Devastating report on Wind Farm performance

A new study by Prof. Hughes (Univ. Edinburgh) makes grim reading for DECC and  government plans for expanding wind farms in the UK. The study analysed the actual electricity generation figures from wind farms both in UK and in Denmark. They show that the performance falls dramatically after just a few years of operation. The lifetime for turbines is at least  10 years less than previously assumed, and runs a cart and horses through renewable energy plans.  The load factor falls from 24% to 11% after 15 years !  So a “2 megawatt” turbine actually produces 480 Kwatts when new, but only 220 Kwatts after 15 years. In order to replace the DRAX coal power station (4 GW) with such wind turbines would now need 25,000 of them covering  a staggering 4000 square kilometers ! The over-generous subsidies paid to wind farm operators may have actually acted as a disincentive  to improve efficiency !

The report can be found here, and the executive summary is quoted below.

Executive Summary

1. Onshore wind turbines represent a relatively mature technology, which ought to have achieved a satisfactory level of reliability in operation as plants age. Unfortunately, detailed analysis of the relationship between age and performance gives a rather different picture for both the United Kingdom and Denmark with a significant decline in the average load factor of onshore wind farms adjusted for wind availability as they get older. An even more dramatic decline is observed for offshore wind farms in Denmark, but this may be a reflection of the immaturity of the technology.

2. The study has used data on the monthly output of wind farms in the UK and Denmark reported under regulatory arrangements and schemes for subsidising renewable energy. Normalised age-performance curves have been estimated using standard statistical techniques which allow for differences between sites and over time in wind resources and other factors.

3. The normalised load factor for UK onshore wind farms declines from a peak of about 24% at age 1 to 15% at age 10 and 11% at age 15. The decline in the normalised load factor for Danish onshore wind farms is slower but still significant with a fall from a peak of 22% to 18% at age 15. On the other hand for offshore wind farms in Denmark the normalised load factor falls from 39% at age 0 to 15% at age 10. The reasons for the observed declines in normalised load factorscannot be fully assessed using the data available but outages due to mechanical breakdowns appear to be a contributory factor.

4. Analysis of site-specific performance reveals that the average normalised load factor of new UK onshore wind farms at age 1 (the peak year of operation) declined significantly from 2000 to 2011. In addition, larger wind farms have systematically worse performance than smaller wind farms. Adjusted for age and wind availability the overall performance of wind farms in the UK has deteriorated markedly since the beginning of the century.

5. These findings have important implications for policy towards wind generation in the UK. First, they suggest that the subsidy regime is extremely generous if investment in new wind farms is profitable despite the decline in performance due to age and over time. Second, meeting the UK Government’s targets for wind generation will require a much higher level of wind capacity – and, thus, capital investment – than current projections imply. Third, the structure of contracts offered to wind generators under the proposed reform of the electricity market should be modified since few wind farms will operate for more than 12–15 years.

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14 Responses to Devastating report on Wind Farm performance

  1. I’m glad you are looking into this. A a new 2 MW turbine operating at load factor 24% produces 480 kW on average. A fifteen-year-old 2 MW turbine operating at load factor 11% produces 220 kW. So after 15 years they are producing just under half as much power as they did when they were new. The way your post reads now, you don’t give the 480 kW initial power output so we can compare it to 220 kW. Anyway: a 50% drop in power output is pretty disappointing. I suppose after another 15 years they would be operating at a load factor of 5%. Happy New Yar.

    • Clive Best says:

      Thanks. I have updated the text to better explain the actual net power rates. One trick the wind industry uses is to quote the capacity power for a wind farm. So they say this wind farm consisting of 10 x 2 MW turbines produces power for say 5000 homes. However this only happens rarely, and often at 3am when there is no demand. Without finding a simple and efficient energy storage system, wind power will remain ineffective and expensive.

      I think it really means that the lifetime of one turbine is actually 15 years and not the quoted 25 years. So either the UK countryside will end up being strewn with rusting relics or they will all need to be replaced at public expense.

  2. Bob Peckham says:

    Hello Clive

    I read the report and found it very worrying. Apart from the main conclusions which you reproduced, this, on page 39, seems especially negative for offshore wind farms:
    “If this were to continue and/or to be reproduced in other countries where offshore wind is being developed, then there can be no prospect that offshore wind farms will ever be financially viable at reasonable prices for electricity. “

    In Scotland plans are being drawn up for large offshore wind farms e.g. in the Moray Firth, and it is a major part of Alex Salmond’s strategy for energy independence for Scotland. It is worrying because engineering firms are gearing up to deliver and install the turbines and hopes are high for job creation and economic activity. If they do not perform as well as expected there will be a lot of disappointments and recriminations later on. Surely this report – coming from Edinburgh – will cause them to think again.

    There seems to have been very little mention of the report in the Scottish press so far. I could only find one letter to the Scotsman by a reader asking if we could get our money back (meaning contribution to subsidies I suppose). That stimulated some discussion on the web and one contributor gave this technical insight about the turbines which I found very interesting:
    “ One of their big problems is that they are too large to be held into the wind by a simple tail fin. Instead they have electronically activated hydraulic pumps and motors the control side of which gives endless trouble.
    They also have a number of fail safe systems to shut them down, too much wind, too hot, overspeed, vibration (if a blade falls off!) over current etc.
    The older the turbine the more outages and that is precisely what this report found.
    If you don’t believe me, go speak to a turbine engineer, if you can find one, they are usually very busy.”

    Bob P

    • Clive Best says:

      The engineering problems of large 2-6 MW wind turbines in the North Sea and Atlantic coasts of the UK are huge. They will have to cope with regular severe force 10 storms and unlike far sturdier North Sea Oil Rigs, is that they are supposed to thrive on strong winds, and not protect against them.

      The second problem is that they are very low energy density and must cover large areas (sq. kilometers) of Ocean in order to rival even small fossil fuel power stations. Their inaccessibility, their high maintenance costs and seemingly small lifetime all work to perhaps double generation costs. Electricity generated by wind after this new report would appear to be at least 4 times more expensive than gas or coal fired stations. I hope Scotland is prepared for high electricity prices after independence.

      As Britain sets about dismantling its industrial base due to high energy prices, India and China burn more and more coal. So it is all futile so far as reducing CO2 levels are concerned. If the UK switched off the lights tomorrow and we returned to Neolithic living, it would change absolutely nothing. It might just about offset China’s increase in emissions for about 12 months, after which there would be exactly the same increases as before.

      Cameron, Milliband and Salmon are leading us all in a new the “Charge of the Light Brigade” to combat “Climate Change”.

  3. oldfossil says:

    Because we get so much exaggeration and general BS from the CAGW mob it would be nice if we applied the opposite policy. The output of the Danish onshore wind farms deteriorates the least (18%) so that could have been the headline statistic. It would also create more impact when you progressed to the 62% decline in output of the Danish offshore installations. I’m guessing the reason for this huge discrepancy is, as Bob Peckham remarks, higher outages. Offshore turbines would seem to be more difficult to repair, especially when “CO2-caused severe weather” makes it risky even to access the turbine.

  4. Bob Peckham says:

    Hi Clive.

    It does not look very promising. It saddens me to think of engineers battling against the elements offshore to build and maintain them if they are going to be so inefficient and uneconomic.

    You say “Cameron, Milliband and Salmond are leading us all in a new “Charge of the Light Brigade” to combat “Climate Change”….. but if that is the case, who led them up the garden path in first place ? Maybe scientists had something to do with it.

    News in today from The Sotsman: Iceland is (again) considering laying a 1000km sub-sea cable to supply electricity generated from their volcanic/geothermal resources to the UK and Europe. The article says it was considered 60 years ago but found to be too expensive. It is now being considered again in the light of increasing electricity prices. Anything to do with wind farms ?

    Maybe if they can get the cable laid quickly enough it will stop some of the wind farms being built.

    The article concludes with a very nice paragraph: “A Scottish Government spokeswoman said “We recognise that there are emerging and existing technologies which have yet to make a substantial impact on the energy landscape in Scotland” “.
    Bob P.

  5. Tim Richards says:

    Hi Clive,

    Before accepting Professor Hughes’ analysis I think it might be worth asking if it has undergone any peer review, who exactly has published it and what else is Professor Hughes is know for.

    Is it peer reviewed? According to the author’s note “a referee” has commented on it, under which peer-review process?

    Who are the Renewable Energy Foundation? REF was set up in 2004 by Noel Edmonds (yes that Noel Edmonds) and is well known for its anti-wind stance. It it frequently described as an anti-wind lobby organisation and the Charities Commission has received complaints about its activities in the past. It is not an impartial source.

    Who is Prof. Gordon Hughes? As you say he is Professor of Economics at Edinburgh University. He is also well known for his collaboration with the Global Warming Policy Foundation which, like REF, is generally known as a lobby group interested in pushing its own agenda, rather than for its objectivity (to put it mildly). Professor Hughes has authored 3 GWPF reports and last year gave evidence on behalf of GWPF to the Energy & Climate Change Select Committee on the economics of wind energy. Imperial College, which also gave evidence to the same hearing, submitted a written response to the GWPF evidence and systematically demolished it as ‘nonsense’, adding ‘it does not align with the evidence from simulation studies or indeed a common-sense investigation of the basic statistics’. This view is backed up by the UKERC, see

    Is there any merit in his turbine performance report? I have got no idea, but I look forward to seeing a peer-reviewed version.


    Tim Richards

    • Clive Best says:

      Hi Tim,

      Yes – someone else on another Blog warned me that the analysis may not be exactly “impartial”.

      When I find time I am going to try and analyze all the data myself. One simple thing I did do was to simply to calculate the total average load factor across all UK wind farms since 2000. The answer was 26%.

      Currently the UK has an installed capacity of about 6GW (I think), and the plans are to double this by 2020. So with a load factor of 26% this then yields a net average power output of about 1.6 GW. UK gross requirements are for about 60Gw continuous power. So even if load factors can get above say 30% we can only expect a maximum wind power production of 3.6GW. So realistically wind can only ever meet about 5% of UK’s electricity needs. The targets for 15% renewables can only be met by Biomass – which has serious environmental problems of its own.

      The main technical challenge for wind is to develop an effective energy storage system so that power out can be controlled to meet demand.



  6. Bob Peckham says:

    Hi Clive
    A load factor of 26 per cent does not seem too bad when you consider it is production of electricity fuel free, with no need for imported fuel. However, if it drops to around 15 per cent in 15 years, that must alter the picture and the economics pretty drastically.
    Tim Richards rightly points out the need for a peer review of the Prof. Hughes paper. However two files containing the data were published alongside the report. It would seem a fairly simple exercise to average the load factors and produce the graphs showing the decline over time. It is hard to imagine that any re-analysis with subtly different statistical techniques would produce graphs with much different slope. The final conclusion was worded rather moderately – suggesting a review of the subsidy regime for wind farms. Who could possibly argue with taking another look at the subsidies in view of recent performance data?
    My main criticism on first reading it was that it would have been interesting/useful/important to see the analysis repeated for wind farms in a few more countries, e.g. Germany and the Netherlands, to see if they gave similar results. Admittedly the wind statistics will be different in different countries, but if there is “wear and tear” on the turbines we need to see how the decline goes over time.
    Thanks also to Tim for providing the links to the earlier Prof. Hughes report and the subsequent criticisms of it. It was fascinating to see the simulations and to read that even a professor working in the field can construct scenarios which are regarded as nonsense by other professionals – it is a tricky business with different types of plant being allocated to the grid according to priorities and economics..
    For me it is important to try to understand what is going on because I actually invested in a local wind farm cooperative a few years ago. It seemed like a good thing at the time but I am not so sure anymore – indeed I am more confused than ever. So I look forward to your analysis of the load factors, or to the criticisms from Imperial College or UKERC or any other reputable body. Please keep us informed.
    By the way the Italian Alpine Club is calling for no more wind turbines to be built in Italy as they find the average Italian plant works for only 1421 hours out of 8760, and 80 percent of them are working for less than 2000 hours per year which is considered to be the economic threshhold (Rivista del Club Alpino Italiano, Gennaio 2013). But we know there is less wind in Italy, don’t we.

    Bob P.

  7. Johannes Theron says:

    A load factor of 26% is pretty low – many US wind farms exceed 40%. This is not a function of the turbines only, but strongly influenced by the wind source and the care that was taken to find a good site. This low value seems to imply that the UK wind farms were perhaps sited with less care and lower quality wind data that that used in other markets such as Germany, Denmark and the US. Perhaps the expansion was too fast and incentives too generous to force developers to take greater care in siting and designing their wind farms.

    A peer review would be great to check the finding of this report, but I am not sure it will greatly influence the conclusions.

    Capacity factor includes the wind speed distribution and therefore a decline in capacity factor can also be caused by the potential fact that the last 10 years had unusually low wind speeds. It looks like Prof. Hughes tried to compensate for this effect by normalizing his capacity factors, but unless exact data is available for each wind farm, this approach is subject to potentially large errors. He shows that his conclusions are statistically significant, but I very much doubt that his data was fine-grained enough to accurately compensate for the variation in the wind speed distribution for each wind farm in the study.

    Jan Theron

  8. DirkH says:

    Johannes Theron says:
    April 5, 2013 at 11:09 am
    “A load factor of 26% is pretty low – many US wind farms exceed 40%. This is not a function of the turbines only, but strongly influenced by the wind source and the care that was taken to find a good site. This low value seems to imply that the UK wind farms were perhaps sited with less care and lower quality wind data that that used in other markets such as Germany, Denmark and the US.”

    The average load factor of wind turbines in Germany is currently 17% according to an EON report.

    40% is ONLY achievable offshore; inland wind turbines achieve at most 25% in top spots in Germany.

    And yes, the average load factor deteriorates over time as overgenerous inventives encourage erecting wind turbines in worse and worse spots; as the good ones are already taken. But this is of course an inevitability under a policy of expansion of wind power; in fact subsidies must RISE as quality deteriorates to make further expansion possible. Which will not happen given the impending bankruptcy of the Eurozone.

    • Clive Best says:

      I accept that your figures are correct, but it doesn’t change the argument that wind is the most inefficient way to generate electricity known to man. The massive German investment in wind has been 70% wasted as far as carbon emissions go just by offsetting the early shutdown of nuclear plant due to green hysteria to Fukushima. Some 200,000 died from the Tsunami but no-one died at all from FUkushima.

      If Angela Merkell had the balls she would reverse the decision to abandon nuclear power. She doesn’t need Green support any more.

    • Billy says:

      The “exceed 40%” seems to come from old propaganda reports and is projected.
      DOE, openei – -newest information is 2009.
      I found one report of 26%. It is not clear if out of service time is counted. I do not see that there is any industry standard for creation of these reports. Up to date information is curiously hard to find. If the results are so good, information would be readily available.

  9. wind farm is; blowing money in the wind

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