B+-+Fuel+Cells

What types of chemical reactions occur in different types of fuel cells? Charlie Choi **Intro to Fuel Cells** media type="youtube" key="esuAlB4NVi0?fs=1" height="385" width="480" align="left"
 * Fuel cells are electrochemical cells that are composed of electrodes (the anode, and cathode), and an electrolyte in the middle.
 * Fuel cells convert chemical energy to electrical energy by combining hydrogen from f﻿uel with oxygen from the air.
 * The difference between a fuel cell and a battery is that a fuel cell can be used (in theory) as long as the fuel is replenished, whereas a battery will have stored energy inside. In other words, a fuel cell is an open system, and a battery is a closed system.
 * Here is a Youtube clip explaining the basics of a fuel cell:**

2) low temperature operation, so less thermal wear to components 3) quick starts, with full power available in minutes or less
 * Reactions in Fuel Cells**
 * At the anode, a catalyst oxidizes the fuel into a positive ion and negatively charged electrons.
 * At the electrolyte, positive ions are allowed to pass through to the cathode, but the electrons are not. Basically, the electrolyte is a subtance specifically made so that ions can pass through but electrons cannot.
 * The electrons have to travel through a wire to get to the cathode. Usually there is a load connected to the wire so that the energy is actually used.
 * At the cathode, the ions and the electrons are united again, and then react with another chemical to produce H 2 O or CO 2﻿.
 * Types of Fuel Cells**
 * There are many different types of fuel cells
 * The type of fuel cell is usually determined by the electrolyte. Four popular ones are: PEM, PAFC, DMFC, and AFC fuel cells.
 * PEM Fuel Cells**
 * **PEM** (proton exchange membrane) fuel cells have a solid polymer membrane as the electrolyte.
 * Advantages of PEM cells: 1) low weight and volume with good power-to-weight ratio
 * The disadvantages of PEM fuel cells are that they require platinum as the catalyst which is very expensive and also poisoned easily by CO. Also hydrogen storage is a problem. (PEM require hydrogen as the fuel.)
 * These fuel cells are used in vehicles such as scooters and forklifts.


 * PAFC**
 * **PAFCs** (Phosphoric acid fuel cell) use hydrocarbon sources such as natural gas, propane or waste methane. They are the most used fuel cells in the world for commercial purposes. They are used all over the world to in hospitals, nursing homes, hotels, office buildings, schools, utility power plants, airport terminals, landfills and waste water treatment plants.
 * PAFCs can reach an efficiency of 85% with co-generation of electricity and heat.
 * PAFCs use liquid phosphoric acid as the electrolyte, and platinum as the catalyst in the anode.


 * DMFC**
 * **DMFCs** ( Direct methanol fuel cells) use unreformed liquid methanol fuel. They operate at slightly higher temperatures then PEM fuel cells.
 * DMFCs are used in small mobile electronics such as laptops and cell phones.


 * AFC**
 * **AFCs** (alkaline fuel cells) have potassium hydroxide as the electrolyte and can use a variety of non-precious metals as the catalysts in the anode. Operating temperatures range from 23-250°C.
 * AFCs reach a relatively high efficiency of 60-70% and they have a high reaction rate.
 * A disadvantage is that AFCs are very easily poisoned, so they are usually only used in controlled environments like underwater and in space shuttles.
 * They have been used by NASA to produce drinking water and power for astronauts.


 * Bibliography**
 * 1) "Alternative Energy eMagazine - | AltEnergyMag." //Alternative Energy Resources, News, eMagazine & Library | AltEnergyMag//. N.p., n.d. Web. 24 Nov. 2010. .
 * 3) "Government of Canada: Alternative Fuel Information Portal." //Office of Energy Efficiency | L'Office de l'efficacité énergétique//. N.p., n.d. Web. 24 Nov. 2010. .
 * 4) Ramani, Vijay. "Fuel Cells." //Electrochem//. The Electrochemical Society Interface, n.d. Web. 22 Nov. 2010. .