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Hydrogen-powered buses

Bus assembled in Brazil is among the global experiments aiming at lower air pollution

EDUARDO CESARBus to cover 250 km a day and emit only water vaporEDUARDO CESAR

A hydrogen powered bus will probably start circulating this June, on a conventional city line between the districts of Jabaquara, in the southern part of the city of Sao Paulo, and Sao Mateus, in the Eastern part of the city, going through the towns of São Bernardo do Campo, Diadema, Santo André and Mauá, all of them part of the Greater São Paulo. The feat is unprecedented in Brazil and includes a number of new features. Vehicles powered with this technology are silent and do not emit pollutants. They only release water vapor into the environment and bring health benefits because they do not add to the increase in respiratory diseases. They also humidify the air in large cities.

Along with biofuels and electrical vehicles, hydrogen is regarded by experts as a real alternative to oil products, which emit pollutants and will tend to become scarcer in the future, because natural oil and gas reserves are finite, both as a result of their depletion following years of exploitation and because of the  increase in worldwide consumption. Thus, the Brazilian experience fits in with a series of experiments that are being carried out around the world with cars and buses powered by hydrogen rather than gasoline or diesel, aiming at a reduction in the gases that are harmful to people and the planet.

The bus was assembled in Brazil with financing provided by the Global Environment Facility (GEF), a World Bank agency, which finances sustainable development initiatives in many countries. “We established partnering arrangements in Brazil and abroad to assemble the bus and transfer technology into the country, because, at first, the project was meant to buy readymade buses from Europe. The argument was that Brazil is the world’s largest producer of buses [in 2008, the country produced 44,111, of which 27,948 were exported, according to Anfavea, Brazil’s National Association of Manufacturers of Automotive Vehicles] and we have a long-standing tradition in the bus bodies’ industry,” says Carlos Zündt, the planning manager of EMTU, the Metropolitan Urban Transport Company of the São Paulo State Urban Transport Bureau, an institution that was made responsible for the development and management of the project and that is going to run the hydrogen bus on the exclusive, 33 km long metropolitan corridor. The aim here is to incorporate, integrate and develop technology to use hydrogen as fuel and to prepare companies for this future market.

In other similar projects being carried out around the world, what has prevailed is the purchase of ready-made buses, especially from Mercedes-Benz, which has a model of the Citaro series that runs on hydrogen and that is already operating in several European cities, especially in Berlin, Germany, which has 18 of them. In Europe, since 2004, the Cute – Clean Urban Transport for Europe project, financed by the European Union, has allowed 38 hydrogen-powered Citaro buses to run in nine cities, such as London, Madrid, Barcelona, Amsterdam, Hamburg, Stuttgart, Luxembourg, Oporto and Stockholm. They have already run for 135 thousand hours and the experience has proved to be environmentally sustainable. Another three projects were conducted in Reykjavik in Iceland, Beijing in China, and Perth in Australia. Overall, 47 buses were used. The project has 31 partners, comprising government bodies, industries and universities. All of the projects, including the Brazilian one, are projects of demonstration and tests of technology under real conditions, and none of them has a merely commercial objective. In the Brazilian case, the EMTU company, as part of the commitment forecast in the investment, will be required to test the bus and to submit the results and the experience to GEF, which may share reports of the experiment with other countries.

DAIMLERNew Citaro model is hybrid because it uses hydrogen power to recharge batteriesDAIMLER

In Brazil, the project began in 2004, bringing together an international consortium of construction and supply firms. The bus has nine hydrogen cylinders and an air conditioner on the roof; all the other equipment is at the back of the bus. The Citaro design is different. All the equipment is installed in the roof, which means it needs very special, very expensive electronic suspension. But it is equally dependent on a fuel cell. This is what transforms hydrogen into electricity and moves the bus by means of two electric motors. The cell comprises a set of electrode plates, normally made out of graphite, which are shaped like a sandwich, and contain a polymer membrane called a PEM (Proton Exchange Membrane) between the plates. When the hydrogen molecules (H2) pass through this membrane they are broken down and electrons are freed, generating electricity. To conduct this electrochemical process, the hydrogen also bonds with oxygen drawn from the air, forming water vapor at the end. This technology – the key component of the entire system – was acquired from Ballard, a Canadian enterprise that began developing fuel cells in 1983 and  presented the first prototypes between 1992 and 1994.

In 2007, Daimler, the holding company to which Mercedes-Benz belongs, and Ford became majority partners in a Ballard subsidiary, the Automotive Fuel Cell Cooperation (AFCC).  Outside hydrogen electronic control and hydrogen transport systems, the two cells looks like two metal boxes, 81 cm long, 24 cm deep and 30 cm wide each. “These are two independent cells that operate in an interconnected manner, like those that equip the hydrogen-powered Mercedes-Benz Class A automobile, which has been on show in Europe since 2003, and the Ford Focus presented in 2006 in the United States, Canada and Europe. Each of Ballard’s cells generates 68 kW of maximum power, or 91 hp. For the purpose of comparison, a two-bedroom house for a middle-class couple with two children needs 5 kW of power.

Brazil already has at least three firms, Electrocell, Unitech, (see Pesquisa FAPESP issues 92 and 103) and NovoCell – all of them from the state of São Paulo and financed by FAPESP’s Innovative Research in Small Companies Program (Pipe) –  developing fuel cells and parts for this equipment in specific projects for stationary power generators, rather than automotive, and mainly for companies.

The auxiliary systems of the cell for buses, such as the system for the injection and circulation of hydrogen and air from the atmosphere at  pressure and moisture levels that the main piece of equipment requires, and the electronic control parts were developed by the German company Nucellsys, whose partners include Ford and Daimler. The management of all the systems, including durability trials, is carried out by EPRI, the Electric Power Research Institute, headquartered in California, USA, which has experience in managing projects of this kind.

EDUARDO CESARBus panel monitor informs the kilowatts and amount of hydrogen EDUARDO CESAR

National cooperation
On the Brazilian side of the consortium, the body comes from Marcopolo, one of the world’s largest body manufacturers, which has 3 plants in Brazil and 11 abroad, in countries such as China, India, Russia, Portugal, Argentina, Mexico and Egypt. The hydrogen model belongs to the Gran Viale series, used for urban buses. It is 12.5 m long and can hold 63 seated passenger plus 20 standing. Adaptation of the bus to the fuel cell system and  other equipment for the hydrogen system was carried out by another Brazilian firm, Tuttotrasporti, established by Brazilians of Italian origin in the town of Caxias do Sul, state of Rio Grande do Sul. This company specializes in the production and modification of chassis (the metal structure that supports the vehicle, including the wheel axles) for special vehicles, such as gas-powered buses or hybrid ones, with batteries and diesel-powered, with a second floor, with two axles in front, or with the inverted steering system required to export to countries such as England and Japan. “Tuttotrasporti was the Brazilian company that benefited the most, because it was their engineers and technicians that acquired the know-how for adapting, assembling and integrating the systems, including the central processing unit, which comprises the processors that manage the bus’s electric power as well as the hydrogen pressure and other systems,” says Zündt. “The software was molded by us in such a way as to control all the points. Each subsystem, such as the cells, has its own processor that indicates, for instance, their temperature [they run at 60 to 80°C], and they are connected to a large computer that has access to all the operating protocols which enable the entire bus to be managed,” says engineer Sidney de Oliveira Sobrinho, from Tuttotrasporti.

Fuel cells from Class A, undergoing trials in Europe, are used on the Brazilian bus

MERCEDES-BENZFuel cells from Class A, undergoing trials in Europe, are used on the Brazilian busMERCEDES-BENZ

Constant power
The Brazilian hydrogen bus is also a hybrid vehicle, because it can accumulate power in three special high-performance nickel-sodium batteries that can store a lot of power. They are supplied by MSDea, a Swiss firm. Both these batteries and  cells transfer power to the two Siemens water-cooled electric motors, manufactured in Germany. “The cell releases power constantly. When the bus is stationary, the unused power goes into the batteries. Activation of the brakes also generates storable power. Thanks to the batteries, the bus can do 50 km more than the 300 km it can do on hydrogen. In the bus-lane, along which it is going to run, the diesel buses do 250 km a day,” says Zündt. Until Mercedes-Benz presented its hybrid Citaro Fuel Cell model this year, the Brazilian bus was the only one with the hybrid feature. After almost three years dedicated to its design and construction it was ready in July, 2008 in Caxias do Sul, which is when a series of trials began. By May, when it got to São Paulo, it had already done 2,200 km. This, however, did not include driving from Caxias do Sul to the São Paulo State capital because it would have been impossible to supply it with hydrogen along the way.

The knowledge acquired by the Brazilian firms will be useful when it comes to building the three new vehicles that have been planned in the series in Brazil, in addition to the first one, which is considered a prototype. They are to run in the same bus lane, but will incorporate some changes thanks to the experience already acquired. “The lessons learnt thanks to this first prototype will be implemented in  subsequent buses and then it will be possible for Tuttotrasporti to make them on an industrial scale,” says Zündt.

“The motor compartment where the equipment such as the cell is installed, the electric motors, radiators and other devices are expected to drop in size by 50%.” The next buses, whose delivery date is yet to be determined, will be 15 m long, have three axles and other Brazilian pieces of equipment and components. “The axle, which is Hungarian, will perhaps be made here, a possibility that also applies to the electric motors and other devices such as radiators and voltage converters, to be made in Brazil,” says Sobrinho. “We will carry out cost-reduction studies, nationalizing whatever we can, and using the knowledge for other projects.”

The parties are not revealing the total price of the bus. All that is known is that it costs more than the diesel ones. What has been divulged, however, is the total investment in the Brazilian Hydrogen Bus Project, which amounts to R$38.5 million, including the other three possible vehicles, as well as the hydrogen production and supply unit that is being built at the EMTU headquarters. GET, through the United Nations Development Program, which provides technical and administrative aid for the project, financed R$22.3 million. The Ministry of Mines and Energy, with funds from Finep (Studies and Projects Finance Agency), footed the bill for another R$8.3 million, whereas EMTU invested R$3.09 million and the participating firms another R$4.75million.

Ônibus_INFO_IngRe-fuelling station in the garage
The Brazilian firms that are investing in the project include Petrobras and Eletropaulo. Both are involved in the hydrogen production unit. This gas is not found on its own in the wild, although it is present in water, in ethanol, in natural gas and in gasoline, so that it can be extracted by breaking down molecules of these substances. The bus is to be filled up at the EMTU garage in the town of São Bernardo do Campo, where the buses that run on this corridor are parked. A production station is to be built in the garage and it will be run by Petrobras’s distributor BR. The system used will be water electrolysis, whereby an electric current separates the hydrogen and oxygen molecules. This production and supply unit is coming from a Canadian enterprise, Hydrogenics, which specializes in producing hydrogen through electrolysis. Eletropaulo will build a special network to run the station as inexpensively as possible, with the preferential supply of power for hydrogen being carried out in off-peak hours. As this station is still being built, in the first few months of the trial the hydrogen will be brought in by truck from a Petrobras refinery in the town of Cubatão.

A factor of concern whenever one talks about hydrogen or any gas is safety. “The cylinder walls are stainless steel and very thick; hydrogen is a very small molecule that can leak at a molecular level if it isn’t well sealed with the right technique and material,” says Zündt. Moreover, there are sensor and valve systems that quickly shut off the nine cylinders if the bus crashes. The hydrogen tanks, which are American, each carry some 5 kg of this gas. Overall, there are 45 kg at a 300 bar pressure, the same as in a 300 m dive in the sea. Within the cell, the pressure is cut to 2 bar by a valve system. However, at the start of production at the station, the gas is stocked at 700 bar. At this station one can also store the oxygen that the reaction releases. It is fairly pure and can be used for medicinal purposes, if the costs are competitive. Concerning the price of a kilogram of hydrogen, it is more expensive than diesel. A kilogram in the market (which uses hydrogen for industrial purposes and in food manufacturing to make hydrogenated fats, extracting it from natural gas through equipment called reformers) is not competitive in relation to diesel, even considering in-house production via electrolysis, because power consumption and its cost are high.

For Zündt, the technology for use in transportation is still expensive relative to the traditional technologies, if one disregards the environmental and health toll. The system used in the Brazilian project is a closed cycle, which begins and ends with water, which comes out in the form of vapor released into the atmosphere. Another element to be taken into account is that the level of energy efficiency in fuel cell systems is far better than that of other systems. “Of every kilogram, one uses as much as 90% of its energy potential, whereas a liter of diesel is, on average, 25% energy efficient,” says Zündt. The bus’s expenses will be better known after it has been running for some months on the metropolitan bus-lane along which the vehicle is to operate. However, even before going into operation, the Brazilian hydrogen bus is already drawing the attention of future buyers. “A European group in the transport area consulted us about the technology and the cost of the bus, with the idea of selling it to Asian countries,” said Zündt, without going into further detail, as this is confidential.

“Brazil’s hydrogen bus is part of a world program whose aim is to not emit carbon (CO2) from vehicles and has the merit of being a demonstration project,” says professor Ennio Peres, coordinator of Ceneh, the National Reference Center for Hydrogen Power, at the Hydrogen Laboratory of Campinas State University (Unicamp). “It’s very important to make hydrogen technology known, showing its advantages and that it isn’t dangerous to use.”

Total replacement
Hydroelectric power stations may become hydrogen producers

Supply is regarded as an obstacle for the automotive hydrogen market. Hydrogen stations in larger numbers only exist in the state of California in the USA, in Japan and in Iceland, using hydrogen taken through electrolysis from water or natural gas. In Brazil, hydroelectric power stations provide a good opportunity. Besides cheap energy produced in the small hours of the morning, when consumption drops, one can use “spillway turbinable” power, namely, the electricity that can be taken from the water diverted into the spillway when the reservoirs are overfull or at times when demand is low. The water is wasted because the power cannot be stored. The solution is to turn it into hydrogen.

Professors Ennio Peres, from the Hydrogen Laboratory, and Carla Cavaliero, from the School of Mechanical Engineering, both from Campinas State University (Unicamp), along with Gustavo Riveros-Godoy, a Paraguayan researcher from the National University of Assuncion, carried out a study on the production and distribution of hydrogen for city buses in the town of Foz do Iguaçu in the state of Paraná, where the headquarters of the Itaipu Hydroelectric Power Station are located. They presented their work at the 4th International Workshop on Hydrogen and Fuel Cells held in October 2008 at Unicamp, which shows the operational viability of replacing diesel buses by hydrogen vehicles in  four companies in Foz do Iguaçu, a town with 309 thousand inhabitants. Without taking into account the cost of the buses, they used data from the Mercedes-Benz hydrogen model, the Citaro Fuel Cell. The best gas production model would be the one centralized in Itaipu itself, where the buses could fuel up once a day. The cost of a kilogram of hydrogen would be US$2.86, and the mean consumption would be 0.205 kg/km covered. In financial terms, diesel still outperforms this, but hydrogen has environmental advantages that are increasingly being taken into account.