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General information
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General criteria
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Status of development: in use |
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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. |
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Time horizon for broad application: 5 - 10 years |
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According to WTZ Rosslau, stationary applications in light city rail systems could reach 30% market diffusion within 5 years (as of 2002). |
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Expected technological development: dynamic |
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cf. Application outside railway sector - Expected technological development outside railway sector |
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Motivation:
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If used as a storage technology for braking energy, the motivation is saving energy.
Other possible applications include catenary-free operation of city trams. |
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Benefits (other than environmental): not applicable |
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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. |
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Barriers: high |
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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. |
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Success factors:
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(no details available) |
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Applicability for railway segments: medium |
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Type of traction: electric - DC, electric - AC, diesel
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Type of transportation: passenger - main lines, passenger - regional lines, passenger - suburban lines, freight
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- 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
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Grade of diffusion into railway markets:
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Diffusion into relevant segment of fleet: 0 % |
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Share of newly purchased stock: 0 % |
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- No on-board in-service application yet.
- Very few stationary applications.
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Market potential (railways): low |
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- 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.
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Example:
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Lirex experimental train (planned for in the future). |
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Environmental criteria
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Impacts on energy efficiency:
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Energy efficiency potential for single vehicle: > 10% |
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Energy efficiency potential throughout fleet: (no data) |
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Other environmental impacts: neutral |
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Economic criteria
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Vehicle - fix costs: high |
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WTZ Rosslau that the market price of the fly-wheel currently developed (6 kWh / 350 kW) will be roughly 200.000 EURO. This is the market price and does not cover the total development costs of the joint project between Alstom and WTZ Rosslau. |
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Vehicle - running costs: significant reduction |
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Energy costs
Energy costs are significantly reduced.
Maintenance
The only known in-service use of fly-wheels in railways is a stationary fly-wheel storage system in a substation at Kölner Verkehrs-Betriebe AG (KVB), Cologne, Germany. There is however no data available on maintenance experience.
Maintenance experience with Magnetmotor fly-wheels used in Basel trolley busses
The maintenance intervals of the fly-wheels used in trolley busses in Basel are defined to 3500 operation hours. The manufacturer Magnetmotor claims that specific tests with bearings and lubrication prove that maintenance intervals of 6,000 h are possible and that for the power electronic the statistic MTBF (mean time between failure) is more than 40,000 hours.
Currently the maintenance of the MDS fly-wheel is done at Magnetmotor, i.e. the system has to be removed from the vehicle sent to the manufacturer. Typical maintenance includes checking of components and the system as a whole, cleaning and lubricating or exchanging the bearings. The average maintenance time is about one working day.
By 2000, the average repair requirements was down to one repair every 38,000 hours of operation (equivalent to one repair in 8 years per fly-wheel). |
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Infrastructure - fix costs: none |
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(no details available) |
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Infrastructure - running costs: unchanged |
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(no details available) |
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Scale effects: low |
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Scale effects are to be expected from a more wide-spread use of fly-wheels. However, a mass market for fly-wheel technology will not exist in the foreseeable future. According to WTZ Rosslau production of 100 fly-wheels will not yield any price effects. This would require selling at least 10.000 systems, a figure only to be reached in automotive mass market where fly-wheels have little or no potential. |
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Amortisation: > 5 years |
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Payback time depends on application context but is generally long. Study at NS In a study made in 1998, NS calculated that the energy savings pay off the investment to a great extent but not completely. The amortisation period is between 17 and 30 years. For an energy price of 13 ct/kWh at NS, the return on investment is 0,35-0,6. NS expects that this situation could improve in the future by growing energy prices. The payback time is quite pessimistic. Lirex The situation should have improved in the meantime due to technological progress. DB AG assumes that the investment for the Lirex fly-wheel system will pay off easily within the lifetime of the vehicle currently planned to be around 15 years. Diesel-electric vs. stationary applications in DC systems According to WTZ Rosslau, stationary applications in local DC systems will generally have a better cost-benefit ration than on-board storage systems in regional diesel-electric stock. |
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Application outside railway sector
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Status of development outside railway sector: in use |
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Time horizon for broad application outside railway sector: in 5 - 10 years |
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Expected technological development outside railway sector: highly dynamic |
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Market potential outside railway sector: small |
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Overall rating
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Overall potential: promising |
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Time horizon: long-term |
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Fly-wheel technology is a promising solution for energy storage systems. First in-service experience from trolley busses and stationary storage in a light city rail DC system show principal technological feasibility and reliability. High power fly-wheels for on-board storage in DMUs are still under development. Main barriers for fly-wheels are high initial investment and long payback times. Best cost-benefit ratio is reached for stationary storage systems in local DC systems. Scale effects will be small in the foreseeable future since no mass markets exist. Growing technological competition from double-layer capacitors make a wide-spread use of fly-wheel technology uncertain. Nevertheless, due to long life-time and relatively high maturity, fly-wheels are still a promising technology. |