Wind farms and solar installations are often located in places where they
will have the least impact on climate and health, a report finds.
These renewable energies emit less carbon dioxide and air pollution than
burning fossil fuels for electricity. But the windiest and sunniest places in
the United States — such as the southwestern plains and deserts — are not
always the most socially and environmentally beneficial sites for wind turbines
and solar panels. The benefits, according to a study published today in Proceedings
of the National Academy of Sciences, vary depending on what energy sources
are being replaced.
New wind and solar installations displace the most carbon dioxide and air
pollutants where they replace the coal-fired plants found predominantly in
eastern and Midwestern states such as Indiana and Pennsylvania. The benefits
are much smaller in California and the US southwest, where cleaner gas-fired
plants are more common.
“One would think it makes most sense to install the next solar panel in
sunny California, because the solar resource is better there,” says Inês Lima
Azevedo, an environmental engineer at Carnegie Mellon University in Pittsburgh,
Pennsylvania, and a co-author of the study.
“But if we start thinking about the emissions that are displaced by adding
that solar panel, the story is different: in Pennsylvania, one will be
displacing old and dirty coal power plants and thus avoiding more health and
environmental damages associated with the emissions from those plants.”
The team calculated the power-generation capacity of thousands of wind
turbines and hundreds of solar panels across the United States and evaluated
the corresponding health and environmental benefits. Assuming a social cost to
the environment and human health of US$20 per ton of carbon dioxide emitted,
and $6 million per air-pollution-caused death, the combined climate and health
benefits per megawatt hour used from electricity produced by solar power range
from about $10 in Arizona, to $100, in some northeastern states, the
researchers estimate.
Social benefits
As for wind energy, the overall health and environmental benefits in the United
States amount to $2.6 billion per year. This is 60% more than the yearly US
subsidy of $1.6 billion for wind power diffusion, the researchers say. But the
US production tax credit — the main policy mechanism to induce wind-power
development — encourages investors to seek sites with the highest energy output
rather than those with high social benefits, says Lima Azevedo.
As a result, 30% of the 34,000 megawatts of wind capacity in the United
States is installed in Texas and California, where social benefits are lowest,
and less than 5% is in Indiana, Ohio and West Virginia, where wind power offers
the greatest benefit from displaced pollution.
To maximize benefits for taxpayers, Lima Azevedo says, policy-makers should
think about a subsidy scheme that encourages operators to build plants where
they will yield the biggest health and climate gains. The easiest way to do
that, she says, would be to price air-pollutant emissions at their source — the
power plants.
The findings are “exceedingly interesting” and relevant for any nation
weighing the costs and benefits of moving towards more wind and solar energy,
says Nebojsa Nakicenovic, an energy-systems analyst at the International
Institute of Applied System Analysis in Laxenburg, Austria. “This study clearly
shows that, if installation sites are well chosen, the costs that some may feel
worried about are in fact more than offset by avoided damages to human health
and the environment.”
