|Getting Real on Wind and Solar |
By James Schlesinger and Robert L. Hirsch
April 24, 2009
Why are we ignoring things we know? We know that the sun doesn't always shine
and that the wind doesn't always blow. That means that solar cells and wind
energy systems don't always provide electric power. Nevertheless, solar and wind
energy seem to have captured the public's support as potentially being the
primary or total answer to our electric power needs.
Solar cells and wind turbines are appealing because they are "renewables" with
promising implications and because they emit no carbon dioxide during operation,
which is certainly a plus. But because both are intermittent electric power
generators, they cannot produce electricity "on demand," something that the
public requires. We expect the lights to go on when we flip a switch, and we do
not expect our computers to shut down as nature dictates.
Solar and wind electricity are available only part of the time that consumers
demand power. Solar cells produce no electric power at night, and clouds greatly
reduce their output. The wind doesn't blow at a constant rate, and sometimes it
does not blow at all.
If large-scale electric energy storage were viable, solar and wind intermittency
would be less of a problem. However, large-scale electric energy storage is
possible only in the few locations where there are hydroelectric dams. But when
we use hydroelectric dams for electric energy storage, we reduce their electric
power output, which would otherwise have been used by consumers. In other words,
we suffer a loss to gain power on demand from wind and solar.
At locations without such hydroelectric dams, which is most places, solar and
wind electricity systems must be backed up 100 percent by other forms of
generation to ensure against blackouts. In today's world, that backup power can
only come from fossil fuels.
Because of this need for full fossil fuel backup, the public will pay a large
premium for solar and wind -- paying once for the solar and wind system (made
financially feasible through substantial subsidies) and again for the fossil
fuel system, which must be kept running at a low level at all times to be able
to quickly ramp up in cases of sudden declines in sunshine and wind. Thus, the
total cost of such a system includes the cost of the solar and wind machines,
their subsidies, and the cost of the full backup power system running in
Finally, since solar and wind conditions are most favorable in the Southwest and
the center of the country, costly transmission lines will be needed to move that
lower-cost solar and wind energy to population centers on the coasts. There must
be considerable redundancy in those new transmission lines to guard against
damage due to natural disasters and terrorism, leading to considerable
The climate change benefits that accrue from solar and wind power with 100
percent fossil fuel backup are associated with the fossil fuels not used at the
standby power plants. Because solar and wind have the capacity to deliver only
30 to 40 percent of their full power ratings in even the best locations, they
provide a carbon dioxide reduction of less than 30 to 40 percent, considering
the fossil fuels needed for the "spinning reserve." That's far less than the 100
percent that many people believe, and it all comes with a high cost premium.
The United States will need an array of electric power production options to
meet its needs in the years ahead. Solar and wind will have their places, as
will other renewables. Realistically, however, solar and wind will probably only
provide a modest percentage of future U.S. power. Some serious realism in energy
planning is needed, preferably from analysts who are not backing one horse or another.
James R. Schlesinger was the first secretary of energy and established the
National Renewable Energy Laboratory. Robert L. Hirsch is senior energy adviser
at Management Information Services Inc. Previously he managed the federal
renewables program at the Energy Research and Development Administration, the
predecessor to the Energy Department.