March 31, 2011
Low Wind Power Output Too Frequent In Britain

A study from the John Muir Trust finds that British wind power output sometimes falls to less than 5% of peak (nameplate) capacity.

The report, Analysis of UK Wind Generation, is the result of detailed analysis of windfarm output in Scotland over a 26-month period between November 2008 to December 2010 using data from the BMRS (Balancing Mechanism Reporting System). It's the first report of its kind, and drew on data freely available to the public. It challenges five common assertions made regularly by wind industry and the Scottish Government:

1. 'Wind turbines will generate on average 30% of their rated capacity over a year'
In fact, the average output from wind was 27.18% of metered capacity in 2009, 21.14% in 2010, and 24.08% between November 2008 and December 2010 inclusive.

2. 'The wind is always blowing somewhere'
On 124 separate occasions from November 2008 to December 2010, the total generation from the windfarms metered by National Grid was less than 20MW (a fraction of the 450MW expected from a capacity in excess of 1600 MW). These periods of low wind lasted an average of 4.5 hours.

3. 'Periods of widespread low wind are infrequent.'
Actually, low wind occurred every six days throughout the 26-month study period. The report finds that the average frequency and duration of a low wind event of 20MW or less between November 2008 and December 2010 was once every 6.38 days for a period of 4.93 hours.

4. 'The probability of very low wind output coinciding with peak electricity demand is slight.'
At each of the four highest peak demand points of 2010, wind output was extremely low at 4.72%, 5.51%, 2.59% and 2.51% of capacity at peak demand.

5. 'Pumped storage hydro can fill the generation gap during prolonged low wind periods.'
The entire pumped storage hydro capacity in the UK can provide up to 2788MW for only 5 hours then it drops to 1060MW, and finally runs out of water after 22 hours.

What I wonder: over how big a geographic area would wind farms need to be built and connected up via long distance transmission lines to allow wind farms to provide back-up for each other? Britain does not cover a large area as compared to, for example, the North American continent. Would wind power output be sufficiently uncorrelated over a couple of thousand mile range to allow a much higher worst case power output? California alone suffers very low min outputs across its wind farms.

Political opposition to long distance electric power transmission lines already makes it hard to sell wind electric power hundreds or thousands of miles from where it is generated. So wide geographic distribution of wind farms does not currently enable distant wind farms to back up each other as electric power sources. Costs of long distance lines might also argue against trying to use wind as base load power. If wind can't work as base load power it will hit a wall over how much its use can grow.

Share |      Randall Parker, 2011 March 31 11:18 PM  Energy Wind


Comments
John Davis said at April 7, 2011 2:15 AM:

Nothing remotely surprising here. A similar study of Danish wind farms a few years ago produced essentially identical data. The only way they could cope with the wildly erratic output was by selling the power to Norway, where fast-reacting hydroelectric plants allowed the grid to cope. The bottom line is that wind needs 100% backup available at short notice and at all times. Just build a new gas or coal power station alongside every wind farm (nuclear can't really react fast enough).

red said at April 7, 2011 3:22 AM:

Gas can provide outage coverage, but coal generally has a warm up and cool down period to it. I've read in Germany that the coal plants get loaded once a week so when the wind's blowing they simply blow off their extra power as steam so that the greens can claim Germany's wind power works. Never mind that the coal plants use just as much coal wither the wind turbines are producing or not.

The problem with gas is we don't have enough of it to produce baseline power on a large scale and that's not changing. So at the end of the day it's go nuke or go coal, but no way can you power a technological society on wind power.

Rogoff said at April 8, 2011 8:00 AM:

Rather than to tie oneself into a knot trying to make an unworkable system to work, does it not make more sense to go to more workable systems from the start? Advanced generation nuclear fission reactors should be set free from a preening, do-nothing US Nuclear Regulatory Commission that seemingly exists only to build palatial headquarters buildings and pay an ever larger staff of bureaucrats to do nothing.

Nick G said at April 8, 2011 1:32 PM:

It challenges five common assertions made regularly by wind industry and the Scottish Government

I'd say these are strawmen. Sure, some of them are sometimes asserted, but this presentation is misleading.


Britain does not cover a large area,

This study mostly just covers Scotland. That's not very large. The example given in Appendix A of an assertion that large geographical coverage is important says the following:

"Extreme lows or highs in wind speed are a natural feature of the UK wind climate; however a diversified wind power system would be less affected
as it is rare that these extreme events affect large areas of the country at the same time."

Note that they don't claim that low output never happens, and more importantly the geographical coverage is the whole UK, not just Scotland.


over how big a geographic area would wind farms need to be built and connected up via long distance transmission lines to allow wind farms to provide back-up for each other?

See "Equalizing Effects of the Wind Energy Production in Northern Europe Determined from Reanalysis Data". It shows a correlation coefficient of wind patterns across all of Europe is between -0.2 and 1.

The total hourly outputs for Spain, Britain and Denmark show correlation coefficients of 0.08 (Spain and DK), 0.09 (Spain and the UK), and 0.32 (UK and Denmark). Barcelona (Spain) and Copenhagen (Denmark) are in the same time zone. They are separated by 14.5 degrees of longitude about 500miles.

This tells us that a modest separation (UK and Denmark) gives good independence, and a reasonable separation (Spain and DK&UK) gives almost complete independence.

So, as we add more countries, and connect wind resources at greater distances, the ratio of variance to mean output will continue to fall dramatically - the Law of Large Numbers.

http://130.226.56.153/rispubl/vea/veapdf/ris-r-1182.pdf

Fat Man said at April 8, 2011 9:55 PM:

As for the correlation of wind across the US, I watch the weather every day. Storm systems and fronts that run from New England to Texas are quite common. Wind power is a fairy tale, not a viable strategy.

Every watt of wind capacity must come with a watt of back up or a couple of watts of storage.

Red needs to read up on shale gas. We have a whole lot of it. I would still like to see us work on covering 80% of base load with nuclear, but it is clear that gas is going to be our major source of new capacity for the next few years.

Tom D said at April 9, 2011 1:27 PM:

Britain and particularly continental Denmark are small (or tiny) geographic areas, both relatively flat and surrounded by sea from all sides. Therefore it may be that their wind conditions are particularly uniform at any chosen moment of time. Similar study from a distinctly different geographic location would be interesting. Or carry out a new study including for example wind data from Spain, The Netherlands, France and Germany to the same comparison with Britain, covering the same period of time.

Regarding the last point:
> 5. 'Pumped storage hydro can fill the generation gap during prolonged low wind periods.'
> The entire pumped storage hydro capacity in the UK can provide up to 2788MW for only 5 hours
> then it drops to 1060MW, and finally runs out of water after 22 hours.

Isn't this to say that pumped hydro capacity of 2788/1060MW easily fills the gap between expected 450MW and realized 20MW for a duration 5/up to 22 hours, when a low wind period last on average only for 4.5 hours, as was stated above?

Randall Parker said at April 9, 2011 3:29 PM:

Nick G,

Doesn't the lower right hand corner of figure 9 of your PDF speak to a serious problem? Production goes to near 0 across a wide area? Still seems like close to 100% backup power is needed.

That PDF is from 2000. I'd love to see something 10 years newer with a far larger installed base of wind turbines. A similar recent analysis from the US would help too.

Separation between countries: It really only matters between countries that can each produce a substantial amount of wind.

Nick G said at April 9, 2011 10:32 PM:

Doesn't the lower right hand corner of figure 9 of your PDF speak to a serious problem? Production goes to near 0 across a wide area? Still seems like close to 100% backup power is needed.

First, new wind production only needs backup if more peak capacity is needed. Right now, for instance, US electrical consumption is pretty flat. The US has enough peak capacity, and no new peak capacity is needed. So, new wind farms wouldn't need any backup?

2nd, and this is related to the first: US utilities have handled peak capacity needs with generation because their regulators have tied profits to capital investment, in the form of guaranteed ROI. That means we have far too much peak capacity generation, and far too little Demand Side Management, which is far, far cheaper. A rational regulatory environment would change this incentive, and the US would have enough peak capacity generation to handle far more demand than we have currently. We could build wind to handle new kWh demand for many years, and not need more peak capacity generation.

3rd, one would never backup 100% of generation, as wind farms very get close to 100% of capacity, and whole regions would do so very, very rarely. Maybe you'd go as high as 50%. Higher levels of generation would be handled by DSM (probably with EVs stepping up charging), and very occasionally by curtailing wind production.

4th, the cost of backup is very, very closely tied to the frequency with which it's needed. Diesel fuel is costly, but the capital cost is very low - perhaps $.10 per watt, or only 5% of the cost of windpower (nameplate). So rarely needed backup of 50% of wind capacity with diesel would only add 2.5% to project costs.

There is a very large amount of diesel generation available in institutions that need uninterruptible power, like hospitals and oil refineries - this generation needs to be used at least 2x per year for testing and "exercise". If backup were only needed 2x per year or less, this backup capacity would be free.

Natural gas generation is slightly more efficient and the fuel is much less costly, but the capital cost is somewhat higher - perhaps $.50 per watt, or 25% of the cost of windpower (nameplate). Backup of 50% of wind capacity with NG would add perhaps 12.5% to project costs.

In the very long run, gasified biomass and synthetic fuels could be used in inexpensive "peakers". V2G will also work, and would provide very, very large capacities. Again, these would be very cheap if not used often.

So, if we reduce the frequency and length of low output periods with geographical diversity, we greatly reduce the cost of backup.

Nick G said at April 10, 2011 7:45 AM:

oops. That should be:

3rd, one would never backup 100% of generation, as wind farms rarely get close to 100% of capacity, and whole regions would do so very, very rarely. Maybe you'd go as high as 50%. Higher levels of generation would be handled by DSM (probably with EVs stepping up charging), and very occasionally by curtailing wind production.

Also, I think you meant:

Doesn't the lower left hand corner of figure 9 of your PDF speak to a serious problem?

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