John Muir Trust Study Reports Wind Farms at 22% Efficiency

Front page article on today’s Sunday Times (UK) reports (behind a paywall so no link):

“One of Scotland’s leading conservation bodies has called on ministers to ditch their ‘obsession’ with wind power amid evidence that turbines produce about a quarter less energy than developers claim. The John Muir Trust (JMT) said a study of 47 wind farms in Scotland and England over a 13-month period revealed that they ran at 22% capacity. The wind farm industry has claimed that during the course of a year a turbine operates at 30% efficiency.”

The paper reports Helen McDade, head of policy at JMT says

“Wind farms are costing huge amounts of money, much of it from consumers’ bills, yet it isn’t delivering what the industry claims. The economics of this is a scandal and needs to be urgently reviewed.”

JMT’s results are in line with my initial analysis and is consistent with that experienced in Denmark over the last 25 years. While I have what I think is good wind power generation data from National Grid, I don’t yet have much authoritative information about what wind farms are reported in the National Grid data to enable a good assessment of the “efficiency” or load factor.

I’ve looked the JMT website, and I don’t see any reference to any report. I’ve sent them an email asking for more information.

More posted here as I get insights from them or elsewhere.

I’ll close with an interesting quote attributed in this article to Niall Stuart, chief executive of Scottish Renewables, which said that the winter of 2009/2010 was one of the calmest on record and that it was “no surprise” that output figures for the year were below average. Further they report he said:

“It’s well understood that there are variations with and between years, but no form of electricity works at 100% capacity 100% of the time”

We do not expect 100% efficiency (thermodynamically impossible!), and Mr. Stuart suggesting this as a reasonable thing “not to expect” is a red herring probably meant to help justify continued support in future investments in “high-yield” wind energy generation and usurp the figures reported by JMT. But there is a big difference between design load factors of 30-45% [I’ve heard some wind farm developer’s expect the high-end of this range as that’s what they say has been achieved in Scotland … as yet an unconfirmed “sighting”, though] and getting 22% as reported by the JMT. The first step, seems to me, that we need to get our expectations closer to reality, e.g. get the numbers and system designs right, to help make prudent investments where warranted.


Update 2 Jan 2011: “Andy” reports at Bishop Hill web site that this JMT report came in out September 2010 (!) and that JMT has always been against wind. A mystery, then, why the Sunday Times doesn’t say either of these things (date of the report or the position of JMT) and why it would be put on the front page of the Sunday Times today. I can’t take exception to the blatant message–that wind farm efficiencies appear to be well under that claimed. That concerns me as we don’t need more “toxic investments”. What else is going on is unknown to me.

Update 3 Jan 2011: The referenced article appeared in the Scottish edition of the Sunday Times. It reportedly was not published in other editions.

Update 5 Jan 2011: I have received email from Helen McDate at JMT. She indicates that they do not have a report yet on this topic which they can send me. She also reports

“I can tell you the data quoted is based on analysis over 14 months from November 2009 to December 2010 and that we hope to have a report looking at 26 months data to December 2010 in due course. I note from an indirect link from your website that there was the suggestion that this is old news. On the contrary, the data runs to December 2010.”

11 Responses to John Muir Trust Study Reports Wind Farms at 22% Efficiency

  1. coconutdog says:

    “It’s well understood that there are variations with and between years, but no form of electricity works at 100% capacity 100% of the time”

    “We do not expect 100% efficiency (thermodynamically impossible!)…”

    He’s talking of capacity here, not efficiency.

    • rms says:

      That’s my understanding too. My understanding is that the word “capacity” for a wind farm is as best explained at Wikipedia as being

      The ratio of actual productivity in a year to this theoretical maximum is called the capacity factor.

      There is no dispute that 100% is unrealistic and to give that as an unrealistic expectation is disingenuous. The issue as I observe it is that the expected capacity factor which underpins the investments appears to be overstated at each place I look. This information is not easily available, but where I’ve seen it in planning documents (government, NGO’s, and a few business cases), the economics are based on capacity factors 30-45%. When actuals seem to be a fraction of those expected, then the economic basis appears to be non-prudent.

  2. coconutdog says:

    Rob, I totally agree. Wind farms are a totally useless entity. The capacity is not there nor is the reliability. I was just nit picking.

    A wind generator can be very useful when it is used on a small scale. Say a 100A 24Vdc generator charging a bank of deep cycle lead acid batteries which in turn supply 240VAC 50Hz via an inverter. This with solar cells and a backup diesel generator would power a household. The difference here is the storage ability which wind farms cannot hope to give. Unfortunately not all of us have the technical knowledge and ability to look after such a system.

    • fujirobin says:

      coconutdog – I have a 12V wind/solar system that I built to try out this idea. It is far harder than it seems, and the overall efficiency is abysmally low. For instance when batteries get near fully charged you are forced to waste energy. In fact energy losses mount up enormously in this type of system, unless you can use it as and when it is generated. The construction of the batteries themselves seems to be inferior to those of 100 years ago (our culture of disposability I guess). And I used to think that low voltage was safe. I have now learned the error of my ways – a loose connection can cause a fire at the high currents involved! I don’t regret doing it though – I’ve learned a lot!

  3. rms says:


    Cool. I’m not ready to say they are totally useless. Wind power may have a place in the scheme of things. I’m convinced that we should not, as we are in UK, using Renewable Obligation Certificates or other forms of customer/government subsidisation to fund projects where the basis appears to be so non-prudent. If due to realistic estimates (among other things) risk factors, capacity, reliability, security of supply, “greenness”, and ROI the investment can’t be justified–well, don’t invest. Everywhere I look, all of these attributes appear to be unrealistic. I seek better information to confirm or to correct that appearance.

    • fujirobin says:

      Well it seems fairly clear from this winter so far that we need enough despatchable plant margin to cope with 95% non-availability of wind capacity. It would be nice to see some acknowledgement of this by the government, and for it to be put in the context of the forthcoming retirement of our large coal and nuke stations. I think we will need ALL types of generation… and pretty quick too.

      • rms says:

        My prediction: this episode will be declared to be a “Black Swan” that nobody could have anticipated, nor is it likely to occur again. Sigh.

  4. […] 5. Musings On Interesting Things on John Muir Trust Study Reports Wind Farms at 22% Efficiency […]

  5. fujirobin says:

    re Black Swan – there must be stats on this (duration and frequency of high-pressure/no wind winter weather) available from the Met Office. I did try and get hold of them a few years ago, but the Met Office wanted to charge me commercial rates for the data. ??? We have a bonkers idea of public data in this country !

  6. rms says:

    My hunch is that any data that would/could be obtained will be of marginal value for the same reasons as the world’s temperature “record” has many holes. I suspect it will be even worse. While the data collected probably is sufficient to meet the needs for which the data was collected, going from there is probably going to be difficult. I say this as I did have one project many years ago where we did extensive wind speed surveys (only for a year) in support of site selection for a new harbour/port. My hunch is that the wind power can serve as a “proxy” (as does ice cores, tree rings, etc. etc.), especially since we have 5-minute interval data available for that.

    Related, see

  7. […] but optimistic ‘capacity’ number rather than the actual generating performance.  How does 22% efficiency sound.  Anyone?  Wind farms also do not create […]

%d bloggers like this: