Bad Power


The map shows mean 10m wind speeds at 1.5o resolution during the period 2009-2010. Ireland is ideally located for wind power, at the end of North Atlantic storm tracks. For many wind advocates, discussion begins and ends with maps like this one. Some advocates even argue that wind power is a reliable source of electric power and the solution to global warming, peak oil, sustainability etc. Critics say that wind power is too intermittent to be a substitute for thermal power sources. Intermittency imposes wasteful duplication and costs. Critics question to what extent it is a resource worth exploiting. Wind advocates are winning the argument; Ireland increased installed wind generation capacity from 1100MW to 1465MW (34%) in the last two years.

Opinions need to be checked against good data. Fortunately, the Irish grid operator Eirgrid provides very high quality data – total wind power generation every 15 mins.

The chart shows power generation as a % of installed wind power capacity or instantaneous “capacity factor”. Generation is certainly intermittent, with frequent jumps between periods of high ~ 80% and low ~ 5% power. The mean power is 25%. The distribution of power generation values in the above chart are shown below:

This distribution looks nothing like a bell-curve about the mean value. The most probable instantaneous power output is only 5% of installed capacity (~ 70MW currently). There is a long tail extending up to ~80%. Ireland has a favourable Atlantic location, but wind generation is intermittent and unreliable like everywhere else.

One gigantic wind turbine

Some wind power enthusiasts claim that installing more capacity and extending the grid to more locations can “fix” the intermittency problem. Another version of this idea is “the wind is always blowing somewhere”. Install enough turbines, they say, and the intermittency problem will be solved.

To test this opinion,  I used twice daily (00UTC and 12UTC) 1.5o x 1.5o global wind speed maps from ECMWF ERA for the period March 2009 to December 2010 (1342 maps). A time-series of averaged 10m wind speed over ireland was computed using a rasterized map of Ireland at the same resolution. Wind speed data can be compared to the Eirgrid wind generation data. The result is a binned scatterplot of instantaneous averaged wind speeds versus instantaneous power generation:

Clearly wind generation follows the averaged wind speed quite closely. In fact this Ireland-scale power curve is very similar to the power curve of an individual wind turbine. e.g.



In other words the entire portfolio of >50 Irish wind farms effectively behaves as a single gigantic 1,465MW wind turbine driven by the average wind speed over the island. The reason is that Ireland is small ~350km compared to the scale of synoptic weather systems >1,000km. It is either a windy day in Ireland or it is not.


No matter how much additional wind capacity is added to the system, the power curve will still look the same as the one derived from the Eirgrid-ERA data above. No amount of costly additional grid infrastructure to new locations can change that. Building more wind farms does not diversify the power supply or fix the intermittency problem. It effectively just increases the size of a gigantic 1,465MW wind turbine.

Installed wind capacity is supposed to increase to 5-6GW by 2020 under ambitious renewables targets. Policy and reality are about to collide.




  1. Hi Joe,

    All of your facts are correct and they are excellently presented and your conclusion is deriveable from the facts. But, you are not telling the entire story….

    If you are used to eating cake then porrige can seem like bad food. If you are used to cheap gas from Norway and Siberia then wind energy seems like bad power. Wind energy doesn’t just blow it sucks! But unfortunately it’s all we have. We’re at peak oil. Peak gas will be in the 2020s sometime. We can’t burn coal and keep Temple Bar above water. Nuclear don’t seem so great any more. 🙁

    So if wind power is porrige, what can we do to add honey and raisins? Quite a lot actually.

    1) Interconnects help.
    2) Storage aka Spirit of Ireland is a super idea.
    3) Demand Response driven by real time pricing (RTP) for electricity.

    I have been championing Demand Response (DR) for a number of years. Wholesale electricity prices, in Ireland, vary by 300% to 400% every day. Yet consumers are not exposed to the variation. Demand Response is the ‘killer app’ for the Smart Grid. Lately the IWEA have setup a group to promote thinking on the topic. Several small startups are getting in on the act such as, Crystal Energy, and Activation Energy. If the supply becomes uncontrolled, try controlling the demand. This includes stimulating the demand at certain times when wind generation exceeds unstimulated demand (e.g. charging electric cars when the wind is blowing or producing ice banks at pharma companies that needs lots of chilled water). It means reducing demand when electricity is scarce , aka expensive on the wholesale market (e.g. reducing water heater setpoints, starting CHP plants (preferably waste/biomass fired).

    Imagine if we had an industry in Ireland that produced Ammonia (Nitrogen Fertiliser) when electricity dropped below a certain price.

    One final point. We will have other renewable sources other than wind. Even if they are also tide/weather affected they will not directly correlate with wind generation. We currently have hydro and pumped hydro that are dispatchable when the wind isn’t blowing. Ireland has its first tidal turbine in Strangford Lough. We will have a wave and tidal industry to support wind by 2025.

    I am hoping that Ireland will solve the problem you describe (using RTP driven DR to create a dynamic market) and build an export business based on delivering that solution globally. We are meeting the problem first but the world will follow.

    When oil is €300 a barrel, wind may seem like very good power indeed. We just need to add raisins and honey.

  2. I agree opinions need to be checked against data and I am delighted to see your excellent analysis. However, I disagree with your conclusions.

    A question in relation to your data, at what height above ground do the mean wind speeds quoted refer?

    According to Prof Owen Lewis, CEO of SEAI, wind farm capacity factors nationally averaged 32% over 2002 to 2009 reaching a peak of 35% in 2003 and falling to 29% in 2007. Interestingly for me, as I live in Mayo, Mayo/Galway under performed with 28% average capacity factor over the same period.

    Take a look at the map and ask yourself why is that? I suggest it is due to hub heights and area swept by the wind turbines presently deployed. We currently subsidise sub optimal exploitation of the wind resource and focus on extracting energy between 15m and 90m above ground where the air is most turbulent and where power density is far lower that the zone 70m – 200m above ground.

    The best wind resource data for Mayo is from the Bord na Mona Bellacorick 6.45MW wind farm in NW Mayo and the nearly Belmullet Met station. Bellacorick is the site of Ireland’s first wind farm, now in operation 20 years. Hub heights are 30m and mean wind speed ~7.28m/s. Three anemometers in place nearby since 2003 at 50m show mean speeds ~7.8m/s. This suggests mean wind speeds at 100m – 120m above ground will be in the 10m/s range, the design wind speed for class 1a wind turbines. Capacity factors of 50% or better may be possible with hub heights in this range. The Danish technical university has identified Red Sea sites where the capacity factors are almost 70%.

    Data from three masts at 80m above ground in West Clare in place for two years predict that an average 46% capacity factor would have been achieved with 3MW turbines over the period. Achieving significantly higher production does not require new turbine technology just taller towers.

    Our County Council estimate a total on-shore wind capacity of 28,141MW in areas “preferred” or “open to consideration” for wind farming in Mayo. That is the equivalent of total US wind capacity today. That’s just Mayo.

    The volatility of wind requires both backup and flexible generation capacity. At present Ireland sources backup and flexibility from peaking plant, mostly open cycle gas and distillate fossil fuel plant. Interconnection also contributes. The CERs Gate 3 licensing programme contains applications to build some 2,000MW of fossil fuel peaking plant at a cost of about €1bn, much of it by the semi-state energy sector. The CERs own computer simulations of the system predict that this new plant, on top of existing peaking plant, will generate for less than 10 hours per year on average and contribute 0.026% of total electricity generation despite amounting to well over a quarter of total fossil fuel capacity. Under market rules, this new plant will produce a good return on the investment cost for their owners while fuel and labour costs are treated as expenses and passed onto consumers. This is why wind is so expensive.

    What is the alternative to this peaking plant? I agree with Prof Steven Chu, US Energy Secretary and holder of a Nobel Prize in Physics, who has describe pumped storage as “the perfect system for going to a much higher renewable system”. He does not use the word perfect lightly as pumped hydro provides both backup and huge flexibility as well as arbitrage and vital system services. Scottish and Southern Energy have recently announced big plans for pumped storage Scotland. As yet, there has been no worthwhile computer simulations studies of pumped storage in the Irish system. The results would cause embarrassment and upset to very well paid managers, executives and officials in DCENR and the heavily subsidised semi-state energy companies.

  3. May I point out that the wind farms are not currently located where the wind is ( when it is there) in either Galway or Mayo. They are currently located in the suboptimal eastern parts of those counties as there is no grid to carry wind out of the optimal areas.

    Bit like drilling for oil in Somalia when you know it is in the Gulf 🙂

  4. reply to 4. Sponge Bob:
    You’re right and you’re wrong. The ‘oil’ is actually everywhere in the Irish state. It just doesn’t look like oil because it is packaged to look like wind, but in reality is electricity consumers’ money paid to renewable energy developers and investors as REFIT. This way, it is irrelevant where the wind plant is located or whether the wind ever blows or the plant ever generates anything. Better than oil!

  5. A recent study on wind power in Scotland found that wind farms were producing at a much lower capacity than generally claimed by wind farm lobbyists:

    “Stuart Young, author of the report, comments: “Over the two-year period studied in this report, the metered wind farms in the UK consistently generated far less energy than wind proponents claim is typical. The intermittent nature of wind also gives rise to low wind coinciding with high energy demand. Sadly, wind power is not what it’s cracked up to be and cannot contribute greatly to energy security in the UK.”

    He adds: “It was a surprise to find out just how disappointingly wind turbines perform in a supposedly wind-ridden country like Scotland. Based on the data, for one third of the time wind output is less than 10% of capacity, compared to the 30% that is commonly claimed.”

    Interesting to see that the “Spirit of Ireland” founder has already responded to your article albeit without declaring his vested interest in negating your conclusion.


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