From the early 19th century on, hydrogen obtained from coal and combined with carbon monoxide in a mixture called "town gas" was widely used to heat and light homes, apartments, businesses and to provide street lighting. However, with the advent of electricity, and the development of naturally occurring oil and natural gas that could be used directly without former processing, the importance of hydrogen as a fuel rapidly declined. Today, the use of hydrogen as a fuel is limited to niche markets, principally as a rocket propellant and to potential development as a transportation fuel. Nevertheless, starting in the 19th century, the unique properties of hydrogen fascinated generations of scientists, futurists and even science fiction writers. As early as 1874, Jules Verne in one of his visionary books, The Mysterious Island, describes in a discussion between his characters what would happen to America's commerce and industry when the world runs out of coal several centuries later. Cyrus Harding, the engineer of the group explains that one will then turn to another fuel, proposing to the astonishment of his companions that water would be the fuel of the future. Or more precisely, "... water decomposed into its primitive elements and decomposed doubtless, by electricity which will then have become a powerful and manageable force".
"Yes my friends, I believe that water will one day be employed as fuel, that hydrogen and oxygen which constitute it, used singly or together, will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable. Some day the coalrooms of steamers and the tenders of locomotives will, instead of coal, be stored with these two condensed gases, which will burn in the furnaces with enormous calorific power. . I believe, then, that when the deposits of coal are exhausted we shall heat and warm ourselves with water. Water will be the coal of the future."
To our knowledge this is probably the earliest reference to a "hydrogen economy". Verne, however, never mentioned where the primary energy necessary to produce the needed hydrogen from water electrolysis would come from.
In the 1920s, Canada's Electrolyser Corporation Ltd. opened the way to commercial-scale hydrogen production through water electrolysis. This technology allowed hydroelectric power plants to utilize their excess capacity to produce hydrogen and oxygen. The generated gases were used mainly for non-fuel-related applications such as steel cutting and synthesis of fertilizers. At about the same time, German engineers, especially Rudolf Erren, experimented with hydrogen as a fuel for trucks, automobiles, trains, buses and other internal combustion driven devices . In aviation, hydrogen was first exploited in the German Zeppelins which offered regular transatlantic flights, some 20 years before airplanes did (Fig. 9.2). During these trips, large amounts of liquid fuels were consumed, gradually reducing the weight of the airship. To maintain the buoyancy, part of the hydrogen that kept the vessel afloat in the air was used as extra fuel instead of being simply blown-off. The catastrophic fire of the airship Hindenburg in 1937, however, ended the era of the hydrogen-filled Zeppelins. During World War II, hydrogen fuel attracted some interest for submarines and trackless torpedoes. After the war however, and during the era of cheap oil and gas, the potential
use of hydrogen as a fuel (except for space and military applications; Fig. 9.3) was widely ignored. It only resurfaced with the oil crises of the 1970s and the necessity to find alternatives to petroleum oil. Also, helped by a growing public awareness of pollution problems, suggestions involving hydrogen fuel flourished. This was also the time when the term "hydrogen economy" was introduced and the International Association for Hydrogen Energy was created. Interest by governments and private companies however, lasted only as long as the cost of oil remained high. With sharply declining oil prices in the 1980s, funding for the development of hydrogen energy and alternative energy sources was significantly reduced. For example, the budget for renewable energy in the United States was cut by almost 80% in the early 1980s. Regardless, in the former Soviet Union, a Tupolev 155 experimental airplane tested the use of liquid hydrogen and natural gas as alternatives to jet fuel in 1988 . The use of cryo-fuels however was found impractical, and technically too challenging for regular operation. The large insulated spherical tanks needed to keep the gases liquid were too voluminous and had only enough capacity for relatively short flights. Liquid hydrogen was also deemed too expensive compared to kerosene fuel. Interest in hydrogen fuel began to rise again in the 1990s, based on concerns about decreasing petroleum and gas reserves, and reports on increasing CO2 emissions that were considered to be a major cause of global climate change. At the same time, considerable advances in the development of fuel cells, and especially Proton Exchange Membrane (PEM) fuel cells, have made a commercial hydrogen fuel cell-powered motor car potentially feasible. This resulted in the transportation sector making by far the most of hydrogen-related investments. Most major carmakers, including Daimler-Chrysler, Honda, Toyota, General Motors and Ford, have built prototype fuel-cell cars, buses or trucks, and consequently the term "Hydrogen Economy"
became very popular and attracted much public attention. Today, hydrogen-powered vehicles are attracting funding and wide media coverage, and numerous organizations have been created to promote hydrogen fuel via publications, television, meetings and exhibitions. As earlier indicated, governments in the industrialized world themselves have also pledged and provided significant funding for the development of the hydrogen economy.
Hydrogen as a fuel, undoubtedly has many advantages. Its oxidative conversion to produce electricity or heat is clean, producing only water and generating no pollutants. But the crucial question is how to generate, economically, the large quantities of hydrogen needed. If a significant part of this hydrogen is to be produced by reforming of fossil fuels, as is the case today, it would only displace and possibly even increase - but not solve - the pollution and greenhouse gas emissions problem. However, if hydrogen could be generated by the electrolysis of inexhaustible water sources using nuclear and renewable energy, it could become a low-emission or emission-free source of fuel and energy storage medium. On the other hand, because of its unfavorable physical properties and high reactivity, hydrogen storage, transportation and use present major challenges.
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