Hydrogen Fuelled Cars

     In this section we will look at some of the current hydrogen technology and processes.  There are many types of hydrogen fuel that we will explore. The example of the new BMW engine will show how a hydrogen engine is used in an internal combustion vehicle.

Types of Hydrogen Fuel

    There are two different ways that hydrogen can fuel a vehicle. One way is to use hydrogen to fuel an internal combustion engine. The other method is a hydrogen fuel cell electric vehicle.

     Compressed hydrogen in either liquid or gaseous form can power an internal combustion engine. Compressed  hydrogen is efficient but it is bulky and flammable. Liquid hydrogen, which is the most compressed form of hydrogen, is still lightweight although it is less efficient and also flammable. Sometimes hydrogen is delivered to the engine by materials that absorb and then release hydrogen. Some examples are metal hydride and ultra-porous nanotech material. Metal hydride is extremely compact but the down side is it is heavy, runs hot and is flammable. Ultra-porous nanotech material is compact and efficient, the only disadvantage is that it takes a long time to fill up a tank (15-30 min.).

    There are serious storage problems with hydrogen gas. The amount of space that is needed to store hydrogen is one problem. One pound (0.454 kg) of gaseous hydrogen at normal atmospheric pressure takes up 1450 gallons (5500L) of space. In liquid form, one pound (0.454 kg) takes up 5.5 L of space. Most hydrogen cars now carry liquid hydrogen in metal alloys because it takes up less space. To stay liquid, hydrogen needs to be cooled to -423°F and be under intense pressure, up to 20 000 pounds per square inch. In the BMW hydrogen car, the hydrogen is kept in metal containers under a pressure of 5 times normal atmospheric pressure (See Fig. 9).  High pressure makes a potential risk of explosion. However, the risk is no greater than that of a normal gasoline tank. Hydrogen storage is one of the biggest focuses of development and research.

 Hydrogen fuel cells are another way to power a car. In this case hydrogen is used to power an electric vehicle. The chemical reaction of hydrogen and oxygen is used to create electricity. Hydrogen and oxygen from the air pass through an electrically charged permeable membrane. Electricity is produced from the charged ions. The electricity is used to power an electrical motor. The only by-products are heat and water. Ballard is a leading edge fuel cell developer based in Canada.  Their system uses a proton exchange membrane like the system shown on the left.

How A Hydrogen Engine Works In A BMW 750hl

     Electricity generated from solar power is used to split water into hydrogen and oxygen. Oxygen is released into the atmosphere, while hydrogen is liquefied and stored at a very low temperature (-253 °C). 

     During internal combustion, the hydrogen combines with oxygen. The resulting energy powers the vehicle, while the hydrogen is returned to the environment as water. Harmful emissions are virtually eliminated.

     By cooling hydrogen to -253°C, hydrogen is shrunk to a thousandth of its original volume. Seventy layers of aluminium and fiberglass sheets between the exterior and interior vehicle walls ensure that the liquid hydrogen remains at extremely low temperatures.