Huge US study slashes windmill emission cut claims

[An Inspector Calls]

You do make the statement that "no CO2 savings from wind" but this is refuted by the very study you started this thread with!

How so? There's a small exaggeration in my claim: wind in a gas mix does cut emissions but the amount is piddling - probably in the noise of the study's statistics.

However, to me its clear that if we are using substantial standing reserve, then it cannot be that the CO2 savings of wind turbines reduced.

Again, how so?

If standing reserve were all that was required, the impact on the emission savings would be smaller than seen in the study. But the mere fact that you must at some time stop and start and then run your standby reserve means you'll have am impact on the savings. And on top of that, you must run either spinning reserve or part-loaded plant to cope with wind variability.

“Integrating intermittent, volatile electricity into the grid can cause a surge or a sag that can lead to brownouts or blackouts. So grid operators, like Xcel Energy, must balance the wind-generated electricity with electricity online, ready and available to the system. In order to do that, plants that are already operating and connected to the grid must suddenly and rapidly increase or decrease their output to maintain balance. In some cases, this means that plants that are offline must be brought online quickly. The rapid starts and stops or increases and decreases in output are called „cycling.‟” Aptech. (n.d.). Integrating Wind: Cost of Cycling Analysis for Harrington Station Unit 3 Phase 1: Top-Down Analysis.
http://www.blankslatecommunications.com ... tation.pdf

There is a way of making wind an effective tool in cutting emissions: don't consider its production as electricity but as a heat source. Use wind output as low-grade energy to heat urban, domestic hot water schemes. But don't mess up the grid with wind electricity.

[goslow]

Well, Inspector, thanks for clearing that up a bit....so you accept wind can do something at least!

I get the point that its possible that running a thermal plant on part load is less efficient than on full load, and that is also applies to some extent to standing reserve. However, there are plenty of people that do not agree with you (and er...REF) that these related emissions are significant against what is saved by windfarms. What about these statements, from the House of Lords report:

Calculations based on the loss of efficiency from running a power station at part load, and the amount of extra reserve required,
also suggest that the extra carbon emissions in the UK from additional spinning reserve would be very small in comparison to the
savings from renewable generation. The Government has estimated the net saving from raising the share of renewable electricity to
32% to be about 45-50 million tonnes of carbon dioxide—about 8-9% of total CO2 emissions—after taking account of the cost of
part-loading plant.[39] The need to part-load conventional plant to balance the fluctuations in wind output does not have
a significant impact on the net carbon savings from wind generation.

Did you get the last bit? Any comment on that?

Over the timescale we aim to introduce much larger amounts of wind, I'd like to see a move to other approaches: gas back-up can only be a short-medium term solution. Then, we won't have this question coming up at all, as the main sources of energy would be low carbon (even lower than gas, which is admittedly better than coal!)

Its an interesting suggestion of using wind as a heat source, and relevant if people are already using e.g. immersion heaters. But not normally if they are using gas heating. I had the same thought concerning what to do with any spare solar PV, in the end better to export to the grid rather than heat water, for max CO2 savings.

[An Inspector Calls]

I note our Lordships comments - I wonder how they reach that conclusion?

Suppose we introduce 32 % renewables to the UK grid. I assume that's rated capacity. At present, about 20 % of our generation is non-emitting nuclear, the remaining 80 % is CO2 emitting. After the introduction of the renewables (and let's assume that's all wind - their example is rather short of the detail we see supplied in the various reports of Bentek, Liik, Trebilcock, Pair et al) with a capacity factor of 30 %, we'd have expected to have added the equivalent of ~9 % firm, emission free generation. The remaining, dirty generationn percentage should have fallen from 80 % to 71 %, equivalent to a cut of 12 % CO2 emission savings. Just slightly higher than our Lordships claim. Thus, they're saying part loaded plant is nearly as efficient as fully loaded plant! Well, sorry, but it isn't!

Save me the bother, can I have the reference, and sub referebce for their report - hope they're peer-reviewed!

[kenneal - lagger]

Personally, I don't give a sh*t about CO2 savings.

Oh, I didn't have you down as an arch AGW denier.

I'm not a denier, I just believe that the world economy will break before anything is done about CC/GW. We, in the UK, have to mitigate against our economic problems and these measures will involve the use of less energy and imported fuels by externally enforced power down and, hopefully, increased insulation and efficiency gains on appliances.

[biffvernon]

Ah. Glad we got that clear.

[goslow]

hey, Inspector, you're welcome to go through this Lords committee report. I am surprised you did not have it already. It has a full list of references.

http://www.publications.parliament.uk/p ... /19507.htm

To be fair the point in bold about carbon emissions reductions is a government department report, but maybe its possible to get hold of this if you want to find their original references (and calculations).

I don't understand your assertion that renewables means that a whole lot of thermal plants will have to be part loaded. Is it not the case that we ask plants to operate as much as possible on full load, and its only the plants providing the "last bit" that have to be on part load?

[An Inspector Calls]

Thanks for the link. I have read the report before, but dropped the reference to it.

This business about 'a whole lot of thermal plants will have to be part loaded' . . .

I've no precise idea how much part loaded plant we will need to cope with variability and intermittancy.

At the moment we run 1,500 MW of part loaded plant in summer, and 800-900 MW in winter. This is to provide response to protect the grid against loss of load or generation. It might seem the wrong way round - summer/winter. That's because the grid is more heavily loaded in winter and thus there's more spinning inertia in the on-line plant - the grid is said to be stiffer.

The diurnal load variations are compensated by two-shifting plant (at reduced efficiency, of course) and by carrying plant on standby (kettle boiling, steam valves closed, fuel supply throttled back).

Introducing wind will require dollups of both types of service. How much will depend on how much wind. How much can best be determined by reading studies like those from Bentek (USA) and Trebilcock (Denmark) because they are based on observation of what really happens, not models. It might be useful to note the scope of the Bentek report:

The report analyzes emission savings on an hourly level, in addition to a daily, weekly and monthly level. Three years of data are utilized to develop a full understanding of wind generation and emission reduction. The analysis covers territories which represent over 70% of total wind generation in the U.S., and uses this data to estimate the remaining 30%.

[goslow]

Thanks for the info - we'll just have to see how it pans out!

[An Inspector Calls]

Just come across another paper from the US which echoes many of the points of the Bentek paper, and gives alot of explanation of the impacts of wind's variability and intermittancy upon costs, CO2 emissions and fuel savings.

http://www.hwecoop.com/advice/Rational% ... 01%202.pdf