Environmental Engineering Reference
In-Depth Information
The final uses of energy are usually classified as industry, transport, residential,
commercial, and public services, and nonenergy uses, as indicated in
Table 3.3
.
Table 3.3 The world's final uses of energy—2008
The most important transformations in the transition of primary energy sources to
consumable end products are the production of electricity and motive power. This
process is usually done by burning fossil fuels to produce steam, which then is used
to produce mechanical power or electricity.
The idea of using vapor from boiling water to produce mechanical power has a
long history. For example, the Greeks used the expansive force of gases to open the
doors in temples without the intervention of human hands 2,500 years ago. This
probably had an extraordinary impact on the Athenians.
However, to produce mechanical work in a sustained way, one needs a machine
that will operate in a cycle, that is, will continually resume an initial operation and
repeat it successively. To open the doors of temples does not meet that requirement.
By the late 18th century, the English blacksmith and mechanic Thomas Newcomen
(1663-1729) managed to do it, with a huge low-power machine (approximately 4
hp) that consumed coal at a high rate and an efficiency of less than 2%. This ma-
chine was originally used in coal mines to pump water. Newcomen's engine, be-
sides being very big, needed a man to operate the valves. The cycles were spaced
over time.
James Watt (1736-1839) improved the system in the early 19th century,
thermally insulating the cylinder and introducing an external condenser that cooled
