Fact check: Post repeats false claims on wind and emissions

Willem Post has an article on the EnergyCollective blog regarding wind power and emissions reductions.  The following was posted as a comment.

Unfortunately for Mr. Post, repeating a myth does not make it true. Regular readers of EnergyCollective have probably seen a nearly identical posting from Mr. Post almost a dozen times already. In fact, since everything in this posting has already been debunked, I'll just copy and paste the previous debunkings below. However, I would be curious how Mr. Post would attempt to explain away this inconvenient truth, which conclusively tests and refutes his entire hypothesis:

The Department of Energy collects detailed data on the amount of fossil fuels consumed at power plants, as well as the amount of electricity produced by those power plants. By comparing how the efficiency of power plants has changed in states that have added significant amounts of wind energy against how it has changed in states that have not, one can test the hypothesis that wind energy is having a negative impact on the efficiency of fossil-fired power plants. The data clearly shows that there is no such relationship, and in fact states that use more wind energy have seen greater improvements in the efficiency of their fossil-fired power plants than states that use less wind energy. Specifically, coal plants in the 20 states that obtain the most electricity from wind saw their efficiency decline by only 1.00% between 2005 and 2010, versus 2.65% in the 30 other states. Increases in the efficiency at natural gas power plants were virtually identical in the top 20 wind states and the other states, at 1.89% and 2.03% improvements respectively. The conclusion that adding wind energy actually increases fossil plant efficiency makes intuitive sense, because adding wind energy to the grid displaces the output of the most expensive, and therefore least efficient, fossil-fired power plants first.

Previous debunking of playing statistical tricks with Irish grid operator data

Regarding Fred Udo's report on wind and emissions in Ireland, it only took a few minutes to unravel the statistical trick Mr. Udo was using to get his results, which might explain why his analysis wasn't published in a peer-reviewed journal and rather appears on an obscure Dutch anti-wind website.

This appears to be a classic case of a lurking (or confounding) variable being used to misleadingly present correlation as causality; a comparable example is arguing that cigarette lighters cause lung disease since people who buy them tend to develop lung disease. In this case, the lurking variable that is the actual causal factor appears to be cold weather and its impact on heating demand, data that Mr. Udo should have had access to but that (for reasons we can only speculate) he chose not to use in his correlational analysis.

What tipped me off was part 3, Figure 3 of his text, where Mr. Udo called out an event in Ireland around June 9-12, 2011, when the carbon intensity of Ireland’s electricity production surged. I was curious as to what might have caused that event so, on a hunch, I pulled weather records for Ireland. Sure enough, there was an abnormally cold spell when temperatures fell into the 30’s and 40’s F, 10 to 20 degrees below normal for that time of year. Aha! Cold temperatures cause a spike electric heating demand, causing the grid operator to turn on more expensive, less-efficient fossil plants to operate to meet the abnormally high electric demand.

Another factor is that cold weather could force some of Ireland’s fossil-fired combined heat and power (CHP) plants to fire up and run at a high level of heat production (and subsequently more emissions per megawatt-hour, MWh, of electricity, since CHP plants relative to the rest of the fleet are not optimized for electricity production, and CHP plants being run to produce maximum heat are not being operated in a way that is optimized for electricity production; moreover, it appears that the emissions associated with heat production are rolled into the data that Mr. Udo is using, so a CHP plant producing only or mostly heat and little or no electricity under cold conditions like these would score at infinite emissions/MWh).

As one would expect, cold spells and home heating demand often correlate with high wind speeds, which is how Mr. Udo was able to draw his false conclusion that wind was the causal factor. Sure enough, a closer examination of the spikes in emissions/MWh in his data show that all are associated with cold spells, and only some are associated with an increase in wind output. It doesn’t take a statistician to tell you which is the causal factor in that relationship. Had Mr. Udo himself been more interested in finding the actual causal relationship at play here, he might have noted that the correlations between wind output and emissions intensity varied widely from month to month (as one would expect for weather-driven seasonal changes in electric demand), usually a strong indication that another variable may be the actual causal factor.

I should also point out that, contrary to Mr. Udo’s claims, the method Irish utility system operator EirGrid uses to calculate emissions savings from wind is accurate. The plant-specific heat rate curve that they are using would account for all of the impacts wind energy would have on the efficiency of the fossil fleets under all operating conditions.

Summaries of government and grid operator data showing emissions have decreased as or more than expected in Colorado, Texas, and other regions as wind energy has been added to the grid, directly refuting Mr. Post's claims to the contrary:


Related articles:

Fourteen wind energy myths debunked, June 20, 2012
Fact check: Coverage of Argonne wind and emissions study flawed, June 1, 2012
Fact check: Bell missteps on utility integration of wind power, May 24, 2012
Fact check: Lomborg lacking on wind's economics, emissions reductions, March 23, 2012
Fact check: Roanoke Times op-ed misses a few key facts, March 13, 2012
Fact check: Silverstein errs on wind's variability, emissions cuts, February 27, 2012
Fact check: Pavlak errs on wind integration, February 14, 2012
Fact check: Trzupek Washington Times op-ed off base on wind's cost, utility integration, January 25, 2012
Fact check: New Dutch report misinformed on wind power and emissions, January 13, 2012
Fact check: Martikainen misguided on capabilities of renewable energy, December 1, 2011


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