Environmental Engineering Reference
In-Depth Information
in the United States, where some 80% of all transporta-
tion fuel is used by passenger cars, SUVs, and light
trucks, the combined share of TPES that is determined
by individual decisions is now approaching half the total,
and this decision-making decentralization has made it
much harder to anticipate future consumption trends.
This situation would be reversed only with a new pro-
gram of aggressively set corporate automobile fuel effi-
ciency (CAFE) standards.
The energy requirements of buildings and transporta-
tion combine to reach their highest densities in cities
and industrial conurbations. Surprisingly, the power
densities of built-up areas, including roads, in such poor
hot-weather cities as Kolkata or Mumbai (Bombay) are
10-15 W/m
2
, the same as in warm but affluent Los
Angeles or Tokyo. In the former instance low per capita
energy use and relatively low rate of car ownership are
counterbalanced by high dwelling densities and the pre-
sence of energy-intensive industries in residential areas.
In the latter case the extraordinary urban sprawl that
characterizes Los Angeles and the mostly low-rise hous-
ing of Tokyo dilute the effect of very high demand for
transportation fuels and air conditioning. Some of the
highest power densities of total energy use are found in
Asian megacities. Shanghai's density is about 80 W/m
2
(in the city's built-up area, not the entire municipality,
which includes a great deal of farm land); Seoul's close
to 50 W/m
2
; and Hong Kong's (with only 130 km
2
of
built-up land) has surpassed 110 W/m
2
(Warren-Rhodes
and Koenig 2001).
heat content, easier and safer extraction, inexpensive
seaborne and virtually invisible continental transporta-
tion, cleaner and much more convenient combustion,
and incomparable flexibility of utilization account for
the ascent of hydrocarbons in general and refined liquid
fuels in particular, and for the relative decline of solid
fuels. Shifting patterns of final uses mark distinct eras of
fossil-fueled civilization. When coal overtook wood in
the United States in 1885, 40% of it was used by rail-
ways, about 15% was converted to coke, and the rest
was split among industrial boilers and residential heating.
By 1945 railways used just over 20% and power plant
consumption and coking were about equal. The railway
market disappeared by the early 1960s, and by 2005 the
coking share fell to just over 2% of the total, whereas
electricity generation took more than 92% all coal (EIA
2006b). The breakdown of final uses is similar for afflu-
ent countries as a group. By 2003 they used nearly 75%
of
their coal
supply for electricity generation (EIA
2005b).
Crude oil's first market was to replace whale oil in
lighting, and only the invention of Otto and diesel
engines made its lighter fractions dominant in transporta-
tion. Replacement of coal-fired steam locomotives by
diesel engines boosted the typical conversion efficiency
by nearly 1 OM. Even the best post-WW II steam loco-
motives were no more than 10% efficient, and large rail-
way diesels have e
1
of at least 35%. Particularly after
engine knocking was solved by the addition of tetraethyl
lead, first introduced in the United States in 1924, gaso-
line helped to sustain successive waves of automobile use,
first in the United States, from 1950 in Europe and Ja-
pan, and then in China. The automobile was a European
invention, but U.S. affluence and mass production com-
bined to give that country more than 90% of the world's
9.4 Qualitative Changes: Transitions and
Efficiencies
A key qualitative shift in modern energy consumption
was the substitution of coal by hydrocarbons. Higher
