Hydrogen economy (Encyclopedia of Environmental Issues, Revised Edition)
The term “hydrogen economy” first appeared during the energy crisis of the 1970’s. The use of hydrogen as a fuel source was proposed as a way to avoid energy crises resulting from the use of nonrenewable fuels. Interest in a hydrogen economy was resurrected in the 1990’s when increasing numbers of people started to understand that the burning of fossil fuels generates carbon dioxide (CO2), a greenhouse gas that has been linked to global warming; the use of molecular hydrogen (H2), or hydrogen gas, as a fuel does not generate CO2. It is interesting to note that nineteenth century science-fiction author Jules Verne imagined the use of hydrogen as a fuel in 1874, in his novel Le Secret de l’île (The Mysterious Island, 1875).
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Hydrogen as a Fuel (Encyclopedia of Environmental Issues, Revised Edition)
H2 is an ideal fuel for transportation, because the energy content of hydrogen is three times greater than that of gasoline and four times higher than that of ethanol. By the early years of the twenty-first century, growing numbers of automobile manufacturers around the world had begun making prototypes of hydrogen-powered vehicles.
H2 can be used as a fuel in vehicles with internal combustion engines, but a more environmentally friendly way to use hydrogen power in motor vehicles is to replace their internal combustion engines with fuel cells that generate no greenhouse gases. Hydrogen is used in such fuel cells to produce electricity that powers the vehicle. Fuel cells are like batteries—that is, they generate electricity through a chemical reaction, in this case, between H2 and oxygen (O2). The resulting emissions consist of just water and heat with no CO2 or other greenhouse gases. In addition, a fuel cell is two and one-half to three times more efficient than an internal combustion engine in the conversion of H2 energy.
One problem with creating a hydrogen economy is that H2 is not abundant on the earth. Although many microorganisms produce H2 during fermentation, it is used almost immediately by other microbes because it is an excellent source of energy. If H2 is to be used as a primary fuel source, it must be generated from other energy sources. Hydrogen as a chemical element (H) is the most plentiful...
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Obstacles (Encyclopedia of Environmental Issues, Revised Edition)
Several technological and economic problems have so far hindered progress toward a hydrogen economy. These problems include difficulties in storing and distributing H2, as well as in convincing the general public of its safety. Hydrogen has gained an unwarranted reputation as a highly dangerous substance. Like other fuels, H2 may produce explosions, but it has been used for years in industry and has earned an excellent safety record when handled properly.
Hydrogen has much lower energy density by volume than other fuels, and as a gas it requires three thousand times more space for storage than gasoline. Hydrogen storage, especially in motor vehicles, represents a challenge for scientists and engineers. For storage, H2 is generally pressurized in cylinders or liquefied in cryostatic containers at −253 degrees Celsius (−423 degrees Fahrenheit). Both processes require a significant expenditure of energy and generate large quantities of waste CO2. In most hydrogen-powered vehicles, H2 is stored as compressed gas.
Another problem hindering the growth of a hydrogen economy has been the scarcity of refueling stations for hydrogen-powered cars. Gasoline stations cannot be converted into hydrogen stations, because H2 stations require different pump technologies. Considerable monetary investment will be required to build and operate sufficient H2 fueling stations to increase the attractiveness of owning hydrogen-powered...
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Further Reading (Encyclopedia of Environmental Issues, Revised Edition)
Ball, Michael, ed. The Hydrogen Economy. Opportunities and Challenges. New York: Cambridge University Press, 2009.
Cammack, Richard, Michel Frey, and Robert L. Robson. Hydrogen as Fuel: Learning from Nature. London: Taylor & Francis, 2001.
Ogden, Joan. “High Hopes for Hydrogen.” Scientific American, September, 2006, 94-99.
Rifkin, Jeremy. The Hydrogen Economy: The Creation of the Worldwide Energy Web and the Redistribution of Power on Earth. New York: J. P. Tarcher/Putnam, 2002.
Service, Robert F. “The Hydrogen Backlash.” Science 305 (August 13, 2004): 958-961.
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