Many of you will remember the original Star Trek episode, “The Trouble With Tribbles.” The Enterprise is transporting grain to a planet with the unlikely name of Sherman's Planet, which is in dispute between the Federation and the Klingon Empire. But Kirk et al discover their ship has been invaded by thousands of cute, furry, purring little critters called tribbles. They do no harm, except they eat voraciously and reproduce prodigiously. They're so cute that no one has the heart to do them any harm, but pretty soon, they've eaten all the grain and threaten to take over the ship. (Without going into plot details, Kirk and crew escape this predicament when Scotty, ever the resourceful engineer, beams the tribbles from the Enterprise onto a Klingon ship.)
Wind turbines are a little like tribbles. They're appealing, they can displace kilowatt-hours from carbon generators, and they seem to do no harm; but they consume prodigious amounts of money, and they're reproducing all over the countryside. Everybody seems to think they're wonderful, but are they going to contribute anything to our energy requirements? And, if they do, what are the downsides, if any?
Unfortunately, whatever wind turbines can do to reduce carbon emissions, wind capacity is not the silver bullet that will solve all our future electric supply needs. First, there's the concept that wind generation can eliminate other sources; this can be explicitly rebutted by the fact that it has a very low probability of being available during peak load periods.
For example, an independent study done for New York state in 2004 found that wind capacity has only a 10% to 11% probability of being available during summer peak hours (2 p.m. to 5 p.m.). And geographical diversity doesn't change that a bit — 1,000 MW spread over hundreds (or thousands) of miles would have the same 11% availability as 1,000 MW in a single location. That's not from a study, that's the laws of probability.
Perhaps more important, the more wind capacity an area has, the higher its Installed Reserve Requirement must be. To quantify this, I extrapolated sensitivity findings from a recent Loss of Load Expectation (LOLE) study, which used the 11% noted above. I discovered that, for every 1,000 MW of wind capacity, installed reserves would have to be increased by 80% (800 MW) to maintain the same “one day in 10 years” LOLE. Putting that another way, to displace 500 MW of thermal capacity, you'd need 2,500 MW of wind capacity.
The only way around this problem is major energy storage, but of course that would greatly increase the cost and could have environmental impacts of its own.
Then there's the unpredictability of wind output, or what I call its lack of “dispatchability.” A few years ago, I did an informal survey of operating managers I know in various parts of the country. I asked each of them how much wind penetration they thought their system could handle, given wind's lack of dispatchability. Independently, their answers all fell within a 20% to 25% range.
It won't be practical to move wind generation long distances over the grid, either. That's because of wind's low availability, as discussed above, coupled with the increased incremental I2R losses incurred for transfers. Again, without energy storage, wind capacity will not be economic over long distances. Those who are promoting massive transmission construction to accommodate remote and widely dispersed wind resources have a totally different agenda. As I said above, 1,000 MW spread over hundreds or thousands of miles would have the same 11% availability as 1,000 MW in one location.
Following the variations in wind output will be another problem. The amount of generation that control areas (a.k.a. balancing authorities) now devote to “regulation” — following the ever-changing load — in my opinion, will be inadequate to follow the ever-changing output of the wind turbines and the load. This is critical, of course, as any load/generation imbalance on the grid causes changes in grid frequency and even minor deviations from 60 Hz can be disastrous.
About a year ago I visited the smart grid lab of a major manufacturer. My impression after listening to and talking with the researchers was that a lot of people are planning to use what amounts to high-speed load management through smart grid chips in appliances to perform regulation function, and thereby keep load and generation in balance and thus maintain 60 Hz. I think it's highly questionable whether customers will tolerate this for very long. But there may be a more fundamental problem: I doubt that smart grid technology will be able to act quickly enough to effectively regulate the system. If I'm right, blackouts are inevitable.
Like most things, wind capacity has its pluses and minuses. We all need to be careful lest we embrace the former while ignoring the latter — and wind up with a shipload of tribbles … and no Klingon vessel by which to transport them.
George C. Loehr (gloehr@eLucem.com), the former executive director of a Regional Reliability Council, works as a consultant and expert witness, serves on several industry boards, teaches, writes and lectures on power system planning and reliability.