Urban buses in big cities are essential both to serve the population and to reduce the number of cars on the streets, if the service is of good quality. However, buses are also a means of transport that, because of their powerful diesel engines, produce a considerable level of gas emissions that harm the environment. The solution to the problem is known and consists of using vehicles that produce fewer pollutants, such as those that run on ethanol, or no pollutants at all, with hydrogen or electricity. Projects along these lines are under development in various parts of the world and Brazil already has a hybrid prototype, powered by hydrogen and energy-accumulator batteries that were developed in the country. It is an apparently conventional bus for 29 seated and 40 standing passengers, designed and built over five years by the Hydrogen Laboratory (LabH2) of the Alberto Luiz Coimbra Institute for Graduate Studies and Research in Engineering (Coppe) at the Federal University of Rio de Janeiro (UFRJ).
“The hydrogen buses developed so far, such as the European Cute project, had large, very expensive fuel cells that consumed a lot of hydrogen. The evolution is carrying out hybridization projects with a fuel cell that produces energy for rechargeable lithium ion batteries, similar to those in cell phones, but much larger and suitable for vehicle traction, which make the electric motor work and propel the bus,” says Paulo Emílio Valadão de Miranda, a professor from Coppe and the project’s coordinator. Cute is the Clean Urban Transport for Europe project, financed by the European Union and consisting of 28 buses that have been circulating in several European cities since 2004. Fuel cells, the name preferred by Professor Miranda, is equipment that generates power through an electrochemical reaction of hydrogen and oxygen from the air. They work on the Coppe bus as a generator within the vehicle, powering the batteries, which provide autonomy of just over 100 kilometers, when fully charged for four hours at night from a special socket installed in the garages of the public transport company. “The cell starts working when the battery charge reaches a level predetermined by the main control system,” says Miranda. With this cell, the bus can run about 300 km in all without having to be recharged. The fuel cell system, with 77 kilowatts of power, was produced by Electrocell (see story) and the batteries were purchased from a Chinese company by another Brazilian company that has collaborated on the project, WEG, headquartered in Jaraguá do Sul, Santa Catarina and which produced the electric motor for the bus.
Another way of obtaining electricity inside the vehicle is from braking. The kinetic energy resulting from the movement of the vehicle is transformed into power when the brakes are applied or when decelerating. This is stored in batteries – or ultra-capacitors, equipment that also stores and release power quickly – for use in any of the vehicle subsystems. “It’s the transformation of the kinetic energy from the brakes into electricity,” says Miranda. To control all these energy flows and make them work in the most economical and efficient way, Miranda’s team developed an intelligent electronic bus system that manages the energy on board. “It consists of hardware and software that optimize the energy functions of the bus.” This system distributes the vehicle’s electrical power and is also connected to the traction system, consisting mainly of the electric motor and the auxiliary system that powers the lights, air conditioning, and door opening and closing.
Besides Electrocell and WEG, Coppe has a technical partnership with other industries such as Busscar, from Joinville, in Santa Catarina, which supplied the chassis and the body, Rotarex, from Mogi Guaçu, in the state of São Paulo, a manufacturer of valves and connections for gases, and a further four companies from Rio de Janeiro, EnergiaH, with its electric traction systems, Energysat, which makes control equipment, Controllato, analysis and solutions for the vibrations to which the equipment is subject within the vehicle, and Guardian, which makes electronic components. Initial funding for the project came from Petrobras and the Studies and Projects Funding Agency (Finep), by means of sector funds in the amount of R$ 2 million. “This is 30% of the total investment made [about R$ 7 million], including the added value from the partnerships that invested not only money, but also equipment, engineers and labor for building the bus.”
In the second half of this year, the bus will start running on the UFRJ campus, on Fundão Island in Rio de Janeiro. Then, under the coordination of the Municipal Department of Transport and Fetransport (the Federation of Passenger Transport Companies of the State of Rio de Janeiro) it will be included on a conventional urban bus route in the city. The idea is to build this bus commercially in Brazil after the trials and the final adjustments. “There is an agreement between the industrial and commercial partners to make it feasible to produce this bus,” says Miranda. The initial idea is to have them in the Rio city bus fleet for the 2014 Soccer World Cup and the 2016 Olympic Games. Another experiment with hydrogen buses is being carried out in São Paulo by EMTU (the city’s Metropolitan Urban Transport Company), in a project financed by the World Bank (see story in Pesquisa FAPESP nº 160).
The next LABH2 technological steps will be to produce two more buses. One will be a hybrid as well, but instead of the fuel cell, it will carry an ethanol generator to power the lithium ion batteries that supply electricity for the bus to run. The third in the series will be an all-electric bus that will cover about 200 km without needing to recharge the socket in the garage. “In Rio, it must be able to cover about 240 km a day, on average,” says Miranda. All these solutions have a single objective, which is to contain the 100 ton of carbon dioxide (CO2) pumped out of the exhaust pipes of every single bus in Rio de Janeiro in just one year, “and that is quite apart from pollutants such as nitrogen oxides (NOx) and others.” In Rio de Janeiro, there are 9,000 public buses and in the state there are 17,000. Changing the engines that drive these vehicles, or parts of them, would have a major environmental impact. The buses that run on hydrogen only release water vapor and electric buses emit nothing. Moreover, they are extremely silent, which also counts for points against noise pollution in large cities.Republish