Hydrogen Fuel Cells (HFC)

The Hydrogen fuel Cell is the most promising of all fuel cells in that it can be run completely independent of any hydrocarbon fuel. Of course, this independence comes at a price as this article will show.

Function and Reactions of HFCs

HFCs are the most basic form of PEMFC. In fact, they are often called this because they are the basis on which other PEMFCs, like direct methanol fuel cells, are built. Hydrogen enters the anode where it is broken down, with the help of a platinum catalyst, to produce protons and electrons. It is as simple as that.

Benefits of HFCs

HFCs have several important benefits that have resulted in the government of the United States committing well over $1 billion dollars to their research and development. In the European Union, nearly €1 billion has also been invested.

The biggest benefit of hydrogen fuel cells is that they produce only water as a byproduct because there is no carbon involved in the cell at all. Hydrogen combines with oxygen at the anode to produce water. Since there is no carbon involved in the process, carbon dioxide and carbon monoxide are not produced. This means no greenhouse gas emissions and no potential for poisoning the platinum catalyst.

Because these are the simplest form of PEMFC, they have the fewest moving parts and are the most reliable. Besides keeping HFCs simple and reliable, the reduced number of moving parts also means there is less noising and vibration produced.

Drawbacks of HFCs

Despite their advantages, hydrogen fuel cells have one major drawback and that is the hydrogen they run on. There are several problems associated with hydrogen as a fuel, the first of which is production. Hydrogen can be produced from water via electrolysis, which is the addition of electricity. This produces hydrogen and oxygen, which is quite good. The problem arises from the fact that it takes a great deal of electricity to do this, most of which is generated by burning coal and other fossil fuels. The end result is actually the same amount or even more carbon dioxide emissions than if hydrocarbons were simply burned.

It is possible to produce hydrogen from other fuels through reform processes. This is, in fact, how other PEMFCs that run on things like ethanol and methanol produce hydrogen. The problem here is twofold. First, there is still carbon dioxide being produced. Second, there is the potential for carbon monoxide contamination, which would damage the platinum catalyst.

Another problem related to hydrogen is the lack of infrastructure for delivering it. The U.S. government estimates that an infrastructure large enough to support 10 million cars would cost roughly $8 billion to build. With nearly 300 million cars in the United States, this translates into an infrastructure cost of roughly $160 billion dollars. While this is a large sum, it would probably be manageable if not for the next problem that hydrogen presents.

At standard temperatures and pressures, hydrogen is a highly explosive gas. It is possible to liquefy hydrogen, but this requires either extremely cold temperatures or high pressures. Only high pressure storage systems are energy efficient, but they suffer from the problem of capacity. If a storage system for hydrogen is produced that is roughly the size a standard gas tank, most vehicles would be able to travel less than 200 miles between refueling.

There is some research into materials that can actually absorb hydrogen when it is at high concentration and then release it as the concentration drops. These would solve the storage problems both in terms of danger and capacity. These systems are currently experimental and very expensive.