Environmental Engineering Reference
In-Depth Information
THE EFFICIENCY PROBLEMS OF SOLAR AND WIND: DILUTENESS AND
INTERMITTENCY
Solar and wind energy both work with energy flowing directly from the sun; solar through sunlight and
wind through the sun's heating of different parts of the atmosphere, which is the main cause of wind.
Solar energy typically works in one of two ways: solar photovoltaic (abbreviated solar PV) and concen-
trated solar power (CSP). Solar PV generates electricity through a phenomenon, discovered around 1839
by Edmond Becquerel, called the photovoltaic effect, by which certain materials emit electrons when hit
bylight. Throughextremely impressive feats ofengineering involving precision (andoften expensive) ma-
terials, solar PV can generate an electric current when it is exposed to sunlight. The first “solar cell” was
patented in the United States in
1888.
CSP, by contrast, concentrates sunlight into heat, much as a child
with a magnifying glass does when he uses the sun to ignite a dried leaf. Using, in effect, a massive array
of magnifying glasses (in this case, mirrors), CSP concentrates sunlight into heat, which is used to heat a
liquid, which generates steam that can power an engine.
Windelectricity workswhenhigh-velocity windturnsthebladesofawindturbine,whichareconnected
to a generator that converts the wind's power into electric current.
In practice, solar and wind technologies have, as we saw before, produced very, very little energy.
The top five countries ranked by solar energy consumption are Germany, Italy, Spain, Japan, and China.
The percentage of each country's electricity that comes from solar energy is, respectively: 4.5 percent, 6.3
percent, 4.0 percent, .09 percent, and .6 percent.
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The top five countries ranked by wind consumption are the United States, China, Spain, Germany, and
India. Faring slightly better than solar, the percentage of each country's electricity that comes from wind
energy is, respectively: 3.3 percent, 2.03 percent, 16.5 percent, 7.44 percent, and 2.96 percent.
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(If this
seems impossibly low, because we frequently hear numbers such as “50 percent solar and wind,” stay
tuned.)
Don'tletthe16.5percentinSpainmisleadyou.Spainsufferedfinancialdevastationfromitsinvestment
in wind, among other bad investments.
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But more important, certain fundamental problems with solar and
wind mean that the more energy they attempt to produce, the more of a problem they create.
Why?
The basic problem is that the
process
for solar and wind to generate reliable electricity requires so many
resources that it has never been cheap and plentiful. In fact,
modern solar and wind technology do not pro-
duce reliable energy, period
.
Traditionally in discussions of solar and wind there are two problems cited: the diluteness problem and
the intermittency problem.
The diluteness problem is that the sun and the wind don't deliver concentrated energy,which means you
need a lot of materials per unit of energy produced. For solar, such materials can include highly purified
silicon, phosphorus, boron, and compounds like titanium dioxide, cadmium telluride, and copper indium
gallium selenide.
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For wind, they can include high-performance compounds (like those used in the air-
craft industry) for turbine blades and the rare-earth metal neodymium for lightweight, high-performance
magnets, as well as the steel and concrete necessary to build thousands or tens of thousands of structures
as tall as skyscrapers.
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Figure 2.2 indicates how steel (and iron) intensive it is to generate electricity from wind as compared
with coal, nuclear, or natural gas.
