Article claims if gas rather than hydro is used as a backup the overall impact of wind energy might be to increase rather than decrease C02 emissions.

http://www.clepair.net/IerlandUdo.html

Wind energy in the Irish power system
Fred Udo

Selected Quotes

The April data of the Irish electricity system shows clearly, that the combination of wind energy with gas turbines does not achieve the goal of CO2 emission reduction, if no storage of energy is present. In general it is shown that the CO2 saving decreases with increasing wind contribution to the electricity supply.

This analysis does not take into account the energy necessary to ramp the conventional generators up and down nor the energy to build windturbines nor the extra transmission lines with their additional losses. It is highly probable, that taking al these effects into account will show, that the few per cent gain in CO2 will revert to a loss (i.e. an increase in CO2).

Errr...

"The Irish system performs slightly better in other months probably due to the greater contribution of hydropower, but it never comes near to the promises made by wind energy advocates."

It's worth taking time to actually read the article very carefully.

"It appears, that the drought in the first half of the year 2011 has adversely affected the use of hydropower in the months April to June 2011. This enables us to study the CO2 emissions in absence of hydro power."

"The utilisation of the pumped hydropower station during 2011 is affected by a renovation of the installations."

The answer is not gas vs any other kind of stopgap instant-on generation backup - but is storage. That's the future, and inseparable from any kind of interruptible generation.

All we need is national fleets of electric cars/vehicles, a predictable %age of which will be 'on charge' at any given time, and which can discharge (when the grid needs a boost) as well as charge. All incentivised by instantly-fluctuating tariffs via smart metering. So someone who's happy to accept a long slow charge-up gets a v low tariff, allowing charge/discharge periods as and when the grid requires, but with guarantee to be fully charged at the end of the specified time. Whereas those requiring rapid uninterrupted re-charge pay dearly for it. http://www.rmi.org/cms/Download.aspx?id=1112&file=PreRead_v2.1_Core.pdf&title=Smart+Garage+Charrette+PreRead+Core

Bang on ST.

I can't make much sense out of it at all. One of his graphs seems to show that CO2 emissions dip when 'wind penetration' peaks. His wind penetration metric is calculated by dividing wind energy by the total energy demand, so like Chris says, wind penetration would tend to be higher when the total energy demand is lower. This is when the share of energy generated by the baseload coal and peat plants is higher as gas is turned off. However, he also says,

"The data at low wind penetration shows, that the fuel mix has been switched from gas to coal/peat several times during this month."

This seems to suggest that gas is used as baseload with coal/peat switched on to meet peak load when there's insufficient wind. I still can't see how that would cause higher CO2 emissions to correlate with higher wind penetrations.

I also do not understand his CO2 intensity calculations. For example, in one graph he gives the average CO2 emissions as 547g/kWh with a wind penetration figure of 28%, so he calculates the CO2 intensity as

547g/kWh * (1 - 0.28) = 394g/kWh.

I don't understand that calculation at all. On the same graph he's drawn a trendline that intersects with the zero wind penetration axis at 398 g/kWh and this is the figure he uses to compare CO2 intensity with 40% wind penetration.

I think he's made some mistakes, but even if he has not, his graphs could be more informative. The wind penetration metric is a poor one because it is dependent on two variables, wind energy production and total demand. When wind penetration varies, you don't which of the two variables is changing. It may have helped to have similar ratios of gas penetration and peat/coal penetration on the same graphs along with total demand.

Good stuff steamy. You are saying that Udo is simply wrong, right? Can you give a little more detail on the analysis you performed?

There is a huge thread on this whole subject here:
http://bravenewclimate.com/2011/05/21/co2-avoidance-cost-wind/
with piles of links to reports suggesting that adding wind to a network makes the remaining supply run less efficiently. It includes that Fred Udo report.

But it does also point to this from South Australia where they found that 23% wind penetration caused a just-about 23% CO2 emissions reduction, so not everyone is getting poor results:
http://www.aemo.com.au/planning/SASDO2011/sasdo.html

I discussed that thread here too:
http://www.navitron.org.uk/forum/index.php/topic,14172.0.html
and particularly the fascinating treatment of 5 highly-dispersed wind datasets by two analysts reaching opposite conclusions with the same data(!):
http://seekingalpha.com/article/265055-avoiding-wind-power-stocks-geographic-diversity-debunked
http://seekingalpha.com/article/265511-wind-power-investors-should-also-be-transmission-investors

The thing that annoys me about this subject is that the people who run grids with non-trivial amounts of wind must already know the answer to this. Can we not have some definitive data and work out who's wrong and who's right.

There are standards and methods for gauging almost every conceivable thing there is, and standards for sampling rates etc. Then there are the statistical quirks like type 1 and type 2 errors, lurking variables, small samples, large samples, samples of sub-sets, tests to compare the means and modes, variances and outcomes against expected. Then you can move onto Baysian stuff, where you know it is loaded from the start (why it is used).

I think, from what I have read on that report that the quality of the data was poor and there was an assumption that wind power has a CO2 contribution, either negative or positive. If, and I have not looked at the source data, you cannot isolate accurately the energy mix types and their CO2 contributions at different loads then it is a hiding for nothing really.
Interestingly though I do a similar thing from Damon's excellent website (knowing the limitations, which I think are fewer than the Irish data) and coudl easily show that UK turbines are doing the same thing.
One of the big unknowns is the spinning reserve and standby capacity, ramp up and down times, CO2/efficiency figures, imports/exports from NI/UK, tolerances ect. They would skew the figures enormously. I also suspect that the distribution losses in Ireland are higher as a fraction than the UK as it is more rural.

To much speculation to get the true signal out of the noise I think. You only have to look at the R^2 values to see that.

what he's actually doing is measuring the carbon intensity of the none wind generators, and showing that in times of high wind the none wind side of things has a slightly higher level of carbon intensity.

unfortunately he describes what he's done as if it actually means the grid intensity is higher with wind, or only marginally lower, which is wrong as a quick look at the graph with both wind power and carbon intensity of the entire grid clearly shows.

I read something last night refuting this article that also stated that they'd checked the date ranges he'd used for high wind, and these periods were also periods of cold weather, when heat demand increases, and apparently more CHP plants are operating at full heat capacity, which raises the nominal carbon intensity for the actual electricity generation from these plants. The carbon intensity of the none wind elements also rose during periods of cold with low wind, so the increased carbon intensity is far more likely to be down to the cold than the wind.

so in a nutshell, it's utter tosh (great phrase) for multiple reasons.

That's a better report eventhough not checked the figures that closely.

Posted By: SteamyTeaI bet I could make any figures read which ever way you like, and still be factually correct" alt="" src="https:///forum114/extensions/Vanillacons/smilies/standard/wink.gif" >

There's little truly new in this world:

"There are three kinds of lies: lies, damned lies, and statistics."

"Attributed to the 19th-century British Prime Minister Benjamin Disraeli (1804–1881)."