Letters to the Editor

Fortnightly Magazine - October 2010

Green Blackouts?

While Robert Blohm’s article (Op-Ed, “Green Blackouts,” August 2010) did correctly highlight the problem of declining frequency response on our power grid, his attempt to blame the problem on wind energy defies logic for several reasons:

1) Modern wind plants can provide frequency response as well as, or better than, conventional power plants. NERC, the entity responsible for maintaining bulk power system reliability in North America, noted in a report last year that modern wind turbines, with their advanced power electronics, “can provide comparable inertial response/performance to a conventional generator.”

2) As the chart in Mr. Blohm’s article makes clear, frequency response on our power grid has been steadily declining for decades. This decline pre-dates the rapid growth of wind energy over the last five years by at least a decade, making Blohm’s decision to blame this problem on wind akin to accusing someone of committing a crime that occurred a decade before they were born.

3) As Blohm also discusses in his article, nuclear power plants, which provide roughly 20 percent of America’s electricity, don’t provide frequency response. Coal power plants, which provide nearly 50 percent of America’s electricity, are increasingly operated so that they also provide little or no frequency response. Anyone attempting to determine what caused the decline in frequency response over the last several decades might be better served by looking at the resources that accounted for 70 percent of the generation mix, rather than focusing on wind energy, a resource that accounted for a fraction of 1 percent of the generation mix over the bulk of that period.

4) It’s also important to remember that frequency response capability is primarily needed to maintain power system reliability in case a large fossil or nuclear power plant experiences a forced outage and suddenly goes offline. Contrary to what Mr. Blohm claims, the variability of wind plants contributes little or nothing to the need for these fast-acting reserves. Changes in wind energy output occur gradually over the course of an hour or more, particularly when a number of wind plants are aggregated over a large area. In contrast, large nuclear or fossil plants can take 1,000 MW or more of generation offline in a fraction of a second, making the use of fast-acting frequency response a necessity.

Mr. Blohm was somehow able to twist these facts and take what should have been a success story for wind energy: “Wind plants are stepping up to provide frequency response capability, filling the void as conventional generators have failed to self-provide the reserves that they need to reliably integrate themselves with the grid,” and instead turn it into an attack on wind energy. Unfortunately, it’s all too easy to blame a problem on the new guy instead of taking an objective look at the facts and assigning blame and credit where they’re due.

Michael Goggin, Manager of Transmission Policy, American Wind Energy Association, Washington, D.C.

 

The Author Responds:

I don’t blame the national frequency response shortage on wind energy and I don’t twist facts.

1) I say the renewable energy agenda will make the “free rider” problem of not apportioning responsibility to the parties creating and offsetting rapid frequency change worse before we’ve solved it. Not only does wind penetration fail to increase our capability of managing variability that wind contributes to, but also it means displacement of fossil generation that could have provided that capability.

2) To provide rapid “governor response” reserve comparable to the 5 to 7 percent of capacity traditional fossil provides, wind, whose capacity (utilization) factor is a mere 5 to 30 percent, would need to back-down a reserve margin of 17 to 140 percent. Anything approaching 100 percent or more is, of course, impossible, while the rest of the range is easily uneconomic.

3) Yes, wind turbines can be programmed to provide inertial response (by the rotating blades), but only newer wind turbines have this capability, which only slows down frequency deterioration. Only governor response stops and begins reversal of the deterioration. This is illustrated by an alarming graph [in a presentation to NERC last year] showing the Eastern Interconnection’s inability immediately to begin reversal of, or even to stop completely, a sudden drop in frequency, contrary to the normal picture in Fig. 2 of my article. [See Robert W. Cummings “Overview Frequency Response Initiative,” North American Electric Reliability Corp., (Princeton, NJ), July 28, 2009, p. 30.]

4) Yes, change in wind is often in a somewhat slower but still rapid “regulation” range, but the megawatt changes are large and have huge requirements for regulation reserves. Those reserves are not redeployable, like governor response is, and are no substitute for governor response; to the contrary, they require proportionately more governor response on the system to back them up once those reserves are exhausted.–Robert Blohm