In Cornwall Today magazine this month they ran quite a big piece on Wind Turbines, one of the guys (Danny Mageean) putting the case against WT's made the following comment:

"The National Grid operates back-up generators to cover the sudden and unexpected loss of wind power to avoid power cuts. Last year one electricity generator admitted that for every 1MW of wind electricity penetrating the grid, there was at least 0.9MW of back-up operating. These back-up generators are gas-fuelled, producing carbon dioxide."

The wording of this seems to me to be a bit disingenuous as surely the back-up needs to be available not operating?
He actually makes a strong case against W.T's but some of the figures seem high eg:

"Costs of back-up generation are estimated to rise from £18m currently to £400m in 2020"

Really? if all this is true then the more I read about W.T's the more uneasy I become about the:

"125m industrial white elephants changing the face of Cornwall"

Quoted By: candlemakerLast year one electricity generator admitted that for every 1MW of wind electricity penetrating the grid, there was at least 0.9MW of back-up operating.

That doesn't make clear whether that 0.9 MW of back up is actually using fuel for 0.9 MW or using, say, 0.1 MW's worth in order to be able to produce 0.9 MW at very short notice. Anyway, what Seret says.

That's about the size of it Tom. Papers I've seen project that impact from renewables in the grid should be pretty minor up to about 20%. So a long way to go yet before it starts to become a big issue for the UK.

After all, the grid is designed to swallow variation in demand, why should it have any real problem coping with variation in supply? Flexibility has always been a feature. As the article mentions, weather forecasting is getting a lot better, so wind can be planned for fairly well, and as we install more it only serves to even out the smaller and more unpredictable lumps.

The grid's main headache with accommodating new renewables is providing the connections, not balancing the load AFAIK.

Not read the article, in fact, never read it at all after the front cover had a picture of Portreath with the caption 'Taste the Sea'. Anyone that has been there knows that it is something else beginning with S that you can smell and taste.

Load balancing is well understood, as is the variation in grid supply and demand.
Now I would never claim that for every MWh of renewable (remember that it is not unlimited) supplied there is a corresponding reduction in FF generation.
But what it can do, and does do, is allow for the grid to become overall 'cleaner', but it is early days yet and we do not have enough renewables connected to cause a problem.

This is what is happening at the moment as an example:
Demand: 43455MW
11:45:00 GMT
Frequency: 50.049Hz
11:49:45 GMT

System Transfers

N.Ireland to Great Britain: -254MW
France to Great Britain: -4MW
Netherlands to GB: 992MW
22/10/2012 11:30:00 GMT

North-South: 6087MW
Scot - Eng: 1329MW
20/10/2012 05:02:00 GMT

And

fossil @ 78% 34108MW [CCGT, COAL, OCGT, OIL]
import @ 2% 992MW [INTEW, INTFR, INTIRL, INTNED]
nuclear @ 14% 6014MW [INTFR, NUCLEAR]
renewable @ 2% 1000MW [NPSHYD, WIND]
storage @ 3% 1226MW [PS]
zero-carbon @ 16% 7014MW [NPSHYD, NUCLEAR, WIND]

If we do get somewhere around 20% renewable penetration, and the weather forecast system totally breaks down, and we have an unexpected severe drop in temperature at night, spasmodically for weeks and weeks, then yes, we have a problem with spinning reserves (well actually we don't as they just become part of the supply).

Spinning and hot reserves (they are different) do not have a linear relationship with capacity (anyone who lives off grid will know about this). So at the small scale you need a lot more than at the larger scale because not everything fails at the same time.

Are we talking about this chart, based on today's penetration of both gas and wind.
Without seeing the underlying data I can't really comment on the regression line and if it is a best fit. Does seem strange that they have used a straight line though (the R^2 is pretty low at 0.25)
Also have they used installed capacity of both the gas facilities and the wind facilities, or MWh or a mixture of both at the half hour level?
I find it hard to believe that you need so much back up (the Cornwall Today article not the Guardian one).

What is really needed is more storage, say 5 to 10% of the peak nation's need, so about 4 to 8 GWh that can deliver at double that rate. If they can't sort the problem out in half and hour then it is time to start cutting off the supply to the extremes (so I will get hit). That way we do not have to totally replay the national grid which we would have to do with decentralised generation.

Question is with the wholesale price being around £50 to £100 MWh, how much are we willing to pay for this safety net, double, quadruple?
Hard decision.

Posted By: jms452why is everyone so up in arms?

No idea, not as if we are replacing coal with nuclear (which we should be doing), so we may as well replace it with gas as no other technology is available today that can do what is needed.

Posted By: SeretThe grid does operate a certain amount of spinning reserve and backup, but this isn't entirely to support wind as you need to cover faults and maintenance anyway, not to mention following demand.

How can the same spinning reserve be used for several purposes when they can easily occur at the same time?

The 'chance' of losing all wind is quite high, i.e. when there is no wind across the whole of the UK the chance will be 100%. This does happen and the fact that it is predictable doesn't remove the need for a reserve.

But I think calling this a 'reserve' is actually the wrong way to look at wind. Wind generated electricity should just be thought of as a way of increasing the fuel efficiency of existing power stations.

And I still don't understand why there is not more research into large scale batteries such as Vanadium Redox.

Also, even if there is an un-forecast drop in the wind it won't, on a country-wide scale, happen that quickly. A block of air 1000 km × 500 km × 100s of metres thick doesn't just stop instantly. It's a good reason to spread the turbines around, though. I'm not sure how fast gas power stations can be spun up but my impression is that it's pretty quick, much less than an hour or so, as opposed to coal or nuclear which is much slower.

Nobody is claiming that changes in output due to day to day changes in weather can't be predicted. What's more concerning are reports that rapid changes in total output are more frequent than expected..

http://www.jmt.org/assets/pdf/wind-report.pdf

"The frequency of changes in output of 100MW or more over a five minute period was surprising. There is more work to be done to determine a pattern, but during March 2011, immediately prior to publication of this report, there were six instances of a five minute rise in output in excess of 100MW, the highest being 166MW, and five instances of a five minute drop in output in excess of 100MW, the highest being 148MW."

http://www.ieawind.org/annex_XXV/PDF/Task%2025%20Paper_Bremen_final20090814.pdf

"From both the experience and results from studies performed, a significant challenge is the variability of wind power within 1–6 hrs. Frequency control (time scale of seconds) and inertial response are not crucial problems when integrating wind power into large systems at the present time, but can be a challenge for small systems (like Ireland) and will become more of a challenge for systems with high penetration in the future."

The amount of short term reserve needed seems to vary a lot but I agree it's not a large percentage...

"The estimated increase in short term reserve requirements in the studies has a large range: 1–15 % of
installed wind power capacity at 10 % penetration (of gross demand) and 4–18 % of installed wind power capacity at 20 % penetration. Time scales used in the estimation explain much of the differences in results:

• If only hourly variability of wind is taken into account when estimating the increase in short term reserve
requirement, the results are 0.5–4 % of installed wind capacity or less, with penetrations below 10 % of gross
demand.

• When 4 hour forecast errors of wind power are taken into account, an increase in short term reserve requirement of 4–5 % of installed wind capacity has been reported, with penetration levels of 5–10 % of gross demand."

"The highest results in Fig 4 are from a study where four hour variability of wind (not forecast error), combined with load forecast error, results in 15 % reserve requirement at 10 % penetration and 18 % reserve requirement at 20 % penetration of gross demand"

So somewhere between 1 and 18%.

Posted By: CWattersNobody is claiming that changes in output due to day to day changes in weather can't be predicted. What's more concerning are reports that rapid changes in total output are more frequent than expected..

Posted By: CWatters"The frequency of changes in output of 100MW or more over a five minute period was surprising.

100MW change over five minutes is 1.2GW/hour

To put the concern into perspective the grid currently handles demand climbing by about 13 GW between 6.30am and 8.30am. That’s a slew rate of 6.5 GW/ hour.
http://www.inference.phy.cam.ac.uk/withouthotair/c26/page_188.shtml

The storage is a different matter but this is where the CCGT come in as a cheap interim solution.

Posted By: CWatters"The frequency of changes in output of 100MW or more over a five minute period was surprising. There is more work to be done to determine a pattern, but during March 2011, immediately prior to publication of this report, there were six instances of a five minute rise in output in excess of 100MW, the highest being 166MW, and five instances of a five minute drop in output in excess of 100MW, the highest being 148MW."

given that the spinning reserve of the grid is designed to cope with the simultaneous and instantaneuous disconnected of 2 x 1GW generation units it should be fairly obvious that 5 minutes changes of under 10% of that level are nothing to worry about, and require virtually no additional spinning reserve to cope with it.

When installation levels start heading towards 10 times that figure, then we may require a small proportion of additional spinning reserve to cope with it, unless other measures have been implemented such as dynamic demand controls to allow temporary demand reductions from eg fridge and freezer circuits.

interesting to see more details of the additional 1.2GW of pump storage SSE have in the planning process at the moment, with apparently up to 50 hours of peak generation capacity planned for each.

That should go a long way to balancing high levels of wind penetration in scotland if / when it comes on line.

They seem to be leaving their options open to go for smaller schemes instead, but I hope they opt instead for a full size scheme at one site only if there's not enough initial need / funds for both, which would leave the potential for the 2nd full size facility to be built at a later date.

http://www.sse.com/uploadedFiles/Z_Microsites/Coire_Glas_Hydro_Scheme/Controls/Lists/Resources/CoireGlasPumpedStorageBriefing.pdf

there's something else that bugs me from that article in the way they calculate one of the measures of penetration.

Essentially one measure is based on the level of penetration compared to the minimum demand including the impact of interconnectors, but I'm fairly sure I've seen elsewhere how this is calculated, and it assumes that the interconnector is making the situation worse not better - as if at levels of peak generation and minimal demand we'd somehow actually still be forced to import via the interconnector at peak rates.

This is plainly nonsense, and means that despite the interconnectors being a highly effective method of reducing the impact of high levels of renewables penetration, by this measure they would actually appear to be making the situation worse not better.