The cold wind from last week’s norther spun turbines that helped keep Texas furnaces running – but also stirred up questions about whether the state counts too much on the intermittent power source.
Amid freezing temperatures statewide Monday morning, Texas generating capacity was just one power plant failure away from falling short of Texans’ demand for power.
Wind power helped keep the lights on, providing about 1,800 megawatts of the 56,000 megawatts of generation capacity available that morning – enough wind power to provide electricity to at least 360,000 typical Texas residences.
But the close brush with blackouts Monday has some wondering if the state is depending too much on wind.
“The more the state relies on wind, there is a potential for having a very unstable grid,” said Ed Hirs, an energy economics professor at the University of Houston.
Wind advocates respond that while the breeze itself may be fickle, forecasting technology is such that grid operators can figure fairly precisely how much wind power will be available.
The Electric Reliability Council of Texas, which manages most of the state’s grid, includes a set amount of wind generation when projecting the state’s power capacity.
“The wind that morning was exactly what had been anticipated in the forecasting and modeling that takes place in the days prior,” said Jeff Clark, executive director of The Wind Coalition, an Austin-based nonprofit association focused on wind resources throughout the state and the Midwest. “This is very much a science.”
Hirs said, however, that wind capacity varies enough to make it inferior to nuclear or fossil fuel power plants for base load – the minimum power typically required around the clock – and peak load that occurs as demand rises and more plants come online. “Wind is not 100 percent reliable,” he said.
But wind planners say such criticism may not make enough distinction between wind itself and wind power capacity.
Weather forecasting technology has improved significantly in recent years, and the Texas grid has about a 90 percent to 95 percent accuracy rate in short-term wind projections, said Bill Blevins, manager of operations and planning for the Electric Reliability Council.
California – second only to Texas in wind power generation – uses the Lone Star state as its model for methodologies in predicting wind power, said Case Van Dam, chair of the California Wind Energy Collaborative and a professor of mechanical engineering at the University of California at Davis.
“The forecasts go out several days in advance, and of course there is some uncertainty in that,” Van Dam said. “But as you get closer to the day of operation, you get less uncertainty in those forecasts.”
In 2012, wind provided about 9 percent of Texas’ power, according to the American Wind Energy Association. But on Monday it only contributed about 3 percent of electricity used during peak demand, tempering any perception that wind alone saved the day and kept parts of the grid from going dark in rolling blackouts.
“It’s a nice story for wind, but it’s scary that they are relying on it in emergency situations,” said Adam Sinn, a Houston-based independent energy trader. “I think wind should be looked at as a buffer and that the grid should always have fossil fuel resources to prevent an event.”
The number of wind turbines available doesn’t vary much from day to day, but the wind needed to turn them does. For example, a cold front in February 2013 included strong winds. Wind generation ended up providing 28 percent of the system load on Feb. 9, 2013, adding what then was a record 9,481 megawatts.
But planners can’t count on such windblown bounty, and instead have to predict how much power to expect from wind-driven generators based on weather conditions.
The state has more than 12,000 megawatts of wind capacity – the amount all the turbines could produce if operating at full tilt – and that figure is set to reach 14,000 megawatts by the end of this year.
But because of wind’s variable nature, the Electric Reliability Council only includes 8.7 percent of wind turbines’ total capacity in estimating available power at peak conditions, even though the turbines often generate much more.
While Monday morning’s wind was much lower than the previous or following mornings, it still exceeded the 8.7 percent standard, providing around 15 percent of total capacity – and right on target with forecasts, said Clark of The Wind Coalition.
“The wind is a variable resource, but the important thing is that it is not a random resource,” Clark said. “It is highly predictable, it is forecastable and in this situation, the forecast and the actual generation were very close together.”
How wind is calculated as an available resource will be a key question in continuing debates over whether Texas has sufficient generation capacity to keep a safety margin when demand is greatest, usually to run air conditioners on the hottest summer days.
ERCOT had considered a proposal by technical advisors last year to increase the amount of wind capacity in its forecasts to 14.2 percent for non-coastal wind resources and 32.9 percent for coastal wind resources, but has delayed any decisions on the proposal until later this year.
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