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Appendix C
Comparison of Different Power-Generation Methods 255

Method Cents/KWH Limitations and Externalities
Geothermal
Currently supplies 4.5–30 cents/ New low temperature conversion
approximately 0.23% of KWH of heat to electricity is likely to
the global electricity make geothermal substantially
demand. Geothermal is more plausible (more shallow
considered to be 90-95% drilling possible) and less expen-
reliable. sive. Generally, the bigger the
plant, the less the cost, and cost
also depends upon the depth to
be drilled and the temperature at
the depth. The higher the tem-
perature, the lower the cost per
KWH. Cost may also be affected
by where the drilling is to take
place as concerns distance from
the grid and another factor may
be the permeability of the rock.
Hydro
Currently supplies around 5.1–11.3 cents/ Hydro is currently the only
19.9% of the global KWH source of renewable energy
ptg
electricity demand. Hydro making substantial contributions
is considered to be 60% to global energy demand. Hydro
reliable. plants, however, can (obviously)
only be built in a limited
number of places, and can
significantly damage aquatic
ecosystems.
Solar
Currently supplies 15–30 cents/ Solar power has been expensive,
approximately 0.8% of the KWH but soon is expected to drop to as
global electricity demand. low as 3.5 cents/KWH. Once the
silicon shortage is remedied
through artificial silicon, a solar
energy revolution is expected.

Worldwide Aspects of Hydroelectricity

Because hydro is currently the only source of renewable energy mak-
ing substantial contributions to global energy demand, we’ll take a fur-
ther look at this source of electricity. From the previous table, hydro
currently supplies around 20 percent of global electricity demand.
Hydro plants, however, can (obviously) be built in only a limited num-
ber of places and can significantly damage aquatic ecosystems.