Hydrogen

Published September 27, 2006

Politicians and automakers love to talk about pollution-free cars powered by hydrogen. The media eats it up, and the debate for and against hydrogen resurfaces again.

• Proponents claim hydrogen will someday free us from our dependence on oil and eliminate pollution from our cars.
  
• Cynics say hydrogen may never be practical as a motor fuel, and they accuse energy companies and automakers of focusing on hydrogen at the expense of more realistic, near-term solutions.
  

At this point, it’s hard to tell which side is right: A lot depends on how quickly technologies can be developed to generate, transport, and utilize hydrogen fuel that is both economical and environmentally sound.

> Assuming you could produce a supply of hydrogen fuel, are there other challenges to putting hydrogen fuel cell vehicles on the road?

So Close and Yet So Far

One of the big advantages of hydrogen is that it’s abundant: there is hydrogen in fossil fuels, alcohols—even in water. This means that hydrogen fuel can be made from a large number of feedstocks. Today, common ways of producing hydrogen include reforming natural gas (in which four hydrogen atoms are separated from a carbon atom) and electrolyzing water (which decouples two hydrogen atoms from an oxygen atom). The fact that hydrogen can be produced in so many ways means that, unlike petroleum, supplies of hydrogen can’t run out, nor will they be concentrated in one area of the world. Hydrogen is everywhere—it just needs to be captured and used.

Capturing hydrogen, however, is not as easy as it sounds. There isn’t much pure hydrogen around because hydrogen tends to bond easily with other elements. To make hydrogen fuel, hydrogen must be separated from whatever it’s attached to, a process that requires energy. For this reason, hydrogen is often called an “energy carrier” rather than an energy source.

To get hydrogen, you first have to put energy in. For example, making a kilogram of hydrogen from water through electrolysis requires 45-70 kWh of electricity, depending on the technology. This amount of electricity could power the average American home for roughly two to three days.

Consider the Source

Depending on where that electricity comes from, hydrogen can be clean and efficient or anything but. In many areas of the country, electricity comes primarily from coal-fired power plants. Burning coal to generate electricity—and then using that electricity to make hydrogen—is not such a good idea. The hydrogen at the end of the process may be used in vehicles that are “clean,” but the coal that was used to make the electricity emitted significant amounts of pollution and greenhouse gases. In addition, this process is not very efficient since losses occur each time one form of energy is converted to another.

However, if the electricity used to make hydrogen comes from renewable sources, such as hydroelectric, geothermal, solar, or wind, then hydrogen can be extremely clean. Hydrogen from renewables also releases no climate change emissions, and provides users with complete independence from fossil fuels. This is what appeals to hydrogen’s supporters: the prospect of a fuel that is abundant, non-polluting, and safe for the world’s climate.