“Michael Goggin says that attacking the validity of the CEMS data is a sure sign of desperation. But it can be argued that any possible desperation is on the other side.”
In my 2014 post Where Wind Studies Go Wrong: Cullen in AEJ (Part II) , Michael Goggin of the Amercian Wind Energy Association (AWEA) made a comment that recently came to my attention, which deserves a rebuttal despite the lapse of time. My 2014 post critiqued a paper by Joseph Cullen, Measuring the Environmental Benefits of Wind-Generated Electricity.
In summary, Goggin’s points were as follows:
Goggin concludes his criticism by offering three references rebutting a report by the Renewable Energy Foundation (REF) that showed low wind-turbine lifetimes.
These four points do not withstand scrutiny.
I said the CEMS data was hourly based, which is correct. Cullen also said he used CEMS hourly emissions data.
With respect to the CEMS data, measuring every 15 minutes is subject to the same considerations as that described for load and wind production measurement at this time scale, described here in that it misses a lot of activity even within 15 minutes, and therefore it will not be taken into account.
Averaging these 15-minute measurements to be used for hourly reporting further reduces their value.
Also an IEA paper reports the questionable accuracy of emissions measurement systems (see page 35 here).
Regarding a contradiction between my posts and an article published by the IER re fuel consumption data, I followed Goggin’s link but found no contradictions or comments including such in the IER paper.
No matter. Any apparent contradiction might be explained on the basis that there are at least three ways to determine fuel consumption:
(1) exact measurement;
(2) a more general means of measurement, including some calculations, (like the CEMS approach to emissions); and
(3) back calculation from electricity produced using simplistic efficiency assumptions.
The first is the most difficult because of the nature of the generation technologies, and the other two are suspect because of likely errors in the assumptions and process used.
So it is possible to argue, without contradicting one’s self, that fuel consumption is suspect for the last two and good for the first. I would argue for exact measurement as the best approach, but admittedly not the easiest.
ERCOT and Texas
Turning to ERCOT, Goggin questions my analysis on the matter of interstate trade with reference to the difference between all-Texas and ERCOT. I introduced the term interstate to differentiate with imports/exports, which is often used for international transactions.
This has compounded the issue somewhat because ERCOT does not represent all of Texas, and it would have been better if I had left out this rather fine distinction in terminology.
ERCOT supplies 90% of the electricity consumption for Texas, and so my use of all-Texas data does introduce some imprecision. (Note I did introduce the analysis as ‘a quick test’.) The point was that outside electricity trade for ERCOT, although quite small (Cullen says less than 1%), is still about the same size as wind production (Cullen says about 2%), and these levels are similar to my analysis results for all-Texas as provided in Table 1.
In summary, the impact on emissions of such trade will be sufficiently comparable to wind that it should not be ignored in the analysis as Cullen suggests just because it is small. This level of consideration is often the case in other jurisdictions.
Goggin claims that to ask any Texas electricity regulator if ERCOT engages in interstate commerce in electricity will receive a forceful rebuttal. I think this shows how my introduction of the term ‘interstate’ compounded the issue. Such rebuttals may be based on the deceptively small levels involved, or simply by the use of the term ‘interstate’. All this aside, Cullen does speak to transactions with other jurisdictions, and that is what matters.
Wind Turbine Lifetimes
The issue of wind turbine life-times is more contentious. To start I suggest the reader go to my recent post and the cited Renewable Energy Foundation (REF) paper. (Note the link in my offshore wind post needs updating to that shown here and as indicated in Comment 3 of the that post.)
Goggin has attempted to rebut this with three references, which I have looked at. Those interested should read these three carefully for quality and clarity of analysis and then compare them to the REF treatment. I suggest that there is no absolute winner, and leave it to the reader to decide where the weight of evidence and its treatment lies.
In his lead off comment, Michael Goggin says that attacking the validity of the CEMS data is a sure sign of desperation. But it can be argued that any possible desperation is on the other side.