Sunday, September 5, 2010

Fuel Cells

How Do Solid Oxide Fuel Cells Work?

Fuel cells function like everyday batteries through electrochemical reactions; however, they do not run down or need to be recharged.  The fuel, ideally pure hydrogen gas, enters the anode compartment where a catalyst encourages the electrons to break away from the hydrogen.  The electrons flow away forming an electric current that flows through the load to the cathode, where oxygen from the air "gobbles up" the free electrons.  The oxygen ions then pass through the electrolyte and form water molecules with the hydrogen protons.  The products of this reaction are water, excess oxygen, and waste heat if the fuel used is pure hydrogen; otherwise, carbon dioxide will also be produced.                

Reaction Equation:  H2 (g) + 1/2O2 (g) → H2O (g)

Fuel For Fuel Cells

Hydrogen gas, water, gasoline, methane, ethanol, natural gas, diesel fuel, and other hydrocarbons can be used as fuel for fuel cells.  Since the reaction requires only hydrogen atoms, a fuel reformer must be added to fuels that are not pure hydrogen.  There are three types of fuel reformers.  The most flexible for heat management are autothermal reformers, which mix steam and oxygen with the fuel to produce hydrogen.  Steam reformers combine the fuel with steam and heat to yield hydrogen.  The third fuel reformer is a two step process called partial oxidation reforming.  In this procedure, added oxygen reacts with the fuel to give hydrogen and carbon monoxide.  The carbon monoxide is then combined with steam to produce more hydrogen.  Each fuel reformer causes individual differences in the chemical nature of the fuel. 

Fuel Cell Applications

Because of the constant need for energy in almost every aspect of today's life, new, more efficient energy sources are in demand.  Fuel cells can be applied to just about every process that calls for energy.  Transportation, portable power, residential, stationary (power plants, hospitals, public facilities, etc...), and landfill/wastewater treatment  are many of the categories in which fuels cells can replace conventional methods.  Fuel cells have flexible applications that should be utilized.


• A fuel cell is leagues and leagues less complicated than a conventional gas or diesel engine.

• It Is not subject to high temperatures, corrosion or any of the structural weaknesses found in other engines.

• It will, in theory, continue to operate indefinitely, without complication, as long as it has a fuel source.

• it runs quietly, and its sole tailpipe emission is water vapor.

• Conceptually, replacing the current oil-based infrastructure with hydrogen would cost billions, maybe trillions, of dollars.

• Although abundant in the universe, hydrogen is fairly rare in our atmosphere, meaning that it has to be extracted (for example through electrolysis, as explained above) and currently, the process is cost prohibitive and inefficient.

• Its production at energy plants creates excessive carbon dioxide.

• When it burns, a hydrogen flame is virtually invisible; coupled with the gas’s propensity for escaping, in small amounts, almost any tank, there are concerns about explosions. On the plus side, hydrogen is so light it typically is dispersed in the air very quickly.

• On-board storage is a major issue; a hydrogen tank would currently be too large for a car.

• It is a very flammable gas  which further adds to the on-board storage problems.

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