IEEE Spectrum July, 2012 - 49

best nuclear power plants

nuclear power plants, u.s. national average, 2010

coal-fired power plants, u.s. national average, 2010

hydroelectric power plants, global average

Capacity Factors

best wind farms

Systems that can provide electricity only when the sun
shines or the wind blows have generating capacities that
are effectively much lower than those that operate all the
time, either by burning coal or by exploiting nuclear fission.

global average: 21%
wind power, u.s. national average

solar (thermal and photovoltaics), u.s. national average, 2010

united states
worldwide

photovoltaic plants, average

average percentage of nominal generating capacity
at which installation operates year round

temperature will rise by 2 °C. I wish all
these promises would come true, but I
think instead I'll put my faith in cleareyed technical assessments.
The matter of affordable costs is the
hardest promise to assess, given the
many assorted subsidies and the creative accounting techniques that have for
years propped up alternative and renewable generation technologies. Both the
European Wind Energy Association and
the American Wind Energy Association
claim that wind turbines already produce cheaper electricity than coal-fired
power plants do, while the solar enthusiasts love to take the history of impressively declining prices for photovoltaic
cells and project them forward to imply
that we'll soon see installed costs that are
amazingly low.
But other analyses refute the claims
of cheap wind electricity, and still others take into account the fact that photovoltaic installations require not just cells
but also frames, inverters, batteries, and
labor. These associated expenses are not

plummeting at all, and that is why the
cost of electricity generated by residential solar systems in the United States
has not changed dramatically since 2000.
At that time the national mean was close
to 40 U.S. cents per kilowatt-hour, while
the latest Solarbuzz data for 2012 show
28.91 cents per kilowatt-hour in sunny
climates and 63.60 cents per kilowatthour in cloudy ones. That's still far more
expensive than using fossil fuels, which
in the United States cost between 11 and
12 cents per kilowatt-hour in 2011. The
age of mass-scale, decentralized photovoltaic generation is not here yet.
Then consider the question of scale.
Wind power is more advanced commercially than solar power, but with about
47 gigawatts in the United States at the
end of 2011 it still accounted for less
than 4 percent of the net installed summer generating capacity in that country.
And because the capacity factors of U.S.
wind turbines are so low, wind supplied
less than 3 percent of all the electricity
generated there in 2011.

100

It took 30 years-since the launch of
small, modern wind turbines in 1980-
to reach even that modest percentage.
By comparison, nuclear power had
accounted for 20 percent of all U.S. generation within 30 years of its launch in
1957, and gas turbines achieved 10 percent three decades after they went into
operation in the early 1960s.
Projections of wind-power generation into the future have been misleadingly optimistic, because they are all
based on initial increases from a minuscule base. So what if total global wind
turbine capacity rose sixfold between
2001 and 2011? Such high growth rates
are typical of systems in early stages of
development, particularly when-as in
this case-the growth has been driven
primarily by subsidies.
And a new factor has been changing the
prospects for wind and solar: the arrival of
abundant supplies of natural gas extracted
by hydraulic fracturing, or fracking, from
shales. Fracking is uncommon outside the
United States and Canada at the moment,
wind electricity

nuclear
electricity

nuclear and wind have not reached
25 percent; photovoltaics hardly
registers.

natural gas
oil

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Table of Contents for the Digital Edition of IEEE Spectrum July, 2012