Regenerative braking system lowers carbon footprint of trains

The DDflyTrain project has resulted from a collaboration between Ricardo, who designed the flywheel, digital hydraulics firm Artemis Intelligent Power and rail technology company Bombardier Transportation.

It combines Ricardo’s TorqStor high speed flywheel energy storage system and the Artemis Digital Displacement hydraulic pump-motor transmission system to store and reuse energy using flywheels spinning at 45,000rev/min.

The consortium’s aim was to build a demonstration rig to show that the technology could work in a diesel environment on multiple unit trains.

‘Every train journey involves a lot of stopping and starting, and so also a lot of braking and acceleration,’ said David Rollafson, vice president, global innovation at Ricardo. ‘If we can harvest some of the energy from braking and use this when the vehicle is gathering speed again, we can save a lot of diesel and so a lot of money for train operators.’

There would also be benefits in terms of reducing pollution. ‘When pulling out of a station, diesel engines are noisy and pump out a lot of pollution,’ said Rollafson. ‘Adding stored energy to help acceleration would reduce this.’