A Fuel Cell is a device designed to convert the energy of a chemical reaction directly into electrical energy.
This electrochemical reaction occurs differently than other electrochemical power sources (EPS) like galvanic cells, primary and secondary batteries.
* With a fuel cell there is a constant supply of reactants that can be added to the device and a way to eliminate the products from the reaction.
*It does not depend on only the metals and oxides built into the unit.
* Also a fuel cell EPS can be operated for an extended time.
Fuel cells are very efficient, in contrast to heat engines, (piston, rotary etc) which convert the heat to mechanical energy and then maybe on to electrical energy. The second law of thermodynamics in the Carnot cycle of a heat engine states that a large part of the heat energy is rejected or wasted. 25% is the potential efficiency of the average automotive engine. The hotter the engine the more efficient. The problem is for heat engines to reach even a potential 60% efficiency they must operate at 600° Celsius or 1100° Fahrenheit. On the other hand a hydrogen oxygen fuel cell's potential efficiency is 40% to 83% even at room temperature.
Several inventors contributed to the beginnings of fuel cells development. Two inventors in Italy, first Luigi Galvani, in 1791 created experiments showing the the discharge from a Leyden jar on a frog nerve. Second, Alessandro Volta in 1800 produced "inexhaustible electric charge" with the first example of a EPS known now as the Volta pile, the first battery.
In the 1830's using 2 platinum electrodes in water William Robert Grove used electrolysis to produce hydrogen and oxygen from water. In 1839 he reversed the process to combine the two elements and produce an electric current, the first fuel cell. February 1830 Philosophical Magazine published his gas voltaic battery findings.
In 1894 German physical chemist Wilhelm Ostwald proposed oxidizing standard fuels with oxygen from air using a machine utilizing direct electrochemical process he called the "cold combustion " of fuels. This was published in the Zeitschrift Fur Elektrochemie 1894.
Russian scientist Oganes Davtyan made a fuel cell which oxidized CO with air oxygen at 700 degrees celsius and could operate for days. He also wrote on lower temperature hydrogen oxygen fuel cells.
His work was published in 1947 "The Problem of Direct Conversion of the Chemical Energy of Fuels into Electrical Energy".
The big breakthrough came in 1959 when Francis Thomas Bacon patented his Bacon Cell. In 1960 he demonstrated his cell producing 5 to 6 kilowatts of energy. Bacon's 28 years of experiments produced a cell using alkaline electrolyte potassium hydroxide (Alkali Fuel Cell), with electrodes coated with a gas impermeable barrier with fine pores. NASA used his fuel cells for the Apollo program and the Space Shuttle fleet.
There were other important developments during this time.
These fuel cells ran on medium temperature 180° C to 200° C. Positively charged hydrogen ions migrate through the 85 to 95% phosphoric acid electrolyte from the anode to the cathode. Pratt & Whitney and the American Gas Association, (TARGET) research led to fuel cell power plants from about 15 kw in 1969 to nearly 5 mw in 1983. In 1994 H-Power, Georgetown University, and the U.S. Department of Energy adapted a 50 kw Fuji Electric PAFC for transit buses. The higher temperature PAFC's had the advantage of using less pure hydrogen.
In 1962 the Allis Chalmers agriculture manufacturer built a tractor which pulled a 3000 pound load equipped with a immobilized alkaline electrolyte hydrogen/oxygen, 15 kW fuel cell .
Austrian born Karl Kordesch working with Union Carbide developed multilayer carbon electrodes with platinum on the hydrogen side and cobalt oxide on the oxygen side. He drove a motorcycle and later a electric car on city roads in Cleveland and Parma Ohio in 1963 powered by these hydrogen fuel cells.
The next big development was the proton-exchange membrane fuel cells PEMFC. In late 1950's Thomas Grubb and Leonard Niedrach at General Electric developed these solid ion-exchange hydrogen fuel cells which were used by NASA in the Gemini spacecraft. Later NASA went with the Bacon Cells because they were considered more efficient at that time and the membrane models "PB2" and "P3" cells encountered some technical difficulties.
In a PEMFC, a platinum catalyst is used on both sides of the membrane. Hydrogen atoms are stripped of their electrons, or "ionized," at the anode, and the positively charged protons diffuse through one side of the porous membrane and migrate toward the cathode. The electrons pass from the anode to the cathode externally providing electric power. At the cathode, the electrons, hydrogen protons and oxygen from the air combine to form water. For this fuel cell to work, the proton exchange membrane electrolyte must allow hydrogen protons to pass through but prohibit the passage of electrons and heavier gases.
These are high temperature fuel cells running 800° to 1000° C and use a hard ceramic electrolyte instead of liquids. Zirconium oxide and calcium oxide are used in some models. Oganes Davtyan of the Russian Academy of Sciences built one in the 1930's.
In 2010 [[http://www.machine-history.com/Bloom%20Energy%20Solid%20Oxide%20Fuel%20Cell|Bloomenergy]], FuelCell Energy, Panasonic and [[http://www.clearedgepower.com/|ClearEdge Power]] produced SOFC units from 50kilowatts to 300 kilowatts to 2.8 megawatts mostly running on natural gas.
These cells work at a temperature of 650° C using an electrolyte of carbonates of sodium, potassium and lithium. Hydrogen, hydrocarbons and carbon monoxide can be used as the reactant (fuel). Because of the high heat MCFCs convert the fuel to hydrogen through 'internal reforming' within the fuel cell. The earliest MCFCs devices were made by Emil Baur before 1920. Others like Broers, Ketalaar and Davtyan experimented with them. In the 1960's several companies in the US, Japan and Europe developed large MCFC's. There was a large 2MW cell in Santa Clara, California in the 1990's. They are now being developed for natural gas and coal power plants for electrical, industrial and military applications.
A version of PEMFCs, DMFCs are a promising development in the fuel cell world. Instead of outside conversion of methanol to hydrogen these units internally oxidize the methanol. There are so far shortcomings such as lower efficiency, needs for better membranes, not converting all the methanol, use of water with methanol etc. [[http://www.machine-history.com/node/695|Smart Fuel Cell's M-25]] was purchased by the U.S. Department of Defense for soldiers in the field for extended missions. The M-25 is up to 80 percent lighter than conventional power sources (batteries), has quiet and continuous energy, and offers independent standalone functions such as remote area battery charging and power.