How Ricardo flywheel technology could lead to DMU fuel savings

How Ricardo flywheel technology could lead to DMU fuel savings
10 September 2015

A project to develop an energy recovery system for Diesel Multiple Units (DMUs) using Ricardo technology derived from Formula 1 could lead to fuel savings of up to 10% - and a return on investment within five years.

In an initiative co-funded by Innovate UK and the Rail Safety & Standards Board, the DDFlyTrain project was launched in 2013, in partnership with Artemis Intelligent Power and Bombardier Transportation, with the intent of developing a technology to  emulate the regenerative braking systems found on modern Electric Multiple Units (EMUs). 

And central to the DDFlyTrain is our TorqStor high-speed flywheel energy storage technology.

Ricardo has substantial experience in flywheel hybrid systems. It has investigated many different kinds of energy recovery technologies such as ultra-capacitors, hydraulic systems, electric flywheels and mechanical flywheels – including the engineering of kinetic energy recovery systems (KERS)  for Formula One applications.

The TorqStor differs from other flywheel designs due to its unique permanent vacuum. This is made possible by its advanced magnetic gear system that enables the transmission of torque across a vacuum without the limitation of rotating seals or necessity for vacuum pumps.

On a DMU, the unit connects to the driveline via Artemis Digital Displacement® hydraulic pump-motors, in which computer controlled solenoid valves co-ordinate the responses of individual pistons to the overall power and torque requirements.

Compared with conventional hydraulics, these pump-motors have inherently high part-load efficiencies and controllability, making it economically feasible to use hydraulics in energy-sensitive applications such as DMU regenerative braking.

Fuel savings

To date, the DDFlyTrain has undergone extensive simulations based on field service data, which was used to define the optimal design for rail. The data also helped in the construction of a test rig for demonstration purposes.

The project has also completed an integration exercise to incorporate the hardware and software onto a Turbostar DMU.

The initial indications are that the retrofit of flywheels to DMUs could lead to fuel savings of up to 10 percent, as well as extend the life of the vehicle’s braking components. On this basis, the technology could deliver a return on investment within five years.

According to Ricardo Vice President of Innovation, David Rollafson, the DDFlyTrain has opened up the potential for regenerative braking on DMUs. "The double-digit percentage fuel savings and short commercial payback demonstrated for this technology make it attractive both as a retrofit solution for existing fleets as well as for application on new-build rolling stock."

In addition to its promising application on DMU rolling stock, high speed flywheel technology could also be attractive for EMUs operating on DC conductor rail networks, such as the London DC electrified lines region. Network power capacity issues can place a significant restriction on the number of trains allowed to operate in some sectors, given the high current demand during launch. By applying high speed flywheel technology a significant element of this launch requirement can be eliminated, thus increasing effective capacity.

Even before the initial results were released, the project had received recognition within the industry. In late 2014 it received a Rail Exec award in the safety and sustainability category, whilst our TorqStor flywheel technology received the 2014 SAE Tech Award, as one of the top five technologies on display at the SAE World Congress.

As for the next stage of the project, discussions are ongoing with key rail industry stakeholders with a view to further development and vehicle-based trials.