Texas will have enough power to serve consumer needs within the Electric Reliability Council of Texas (ERCOT) during the fall, a new seasonal assessment of resource adequacy (SARA) shows. The assessment, released on Tuesday, comes on the heels of announced plans by the state’s largest generator Luminant to mothball its coal-fired Monticello 1 and 2 units, each rated 582 MW, for at least six months.

ERCOT’s SARA shows that the grid operator for most of Texas expects to have more than 74,500 MW of generation capacity to serve anticipated peak demand of about 53,000 MW through October and November. Available operating reserves could range from about 12,700 MW, based on five-year average generation outages, to as low as 3,300 MW if more extreme temperatures and above-average outages occur.

"Although there is always the possibility that extreme weather conditions or an unusual number of generation outages could create unforeseen conditions, we expect to have enough power available to serve a range of scenarios," said Warren Lasher, ERCOT’s director of System Planning, in a statement on Tuesday.

A preliminary winter forecast that provides an early analysis of possible conditions later this year and early in 2013 shows that ERCOT would also have enough generation to serve expected load patterns. “Winter in the ERCOT region typically does not drive electric use to the levels the grid experiences during summer. Rare cases of sustained extremely cold temperatures can affect generation performance and drive up electric demand, especially in those areas within the ERCOT region where consumers rely primarily on electricity for heating,” ERCOT said.

But extreme winter weather conditions and more generation outages than usual could prompt the grid operator to implement steps to ensure reliability, including calling on contracted demand response resources or even rotating outages, depending on the severity of the situation, it warned. A cold snap in February 2011 forced ERCOT to begin rotating blackouts throughout Texas to compensate for 7,000 MW of power plants that had tripped due to the extreme cold.

Luminant said in a filing with ERCOT that it would mothball its Monticello 1 and 2 units in North Texas starting Dec. 1 for a period of six to seven months, citing weak wholesale prices. The company had planned to close the units temporarily in 2012 to comply with the Cross-State Air Pollution Rule, but following a stay on that rule by a federal appeals court in December 2011, Luminant continued to run the units.

ERCOT said in its newest SARA that a combined 613 MW are expected to be mothballed this fall, including  NRG’s SR Bertron 3 and 4, Applied Energy G1, and Whitney Dam 1. The SR Bertron units 3 and 4, totaling 460 MW, were mothballed last year but restarted in June to help meet high summer demand.

The grid operator also said it was "evaluating" Luminant’s request to mothball the 1,160 MW represented by the Monticello units. Even without those units, the region was forecast to have 65,843 MW of installed capacity compared to 58,138 MW of projected peak demand over the winter, the grid operator said.

Sources: POWERnews, ERCOT

—Sonal Patel, Senior Writer (@POWERmagazine)