Chap. 14. The Ten Commandments of Sustainability 357
Europe, particularly in Denmark and Germany. In the U.S., areas of California, Kansas,
and West Texas are particularly well adapted to the installation of wind generating
facilities. Some people regard the tall, graceful aerogenerators as ugly, but they are
certainly not as ugly as the landscape will become if massive climate warming occurs.
There is one big problem common to solar and wind energy: their intermittent
nature. Solar energy works poorly when the sun does not shine and wind energy fails
when the wind does not blow (although modern aerogenerators function at remarkably
low wind speeds). Therefore, it is necessary to have reliable means of energy storage to
provide for an even energy flow. For small installations, the means of energy storage is
the lead storage battery, but these would be impractical on the large scale of an entire
power grid. Pumped water storage is a known technology in which electrically-powered
pumps drive water to an elevated reservoir when electricity is available, then use it to
run through turbines hooked to generators when electricity is not being generated from
the source. Energy can also be stored in the momentum of large flywheels spinning
at extremely high speeds on virtually friction-free air-lubricated bearings. Another
means of getting steady supplies of energy from intermittent sources is to use electricity
to electrolyze water to elemental hydrogen and oxygen as noted in the discussion of
photovoltaic electricity above.
Vast amounts of energy can be harvested from moving water. Hydroelectric
installations throughout the world provide significant fractions of total electricity. Water
power harvested from the hydrologic cycle is actually another means of utilizing solar
energy because the water is pumped through the cycle by energy from the sun (see
Figure 7.3). Although conventional hydroenergy is a significant contributor to world
energy supplies, it probably cannot be developed further without causing unacceptable
environmental effects, particularly from dam construction on free-flowing rivers. Indeed,
because of their adverse environmental effects, many hydroelectric installations should
be dismantled allowing the rivers on which they are located to flow freely again.
Another source of energy from moving water is that from tides, changing levels of sea
water resulting from the gravitational pull of the sun and moon. Tidal energy is feasible
as demonstrated by the 240 megawatt tidal power station that has operated reliably in the
Rance estuary region of France since it was constructed in 1966. This facility has about
(^1) / 4 the capacity of a standard 1,000 MW coal-fired or nuclear plant. Several other small
installations have been built including an 18 MW experimental unit at Annapolis Royal,
Canada. Tidal electricity generating stations suffer from the disadvantage that sufficient
water flows to generate electricity only about 10 hours per day. Nevertheless, the amount
of energy potentially available from tides is enormous and it is completely renewable.
Nuclear energy is a source of continuous power that does not contribute to greenhouse
warming. It has the advantage of being a proven technology that has contributed
substantial amounts of electricity in some nations for several decades. Many U.S. Navy
submarines and ships are powered by nuclear reactors, some of which are scheduled to
serve for 28 years before requiring refueling! None of the reactors in the U.S. fleet has
ever suffered a malfunction that harmed personnel or released significant amounts of
radioactivity. Resources of fissionable uranium are abundant enough to sustain nuclear
energy worldwide for several centuries. Latest design nuclear reactors have passive