I heard that Texas has not allowed electric stations to be built for about 15 years. They don’t have the capacity for an extra load like this.
http://www.powermag.com/POWERnews/2371.html
December 23, 2009
Texas has added some 3,140 MW of new generation capacity since May, mostly from coal and natural gas–fired power plants, the grid operator for most of the state said in a capacity, demand, and reserve update released last week.
About 1,690 MW of that new capacity was from new coal plants while 1,093 MW was from natural gas plants, the report (PDF) from the Electric Reliability Council of Texas (ERCOT) revealed. The region’s total resources were projected at 76,363 MW in 2010 and 78,017 MW in 2015.
ERCOT said that the state’s reserve margin’s are forecast to remain above the 12.5% target minimum through 2013—but drop below the desired reserves beginning in 2014 to 12.3% and 10.2% in 2015.
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This peak wasn’t near the summer peaks. The problem[s] seemed to be with plant design that didn’t provide for adequate protection of vital equipment needed when these freezing conditions occurred. Apparently a lot of stuff froze [pipes, instruments, control devices, etc] thus shutting down the generators.
I am without a link, but I read yesterday that some 12,000 MW of generating capacity were off line for maintenance before the event started (note that in areas with summer peaks, winter, late fall, and early spring are peak maintenance seasons). The article also noted some 7000 MW of generation was forced off line, or wasn’t available due to weather issues (burst pipes, unavailable gas, frozen sensors, etc.). That’s 17,000 unavailable out of their capacity (based on your figures) of 76,363 MW. That would put ERCOT below 60,000 MW. Figure in the typical availablity of wind, and that probably takez a little more out of the available mix.
Now, consider that they must operate with contingency reserves, and in an area the size of ERCOT, that reserve probably equals 2 or 3 single contingencies. Otherwise, the loss of a single large generating unit would likely cause a total blackout, after which it would be days before power was restored. So, figuring that they must have reserves for their 2 largest possible contingency events, the actual available generating capacity is reduced 2000-3000 more MW.
I don’t have exact load figures for Texas for this type of weather, but I think that it’s fairly obvious that it was more than the available resources. Otherwise, they would not have resorted to rolling blackouts to maintain the integrity of the grid.
I will note that some of the rolling blackouts might have been due to localized issues as well. For example, El Paso is not in ERCOT but in the Western Interconnection. While there was plenty of power available in the western interconnection to supply the needs of El Paso, the transmission capacity does not/did not exist to move the power from remote locations to El Paso. Consequently, El Paso had to resort to rolling blackouts as well until their local generating fleet could be restored to an adequate level.