Energy Conversion Efficiencies
Sources:
1) Energies, An Illustrated Guide to
the Biosphere and Civilization by Vaclav Smil (MIT Press, 1999).
2) Energy and Problems of a
Technical Society J. J. Kraushaar and R. A. Ristinen (John Wiley
and Sons, 1993).
Types:
M to e = mechanical to electrical
e to m = electrical to mechanical
c to t = chemical to thermal
c to e = chemical to electrical
c to m = chemical to mechanical
t to m = thermal to mechanical
r to e = radiation to electrical
e to r = electrical to radiation
m to m = mechanical to mechanical
r to c = radiation to chemical
Process:
Type:
Efficiency:
Large electric
generator
m to
e
98-99%
Large power-plant
boiler
c to
t
90-98
Large electric
motor
e to
m
90-97
Home gas
furnace
c to
t
90-96
Dry-cell
batteries
c to
e
85-95
Overshot water
wheel
m to
m
60-85
Small electric
motor
e to
m
60-75
Fuel
cell
c to
e
50-60
Large steam
turbine
t to
m
40-45
Wood
stove
c to
t
25-45
Large gas
turbine
c to
m
35-40
Diesel
engine
c to
m
30-35
Best photovoltaic
cell
r to
e
20-30
Large steam
engine
c to
m
20-25
Internal combustion
engine c to
m
15-25
Fluorescent
lights
e to
r
10-12
Plant
photosynthesis
r to c
4-5
Questions:
1) Why is it unlikely that a diesel or
internal combustion engine will ever be as efficient as, say, a fuel
cell or battery? (Hint: The second law of thermodynamics.)
2) Why is it unlikely that photovoltaic
cells will ever be as efficient as, say, a gas furnace? (Hint: Think
about band gaps and the frequency needed to free an electron in a
solid.)
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Page.
Contact Kyle Forinash, kforinas@ius.edu,
for comments/suggestions/corrections.