Fuel+Cells

=What Are Fuel Cells? = A fuel cell is a device that combines a chemical fuel source (hydrogen) with an oxidant (oxygen) to create electricity. A fuel has three basic parts; two electrodes, called an anode and a cathode, and an electrolyte. The electrolyte carries eletrically charged particles from one electrode to the other, and this produces electricity. The only waste a fuel cells produces is water and heat. A fuel cell creates DC power just like a battery. However, unlike a battery which can retain a charge, a fuel cell requires a constant source of fuel to remain running. Each cell produces one volt of DC current. They can be stacked and run in series. 

=Types and Applications =

 Alkaline
Alkaline fuel cells run on compressed hydrogen and oxygen, and use potassium hydroxide as an electrolyte. They run at temperatures between 194-212 degrees Fahrenheit and at an efficiency level of about 60%. The cells can become poisoned by carbon dioxide if the oxygen is not purified. Because pure oxygen is expensive to generate and store, this is not a widely used type of cell. Its main application is in military and space purposes, such as purifying water in Apollo spacecraft

Molten-Carbonate
Molten-carbonate fuel cells use sodium, lithium, and potassium carbonates as electrolytes. They run at very high temperatures, between 1112-1292 degrees Fahrenheit and at an efficiency level of 45-50%. Because of the high run temperature and corrosive electrolytes, these fuel cells do not a a long lifespan. They also have a long start up time. However, the high temperature increases the tolerance to poisoning from carbon dioxide. These cells are well suited for large stationary power generators.

Phosphoric Acid
Phosphoric Acid fuel cells use phosphoric acid as an electrolyte. They run at temperatures between 302-392 degrees Fahrenheit and at an efficiency level of 40%. They are very tolerant to contaminates, so the type of fuel that can be used is broadened.They have a long start up time and low power output. They are best used in small power power generators. They can be used in large vehicle as well, but the long start up time makes this undesirable.

Polymer Electrolyte Membrane
Polymer Electrolyte Membrane fuel cells use a thin, permeable sheet as an electrolyte. They run at low temperatures, between 140-176 degrees Fahrenheit and at an efficiency level of 60%. They have a low temperature and a quick start up time, which makes them ideally suited for transportation. However, they are very susceptible to poisoning and are very expensive to produce due to the need for precious metals such as platinum.

Solid Oxide
Solid Oxide fuel cells use a hard ceramic compound as a electrolyte. They run at very high temperatures, between 1202-1832 degrees Fahrenheit and at an efficiency of 60%. One big advantage to these types of cells is that the waste can be recycled and used as additional energy. Due to the high operation temperature, they are not susceptible to poisoning. However, this high temperature means they corrode quickly and have a long start up time. The solid electrolyte can also crack. This type of cell is best used in large scale power generation applications.

=Commercialization = There are a few problems with fuel cells replacing current technologies, cost and existing infrastructures being the largest hurdles. Fuel cells can be very expensive to manufacture. The types of cells that are susceptible to contamination require platinum in their construction. Platinum is a metal in high demand, and therefore very expensive. As of now, the price per kilowatt produced by a fuel cell is $73. This is in comparison to $35 per kilowatt for existing technologies. In the future, it may be possible to use a different material than platinum, such as gold-palladium. This would reduce the cost of fuel cell production significantly. <span style="font-family: Georgia,serif;">Another problem is storage of hydrogen. Due to the energy produced per volume of hydrogen, it requires a large tank of hydrogen to produce the amount of energy needed to power most devices. In portable applications, it is hard for hydrogen to be stored in a way that makes the device the cell is being used in portable. In transportation, size constraints become an issue. The tank required to run a vehicle the same distance as gasoline would is much too large to fit anywhere on the vehicle. <span style="font-family: Georgia,serif;">Current infrastructures are perhaps the biggest hurdles fuel cells need to overcome, especially in transportation applications. The oil infrastructure has been in place for so long, it would be difficult for a hydrogen infrastructure to become established. This infrastructure would need to include hydrogen generation plants, pipelines, transport, and filling stations. An inexpensive vehicle would be required for this infrastructure to grow. The hope is that the low cost to the consumer would outweigh the convenience of oil, and demand more hydrogen use. The more demand, the more infrastructure development would occur. <span style="font-family: Georgia,serif; line-height: 0px; overflow-x: hidden; overflow-y: hidden;">