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Ultra Capacitor Fuel Cell Technology

Ultra Capacitor Fuel Cell Technology

Tired of paying hundreds of dollars for gasoline?  Well good news!  We are one more step closer to powering our cars with renewable fuels such as hydrogen or methanol.  Solar Station Inc. based in Palo Alto, California, has engineered a new kind of fuel unlike any of the ones developed up to date.  The new fuel cell, dubbed Ultra Capacitor Fuel Cell, or UCFC, belongs to the category of membraneless fuel cells, but by means of a much more innovative way.

Fuel cells are great power backup units. They are cleaner, more efficient, and noisless compared to diesel generators.  However, the true significance of fuel cell technology lies in its use in transportation, because if transportation could be converted to renewable resources also, the dependency on fossil fuels will be totally eliminated.  Today 71% of petroleum and 27% of all resources are used in transportation.  This is a major handicap in the fight against global warming and pollution.  If fuel cells could replace most ICEs, this would be a huge step towards an eco-friendly economy.

The major hurdles for fuel cells to be used in vehicles are these (among others): 1. Price 2. Performance 3. Space.  Let us examine these: Price; the fuel cells cost as much as $8/watt.  That means for a car it could cost 8000 dollars or more. Performance; current fuel cells are not very stable.  They do not respond well to changing power demands.  Worst of all, they detoriate faster than the tennis balls served by Roddick.  The major reason for detoriation is the membrane and its degradation with heat and pressure, and necessitates the replacement of the fuel cells stack every 5 years or so.  Space; fuel cells take up too much space for the cars.  The 1kw fuel cell stack would be bigger than the engine.  Plus you need a fuel tank, which could be big if the fuel is hydrogen.

To overcome these obstacles, one way to tackle the problem is excluding the membrane.  This basically frees the fuel cell off problems such as membrane dehydration or degradation.  There were couple of attempts, such as the capillary flow fuel cell or using selective catalysts, but these had their own challenges.  Folks at Solar Station Inc. thought about the situation and came up with these questions: Why do we need to transport the ions if this is so difficult to do?  What if the charge balance could be established without a membrane?  They seem to have found the answers.

 The conceptual UCFC works this way: The two half cells are divided by an ultracapacitor in the center.  The two surfaces of the ultracapacitor are accessible from inside the half cells, with a thin insulative layer in between preventing the ions to react with the capacitor chemicals.  The cathode side of the fuel cell is fed with peroxide.  It is worthwile to note that since the operations are carried at low temperatures, the catalyst layers are all platinum; not cheap but very efficient.  In the meantime, the cathode is injected with methanol.  The methol reacts at the catalyst to produce carbon dioxide and protons.  The protons will most likely react with the KOH (potassium hydroxide) in the medium.  The result will be an excess of K+ ions.  The electron released during the oxidation of methanol travels from the outer circuit and reaches the anode.  At the anode, the peroxide receives the electron, with the help of the platinum, and reacts with water to form OH- ions. 

After a very short time, the charge in two half cells will be imbalanced.  What is then done is apply some voltage to the capacitor.  This charges the two plates of the capacitor, positive on anode and negative on cathode.  The K+ and OH- ions are attracted to the charges on the capacitor.  They line up at the surface, or near the surface.  Once the capacitor reaches its capacity, the reaction is complete.  Now it is time to reverse the reaction.

At stage two, the cathode and anode switch sides.  Actually, this is simply done by changing the fuel injection.  Now, methanol is injected into the former anode and peroxide is injected into the former cathode.  The reactions take place and H+ ions are generated at methanol side and hydroxyl ions at peroxide side.  In the meantime, the capacitor is reversed.  It actually starts to give out power,which is also added to the power overall output.  The new H+ ions react with the OH- ions from previous reaction, and the new OH- ions react with the K+ ions from previous reaction.  The cycle is completed.

The advantages of this setup are: No membrane dehydration, reduced concentration overpotential, more efficient use of fuels, and better temperature management.  Concentration overpotential can be less because the medium in the half cells can be vigorously mixed.  This will allow the ions to be promptly removed from the catalyst surface and reactants to fill in the opening.  The syncronized injection of the fuels, however, is an important factor that needs to be carefully controlled. Nevertheless, this is an out-of-the-box fuel cell design.

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