Hydrogen economy
The hydrogen economy is an emerging concept where energy needs are primarily met using molecular hydrogen (H₂) as a fuel source, offering a cleaner alternative to fossil fuels. This shift could significantly reduce pollution, as burning hydrogen only produces water vapor instead of greenhouse gases like carbon dioxide (CO₂), which are linked to climate change. The idea gained traction during the 1970s energy crisis and saw renewed interest in the 1990s due to growing environmental concerns. Hydrogen is particularly appealing for transportation, boasting energy content three times that of gasoline and four times that of ethanol.
To harness hydrogen as a fuel, it must be produced sustainably, primarily through water electrolysis or biological methods involving microorganisms. However, obstacles remain, including the challenges of efficient hydrogen storage, public perceptions of safety, and the high costs associated with building a network of refueling stations. While hydrogen presents a promising pathway toward achieving net-zero carbon emissions, its development requires overcoming significant technological and economic hurdles to become a viable component of our energy infrastructure.
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Hydrogen economy
DEFINITION: An economy in which energy needs are met by molecular hydrogen produced predominantly from water
Conversion to a hydrogen economy would drastically reduce pollution because using molecular hydrogen as an energy source generates only water, in contrast to the greenhouse gases produced by the burning of fossil fuels. In addition, the hydrogen gas used for fuel can be made from renewable resources.
The term “hydrogen economy” first appeared during the energy crisis of the 1970s. 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 1990s when increasing numbers of people started to understand that the burning of fossil fuels generates carbon dioxide (CO2), a 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).
Hydrogen as a Fuel
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 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 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 element in the universe, and it is a part of the most abundant on the earth—water. Therefore, to make H2 widely available for fuel, cost-effective and environmentally friendly ways must be found to generate H2 from water or other chemical compounds. H2 has been obtained mainly from natural gas (methane and propane) through steam reforming. Although this approach is practically attractive, it is clearly not sustainable.
Molecular hydrogen can also be produced by electrolysis. In this case, electrical energy is used to split water into H2 and O2. However, the process is not efficient, and it requires significant expenditure of energy and purified water. One promising sustainable method of H2 production is a biological approach. A great number of microorganisms produce H2 from inorganic materials (for example, water) or from materials (for example, sugar) in reactions catalyzed by enzymes—hydrogenase, nitrogenase, or both. Hydrogen produced by microorganisms is called biohydrogen. For industrial applications, the most attractive method of H2 production is one using photosynthetic microbes. These microorganisms, such as microscopic algae, cyanobacteria, and photosynthetic bacteria, use sunlight as an energy source and water to generate hydrogen. Hydrogen production based on photosynthetic microbes holds the promise of generating a renewable hydrogen fuel, as large amounts of solar light and water are available.
As of 2024, scientists were considering the possibility of using clean hydrogen as a potential net-zero option to create electricity. They believe this will help the United States transition to net zero by 2050. However, some challenges exist, such as hydrogen's limited efficiency and high cost. These scientists were attempting to determine how much hydrogen should be used and at which location.
Obstacles
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 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 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 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 vehicles.
Bibliography
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.
Wolfram, Paul. "The Hydrogen Economy Can Reduce the Costs of Climate Change Mitigation by Up to 22 Percent." One Earth, 17 May 2024, www.cell.com/one-earth/fulltext/S2590-3322(24)00202-1?‗returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2590332224002021%3Fshowall%3Dtrue. Accessed 17 July 2024.