Re: Multiple comments on existing windmills that are mostly not running.

Since wind input is a variable quantity, windmills generally can only be used as "peaking sources." The distribution systems require "base capacity" that is always available, and for this fueled generators, whether coal, oil, or nuclear, are about the only things available. Hydro power generally would be included in base capacity, but is only available in limited areas.

As long as the fixed generators can supply all the needed power, dumping additional power in from the windmills would be counterproductive, since it would require reducing the output of the baseline generators to maintain stable distribution network conditions. The fixed/baseline generators operate most efficiently at output near their rated capacity, and actually have little margin for "tweaking" output. A change in baseline output generally requires turning on/off individual machines/plants which is not just a matter of flipping a switch. Restarting a large generator can take several hours, and turning one off takes (often) about half as long as bringing one back on line.

Wind generators may be idle because there is insufficient wind available at a given time (or rarely if there's too much wind for safe operation at a given time) but since as currently used they can only supply "peaking power" when and as needed by the grid, they may be shut down during low-demand periods. It doesn't necessarily mean that they're not available to meet an increase in demand, or that they're broke down and/or inefficient.

A "windmill farm" generally contracts to provide a certain amount of power continuously, based on the minum wind expected, and must have enough individual windmills to "meet contract commitments" when there's little useful wind. Any time there is more than minimum wind, it's more efficient to run only part of the windmills at higher power, and turn off the ones not needed, than to run all of them at reduced output. IF the farm can find a buyer for an additional bit of power, more of them may be started up; but it depends on instantaneous market conditions whether it's profitable to do so.

Some maintenance, and downtime for safety inspections etc., is required, and a "typical" downtime allowance of something like 10% or a little less is "planned maintenance." This means that if 10% of the mills aren't running they're doing what they should be doing.

If 90% of them aren't running, it's more likely that it's inefficiency in the power market than that the windmills are defective. Europe, especially, does have some "early design" windmills that have had reliability problems; but you'd have to talk to the operating engineers to know if that's why they don't run more.

If, as may happen someday, there were enough widely dispersed windmill farms to depend realiable on "one of them somewhere" will always be able to provide at least X kw, then a fraction of the total windmill capacity could be considered part of the "base capacity" and you'd always be getting at least some of your electrons from wind. In some markets that point may have been reached; but I haven't seen confirmation of it.

John