460 CHAPTER 18 Renewable Energy Resources
Iain Materton/Alamygenerates electricity, and then the steam produced during
this process is used rather than wasted. The system’s over-
all conversion efficiency (that is, the ratio of useful energy
produced to fuel energy used) is high because some of
what is usually waste heat is incorporated into the process.
Cogeneration can be cost-effective on both small and
large scales. Modular CHP systems enable hospitals, ho-
tels, restaurants, factories, and other businesses to har-
ness steam that would otherwise be wasted to
heat buildings, cook food, or operate machin-
ery before it cools and gets pumped back into
the boiler as water (Figure 18.16). Larger
CHP systems can produce electricity for local
utilities.that, as larger vehicles became more popular; light trucks
and sport utility vehicles (SUVs) are now a substantial frac-
tion of the passenger vehicles in the United States. Fur-
ther, significant gains could easily be made using current
technology. Automobiles with fuel efficiencies of 60 to 65
mpg could be routinely manufactured within the next de-
cade or so, and manufacturers are developing even more
efficient models for the future (Figure 18.15).
Cogeneration One energy technology that
has a bright future is cogeneration, or com-
bined heat and power (CHP). Cogeneration
involves the production of two useful forms
of energy from the same fuel. A CHP system
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The Daihatsu prototype UFE (ultra fuel economy) III hybrid can achieve 169 miles per gallon.
cogeneration
(CHP) An energy
technology that
involves recycling
“waste” heat.Heat recovery
(from exhaust
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In this example of a cogeneration
system, fuel combustion generates
electricity in a generator. The
electricity produced is used in-house
or sold to a local utility. The waste
heat (leftover hot gases or steam) is
recovered for useful purposes, such
as industrial processes, heating of
buildings, hot water heating, and
generation of additional electricity.