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Fuel Cells
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The first fuel cell was built in 1839 by Sir William Grove. A Fuel cell is an electrochemical device that directly converts the chemical energy of fuels into electric and thermal energy. For example hydrogen (H2) and oxygen (O2) are combined to form water, electricity, and heat. Fuel cells are not like batteries which contain stored energy. Rather, a fuel cell will continue to produce energy as long as fuel is supplied to it. A fuel cell has no moving parts and therefore, the chemical energy can be converted directly into electric current without intermediate mechanical steps. Consequently, they can be much more efficient than steam or internal combustion engines: fuel cells can reach 65-80% efficiency compared to 35% for an internal combustion engine.
Ballard Power Systems Inc. of Burnaby BC has developed a fuel-cell-powered bus that has been operating since January 1993. The bus runs on a proton exchange membrane (PEM) fuel cell which is fuelled by hydrogen. The hydrogen can be supplied directly to the fuel cell or it can be obtained from natural gas or methanol using a fuel processor. The Ballard fuel cell consists of two electrodes, anode and cathode, which are separated by a polymer membrane electrolyte. One side of each electrode is coated with a platinum catalyst. In the presence of the platinum catalyst at the anode the hydrogen fuel dissociates into free electrons and protons. The electrons are then conducted as an electric current through the external circuit. The protons migrate through the membrane electrolyte to the cathode where they combine with the electrons from the external circuit and oxygen from the air to form water and heat. The electrical power can be increased by combining the fuel cells into a fuel cell stack. Increasing the number of cells in a stack increases the voltage while increasing the surface area of the cells increases the current.
The development of the PEM fuel cell system is focused on the transportation market for transit buses and cars and on the stationary market for power plants for electric power generation. Ballard Fuel Cells are currently being used by leading international companies such as Daimler-Benz, General Motors, Ford, Chrysler, Honda, Volkswagen and Volvo. In May 1997, Daimler-Benz demonstrated its NECAR II (New Electric Car) powered by Ballard Fuel Cells. It has a range of 250 km and a max speed of 110 km/h. By the end of 1997 Ballard plans to deliver 3 fuel cell engine powered buses to both the Chicago Transit Authority and BC Transit. The prototype for Ballard’s first commercially available stationary power product will be a 250 kW natural gas power plant which will be completed in 1997.
At present, the fuel cell buses developed by Ballard and the Daimler-Benz are called zero-emission vehicles as they are running on only compressed hydrogen. The hydrogen is stored in on-board fuel tanks and supplied directly to the fuel cells. Consequently, there are no emissions except for water vapour. Another method for suppling the fuel cells with hydrogen involves natural gas or methanol. In this case, the natural gas or methanol is stored on-board the vehicle and is converted to hydrogen by reformers attached to the fuel cell engine. This method is still effective; however, the vehicle is no longer a zero-emission vehicle. The emission is carbon dioxide but this is still advantageous as the total emission is two-thirds of that from vehicles with internal combustion engines.
Air quality is becoming an important issue as cities grow and expand. As the number of vehicles increase the amount of air pollution increases as well. Consequently, Ballard Power Systems Inc. and other international companies are combining their efforts to develop zero emission cars that are powered by fuel cells in the hopes of decreasing the air pollution.
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