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BMW Research, EURECOM and Technische Universität München collaborating on connected vehicle research

Artemis, Ricardo and Bombardier collaborating on rail brake energy recovery project; Digital Displacement hydraulic pump-motor and flywheel energy storage

Artemis Intelligent Power, Ricardo and Bombardier Transportation are collaborating on a research and development project on rail brake energy recovery scheduled to commence in the second half of this year.

The system under investigation combines the Artemis Digital Displacement hydraulic pump-motor system (earlier post) and Ricardo’s Kinergy flywheel high energy density storage system (earlier post) and is intended for use on diesel-powered multiple units. The combined system is expected to offer operating fuel savings of between 10 and 20%, and is conceived of as a cost-effective solution that could be retrofitted to existing rolling stock as well as incorporated into new rail vehicles.

Artemis Digital Displacement technology represents a new approach to hydraulic pump-motors that combines robust mechanics, ultra-fast valves and digital controls. Digital Displacement replaces the port plates and swash plates in conventional hydraulic machines with computer-controlled high-speed solenoid valves. The technology offers the following key benefits:

  • Very high efficiency at full and part-load;
  • Multiple independent variable displacement services from one compact package;
  • Fine output control and very fast response; and
  • Low noise emission.

Digital Displacement machines are typically multi-displacement cylinder pumps and/or motors. Each cylinder has two poppet valves, one connecting it to low pressure fluid (the LP valve) and one to a high pressure output (the HP valve). A microcontroller reads a shaft position sensor and controls at least the LP valve.

The microcontroller is able to choose to operate or not to operate one or more valves each revolution to determine how much flow is generated. Hydraulic motors are achieved with the addition of a controlled high pressure (HP) valve. Motors are also pump/motors—operation as a pump is inherent.

Digital Displacement pumps and motors completely isolate idling cylinders from the load, eliminating losses due to leakage and shear and delivering efficiency across the whole operating range. For example, Digital Displacement machines have idling losses as low as 1% of the rated output power, according to Artemis.

Basic concepts of using Artemis Digital Displacement technology in a hybrid application. Click to enlarge.

At the Low Carbon Vehicle Event 2011 in the UK, Dr. Win Rampen, Artemis Intelligent Power managing director, outlined a conceptual Digital Displacement KERS (kinetic energy recovery system) for rail:

  • Existing engine and mechanical transmission is retained.
  • Digital Displacement Pump/Motor added to driveline.
  • Gas accumulator storage unit installed under floor.

We believe that the Artemis Digital Displacement technology is ideally suited both to railway driveline applications requiring highly efficient fluid power, and to use with an advanced mechanical energy storage system such as Ricardo’s Kinergy.

—Win Rampen

To demonstrate a complete rail driveline incorporating this combined energy storage technology, the system will be coupled to a wheel-set supplied by Bombardier and will be tested on a dynamometer rig at Artemis’ facility in Midlothian, Scotland. It is anticipated that a follow-up project will progress to installing and testing the system on an operating train.

The system can be tailored to suit various operating philosophies, including alteration of the engine demand to enable it to operate closer to its optimum brake specific fuel consumption, hence saving fuel and reducing carbon dioxide emissions. The system may also be configured to use stored energy to augment the peak acceleration of the vehicle and thus increase the operational flexibility of older rolling stock.

Faster acceleration rates—as typified on more modern vehicles—allow for increased network capacity, hence enabling more rapid recovery from delays and minimizing consequential impacts across the network.

While we are already evaluating the Kinergy in a commercial bus application, this project will be the first to deploy this very promising, cost-effective and efficient mechanical energy storage technology in a rail application. Combined with the Artemis high efficiency hydraulic transmission technology and Bombardier’s established position as a leader in rail vehicle design and construction, I believe that this project has the potential to demonstrate a highly compelling fuel saving and performance enhancing solution, equally applicable to retro-fit installation or incorporation in new rolling stock.

—Ricardo head of rail vehicle technology, Jim Buchanan

The “Digital Displacement Rail Transmission with Flywheel Energy Storage” project is a partnership between Artemis Intelligent Power Ltd, Bombardier Transportation UK Ltd, and Ricardo UK Ltd, with co-funding from the UK government-backed Technology Strategy Board. Artemis is the lead company.



Three highly astute organizations. They are bound to succeed with stunning aplomb.


Why not!

Henry Gibson

Parry People Movers already have two hydraulic hybrid flywheel vehicles in revenue service. The fundamental idea of hydraulic hybrids is long proven with both UPS vehicles and the several vehicles of Parry People movers with many years of demonstration.

Artemis has also demonstrated the improvement in automotive service in two vehicles. Artemis proved its technology first in wave power, then in automobiles and now in high power wind turbines. The automotive results have been ignored by all major and perhaps all minor automotive companies since rights were purchaced by Bosch-Rexroth.

The addition of flywheels to the hydraulic mix is not surprising since they were used and proven in racing automobiles. Artemis should just purchase the now disabled Parry prototype which ran a demonstration service that led to the two vehicles now in revenue service. Artemis should then just fit it with their motors and pumps.

Electric flywheel locomotives were very useful where third rail electrification required gaps in said rail. Now more and longer gaps can be tolerated so that electrification can be cheaper.

Flywheels were used on New York underground vehicles many years ago and trackside flywheels have also been tested.

The use of wearing friction brakes can be reduced to almost nothing.

DURATHON batteries from GE will allow gaps of miles.

Artemis is now owned by MHI which had indicated that it will get into the rail serivce as well as jousting at windmills.

Diesel Electric locomotives may have another competitor with the Artemis devices.

Carbon fibres used for flywheels can provide an almost equal service, but less dynamic and costly, as high pressure air tanks for hydraulic fluid energy storage.

This group should not ignore the INNAS NOAX free piston hydraaulic pump or their excellent mechanical but also highly efficient devices. ..HG..


Since for a car of 1.5 tons a hydraulic brake recovery system weighs like 100 kgs or so, can I extrapolate for a passenger rail cart of 60 tons that system will weigh like 4 tons or so to be installed somewhere under the floor? Also, for both the hydraulic system and the flywheel, that seems like a high explosive system waiting for an accident. For the flywheel either lots of shrapnel shredding you to pieces or carbon fiber fragments into your lungs, for the hydraulic accumulator the flying spaghetti monster knows what. As long as things go right, you'll be fine though.


Good to hear Artemis is still alive, that BMW 530i they did 5 years ago was an impressive vehicle..

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