Supercapacitor tram

The Chinese tram powered by supercapacitors. Credit: Zhuzhou Locomotive Co

The first tram powered by supercapacitors has rolled out of production line in China, in the province of Hunan.

The tram has no need for a connection to a power line, it is catenary free, its supercapacitors get recharged during the stops on the way. A 30” stop is enough to fully recharge the supercapacitors, providing the tram an autonomy of 3-5km, much more than the distance to the next stop.

A further advantage is that it is possible to reuse the energy created by braking to recharge the supercapacitors with an efficiency close to 85% (meaning that 85% of the kinetic energy of the tram is converted into electrical energy stored into the supercapacitors, rather than being wasted as heat).

It all boils down to creating a city wide recharging infrastructure providing recharging point at each tram stop.

The tram can carry 380 passengers reaching a top speed of 70kmh.

I was not able to find specific information on the cost of the supercapacitors and of their operation (and cost of replacement). These are clearly important aspects to understand if this is a one of a kind result demonstrating excellence in research by China or if it can become a widespread solution. Current supercapacitor technology support up to 100,000 recharging cycles (five times as a battery cycles) and the average impact on cost of a vehicle like a tram is roughly 20% of the total cost at production. Then one has to add the cost of replacement once their life is over.  As a back of the napkin calculation a tram may make some 300 stops a day. That is slightly over 100,000 per year. Given the 100,000 useful recharging cycle that would require a replacement every year. However, some smart recharging algorithm may ensure that recharge occurs not at every stop but once the power goes below a certain thresholds, and it would seem reasonable to make one recharge, on the average, every three stops. That would increase the life time of the supercharger to 3 years. Much better.

Smart cities will need these kinds of smart transportation…

Author - Roberto Saracco

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