Beyond Intermittency


Forecasting brings wind energy under control.

Forecasting brings wind energy under control.

Fortnightly Magazine - May 2010

Advancements in forecasting have improved the reliability of day-ahead and hour-ahead estimates of wind generation. Wind never will behave like a base-load power plant. But as system operators integrate wind forecasts into their planning and market processes, they’re transforming intermittent wind energy into a variable but reliable resource.

When transmission system operators think about wind power, two problems leap to mind. First, wind resources tend to be located far away from load centers, so new wind farms sprouting up across the countryside will require new long-distance transmission lines. Second, for purposes of system operations, wind is an “intermittent” source of power—unpredictable and non-dispatchable. As a result, operators have viewed wind power as an energy-only resource, essentially useless (and sometimes detrimental) for system reliability and security.

The first issue, the need to build transmission capacity to serve wind farms, is part of the hottest regulatory debate in the industry today. Namely, who should pay for new transmission capacity that arguably won’t benefit all customers equally, and how should it be regulated? ( See, for example, Bruce Radford’s “ Taking Green Private ” March 2010, and “ T Party Revolt ,” October 2009 ). But while this argument has raged in FERC hearings and other forums, the second problem steadily has diminished in importance.

Advancements in wind forecasting in recent years have vastly improved the reliability of day-ahead and hour-ahead estimates of wind generation. And as system operators, utilities and energy traders integrate wind forecasts into their planning and operations, they’re transforming wind’s reputation. What system operators once considered a wholly unreliable resource, they increasingly view as a predictable and manageable source of emissions-free energy.

“The industry is moving away from using the word ‘intermittent’ and started using the word ‘variable,’” says Kevin Sullivan, a senior vice president with KEMA Consulting. “The word ‘variable’ implies control. That change in thinking has happened because the technology has improved to make wind energy more manageable.”

Also, this change might be attributable, at least in part, to the wind industry’s own public-relations efforts. For instance, the American Wind Energy Association advocacy group studiously avoids using the term “intermittent” because it implies complete unpredictability. However, even though forecasting technologies and operational practices are bringing wind out of the “intermittency” ghetto, the industry still has work to do before system operators will treat wind as a generating capacity resource.

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“Wind forecasting helps, because the more you can reduce uncertainty around scheduling, the more you can fit wind generation into the system,” says Mark Ahlstrom, CEO of forecasting company WindLogics. “But you’ll never be able to lock it in a day ahead and treat it like a coal plant, because of the nature of the wind resource. Forecasting will never be perfect all the time.”

System operators don’t need it to be perfect; they need it to be highly predictable. And with recent and ongoing technology developments, that goal now appears to be within sight.

Dispatchable Wind

In mid-April 2010,