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Hydrogen Fuel Cells
Hydrogen in fuel cells technology could deliver the sustainable energy for our needs in the future. A hydrogen fuel cell harnesses the chemical energy of hydrogen and oxygen to generate electricity without combustion or pollution. Contrary to what most people think fuel cell technology isn't new; it has been used for many years to provide power for space shuttles' electrical systems.
Hydrogen Fuel cells take diatomic hydrogen, which is hydrogen in free form (H2) and oxygen (typically from the air) and produce electricity in the process. The by-products are heat and water, which means that they generate electricity without pollution.
This happens because when the hydrogen and oxygen are in their element form they are at a high energy state. Then when they combine together as water they change to a low energy state. As energy is never created or destroyed, only transformed, the energy released to form water is the electrical energy generated by the fuel cell.
There are different types of fuel cells, but the basic components are the same for all kinds: electrolyte, catalyst, anode and cathode. For example, these components for a PEM (Proton Exchange Membrane) fuel cell are:
- Electrolyte – a solid membrane that conducts positive ions but blocks electrons
- Catalyst – a material with a lot of surface area that is coated with a chemical, such as platinum, that encourages hydrogen molecules to break apart.
- Anode – carries electrons stripped from hydrogen molecules off through an external electrical circuit where they are put to work.
- Cathode – this carries the electrons back into the fuel cell where they recombine with hydrogen and oxygen to produce water molecules.
Once the fuel cell or the stack of fuel cells is set up, the major issue is how to obtain hydrogen. Hydrogen is not readily available; you cannot mine it, pump it from a well, or pick it from a tree but we need to get hydrogen from somewhere.
Hydrogen can be produced in a number of different ways from many different energy sources. One of the most prominent ways to obtain it is through a process called electrolysis. Wherever there is water and electricity, electrolysis can be used to make hydrogen. The process works by passing DC electric current trough water, electricity causes the H2O molecules to split apart into hydrogen and oxygen. The oxygen is drawn to the anode and the hydrogen is drawn to the cathode charge where it is collected for use when and where needed.
So, in the same way we can make water with hydrogen and oxygen, we can also make hydrogen and oxygen from water. However, we also need to “input" energy to disassociate hydrogen from oxygen in the process. It takes energy to make energy, and this goes for all forms of energy, renewable or nonrenewable. If the necessary energy to make hydrogen comes from a renewable source as solar, wind, hydro, or tidal power we can produce “green hydrogen" and will have a complete sustainable energy technology.
Future energy sources will have to be cleaner, renewable and more efficient than current sources. Hydrogen Fuel cells present the possibility of utilizing both heat and electricity from them using a renewable fuel in an efficient way, which will represent a significant reduction of atmospheric emissions. There are still several challenges, but definitely an environmentally-friendly source of power is on its way.
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Satyanarayana, A., December 2008, “Know Your Alternative Fuels Part 2 of 5: Hydrogen", http://www.brighthub.com/engineering/mechanical/articles/4938.aspx
Holland, G.B. and Provenzano, J.J., 2007, “The Hydrogen Age", First Edition, Gibbs Smith, Co.