United States

United States

Trent Mesa constrained

American Electric Power (AEP) and Enron Wind completed in November their $160 million Trent Mesa project between Abilene and Sweetwater in West Texas. AEP is taking a portion of the output and selling the remainder to TXU Electric. But until upgrades are made to the transmission grid in the area, the 150 MW project will operate under a special protection scheme that could take the line out of service if local transmission lines fail.

All wind projects built in 2001 are in West Texas, but most of the state's population lives to the east and transmission constraints limit power flow in that direction. According to AEP's Rick Walker, a pending transmission upgrade in West Texas will fix the immediate problem for Trent Mesa, but future expansions at the site will require better transmission in the area.

The Lower Colorado River Authority (LCRA) is planning the first improvement, a $21.7 million upgrade to a transmission line currently owned by TXU Electric. It says it will recover the cost of the project through transmission rates, regulated by the Public Utility Commission of Texas. Once the new line is completed in 2003, LCRA promises to give the West Texas transmission system enough additional capacity to deliver power from projects that are now in the works.

Yet according to the Electric Reliability Council of Texas (ERCOT), which controls 37,000 miles of transmission line in Texas, further upgrades to the West Texas transmission system will still be needed to handle any future wind and other renewable energy generation. ERCOT is identifying those transmission projects, but the process of siting and building new transmission in the state is proving to move much slower than it takes to develop even the largest wind project, according to ERCOT's Juan Santos. He says ERCOT's transmission constraints in the area sometimes top 1000-1300 MW, but his agency is meeting with wind developers and utilities in early December to discuss how to build a wind generation model and what it will need to do to accommodate future wind projects.

Walker says one way to address the problem of the time differences in building wind and transmission projects is for wind power developers to get further ahead of the curve with more advanced planning and to feed that information into the transmission planning process sooner. Mark Kepner of Austin Energy, the City of Austin's municipal electric utility arm, thinks that storage could provide some help. "The transmission system sees lots of swings in loads," he says. "Wind could go a long ways to filling the valleys." Still others say that it takes very little public opposition to a transmission project to slow the process of getting Certificates of Convenience and Necessity, another issue ERCOT could deal with.

AEP had already expanded the Trent Mesa project from 130 MW to 150 MW in July (Windpower Monthly, August 2001) and it could expand even more, says Walker, but that will depend on how quick transmission upgrades are made.

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