Understanding How a Hydrogen Fuel Cell Works

Think of hydrogen fuel cells like a battery that never runs low on power. Where a battery has a limited charge and must be recharged on a regular basis (one of the drawbacks to current electric vehicles), a hydrogen fuel cell always has electricity, as long as it has a supply of hydrogen and oxygen. This means that they make ideal solutions for powering electric motors. 
 
The type of hydrogen fuel cell that will be used in automobiles is called a polymer exchange membrane fuel cell, or PEMFC. These are able to provide a low operating temperature ideal for use in automotive and other transportation applications. They are also highly efficient and supply a large amount of electricity. 
 
The basic way in which a hydrogen fuel cell works is quite simple. Hydrogen is provided through either compressed or chilled liquid hydrogen. Hydrogen is forced through the polymer membrane by pressure, where it reacts with platinum in the catalyst, splitting hydrogen atoms into ions and electrons. The electrons are harnessed for use as electricity, where they power an electric motor. The ions derived from the hydrogen are combined with oxygen to form water, which is then sent through the exhaust system. Pure hydrogen fuel cells produce only water as exhaust. Other types of fuel cells produce trace gases, the types of which depend on the fuel used to derive hydrogen. For instance, alcohol and water can both be used for this purpose.
 
There are several problems currently facing fuel cells. The way in which a hydrogen fuel cell works requires liquid hydrogen. Because hydrogen is a gas when derived from water or from natural gas, this means that the gas must be compressed or chilled and compressed. If chilled, the gas must be brought down to below -430 degrees Fahrenheit. This requires that the automobile have a high-pressure storage tank with the appropriate insulation to keep the gas from warming once more. Warming the liquid hydrogen or decreasing the pressure results in a change back to gaseous form.

Another problem that hydrogen fuel cells face is the issue of power generation. A single fuel cell only produces about .7 volts, which is insufficient to power a vehicle. To combat this problem, automakers resort to fuel cell stacks, which are quite similar to the current hybrid vehicle battery arrays in use today. The fuel cell stack provides sufficient electricity to power the vehicle's electric motor, converting the electricity derived from the fuel cell into mechanical energy and eliminating the need for an internal combustion engine.