An innovative system for a clean and sustainable public transport system in smart cities

Municipal mobility agencies have tried to reduce the carbon footprint of their bus fleets using a range of options over the years, from biofuels and hydrogen to batteries and hybrid-electric diesel. A possible alternative to these options, could be the use of ultracapacitors and their capacity to offer a greener and most economical way of powering city buses. Compared to lithium-ion batteries ultracapacitors lack in range: the best ultracapacitors can only store about 5 percent of the energy that lithium-ion batteries hold, limiting them to a couple of miles per charge. This makes them ineffective as an energy storage medium for passenger vehicles. But what ultracapacitors lack in range they make up in their ability to rapidly charge and discharge. So in vehicles that have to stop frequently and predictably as part of normal operation, energy storage based exclusively on ultracapacitors begins to make sense. This paper illustrates a novel concept for a clean and sustainable public transportation system based on the use of ultracapacitors. Concepts and objectives of the project are discussed and results of test activities are reported. Moreover, in the last section of the paper an application of the proposed system to a real case in the city of Rome is illustrated.