The major problem with wind as a power source is that it doesn’t blow all the time. To remedy that, Texas is spending $30 million a year to bolster its back-up power, in a change to the electricity grid that began on

Depending on the weather conditions and time of day, wind can provide a significant proportion of Texas power – as much as 16 percent at one point in the past week, according to Dan Jones, an independent market monitor for the Texas grid. Wind farms are sprouting so quickly in the western part of the state that Texas’s grid managers decided that they needed extra back-up power to cover shortfalls when the wind stops blowing.

Adding to the sense of urgency, Texas nearly experienced wind-related blackouts in February.

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Back-up power sources are always in place to handle minute-to-minute fluctuations in power supply and demand. Some power plants — usually gas plants — stand ready to deliver power at a moment’s notice as needs arise. These plants are responding not just to variations in wind, but to any unexpected uptick or downtick in demand or supply — say, when thousands of people suddenly turn on their air-conditioning at 2 p.m.

Beyond mitigating these minute-to-minute fluctuations, power systems generally maintain a number of back-up plants that are a bit slower to kick in — it takes about 30 minutes or so — but which really form the primary line of defense against blackouts.

In Texas, these back-up plants — typically natural gas plants — are often needed three to five days a month, according to Mr. Jones. It’s at this level of defense where Texas grid managers recently decided that they needed added capacity to account for wind’s variability and its significant place in the state’s power portfolio.

The requirements now call for some of these plants to be available at night, when demand is usually at its lowest. Why? Because nighttime is when the west Texas winds blow the strongest, and thus the risk is greater if the wind dies down. The new rules also require more of this reserve to be available during the daytime.

(Other, rarely used lines of defense against a statewide blackout include switching off the power to certain large users, in accordance with prior agreements, or — in an emergency — shutting off power to certain neighborhoods.)

Adding extra back-up power is only one of several ways that Texas is handling the influx of wind power into its grid. Grid managers are improving their methods for forecasting the wind day to day, said Mr. Jones. They are also trying to figure out ways to ease the strain caused by the rapid, significant changes in the wind, which unlike other supply sources, can very suddenly ramp up or die down.

More transmission lines are also sorely needed. In Texas turbines are sometimes forced to shut down on windy days, because there are not enough lines to carry the power they produce to the cities that need it.

Although Texas is far ahead in wind power, with 30 percent of the nation’s installed capacity, grid operators elsewhere in the country will be watching the changes there and improving their own abilities to integrate wind. The New York grid operator, for example, is also introducing better wind-forecasting techniques.

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