As conservation groups will tell you, where you put wind turbines (or solar panels) matters, because poorly sited power plants can do needless damage to land and wildlife. But a new study argues there’s another reason to think long and hard about renewable energy siting – and the policies that drive siting: The benefits of wind or solar can vary dramatically depending on location, in ways that are sometimes counter-intuitive.

For instance, the simple fact that it’s a lot sunnier in the southwestern U.S. might lead you to think that a 1 kilowatt solar panel in Arizona would be a better investment than a 1 kW solar panel in Ohio. Not so! The study, out of Carnegie Mellon University, says “(d)espite a poor solar resource, a 1-kW PV panel in Ohio provides $105 in health and environmental benefits per year ($75/MWh) – 15 times more than the same panel in Arizona.”

agua caliente
Agua Caliente, Yuma County, Ariz. (image via First Solar)

The key here is how the researchers measure the benefits of clean energy production. They don’t just look at how much energy is produced; they also factor in the energy source being displaced. That means that even a little bit of solar energy – or, as we’ll see, wind energy – in places that rely heavily on dirty coal can provide extraordinary benefits. Or as the researchers put it, “Remarkably, if the goal is to improve air quality and human health, Arizona and New Mexico are among the worst locations for solar.”

The researchers assumed a social cost, to the environment and our health, of $20 per ton of carbon dioxide emitted. For other pollutants, they adopted a commonly used measure of $6 million per life lost from the exposure. They used hourly power plant data in 22 regions, and crunched the  numbers to measure what would happen if a Vestas V90-3.0-MW wind turbine were installed at more than 33,000 locations and a 1-kW photovoltaic (PV) solar panel at more than 900 locations across the United States.

The wind results were every bit as dramatic as the solar results, with California – which relies greatly on natural gas (about half as dirty as coal) for much of its electrical generation – again losing out:

Under the assumptions used here, wind turbines in Indiana provide the greatest annual health, environmental, and climate benefits – nearly $300/kW installed ($100/MWh).… By contrast, the combined benefits from the average wind turbine in California are $32/y ($13/MWh).

The paper took a stab at assessing whether a key subsidy for wind power, the production tax credit, yields benefits that outweigh its costs. They found that it did – looking at 2009, they saw a social benefit of $2.6 billion against a cost of $1.6 billion. That makes the PTC justifiable, the researchers said, but nationwide production-based subsidies are still “a crude policy instrument because they fail to reflect regional differences in the health, environmental, and climate benefits of renewables.”

They offered a better strategy would be a carbon tax or a cap-and-trade policy. That, the researchers wrote, would lead electricity generators and consumers to internalize the social costs. “Private investors would then choose locations for wind and solar installations according to the full cost of electricity, which would account for the regional differences.”

As with all studies, this one faced some limitations in its analysis. For one thing, it evaluated “the benefits of a near-term, small-scale intervention.” The potential problem there: “With increased penetration of wind or solar, conventional generators may be required to cycle more often, resulting in an emissions penalty.”

Even more importantly, the regulatory treatment of power plant emissions is in a state of flux now, as we all know. The study said that how that all shakes out could have a big effect on the level of estimated social benefits derived from wind and solar – although under at least one scenario, “regional variations persist.”

“Regional variations in the health, environmental, and climate benefits of wind and solar generation,” was published in the Proceedings of the National Academy of Sciences. The full paper is available online here.