A Texas tale of two winds

It was a curious stretch of time for wind power generation in Texas.

From mid-August to mid-September, the availability of wind generation in the most heavily-stocked market did a virtual U-turn.

Mid-August, as usual, was hot, stultifyingly so. On Thursday, August 13, at 1:00 a.m., demand for power in the Electric Reliability Council of Texas market was 43,237 MW. At that hour, the turbines were turning, generating  3,342 MW, meeting 7.7% of the early-morning demand.

Then, at 10:00 a.m., demand for power rose to 52,322 MW. However, the wind just wasn’t there. The wind turbines produced just 709 MW, meeting just 1.3% of the demand. By 4:00 p.m., with temperatures over 100 degrees, demand had reached 67,713 MW, while the wind turbines supplied a scant 844.61 MW, or 1.2% of the total.

The next day, August 14, the drop in wind generation was even more dramatic.  ERCOT wind power production at 1:00 am in the morning, August 14, was 6,341 MW. By 10:00 am, wind generation had dropped to 777 MW.

Then, a month later, things were quite different.

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On Sunday, September 13, wind generation set a new record, climbing to 11,467 MW, serving close to 30% of the demand. ERCOT’s previous record was 11,154 MW, set on February 19 of this year.

Heavy rains had cooled the air and winds were crisper. On Monday, September 14, total wind generation peaked at 11,351 MW.

Total wind output through mid-September was higher than any of the past three years. If wind generation just averages what it has in the fourth quarter from 2012 through 2014, total Texas wind generation output for 2015 will be at an all-time high.

The high winds that drive the wind turbines typically occur at night when demand is low or on the decline.

What can occur, and has, during high-wind times is real-time wholesale power prices have dropped into single-digit or negative territory as the grid operator reacts to an over-generation situation or the possibility of an over-generation situation, when there is too much power on the grid and not enough load to absorb it.

The high wind generation output, coupled with low natural gas prices, has resulted in some downward pressure on real-time wholesale power prices, particularly the off-peak prices.

Wind has always been intermittent(opens in a new tab), and this tale drives home the point that the variability is exacerbated by weather. The change in weather between August and September in Texas was significant enough to drastically affect wind generation, and the differences in generation demonstrate what we're seeing in many places(opens in a new tab) — and what may be seen in many more as wind generation expands(opens in a new tab) in the US.