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   Fly-wheels (storage technology)  evaluated  
The fly-wheel is an electro-mechanical energy storage system based on rotating masses. It is a powerful storage technology which may be used both for on-board and for stationary applications.
Technology field: Regenerative braking and energy management
open main section General information
close main section General criteria
  close sub-section Status of development: in use
   

Stationary storage

Fly-wheel storage was/is used in stationary applications for local trains in Cologne, Hannover and few other European cities. Experience from Cologne showed technical problems which led to the abandoning of the system. The application in Hannover based on a steel fly-wheel is operated successfully.

On-board storage

Deutsche Bahn AG plans to integrate an on-board fly-wheel in their Lirex experimental train. However, the development of the 6 kWh fly-wheel has run into difficulties. Therefore the fly-wheel version of the Lirex will be delayed and Deutsche Bahn plans to start regular service of the Lirex in December 2002 without an energy storage system. It is planned to integrate the fly-wheel system later.
  Time horizon for broad application: 5 - 10 years
    According to WTZ Rosslau, stationary applications in light city rail systems could reach 30% market diffusion within 5 years (as of 2002).
  Expected technological development: dynamic
    cf. Application outside railway sector - Expected technological development outside railway sector
    Motivation:
    If used as a storage technology for braking energy, the motivation is saving energy. Other possible applications include catenary-free operation of city trams.
  Benefits (other than environmental): not applicable
   

Maturity

Despite technological challenges still to be mastered, fly-wheel technology is relatively mature.

Lifetime

According to WTZ Rosslau, fly-wheels have a cycle life of about 5 million which corresponds to a lifetime of twenty years in a railway application, ten times more than today’s double-layer capacitors.
  Barriers: high
   

Costs

Investment costs of fly-wheels available on the market are still high.

Technological maturity

Small fly-wheel systems (~ 2 kWh, ~ 150 kW) as needed for busses are available on the market (Magnet-Motor Starnberg). Early failures (such as false system reactions due to sensor levels adjusted too low or mechanical problems with fixation of certain subcomponents) have been resolved in the meantime.

Reliable higher power/energy classes based on steel technology exist for stationary applications. The operation of a stationary fly-wheel (by Magnet-Motor) in the Cologne KVB network has been stopped because of low reliability.

Technological competition

Recent progress in the development of double-layer capacitors makes a wide-spread diffusion of fly-wheel technology uncertain.
    Success factors:
    (no details available)
  Applicability for railway segments: medium
    Type of traction:  electric - DC, electric - AC, diesel
    Type of transportation:  passenger - main lines, passenger - regional lines, passenger - suburban lines, freight
   
  • On-board use in diesel-electric vehicles to store braking energy.
  • On-board use in DC systems to raise recuperation rate
  • Stationary use in DC systems to raise recuperation rate
    Grade of diffusion into railway markets:
  Diffusion into relevant segment of fleet: 0 %
  Share of newly purchased stock: 0 %
   
  • No on-board in-service application yet.
  • Very few stationary applications.
  Market potential (railways): low
   
  • An economic use of fly-wheel technology will be mainly possible as stationary installation in light rail and mass transit systems.
  • An on-board application in diesel-electric vehicles may be profitable in some networks with frequent stops.
    Example:
    Lirex experimental train (planned for in the future).
open main section Environmental criteria
open main section Economic criteria
open main section Application outside railway sector
open main section Overall rating
References / Links:  Caputo 2000;  Engel et al. 2001;  Hennig, Stephanblome 2000;  NS Reizigers (no year);  Reiner, Weck (no year a);  Reiner, Weck (no year b);  Witthuhn, Hoerl 2001;  www.ott.doe.gov
Attachments:
Related projects:  Flytrain;  Studies performed on energy storage systems
Contact persons:
 date created: 2002-10-09
 
 
© UIC - International Union of Railways 2003
 
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