Environmental Engineering Reference
In-Depth Information
worth of gasoline for a two-car suburban U.S. family is
equivalent to the total annual primary energy consump-
tion of a fairly well-off Indian villager.
Airlines are a minor fuel consumer compared to cars
and trucks (U.S. jet fuel use is equivalent to about one-
sixth of gasoline use). But fuel's large share of airlines'
operation costs has stimulated high-efficiency advances.
Turbofan engines (see section 8.4) have realized the
greatest efficiency gains, and further opportunities exist
to continue this commendable trend. Modernization
of lighting provides another example of energy savings
achievable with existing techniques. Outdoor lighting
already relies on high-performance halide and sodium
lamps. But substituting fluorescent lights (available in
compact form) for indoor incandescent bulbs represents
a large potential for reducing electricity use. Electricity
savings can also be realized by more efficient motors,
especially the AC-polyphase induction machines rated
between 750 W and 100 kW that dominate industrial
applications (pumping, compressors, fans, blowers, ma-
chine tools). Large gains for small motors (
<
1 kW) and
small improvements for larger machines would translate
into significant aggregate gains when multiplied by mil-
lions of operating units.
Co-generation (see section 9.4) addresses a part of the
qualitative mismatch between sources and final uses that
is regrettably common in high-energy-use society. The
most often cited example of this mismatch is the use of
fossil-fuel-generated electricity for resistance heating (us-
ing inexpensive hydroelectricity, as do Norway, Quebec,
and Manitoba, is a different matter). In general, rich
societies need 20%-40% of their useful energy as low-
temperature heat (well below 100
C), and supplying
this demand by burning fossil fuels at temperatures
exceeding 1000
C leads to very low e
2
. This efficiency
would soar with wider application of solar conversions.
Repairing this qualitative energy mismatch has been one
of the principal objectives of the soft energy path (Lovins
1976), but a simplistic maximization of thermodynamic
efficiency should not be the sole guiding reason for
restructuring the energy supply (see chapter 12).
Conservation springs from what Socolow (1977)
labeled an ''inverted emphasis'' in a society facing the
energy dilemma. Instead of a traditional concentration
on enlarging the energy supply, the inverted approach
embraces deliveries of particular energy needs and thus
inevitably discovers huge rationalization opportunities. At
the same time, one must be aware of two practical limits
to conservation: the incremental nature of the gains and
the effect of time horizons. Energy conservation does not
offer the equivalent of spectacular oil field discoveries or
dramatic single-item shortcuts. Even significant conserva-
tion efforts like mandatary efficiency standards for cars,
air conditioners, or refrigerators cannot reduce national
energy use by large margins over short periods of time.
Moreover, successful energy conservation requires long-
term commitment and a prodigious number of informed
individual decisions; both can be a problem in most afflu-
ent societies.
The time factor is important in every investment deci-
sion to raise energy conversion efficiency or reduce waste.
Long amortization spans justify higher energy inputs
and generate greater life cycle savings. But such desirable
long-term commitments are compromised by the high
mobility of U.S. society and the preference, especially in
North America, for lowest first cost. Other affluent but
more settled societies with rising coss of living and higher
energy prices have been able to promote energy conser-
vation more readily, especially if they have traditionally
high savings rates.
