Clean vehicles for the public transport fleet

Summary

Bologna wants to improve the environmental performance of its public transport bus service by building up an advanced fleet of cleaner vehicles that are most suited to the local context.

Implementing sustainable mobility

Bologna has already experience with using alternative fuels on public buses. The city now wants to explore opportunities for a more efficient and advanced use of these fuels in its bus fleet. The public transport company will analyse new fuels and technologies, compare costs and benefits and determine the best suited fuel source for the local context.

The main objective of the measure is to:

• Create the conditions for wider use of alternative fuels for public transport buses in Bologna.

Bologna has occupied itself with alternative fuels for many years now. In 2002, public transport operator ATC launched an implementation plan to fuel buses with methane. By 2007, buses running on compressed natural gas (CNG) represented almost 30 percent of ATC’s urban bus fleet. In addition, 211 vehicles representing about 43 percent of the urban fleet have been equipped with diesel particulate filters (FAP) to improve their environmental performance. Furthermore, three of the main bus lines are running as trolley lines. Despite these considerable investments to improve the environmental record of public transport vehicles, the overall performance remains critical and Bologna is keen to step up its efforts. Bologna now wants to look into alternatives such as electric and hybrid vehicles. This process is carried out under CIVITAS MIMOSA and follows a wide-ranging scientific analysis based on economical, technical and environmental factors.

Progress

Bologna started the measure by contacting bus manufacturers to develop a clean bus prototype. The companies were however not interested in presenting the city with such a prototype without a fixed supply order. ATC has completed a feasibility study aimed at identifying the best technological solution to introduce low-emission buses in Bologna. The study takes into account the market and technology trends within the bus industry and innovations in environmental sustainability for public transport vehicles. Different solutions were investigated by a life cycle and life cycle cost assessment, and well-to-wheel analysis. The well-to-wheel approach was particularly interesting as it evaluated the entire energy chain from fuel production to the energy needs linked to the operation of the bus service. The study concluded that the best performing solution for Bologna would be hybrid buses. Based on this outcome, ATC decided to build up a small hybrid bus fleet. After defining the technical specifications, a call for tenders was launched for two hybrid buses with a length of 12 meters and three doors. Finally, after closing the procedure, in February 2012 Tper, the new public transport company operating in Bologna, awarded the contract to the bus manufacturer Van Hool NV for a total investment of 700,000 Euros, partially co-financed by the Mimosa project. Since April 2012, the two vehicles have been circulating in Bologna. In particular, one has been assigned to the extra T-line that operates during the so-called pedestrianised T-days on week-ends and holidays. The two EEV serial-hybrid buses are equipped with innovative super capacitors that replace conventional electric batteries. Compared to traditional hybrid vehicles, they allow a considerable reduction in fuel consumption. Maintenance costs are also reduced, since these vehicles do not need periodical battery substitution (at a cost of about 30.000,00 euro every 3 years) as conventional Hybrid-buses do. Besides this, super capacitors make it unnecessary to deploy battery charging stations at bus depots and can stand a higher number of charge-discharge cycles, thus lasting longer than conventional batteries, making both super capacitors and vehicles environmentally friendlier. Additionally, super capacitors ensure the buses are more reliable. The two Van Hool vehicles are equipped with an electric generator powered by an endothermic diesel engine. The generated energy is stored by the super capacitors and released by the electric drive engine during the acceleration phases, to support the endothermic diesel engine, thus reducing fuel consumption and improving the performance. During the braking and decelerating phases the energy produced by the generator is driven to the super capacitors to be stored. In other words, the super capacitors work like a type of super condenser, which can very rapidly store and give back energy in great quantities. The hybrid buses procured by TPER can carry 24 seated passengers and 56 standing ones. There is also a reserved area for one wheelchair and a buggy, and a manually folding access platform for disabled passengers (located at the central door). Personnel training activities for maintenance staff have been carried out to have inside the company the necessary know how as concerns the innovative aspects of these hybrid buses.

Outcomes

Bologna expected that at the end of the measure the city will have built up a small low-emission bus fleet tailored to the local context.

Data concerning fuel consumption, collected in real service conditions and during summer, a season featured by an intensive use of the air conditioning system, are encouraging: the average consumption is 2,52 Km/l, equivalent to 39,68 liters/100 km. The average daily consumption is about 80 liters for a daily service of 200 km.  Compared to traditional hybrid vehicles, the new hybrid buses allow a considerable reduction in fuel consumption and maintenance costs are also reduced.