Feb 27 - McClatchy-Tribune Regional News - R.A. Dyer Fort Worth Star-Telegram, Texas

Operators of the Texas power grid scrambled Tuesday night to keep the lights on after a sudden drop in wind power threatened to cause rolling blackouts, officials confirmed Wednesday.

At about 6:41 p.m., power grid operators ordered a shutoff of power to so-called interruptible customers, which are industrial electric users who have agreed previously to forego power in times of crisis. The move ensured continued stability of the grid after electric reserves dropped to alarmingly low levels.

Dottie Roark, a spokeswoman for the power grid, said a sudden uptick in electricity use coupled with a sudden drop in wind power caused the unexpected dip. As a result, grid officials immediately went to the second stage of its emergency blackout prevention plan.

"This situation means that there is a heightened risk of ... regular customers being dropped through rotating outages, but that would occur only if further contingencies occur, and only as a last resort to avoid the risk of a complete blackout," the State Operations Center stated in an e-mail notice to municipalities.

Known as the Electric Reliability Council of Texas, the quasi-governmental agency that manages the power grid must ensure that power generation and power use remain constantly in balance. Otherwise, the whole grid can go dark and the result is a system-wide blackout.

According to ERCOT, those interruptible customers who lost power Tuesday night had it restored within a couple of hours. The interruptible customers are generally industrial businesses that pay less for electricity in exchange for an agreement that they will let ERCOT cut their power during shortages.

Kent Saathoff, vice president for system operations at ERCOT, said Tuesday's event illustrates the inherent challenges associated with using wind power. Because the wind sometimes stops blowing without a moment's notice, engineers at ERCOT must remain nimble enough to respond to instability that can result from the resulting power dip on the grid, he said.

"There is a major workshop going on at our office right now to discuss these very issues," said Saathoff.

Although he said the emergency event was rare, it is not unprecedented. On April 16, 2006, for instance, a much more serious shortage prompted rolling blackouts across much of Texas. ERCOT officials at that time also ordered power curtailments for the state's interruptible customers.

That 2006 event was prompted largely by scorching heat coupled with a shutdown of several generators for spring maintenance. This time the shortage was prompted largely by a near total loss of wind generation.

Although ERCOT did not yet have precise figures Wednesday afternoon, Roark estimated that during the grid shortage wind power plummeted from about a "couple of thousand" megawatts to just "several hundred" megawatts. A single megawatt represents how much electricity it takes to power 500 to 700 homes under normal conditions.

Some critics have said that wind power, although providing a source of clean energy, also brings with it plenty of hidden costs and technical challenges. Besides requiring the construction of expensive transmission lines, the fickle nature of wind also means that the state cannot forgo the construction of other sorts of generators to replace that power on short notice.

"This is a warning to all those who think that renewable energy is the sole answer (to the state's power needs)," said Geoffrey Gay, an attorney representing Fort Worth and other North Texas municipalities in utility issues. "We can't put all our eggs in one basket when it comes to any form of generation. We need to consider the cost and the reliability issues, in addition to the environmental impact."