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Supported by:
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AFD Show Cases |
| Tram in Rhein-Neckar-Region, Germany saves 20% of energy by the use of super capacitors |
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Heidelberg (Germany)
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| The public transport provider of Mannheim MVV and Bombardier Transportation successfully tested a tram equipped with an energy storage system. The system working with double layer capacitors, called super caps, induced energy savings of 20% compared to conventional tram vehicles. |
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Background & Objectives
The idea of the energy storage system is to reuse the braking current of the trams more efficient than today.
Today this current is recuperated into the catenary system, where only 30% of it can be used by other trams in proximity of the braking tram. The rest of this current is transformed to heat in large resistors.
The new concept enables to store the braking current directly in the vehicle, and to reuse it with the next acceleration process. Feasible methods for this like batteries, fly wheels and super caps were considered. The decision fell to super caps, because they deliver high energy density, can run a high number of cycles, are reliable and are expected to become cheaper within the next years.
The interest of the tram operators is to save energy costs, as a common tram vehicle causes energy costs of about 30,000€/a. Other aims are to design the whole catenary system for less peak performance and therefore cheaper, to decrease the carbon emissions of the tram system and to be able to run on short stretches without wire (e.g.: in front of historic buildings).
Implementation
Four years until 2008, a GTN6 tramcar of MVV equipped with a MITRAC energy saver unit, ran on regular service. One MITRAC capacitor unit has a performance of 300kW, weighs 477kg (5 times less than 5 years ago!) and has measures of 190x95x45cm. Extra costs for a tram equipped with MITRAC amount to 270 000€.
Conclusions
- The equipped tram needed 30% less energy for traction
- Together with several auxiliaries like air condition and light, the tram needed 20% less energy
- Energy in value of 10,000 €/a could be saved
- Technology proofed its reliability in daily service
- Maintenance was easy and cheap
- Peak power to be supplied by the catenary could be reduced by 50%
- Tram was able to move 500m with switched off pantograph
Due to the successful test, Rhein-Neckar-Transport Network decided to include the super cap system on 19 trams ordered in October 2007. Eight of them will be used in Heidelberg, where a new tram line on the university campus in the Neuenheimer Feld is planned. The aim is to avoid the erection of wires in front of University buildings that contain sensible scientific instruments. The other 11 vehicles will run in Mannheim and on the “railway-triangle” between Mannheim, Weinheim and Heidelberg. The extra costs are expected to charge off within the first 15 years of operation.
RNV is responsible for commuter transport services in the Rhein-Neckar region, including tram, LRV and bus services in Mannheim, Heidelberg and Ludwigshafen. The RNV operates the largest meter gauged rail network in Germany with a total length of more than 200 kilometres. This network also includes the railway lines between Mannheim - Weinheim - Heidelberg - Mannheim (OEG) and from Ludwigshafen to Bad Dürkheim (RHB), which are licensed as railways unlike the other tram lines. RNV took over the operating business from the five “mother companies” in March 2005. The company employes about 1.700 staff, the vehicle fleet includes 200 LRV an 140 buses.
Transferability
Due to the high weight and large measures of the Energy Saver system it is not possible to install the system on every older tramcar. The best way is to integrate the technology into tramcars which are to be newly procured.
The best performance of the system is to be supposed in flat territory. In hilly territory the performance is worse, because capacity of the energy saver is to less to save all energy which occurs on downhill rides and to less to supply energy for long uphill rides.
The development of the super capacitor technology has not ended yet. The power density will increase within the next years while the prices for super caps will decrease. Under additional consideration of increasing energy prices the application of super caps will probably be paying off faster in the future.
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Author
Carsten Tscheschke
Contact
Georg Nowack-Herdweck
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