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Supported by:
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AFD Show Cases |
| Trams save energy by flywheel energy storage, Zwickau, Germany |
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Zwickau (Germany)
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| A newly developed flywheel energy storage system was installed in Zwickau in 2006. The system is able to absorb the braking power of the trams and to store it as long as another tram needs this power for its acceleration. In best cases such a flywheel storage enables energy savings of 350,000 kWh a year. |
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Background & Objectives
Due to the rising energy costs, public transport providers make more and more efforts to reduce the power demand of their tram systems.
One possibility to save electric power is to reuse the braking power of the tramcars. Nowadays the braking power, which is recuperated to the catenary, is only used to 30%. To use the braking current more efficiently, flywheel energy storage systems can be a solution.
Flywheel storage systems are able to store braking current, which can not be used for an accelerating tram in the same section of the line, as kinetic energy of rotation. The energy is stored until another tram in the same section of the line needs much power, for example for its acceleration. The tram with the high power demand will then be partly provided with power from the flywheel.
Implementation
In the year 2006 the flywheel energy storage was installed by the local public transport provider SVZ, at the new track in Zwickau Planitz. The system “Schwungradspeicher T2” , developed by the German company Rosseta GmbH, is situated in a small concrete container next to the track.
Facts about the flywheel T2:
- The flywheel is made of carbon fiber
- Wheel turns with rotation speeds of 15000 to 25000 rpm
- Storage capacity: 4 kWh
- Peak power: 1 MW
- Auxiliary power demand: 4,5 kW
- Degree of efficiency: 80%
The system has been in permanent operation since October 2006 and is accompanied by a systematic monitoring of engineers. Costs for the installation of such a system vary from location to location, but can be estimated to be about 250 000 Euro.
Conclusions
The monitoring of the flywheel system lead to the following results:
- The flywheel works reliable and can be easily maintained
- In the best case such a storage can save up to 350000 kWh a year
- At the track in Zwickau (1 line, 10 min cycle) 140 000 kWh can be saved every year
- Braking current, which was used to 30% in before, is now used to 65%
- Trams save all in all 25% current in the section with the storage system
- The peak power, which has to be provided by the transformer substations, is reduced
- At prices of today, the system charges off within 6 to 12 years
- Due to the energy needs of auxiliary devices like heating, the energy saving is less in winter time
All in all the system can be used to reduce the power demand of the trams economically. With ongoing growth of the energy prices, the installation of such a system will charge off even faster in the future.
Another effect of the scheme is that power saving trams strengthen the position of the tram as an environmentally friendly means of transport. The scheme can therefore contribute to further political and public support for tram systems in local transport.
Further technical information on the system is available at the website of the manufacturer.
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Author
Carsten Tscheschke
Contact
Rosseta GmbH
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