secanell and Pierre Mertiny have published research demonstrating that the use of flywheels on light rail transit can produce big savings in power and cost.

University of Alberta mechanical engineering professors Pierre Mertiny and Marc Secanell are exploring how to apply the flywheel technology to the Edmonton LRT.

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

One of the main benefits of this type of system is that is loses very little energy to heat or friction because it operates in a vacuum and may even use magnetic bearings to levitate the rotor.

Flywheel technology is used for many applications like at the International Space Station or race cars built by Audi and Porsche.

Currently, trains such as the LRT are designed with dynamic braking which uses traction motors on the train’s wheels for smooth stops. However, this deceleration generates energy that has nowhere to go. Secanell and Mertiny examined the possibility of using flywheel technology to store energy generated when the city’s LRT trains decelerate and stop.

“Electric and fuel cell vehicles, already implement regenerative braking in order to store the energy produced during braking for start-up, so why would trains not be able to do so?” says Secanell, whose research also focuses on fuel cell vehicle technologies.

A flywheel system would take the electrical energy and store it as mechanical energy. This mechanical energy could then be converted back to electrical energy when the train is ready to leave the station again.

According to Mertiny and Secanell, using flywheel technology to assist light rail transit in Edmonton could amount to a savings of 31 per cent and a cost savings of 11 per cent.

“The city of Hannover in Germany is already testing flywheel technology for just this purpose,” says Mertiny. “They have banks of flywheels at each station to capture and re-use the electricity generated when their trains come into the station.”

Secanell and Mertiny are involved in a pan-Canadian Energy Storage Network investigating ways to optimize the flywheel energy storage and cost. Mertiny is also currently working with Landmark Homes of Edmonton, through the U of A’s Nasseri School of Building Science and Engineering, to develop a prototype flywheel to store solar energy for household use.

www.engineering.ualberta.ca