Sunday, October 27, 2013

Revisiting Texas's Electrical Power Predicament—Part 1

I have written about Texas's electric power situation a few times over the past few years, and now, it's time for an update. 

I wrote about Rolling Blackouts in the South Western USA due to the shut down of multiple electrical power generating plants in Texas during a cold snap in February 2011, with cascading effects on the ability of neighboring state New Mexico's ability to receive pipeline shipments of natural gas and have rolling blackout of there own. 

As I discussed in August 2011 Revisiting Rolling Blackouts in Texas, rolling blackouts nearly reoccurred, as the State faced what turned out to be the hottest summer on record, for Texas and some neighboring states. The body responsible for managing electric power flow for ~85% Texas, Electric Reliability Council of Texas (ERCOT), estimated that the State came within 50 megawatts (MW) of interrupting flows to industrial customers, that is, industrial load shedding. 

In January 2012 I took a more in depth look at Texas's Electrical Power Predicament with a three part series (see Part 1, Part2, Part3).  Back then, my assessment was that there were three factors all conspiring to squeeze Texas's ability to sufficiently maintain or grow it's electric power supply to avoid rolling blackouts:

            1) increasing demand due to growth in population and increasing economic activity;

            2)  the implementation of several rules by the EPA that would cause some of Texas's older coal-fired power plants to shut-down; and

            3) the unlikelihood of alternative electrical energy sources being built in time or have sufficient capacity to meet the expected summer power demand.

Maybe some think that should have added a fourth factor: ever-increasing hotter summers, but, I did not see this as necessary condition to cause an increasing mismatch in electricity supply and demand sufficient to cause rolling blackouts.   All that would be needed are summers as hot as the summer of 2011, a continuation of the population and economic growth trends, the announced closure of certain coal-fired power plants and a lack in adequate growth or capacity in new power sources.  For instance, in some of the scenarios I ran in my earlier series (Scenarios 1 and 2, Part2), assuming exactly the same energy demand as in 2011, predicted the possibility of anywhere from 12 to 17 of industrial load shedding and from 1 to 11 days of general rolling blackouts for the month of August, that could be applicable to 2012 and 2013. 

Happily, these predictions were wrong.  Most of the rest of this article explores the three above-mentioned factors to assess what did not happen to cause the prediction to fail.

Texas's population, economy and forward predictions

One possibility is that Texas's population growth or economic growth have stopped or at least slowed down since 2011 and therefore the expected demand for electric power was not forthcoming.

The data shown in Figure 1 suggest that this has not been the case.

Figure 1 shows Texas’s population and annual GDP (left and right axis respectively) from 1987-2012 and some projections through 2015.  The blue line and symbols corresponds to the Texas GDP based on US census bureau estimates with projections for 2012 and on from USA Government Spending.   The red line and symbols shows Texas's population from the Texas State Library based on US census bureau estimates.  The green line and symbols shows population estimates and projections from the Texas Department of State Health Services).  The vertical line divides the 2012 and earlier data estimates from the projections for 2013 to 2015. 

From 2011 to 2012, Texas's population according to the US census bureau data increased by 1.5 percent/year.   The Texas DSHS estimate is higher at 2 percent/year.   A 2 percent/year population growth rate is closer to Texas's average yearly rate of 1.97±0.63 percent/year (last 20 year average and SD) using the US census bureau data.  Texas's population growth rate is about double the USA's yearly rate of 1.05±0.58 percent/year (last 20 year average and SD).  The Texas DSHS projections for 2013-2015 suggest continued growth rates of 2 percent/year. 

From 2011 to 2012, Texas's GDP was estimated to increase 5.8 percent percent/year.  That is slightly lower than the 20 year average of 6.3±3.3.  The GDP is projected to increase by 4.4 to 5.8 percent/year for 2013-2015. 

Overall then, there are few signs of any significant downturn or slowdown in Texas's population, economic growth, or, in government expectations of growth going forwards.  In a previous post, I showed that Texas's electric generation capacity has been growing at about 2 percent percent/year to match the population growth rate (Part 1 Figure 3).  I would expect that the growth rate is power generation would have to stay at 2 percent/year just to keep up with the population growth rate. 

Texas's summer weather

Another possibility is that there have been cooler summers in Texas and therefore less electricity demand, since in the summer, air-conditioning can account for a substantial amount of electric power use. 

Data reported by the Southern Regional Climate Center suggests that the summers 2012 and 2013 were not particularly hot, at least compared to the summer of 2011. 

Figure 2 shows the average monthly temperatures for Texas for the last 20 years for the months of June, July August and September (caution the vertical scales for each month are not the same). 

The red circles highlight the average temperatures for 2011, which was high for June, July and August, but not so high for September, as compare to the previous years since 1993 or compared to 2012 and 2013.  In contrast 2012 and 2013 average temperatures are closer to trend line for this period. 

So, electric power consumption in Texas benefited from having typical summer temperatures in 2012 and 2013. 

Texas's summer electrical power consumption. 

Of course, Figure 1 and 2 doesn't tell us about daily high temperatures, which typically occur in the mid-to-late afternoon, and would typical be the cause of electrical power demand spikes as people return to their residence and turn on the AC to cool the house down.

To get a better view of this, you have to look at the actual hour-by-hour power loads. 

I still have the hourly load date for the July August and September 2011, but sadly I did not save the data for June 2011, which is no longer available at ERCOT's website.  I am saving the data for June-Sept 2012 and June-Sept 2013 before these disappear as well.

Figure 3 shows the hourly loads for August 2011 (red) August 2012 (green) and August 2013 (blue).  The solid pink line shows ERCOTs estimated capacity to produce electricity (73000 MW), and, the orange line shows the point where industrial load shedding would begin (68344 MW), circa August 2011.

In August 2011, there were several days in early and mid-August that got close (e.g., within 1500 MW or 66844 MW) of industry load shedding in the late afternoon): Aug 1, Aug 2, Aug 3, Aug 9, Aug 18, Aug 19.  The all-time peak for 2011 was 68293 MW at 4 pm Aug 3.  That was about 50 MW away from load shedding.

In contrast, for Aug 2012, only one day reach similar levels: Aug 1 at 66489 MW.  In fact, this was the only day in the summer of 2012 that exceeded 66,000 MW.

For Aug 2013, there were a few more days where power consumption exceeded 66,000 MW: Aug 5, Aug 6 and Aug 7, with Aug 7 being the highest at 67180 MW—that's 1164 MW less than the all time peak day of Aug 3, 2011.


Even though Texas's population and economy has continued growing at the same pace as in 2011, its power consumption was not as high in 2012 and 2013 as in 2011.  Probably average summer weather, at least cooler than 2011, had a lot to do with this.  For the last two years, Texas has been lucky by having just average summer temperatures. 

One thing that is apparent to me is that Texas is in a race to grow its power generation at least at the same rate as its rate of population increase, with the severity of summer weather thrown in as a wild card.  

So what about those older coal fired power plants that in 2011 were expected to be shut down under the EPA enforced clean air act and various anti-pollution rules?

In part 2, I will discuss Texas's coal-fired plants and other potentially sources of electricity that may or may not be coming in the near future.
January 19, 2014: clean up the legend to Figure 1 and correct some spelling and grammer issues.

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