Vehicles powered by fuel cells using hydrogen are environmentally friendly – the only emission is pure water. Noise levels are low compared to vehicles fitted with internal combustion engines. As a result, fuel cell-powered vehicles are perfect for urban areas, where emissions and noise are major problems. The only environmental impact arises from energy use and possible carbon dioxide (CO2) emissions in the upstream production and distribution of hydrogen. There are, however, several options for producing hydrogen from renewable sources, such as wind power, waste gasification and biomass. Hydrogen can also be produced on a large-scale from natural gas, with CO2 sequestration and desposition.
The Greater Oslo Transport Authority and Norsk Hydro have been evaluating hydrogen as a fuel for bus operation since 1994. In 1997/98, the possibility of using fuel cell technology became more realistic – major equipment manufacturers announced fuel cell vehicle programmes, and fuel cell-powered vehicles were being demonstrated in Canada.
In 1997, DaimlerChrysler developed Nebus, a demonstration bus powered by fuel cells operating on hydrogen. A collaboration between the Norwegian project and DaimlerChrysler was established in 1998 to focus on this fuel cell technology. In August 1999, the demo-bus was tested in normal operation, on a test drive along an ordinary public transport route.
Nebus is fuelled by compressed hydrogen at
300 bar, which is stored in seven 150 litre cylinders on the roof of the bus. The fuel cell stack contains 10 fuel cells each rated at 25 kW, and the stack provides 190 kW for the drives. The fuel cells also supply electricity to the power-steering pumps, an air compressor and the door control system. The range of the bus is 250 km before refuelling is necessary and the maximum speed is 80 km/hour. The overall energy efficiency is 37%. The only by-product of the fuel cells is water at 80ˇC which can be used in the heating system of the bus. The German Technical Inspectorate (T†V) has licensed the Nebus for use in public transport.
Noise measurements for Nebus, compared with vehicles running on compressed natural gas and diesel, are shown in the table below.
Driving performance, technical data and public response were monitored during the test. Information activities to disseminate the technical data were also completed. Market studies and life cycle assessment studies have now started.
In general, the driver was very satisfied with the performance of the bus, stating that a softer driving pattern is necessary, but that this is pleasant. The weight of the fuel tanks on the roof was noticeable and, when driving around corners and roundabouts, the driver had to take this into account. The bus has not yet been tested on steep hills and this might present a challenge. Refuelling was completed in 10–15 minutes without any complications. The reduced noise levels were said to be excellent.
According to Norsk Hydro, hydrogen consumption was 636.6 Nm3 for the test period. The energy content of the hydrogen was 11 MJ/Nm3. Based on the measured 583 km travelled, the specific average consumption was 1.092 Nm3/km, which is equivalent to 0.33 litres/km of diesel. The average diesel consumption in city driving ranges from 0.4–0.5 litres/km. Therefore, energy consumption for the Nebus is significantly less than that of a diesel bus.
Of the 32 passengers onboard during the test, two thirds had no knowledge of hydrogen or what hydrogen could be used for. Those with any knowledge mentioned fuel, power stations and industrial use. When asked about hydrogen as a fuel, 75% believed that it could replace gasoline and diesel in the future, dependent on technology development and the costs of fuels and vehicles. Nearly all (97%) believed that it is both important and necessary to reduce air pollution from traffic, particularly in cities.
In conclusion, the passengers were very positive about Nebus and hydrogen as a fuel, and welcomed the test drive as a forecast for a future with cleaner transport technology. Their level of knowledge of hydrogen as a fuel was low, but their environmental commitment was high (eg in terms of making choices related to transport, energy saving and waste sorting). The interviews showed a concern for air quality and other pollution problems.
All in all, the test confirmed the significant potential of hydrogen fuel cells as a contributor to more environmentally-friendly public transport in the years ahead.
For more information contact the CADDET Norwegian National Team in Rud.
The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.
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