Environmental Engineering Reference
In-Depth Information
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Hydrogen
Hydrogen is the lightest and most abundant chemical element in the universe, constituting
roughly 75 percent of chemical elemental mass. It is an invisible, nontoxic, light gas that can be
used to power nearly every end-use energy need. Hydrogen has high energy content compared to
gasoline, and its small molecules can diffuse through most materials and make steel brittle. This
creates some difficulties in handling it, discussed below. Hydrogen is used as a feedstock in the
chemical and petroleum industries, principally to produce ammonia, upgraded fossil fuels, and a
variety of chemicals. It is rarely used today as a transportation fuel (Armaroli and Balzani 2011,
280-281).
The hydrogen energy fuel cycle includes hydrogen production, manufacturing of fuel cells, stor-
age, transportation, distribution, and utilization of hydrogen, as illustrated in
Figure 12.1
. The
fuel cycle for hydrogen includes producing hydrogen by conversion from other fuels or water,
transportation to decentralized fueling stations, and utilization in fuel cells. The basic components
of central-station generation facilities are the same except generation of electricity is at a much
larger scale and access to the electric power network is required. Suitable areas must be evaluated,
production and generating facilities must be constructed and operated, and eventually generating
equipment must be decommissioned.
Hydrogen Production
Although plentiful, hydrogen does not exist naturally on earth in its elemental form. Pure hydrogen
stores and delivers energy in a usable form, but it must be produced from hydrogen-rich com-
pounds, such as fossil fuels or water. Hydrogen can be produced from diverse domestic resources,
Figure 12.1
The Hydrogen Fuel Cycle
Hydrogen
production
Storage
Transportation
Waste heat disposal
Utilization
Distribution
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