Offshore wind power critic James O'Neil says wind power is the most unreliable type of renewable energy

The debate over Deepwater Wind’s plans to build two wind energy projects in the waters off Rhode Island and Massachusetts has raised several issues.

Critics say the energy from the five turbines the Providence company initially plans off Block Island and the more than 100 turbines to be built farther offshore would be unnecessarily expensive.

Former Rhode Island Attorney General James O'Neil, a lawyer who is fighting the projects, also questioned the reliability of wind energy when he appeared on the "10 News Conference" program that aired Sept. 1.

"It's not about the green movement. It's about what I call the Green Bucks Movement," O’Neil said. "You have to consider the economic consequences of embarking on a mission which is going into the unknown. We do know a couple of things. We know that wind power is the most undependable form of renewable energy."

That claim caught our ear. We know the wind doesn't blow all the time. But, then again, it does blow at night, when renewable solar energy can't produce electricity. So which form is less dependable?

When we asked O'Neil for his data, he offered some documents that didn't actually compare the various forms of energy. One unpublished analysis offered no basis for that comparison. He also suggested some people to interview.

As we learned, there's a lot of debate over the matter.

When you ask the experts about dependability, they talk about several issues, among them the likelihood of mechanical breakdown, the availability of what we will loosely call "fuel" (which includes wind and sun), whether a source can generate power when it is most needed and, from a broader perspective, whether the power grid can quickly tap power from other sources to compensate when one source fails.

Fossil fuel plants break down all the time, said Willett Kempton of the University of Delaware and coauthor of a 2012 study on integrating renewable energy into the power grid.

When it comes to breaking down, "generally, wind turbines are more reliable than thermal plants" such as those powered by natural gas, coal or nuclear, he said. Solar cells, with few, if any, moving parts, are least prone to mechanical breakdown, giving it an edge over the renewable forms O'Neil was talking about.

So a more relevant issue for renewable sources is the availability of fuel, particularly wind and daylight, which vary by location. (That's not a problem with renewable energy such as geothermal because the Earth is always giving off heat.)

O'Neil, like other critics, argued that a key problem with wind power is its unpredictability, but Kempton said you can predict when the wind will be blowing. We note that the National Weather Service predicts both the amount of cloud cover and the average sustained wind on an hourly basis six days in advance.

That brings us to a third element of dependability: whether the power is produced when you need it.

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William P. Short III, a New York renewable energy consultant who has testified against Deepwater’s Block Island project, said that's why wind is less dependable than solar. Solar usually produces power when the demand is highest, while winds kick up, at least on land-based wind farms, after dark, when demand is lower.

But Michael Womersley, a professor of human ecology at Unity College in Maine, disagreed. "You tend to get more wind during the day than at night."

The other experts we consulted said that's not important because other parts of the power grid can ramp production up or down to compensate.

The ability of power plants to throttle up or down to respond to demand, and to do it quickly, is a fourth issue surrounding dependability. It's what experts call dispatchability, said  Paul Roberti, a commissioner with the Rhode Island Public Utilities Commission. Fossil fuel plants are much more adept at that than wind or solar.

In the end, we turned to the U.S. Energy Information Administration, which regularly analyzes various forms of electrical generation to assess cost and capacity. Its latest report, which looks at projects expected to be working by 2018, is billed as "a convenient summary measure of the overall competitiveness of different generating technologies."

The report includes a measure of capacity, which spokesman Jonathan Cogan said is a way to gauge the reliability or dependability of the latest technologies. The higher the number, the more you should be able to depend on it for power, although the actual percentage will vary by region when it comes to renewable resources.

Nuclear and fossil fuel plants typically have capacity factors ranging from 85 percent to 90 percent. But O'Neil was talking about renewable energy.

In the EIA ranking, geothermal comes in at 92 percent, biomass is at 83 percent, hydroelectric power is at 52 percent, offshore wind is 37 percent, onshore wind is 34 percent, solar panels that generate electricity directly are at 25 percent and solar-thermal, where the sun heats a substance to generate power, is at 20 percent.

So on a nationwide basis, wind power -- whether it's onshore or offshore -- operates at a higher capacity than solar, according to the EIA.

In response, O'Neil said his "statement that wind is the most undependable form of renewable energy remains my opinion" and, in the competition between wind and solar, "it is rather a close call as neither is the most reliable form of renewable energy."

Our ruling

In terms of energy, dependability can mean different things to different people, and both solar and wind have their strengths and weaknesses. And the actual dependability of each technology is going to rely -- to quote the old real estate joke -- on three things: location, location and location.

The only national ranking we found was done by the U.S. Energy Information Administration, which takes various dependability measures into account. In that ranking, wind is less dependable than hydro, geothermal or biomass but more dependable than solar cells and solar-thermal.

O'Neil made an unequivocal and over-arching assertion, but provided no useful support for it. The most convincing evidence we found says he's wrong. We rate his statement False.

(If you have a claim you’d like PolitiFact Rhode Island to check, e-mail us at [email protected]. And follow us on Twitter: @politifactri.)