Hydrogen Vehicles

     Hydrogen cars are starting to catch the eyes of major car companies such as Nissan, Ford, BMW and Mazda. These companies have started to build prototypes of  hydrogen vehicles. Several hydrogen vehicles are already on the roads such as the Daimler-Chrysler Bus, Honda FCX, Toyota Prius and the Mazda Miata (See Fig. 11).

Mazda Miata

     Mazda uses their own Rotary engine and adapts it to hydrogen. The intake system of the hydrogen Miata combines a pre-mix air/fuel system for light load driving. There is also a direct injection system with a special hydrogen port that opens when the air intake port closes. The direct injection system is effective in increasing speed.  The metal hydride tank has a hydrogen fuel line and two lines run cooling water through the tank. During refuelling the metal Hydride in the tank warms as it absorbs hydrogen. The water cools it to allow more hydrogen to be absorbed. While the engine is running, the warm engine coolant water is circulated through the tank to warm the metal hydride, which contains the hydrogen. The warming allows the hydrogen to be released from the metal hydride tank. The hydrogen Mazda Maita weighs 250kg more than the standard Miata due to the weight of the fuel tanks.

     There are a few disadvantages in the Mazda Miata design. One disadvantage is when the fuel pressure gets low, the power drops noticeably and the car's speed slows. Therefore, gearing down is a lot harder. Another problem is that refuelling takes 15min from start to finish. One tank only has a range of 248 miles (400 km). The small tank allows the car design to look the same as a conventional Miata.

Ford Model U

     The Ford Motor Company is not being left behind. Their Model U runs on a 2.3 litre internal combustion engine that is fuelled by hydrogen (See Fig. 12). The combination motor is called a modular hybrid transmission system. The harmful emissions are almost zero and it is 25% more fuel efficient than gasoline engines. The air/fuel mixtures of 86:1 during a highway cruise compares to a 14:7:1 of a normal gasoline car. The engine runs at an energy efficiency of 38% compared to 13% for gasoline engines. The electric motor simultaneously fills the role of the fly wheel, starter, alternator and hybrid traction motor. The car can operate on either hydrogen or electricity. The engine turns off at traffic lights and when you touch the gas pedal the engine restarts. Fuel is saved by only being used when needed. Model U’s carry 7 kg of hydrogen on board.

DaimlerChrysler Bus

Buses are the logical place to start with the change to hydrogen vehicles. Buses are already one of the most efficient methods of urban transportation.  Hydrogen buses will make this type of transportation even more environmentally friendly. Also cities will be able to save on fuel allowing them to account for the higher price tag for the cost of the bus. Several places, including parts of California and Europe, are already using these vehicles (See Fig. 13).