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Since the early 19th century, scientists have recognized hydrogen as a potential source of fuel. Current uses of hydrogen are in industrial processes, rocket fuel, and spacecraft propulsion. With further research and development, this fuel could also serve as an alternative source of energy for heating and lighting homes, generating electricity, and fueling motor vehicles. When produced from renewable resources and technologies, such as hydro, solar, and wind energy, hydrogen becomes a renewable fuel. (reference)
Unlike most other fuels, hydrogen cannot be produced directly by digging a mine or drilling a well. It must be extracted chemically from hydrogen-rich materials such as natural gas, water, coal, or plant matter. Accounting for the energy required for the extraction process is critical in evaluating any hydrogen use option. Production techniques now used include steam reforming of natural gas, cleanup of industrial by-product gases, and electrolysis of water. A number of other technologies are being studied, including several that produce hydrogen from water or biomass using solar or other renewable energy. Hydrogen is the most abundant of all the elements in the universe, and makes up more than three-quarters of the mass of the universe. Based on the "Big Bang" theory, it is believed that all the heavier elements were built up from hydrogen and helium, and that this process is still going on. Hydrogen is found in our Sun and the stars and plays an important role in the reactions that account for their energy.
Hydrogen ranks ninth of all the elements in order of abundance on Earth, and makes up about 0.76% of the weight of the Earth's crust. The most important naturally occurring compound of hydrogen is water, which is the principal source of the element. In the quest for new and improved energy sources and uses, interest has been aroused in employing hydrogen as an energy currency. It has been suggested that solar, wind, hydro, nuclear, or even coal conversion could be used to produce hydrogen. The hydrogen would be stored as a compressed gas or liquid and subsequently utilized in a fuel cell, or combusted to return the stored energy when needed. This is the basis for the hydrogen economy, or hydrogen energy research carried out throughout the world. This research recognizes that fossil fuels will not last forever, and that the hydrogen cycle is simple and non-polluting.
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