Alkaline Fuel Cell(AFC)

http://fuelcells.si.edu/alk/alkmain.htm

First AFC, was a made for a bike by Union Carbide's Karl Kordesch.

NASA building AFC for space.

How does it work? The electrolyte is potassium

hydroxide         electrolyte flows

through the centre of the fuel cell plates with porous membranes between the electrolyte and the hydrogen (anode) and oxygen (cathode) gas supplies.

membranes contain the catalysts (platinum & silver)

Produces Water and some Carbon Dioxide

Works at –40 degrees C for cooling and 70 degrees regularly

http://www.fctec.com/fctec_types_afc.asp

Advantages of AFC

Like PEM works at low temperature and “instant-starting”

Efficiency = 70% (One of the Best)

Companies looking to bring down cost (Astris)

http://www.h2fc.com/technology.htmlhttp://fuelcells.si.edu/alk/alkmain.htm

Uses of AFC

NASA uses them for Space Shuttles

Commercially used in cars Used to generate electricity

http://www.h2fc.com/technology.html

Phosphoric Fuel Cell - Application

golf cart powered by a phosphoric acid fuel cell.

Georgetown University, and the U.S. Department of Energy adapted a 50 kw Fuji Electric PAFC for transit buses (photo at left), and began running these buses in 1994.

New York, the Yonkers Waste Treatment Plant has been powered by a 200 kw ONSI unit since 1997

http://fuelcells.si.edu/phos/pafcmain.htm#apps

Technology

http://voltaicpower.com/FuelCell/pafc.htm

Proton Exchange Membrane

                                                        

 Diagrams and picutres from Humboldt State University

PEM Chemical Reactions

Alkaline Fuel Cell

Molten Carbonate Fuel Cell

How Does It Work Molten Carbonate fuel cells (MCFC) use

high-temperature compounds of salt (like sodium or magnesium) carbonates (chemically, CO3) as the electrolyte. (http://fuelcells.si.edu/basics.htm)

The operation of a MCFC is based on the shuttle action provided by carbonate ions. The carbonate ions also serve as an acidic electrolyte. The CO2 rich gas product gas of the anode is fed to the cathode where CO2 is transformed into carbonate ions during the reduction of oxygen. http://voltaicpower.com/FuelCell/mcfc.htm

Since it operates at high temperatures, multiple fuel types can be used.

Reactions of Molten Carbonate

Advantages of Molten Carbonate

Efficiency ranges from 60 to 80 percent, and operating temperature is about 650 degrees C (1,200 degrees F). Units with output up to 2 megawatts (MW) have been constructed, and designs exist for units up to 100 MW. (http://fuelcells.si.edu/basics.htm)

Molten carbonate fuel cells are not prone to carbon monoxide or carbon dioxide "poisoning"—they can even use carbon oxides as fuel—making them more attractive for fueling with gases made from coal. (http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/types.html#mcfc)

MCFCs don't require an external reformer to convert more energy-dense fuels to hydrogen. Due to the high temperatures at which they operate, these fuels are converted to hydrogen within the fuel cell itself by a process called internal reforming, which also reduces cost. (http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/types.html#mcfc)

Uses of Molten Carbonate Renton, Washington, where a 1-megawatt power plant will be located

at the King County wastewater treatment facility and fueled by wastewater digester gas. Scheduled to begin operations in the fall of 2002, the project is co-funded by a grant from the U.S. Environmental Protection Agency. http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcells_moltencarb.shtml

Los Angeles, California, where the city's Department of Water and Power has ordered three 250-kilowatt plants, the first of which was shipped to the utility's downtown headquarters in July, 2001. http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcells_moltencarb.shtml

Cadiz, Ohio, where Northwest Fuel Development Inc., based on Lake Oswego, Oregon, will operate a 250-kilowatt fuel cell on coal-mine methane gas from the Harrison Mining Corporation and supply electricity back to the mining operation. http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcells_moltencarb.shtml

Solid Oxide Fuel Cells

How Does It Work? First of all, the Solid Oxide Fuel Cell is very

different from the other forms of fuel cells. This fuel cell is composed completely of materials in a solid state, including the electroyte. http://www.fe.doe.gov/programs/powersystems/fuelcells/fuelcells_solidoxide.shtml

They operate at very high tempatures, ranging from 600 to 1000 degrees Celsius

Initially, a gas consisting of hydrogen gas and carbon monoxide is required for this fuel cell.

The anodes are porus allowing for the hydrogen and oxygen molecules (after reacting with the electrolyte) to permeate through to the other side

The hydrogen molecules permeate through the electrode where it will react and form water

The electrons resulting from this reaction will consequently pass through an external electrical load, creating an electrical flow

The excess oxygen will then react with the used electrons forming oxygen gas and giving off as a waste product

Advantages of Solid Oxide Normally, efficiency of this fuel cell is

around 60% However, if the waste heat is utililized in

such a manner is utilized in such a manner that would incorporate it back into the fuel cell stack, effciency can reach anywhere up to 85%

This occurs when the Solid Oxide Fuel Cell is utilized in a tubular form – outputting 100kw of electricity.

Uses of Solid Oxide Fuel Cells

The high-temperature operation of a solid oxide fuel cell and its capability to operate at elevated pressures makes it an attractive candidate for linking with a gas turbine in a "hybrid" configuration. The hot, high pressure exhaust of the fuel cell can be used to spin a gas turbine, generating a second source of electricity.

The world's first solid oxide fuel cell/gas turbine hybrid system is at Southern California Edison for operation at the National Fuel Cell Research Center in Irvine, California. The hybrid system includes a pressurized solid oxide fuel cell module integrated with a microturbine/generator supplied by Ingersoll-Rand Energy Systems (formerly Northern Research and Engineering Corp.). The system has a total output of 220 kW, with 200 kW from the fuel cell and 20 from the microturbine generator. This proof of concept demonstration is expected to demonstrate an electrical efficiency of around 55%. Eventually, such hybrids should be capable of electrical efficiencies of 60-70%.

http://fossil.energy.gov/programs/powersystems/fuelcells/fuelcells_solidoxide.shtml