Environmental Engineering Reference
In-Depth Information
Undoubtedly, these are all factors to consider, but
there is no doubt that relative savings, whether measured
as mineral commodities per unit of GDP or as energy
and materials per specific finished products and delivered
services, have often been accompanied by rising absolute
consumption. The best examples of these trends come
from lighting. By the year 2000 the efficiency of British
lighting was 1,000 times that in 1800, but per capita use
was 6,500 times greater and total lighting consumption
was 25,000 higher (Fouquet and Pearson 2006). The ef-
ficacy of British street lighting improved about 20-fold
between the 1920s and the 1990s. But more roads
(overall length up by less than 50% increase) and a huge
rise in average light intensity (in lumens per kilometer of
road it rose more than 400 times) entirely negated these
advances, and electricity consumption per kilometer of
British roads increased 25-fold (Herring 2001).
Or, as another example, the typical power density of
new houses is now considerably lower than right after
WW II, but the houses have grown larger. The average
size of new U.S. houses increased by more than 50% dur-
ing the last quarter of the twentieth century, to just over
200 m 2 (USBC 2006). Moreover, these houses may
have superefficient air conditioners, used in summer to
maintain indoor temperatures that the inhabitants would
consider too cold in winter. Similar contradictions have
accompanied the supposed trend toward a less materials-
based economy. A rapid increase in paper consumption
coincided with the diffusion of the electronic ''paperless
office,'' and the short lifespans of computers and periph-
erals have created serious waste disposal problems be-
cause these machines contain toxic components.
National histories of energy consumption confirm that
efficiency gains have not brought any long-run decline in
overall energy use. The average energy intensity of the
U.S. economy fell by 34% between 1980 and 2000 as
the country's population increased by about 22%. But
the average per capita GDP rose by more than 55%, and
TPES in 2000 was about 26% higher. During the same
period China experienced perhaps the greatest efficiency
gain in global history as the average energy intensity of
its economy fell by 70% while its population grew by less
than 30%. But its high rate of GDP growth resulted in an
80% rise in TPES (NBS 2000). And during the 1990s,
Japan's TPES rose by nearly 20% even though the coun-
try's GDP expanded by less than 15% and its population
gained less than 4%.
Historical evidence is thus replete with examples dem-
onstrating that on the national level substantial efficiency
gains in conversion or materials use stimulated increases
in fuel and electricity consumption or materials use that
were far higher than the savings achieved by these inno-
vations. Relative gains do not translate into absolute sav-
ings. As Rudin (2004) noted, efficiency disconnects the
problem from the solution (e.g., lm/W from kWh used).
It emphasizes output, which may be optimized but not
necessarily minimized. If we are to see any actual reduc-
tions in overall energy use, we need to go beyond in-
creased efficiency of energy conversions (see chapter 12).
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