Environmental Engineering Reference
In-Depth Information
approaches exists: doing without, maximizing conversion
efficiencies, and reducing the use of energy-intensive
products through better design and extensive recycling
of materials.
Doing without is an underappreciated option in afflu-
ent societies habituated to the idea of growth, but its im-
pact is clear when comparing per capita energy use in the
Western world of the early 1960s with that of the early
2000s. (I chose this span, 1965-2005, because older
readers of this topic will be able to call on their personal
experiences in judging the gains.). Was life with 15% (the
U.S. case), 40% (in Canada), or even 50% less energy (in
France) so unfulfilling, so unsafe, or so unbearable? But
voluntary frugality has been in short supply throughout
the rich Western world, and in the absence of acute social
crises democracies are averse to adopting restrictive and
proscriptive measures.
Only in a minority of cases does any further improve-
ment of conversion efficiencies run into physical limits.
Thermodynamic minima have been approached in vari-
ous energy-intensive chemical syntheses (see chapter 10);
the best large electric motors are near-perfect converters
of electricity to rotary power (e
1
>
97%); and many
boilers and furnaces are, in e
1
terms, more than 90% effi-
cient. But beyond such instances there is an entire uni-
verse of wasteful conversions with many opportunities
for efficiency improvements ranging from relatively
modest to surprisingly large. For instance, in superinsu-
lated houses, halving the total energy needs is not excep-
tional. And modest improvements, multiplied by the
10
6
-10
8
units operating in modern mass consumption
societies, would translate into huge savings. Further sav-
ings can come from structural changes. In comparison
with a three-bedroom, single-story house, an equal-sized
two-story building has an energy efficiency gain of 15%,
a two-story duplex 30%, a two-story triplex 35%, and a
low-rise apartment building 40% (Burchell and Listokin
1982).
Improvements in automotive efficiency are certainly
the most important instance of individually small but col-
lectively massive gains because substantial energy savings
can come from a combination of gradual adjustments
and widespread applications of existing techniques. To
begin with, cars are often designed to be unnecessarily
powerful. Unless the driving requires unusually rapid ac-
celeration, travel on uncommonly steep roads, or heavy
towing, there is no good reason a passenger car used for
urban driving should rate over 40 kW. In 2005 even a
Suzuki Swift was overrated (76 kW), and a Honda Civic
(87 kW) was more than twice as powerful as necessary
for driving from one traffic signal to another. Weight re-
duction obviously lowers power requirements, but de-
spite front-wheel drive, transversely mounted engines,
and lighter-than-steel materials, even compact European
cars got heavier, gaining more than 300 kg/vehicle be-
tween 1970 and 2000 (WBCSD 2004).
Reductions of aerodynamic drag still have far to go
before they encounter a physical limit. Lean-burn
low-friction engines, continuously variable transmissions,
and greater diffusion of diesels, especially adiabatic low-
friction kinds, are other components of a strategy that
could see national car fleets averaging below 5 L/100
km. Only such improvements could stem the incredible
waste of automotive fuels. In 2005, U.S. gasoline con-
sumption (@13 EJ) was equal to about 60% of total pri-
mary energy use in Japan (@22 EJ). In global terms, U.S.
gasoline use in 2005 accounted for nearly 4% of the total
world fossil fuel consumption. In personal terms, a week's
