Fuel Cell Technology
With the search for alternative, environmentally friendly sources of energy intensifying in recent years, particularly as it relates to automobiles, scientists and engineers have once again turned to the idea of fuel cells. The advantage of modern fuel cells, which produce electricity through the chemical reaction of hydrogen and oxygen, is that they produce very little pollution. Used in an automobile, the only emission would be harmless water vapor.
Given the recent focus on fuel cells, the assumption might be that they are a recent technology. But, in fact, efforts to develop an efficient fuel cell go back to the nineteenth century. During the 1880s, Edison, who was always on the lookout for new and efficient ways to produce electricity, became one in a long line of inventors to contribute to the development of fuel-cell technology. The story of Edison’s efforts to create an efficient fuel cell is outlined in a number of documents included in The Papers of Thomas A. Edison, Volume 7, Losses and Loyalties (April 1883–December 1884), forthcoming in 2011 from Johns Hopkins University Press.
Unlike primary and secondary batteries, in which the electrodes themselves are consumed in chemical reactions, a fuel cell operates by the replenishment of an oxidizable fuel, such as hydrogen or carbon, to produce free electrons. In the case of carbon, this could be done directly by the reaction of coal with other substances, such as nitrates, or by the creation of an ionized gas.
In 1882, Edison first began working on a system to convert coal directly into electricity. His first patent application for this process Edison and Early Fuel Cell Technology (U.S. Patent 460,122) was filed in May of that year. In this design, Edison sought to generate a current by efficiently oxidizing a carbon electrode by means of an active oxidizing agent, such as a fusible metal, in a heated iron vessel. Over the next two years, Edison focused on what was in essence early fuel-cell technology. His research led him to predict in an 1885 essay reprinted in the Scientific American that a "marvelous revolution" from the cheap electricity produced by the direct conversion of coal into electricity was in the offing.
Edison filed two additional applications for direct conversion employing fuel cells in 1883. The first, in September (U.S. Pat. 435,688), covered a process for producing an ionized gas from either a metal or carbon in reaction with an oxidizable substance. He employed a vacuum chamber to maintain the gas in a rarefied state and to prevent reaction with atmospheric oxygen. The second application, filed in November (U.S. Pat. 490,953), described an improvement over his 1882 design. In this arrangement, he maximized the production of carbonic acid from the oxidation of the carbon and of the fusible iron oxide in order to oxidize the carbon more rapidly.
Edison's most intensive experimental work on fuel cells, however, occurred in the summer of 1884. During a Florida vacation with his wife Mary, Edison described a new approach to direct conversion in the pocket notebook he kept for recording new ideas. He proposed to use finely divided metal and a peroxide (usually manganese) in a solution of sulphuric acid to catalyze the oxidation of the carbon. By the end of that summer, he had "obtained a very strong current" using anthracite coal, and he planned to show his system at the Philadelphia Electrical Exhibition in the fall. This system, however, proved to be too dangerous after "all the windows were blown out of his laboratory." In an interview he gave about this time, Edison was reported to have said
"The great secret of doing away with the intermediary furnaces, boilers, steam engines, and dynamos will be found, probably within ten years. I have been working away at it for some months and have got to the point where an apparently insurmountable obstacle confronts me. Working at the problem now seems to me very much like driving a ship straight for the face of a precipice, and when you come to grief picking yourself up and trying it again to-morrow. There is an opening in the barrier somewhere, and some lucky man will find it. I have got far enough to know that the thing is possible. … I give myself five years to work at it, and shall think myself lucky if I succeed in that time."
Edison’s “marvelous revolution” did not materialize as he had envisioned. While he conducted a few experiments over the next three years, he largely abandoned efforts to use the catalytic oxidation of carbon following the 1884 accident. Instead, he began to develop an alternative approach to direct conversion using the principle that the magnetic capacity of iron diminishes as its temperature increases. Edison's efforts to apply this idea in the design of a "pyromagnetic" generator and motor will be detailed in Volume 8.
Below are links to images of Edison's notes for his fuel cell research that are included in Volume 7.