Saturday, August 6, 2011

Revisiting Rolling Blackouts in Texas

It was almost six months ago to the day that statewide rolling blackouts were imposed in Texas after frigid weather shut down dozens of generators.

Some may recall that on February 4, 2011, ERCOT (Electric Reliability Council of Texas), instituted the rolling black outs when the cold weather knocked over 50 electricity generating units, taking out about 7,000 megawatts of power generators, or about 8 percent of the installed capacity in the state.  Surprisingly, the rolling blackouts in Texas caused the shut down of compressors in West Texas that send natural gas to New Mexico, resulting in too low a pressure in the gas pipelines feeding several cities.  The lack of natural gas heating in New Mexico, in turn, caused a spike in electricity use, for alternative heating, which in turn, caused overloading of the electrical grid and rolling blackouts in New Mexico.  This was a really nice example of cascading energy failure, in my opinion.

Some pooh-poohed this as a freak, once in a +25 year, event.

But, once again Texas is looking at rolling blackouts, not because weather knocked out electricity generating units, but because of a prolonged heat wave with multiple consecutive weeks of temperatures above 100°F: 

HOUSTON, Aug 4 (Reuters) - The Texas power grid operator has scrambled this week to meet soaring electricity demand in the face of a brutal heatwave, and residents of the second most populous U.S. state are one power plant shutdown away from rolling blackouts.  Power demand for Electric Reliability Council of Texas, Inc, or ERCOT, which runs the power grid for most of the state, hit three consecutive records this week as Texans cranked up air conditioners to escape one of the hottest summers on record. Another record was not likely on Thursday, ERCOT said.  he grid operator on Thursday cut power to some big industrial users, and businesses and households face a repeat of the rolling blackouts they suffered in February, when a bitter cold snap interrupted power supplies.
Power usage in ERCOT reached its highest level ever on Wednesday at 68,294 megawatts, almost 4 percent over last year's peak.
Between 4,000 and 5,000 megawatts of generation was unavailable on Thursday, up about 1,000 MW from the previous day, ERCOT said.

The state's reserve margins have been running razor thin. On Wednesday ERCOT came within 50 megawatts of interrupting flows to industrial customers. That's equal to the output of about 25 industrial-scale windmills.

 One megawatt powers about 200 homes in Texas during hot weather when air conditioners are running for long periods.     More generation supplies would come in handy, but state power generators can't be expected to prepare for every extreme, said Kent Saathoff, ERCOT's vice president of system planning and operations.     "You have to determine if it is worth spending millions or billions to avoid a one in 10-year event," Saathoff told reporters on Wednesday.

ERCOT has about 73,000 MW of natural gas, coal, oil, nuclear and wind generating facilities, but not all of that capacity is available all the time.

Texas has the most wind power in the country, but the wind does not blow during the summer. ERCOT said it got about 2,000 MW from wind during the peak hour on Wednesday. Those wind farms can produce about 9,000 MW when all turbines are spinning.

Even some old, dormant gas-fired electrical generating plants have had to be pushed back into service.  For instance, the 40-year old plant featured in this story has a capacity of 921 megawatts, enough to power about 200,000 homes in the Texas summer:  Power to the people from dormant generating plant to help avoid a grid failure

And, as several power plants go off-line for routine maintenance this weekend, the potential for rolling blackouts continues:  Some power plants to go offline this weekend

Here’s a plot of the power consumption for the day mentioned in the Reuters article, August 3, 2011;

The all-time consumption record, circled in red, was reached at 5 pm in the afternoon of August 3—no doubt as people returning home from work cranked down their air conditioning.

If Texas’s capacity (red line) is about 73,000 MW at maximum—but not all available at one time—and utilization of 68,294 MW is within 50 MW of interrupting flows to industrial customers (i.e. 68344 MW; orange line), then my guess is that interruptions to residential customers will probably start to occur somewhere between 69,000-71,000 MW, unless a power plant generating more than a few thousand MW of power fails, or, goes off-line for maintenance. 

Well, maybe this is just another freak, once in a +25 year event, but I wouldn’t count on that. 

The likely result in the longer run, I think, is that threats of rolling blackout and grid failures will occur with increasing frequency, and, actual periodic blackouts will become a fact of life in the near future.

And, from the sounds of ERCOT’s VP, it doesn’t appear likely that the grid is going to be substantially expanded; perhaps because there just isn’t enough capital to do so. 

Wind to the rescue?

The Reuters article mentions wind power, and Texas has invested substantially in wind power in the past, so let’s consider the possibilities here.

Based on the Reuters article, wind turbines, at least in the summer, may only be about 22% efficient in Texas (i.e., 100% x 2000 MW/9000 MW).  Therefore, to provide a significant amount of ERCOT’s total electricity capacity from wind, say 10 percent, there would have to be a huge increase in the numbers of windmills in Texas. 

For instance, let’s take the Reuters article’s statement, that the output of 25 industrial-scale windmills equals 50 megawatts, as a reasonable measure of the capacity of typical modern-day windmills.  That’s equal to about 2 MW/windmill.  But, in the summer, we might only get about 22% of that power, or 0.44 MW/windmill.

Therefore, to provide just 10% of ERCOT’s total capacity (73,000 MW), in the summer, one would need another 5,300 MWs worth of windmill power, or 12,045 more windmills. 

This is actually pretty close to Texas’s goal to add 5,000 new megawatts of power from renewable sources, by 2015 and of 10,000 MW, by 2025. TEXAS RENEWABLE PORTFOLIO STANDARD SUMMARY. 

But, at a cost of about $3.5 million per 2MW capacity windmill (How much do wind turbines cost?) 12045 windmills will cost about $42 million billion.  Where will that capital come from in the present economy?

Moreover, the wind is variable, so it is quite possible for that 22% efficiency to drop down to 10-11%.  Unless you budgeted for this by over-building windmills, there would still be real risk of hitting maximum power capacity.   

In contrast, the one 40-year-old gas-fired plant's 921 MW capacity is equivalent to about 2093 windmills, each with a power generating capacity of 0.44 MW/windmill in the summer (i,e., assuming 22% efficiency).

If the intent is to replace the aging gas-fired power plants with windmills, then I expect that the  reliability of the power grid will go down, unless there is a substantial overbuild.  Keep in mind we are talking about only 10 percent of a present total capacity of 73,000 MW.  Want to grow in the future?  Well, if that growth requires more power, then I guess the answer is ... more windmills! (reminds me of this old SNL skit).

Anyway, in my opinion, ERCOT better take care of that 40-year-old gas-fired power plant and others like it—it sounds like a bargain to do so—so long as the natural gas lasts. 

It seems very likely that the demand for power will grow.  For instance, if power consumption grows by another 4%, the same percentage as it did this year, and there is an equally hot summer, then there probably would have been rolling blackout for several days this past week.

This story is specific to Texas, but I suspect that other areas of the USA and other countries have, or will be having similar problems, especially if we continue to have weather extremes in both winter and summer.

It is best to make your own plans to handle at least short term periods of electric grid power failure, whereever you live.

--August 9, 2011--

I've learned that the potential for blackouts in the future is even worse than I thought when I wrote this article:

Last month, the EPA included Texas in a new rule on cross-state pollution, catching many by surprise. Coal plants must reduce some emissions by half by Jan. 1, a deadline that has some operators saying they'll cut production or shutter facilities.
That means the state may not have enough electricity to meet spiking demand. The risk became painfully obvious last week after the heat wave set records for electricity usage and emergency measures were taken to prevent outages.
Texas doesn't have much extra capacity when temperatures hit extreme highs or lows, as we've seen this year. Even before the latest EPA rule, regulators worried about attracting more power generation for the fast-growing state.
Yet the EPA says the grid's reliability won't be jeopardized by the pollution controls or the deadline.
"Nearly half of the emissions of soot-forming sulfur dioxide covered by the rule are produced by just three plants, which in turn account for only about one-tenth of the state's electricity generation," EPA Assistant Administrator Gina McCarthy said in a statement.
But regulators, power generators and elected officials see a potential crisis.
"If we're short even three old coal plants, even if they're only [reduced by] 50 percent, we'd have rolling blackouts," Commissioner Kenneth Anderson said at a Texas Public Utility Commission meeting last week.
"I don't know what the EPA administrator is smoking in Washington," he said, "but they're flat-out wrong. It will have a reliability impact."
More shocks to the power supply are coming. The EPA is developing rules to reduce ozone, protect water and capture mercury. Those changes, however necessary, may force generators to reassess the entire fleet in Texas.
More retrofits won't make economic sense, so plants will be mothballed. And more incentives may be needed to attract a wave of new generation. ...
If those three coal-fired plants are shut down, thereby taking away 1/10 of Texas's electricity generating capacity, then rolling blackout will be a sure thing next summer, in my opinion.  A 10 percent reduction would take Texas's maximum capacity from 73,000 MW to 65,700 MW. But the peak use of power every week day last week exceeded that amount, and probably also in the weeks before that as well.    Even half of that, a 5 percent reduction to 69,350 MW, probably means rolling blackouts, as suggested by Ken Anderson, because not all of that maximum capacity is available at anyone time. 

My hunch is that it is unlikely that the EPA rules will get followed.  Continous rolling blackouts throughout the summer would wreck the economy of the state and probably put people in danger.  

No doubt this will make for great political theater come 2012. 

Still, it seems unlikely that any new coal-fired or gas-fired plants will be built within the coming years, and the potential is there for existing plants to get shut down.  All the more reason to make your own plans for having backup power.

Finally, if it does not make "economic sense" to retrofit three existing plants that generates 7,300 MW of Texas's total power, then will it make sense to spend the ~$58 billion needed to build the 16591 windmills needed to replace that power in the summer?


  1. "12045 windmills will cost about $42 million."

    $42 BILLION?

  2. Ha, ha that's a good find Taliesin, thanks. I'll correct the article.

    If ONLY $42 million would cover the cost--but that only buys 12 windmills.

  3. Texas oil wells need electricity to pump the oil and water, so any grid disruption will have an effect on oil production.

  4. To provide 5.3 GW of power, installing 10.6 GWp of PV (2x) would be cheaper. Assuming $3000/kWp (systems are already selling for less than this in Europe), the total cost would be $31.8 billion. PV would bring down the cost the peak wholesale electricity prices, as the most expensive gas peaking plants would rarely have to be fired up any more in summer. PV systems are almost maintenance free and run 25 years +.

  5. DaShui, I agree that this would be an issue if there were long term disruptions. This would also be an issue for natural gas, because natural gas also needs electricity to power the pumps for delievery to the cities, as made clear in the February freeze in 2011, that I referred to in the article.

    Anonymous, you raise interesting points about the Photovoltaics. However, my recollection was that of the 5,000 new megawatts planned to be added by Texas by 2015, only about 500 MW was to be PV. Maybe there should be a better balance between wind (good in the winter) and PV (good in the summer). Still, whether it is $42 billion or $32 billion, or something inbetween, my hunch is that there just won't by the capital available for these projects anytime soon, or, maybe ever.


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