Environmental Engineering Reference
In-Depth Information
freezing point at
47
C, is used on most long interna-
tional flights and on northern and polar routes during
the winter. Jetliners store this fuel in their wings; some
also have a central (fuselage) tank and a horizontal stabi-
lizer tank.
The aviation market witnessed by far the highest
growth rates among all transportation modes as intercon-
tinental flights became an unremarkable experience for
tens of millions of business and leisure travelers. The
annual total of passenger-kilometers flown globally by
scheduled airlines surpassed 40 billion in the early 1950s
and reached nearly 3 trillion passenger-kilometers in
2000 and 3.7 trillion in 2005. Growing even faster than
passenger traffic, worldwide air cargo services rose from
750 million t-km in 1950 to about 108 billion t-km
in 2000, and to more than 140 billion t-km in 2005 of
which 90% was logged on international routes (ICAO
2006). But airplanes carry only a tiny fraction of com-
mercial cargo. Even in the United States the share is less
than 0.5%, compared to just over 40% for railways and
nearly 30% for trucks (USBC 2006).
Another key qualitative shift marking modern energy
use has been the rising importance of electricity. Rising
demand for electricity spurred the expansion of hydro-
generation, whose contribution was negligible in 1900,
and the introduction of nuclear fission, which became
commercially available in 1956 (see section 9.2). But,
above all, modern energy use is characterized by an
increasing share of fossil fuels being converted to ther-
mally generated electricity. In 1900 less than 2% of all
U.S. fuel was converted to electricity; by 1950 that share
had risen to 10%, and by 2000 it had reached 34% (EIA
2001b). The universal nature of this process is best illus-
trated by the rapid rate at which China has been catching
up. That country converted about 10% of its coal (at that
time virtually its only fossil fuel) to electricity in 1950. By
1980 the share surpassed 20%, and by 2000 it was about
30%, not far behind the U.S. share (Smil 1976; Fridley et
al. 2001). Because of this strong worldwide trend, the
global share of fossil fuels converted to electricity is now
above 30%, compared to 10% in 1950 and just over 1% in
1900.
Given electricity's many advantages, this shift has been
unavoidable. Only electricity offers instant, effortless con-
sumer access; the ability to fill every consuming niche
and be converted into motion, heat, light, and chemical
potential; serving as the sole energizer of electronically
transmitted information with unmatchable control, preci-
sion, and speed; silent and clean conversion; extremely
reliable individualized delivery; and easily accommodat-
ing growing or changing uses. And electrical energy can
be produced from a wide variety of (often inferior) fuels;
its conversion to heat can be accomplished with nearly
perfect efficiency; it can provide temperatures higher than
can be attained by combustion of any fossil fuel; and its
utilization requires no inventory.
Not surprisingly, electricity became the energy of
choice for residential use, and with increasing consumer
affluence its consumption became more diversified. At
the beginning of the twentieth century, low-level lighting
consumed nearly all of its use, but in 2001 the largest
U.S. share, for air conditioning, was about 16%, refrigera-
tion 14%, heating 10%, and lighting 9%, and water heat-
ing 9% (EIA 2001a). Refrigerator ownership is now
nearly universal not only in rich countries but also in ur-
ban Asia. Other appliances with high ownership rates in-
clude color TVs (99% in the United States), microwave
ovens (88%), and clothes washers (79%). Clothes dryers,
dishwashers, and freezers are less common outside the
United States. And even when everything is switched off,
