El Hierro completes a year of full operation

At the end of June the Gorona del Viento (GdV) plant completed its first year of full operation, during which it supplied 34.6% of El Hierro’s electricity demand with renewable electricity at a cost probably exceeding €1.00/kWh and lowered the island’s CO2 emissions by approximately 12,000 tons at a cost of around €1,000/ton. This post summarizes these unexpectedly poor results, discusses the reasons for them and concludes that GdV, which was intended to show the world how fossil fuel generation can readily be replaced with intermittent renewables, can already be classified as a “failed project”. GdV’s performance further suggests that replacing fossil fuels with intermittent renewables elsewhere in the world could be a lot more difficult than the proponents of renewable energy are prepared to admit.


Details on GdV plant layout, operation and capacities are given in the September update. Previous posts on GdV are accessible through the El Hierro Portal.

Figure 1 plots the daily average percentage of renewables generation supplied by GdV to the El Hierro grid since June 27, 2015, when full operations began, through June 30, 2016: Noteworthy features are:

  • The low renewables generation from September 2015 through January 2016, a result of low wind speeds.
  • The irregularity of renewable energy deliveries to the grid, which can change from 70% or more of demand to near-zero in the space of a few days, again depending mostly on wind speed.
  • The lack of any significant increase in the percentage of renewables generation with time.

Figure 1: Daily average percent renewable electricity sent to the El Hierro grid

The Table below summarizes generation statistics by month. Note that all the data presented in this post are 10-minute grid readings from Red Eléctrica de España (REE) unless otherwise specified:

And Figure 2 shows generation by source during June 2016:

Figure 2: El Hierro generation by source, June 2016

June started inauspiciously with a grid crash, but the 53.9% renewables generation during the month was the highest yet achieved, marginally exceeding the 53.5% achieved in February. Partly this was a result of the two 100% renewable tests conducted on June 14/15 and 19/20/21 and partly a result of strong and unusually sustained winds during the second half of the month (Figure 3):

Figure 3: Three-hour wind speeds recorded at El Hierro airport , June 2016

El Hierro airport is located at sea level some 3km northeast of the GdV wind park. As shown in Figure 4 airport wind speeds generally track GdV’s wind production, confirming that variations in airport wind speeds are representative of variations in GdV wind speeds, although absolute GdV wind speeds would be expected to be higher. The correlation further suggests that there have been no extended turbine shutdowns since project startup. (The “busts” in May 2016 were a result of a failed generation experiment discussed later.)

Figure 4: Daily average airport wind speeds vs. GdV daily average gross wind generation since the beginning of full-time operations

GdV’s Problems:

These can be divided into the three basic categories discussed below – inadequate wind capacity, failure to solve grid stability problems associated with high levels of wind penetration and hopelessly inadequate energy storage. However, it should be noted that GdV does not publish any performance data or supply any information on its operating procedures, so these conclusions are deduced from REE’s grid data plus whatever background information could be obtained from other sources, such as the reservoir level photos and grid frequency data compiled by Rainer Strassburger. It’s therefore possible that some of them are wrong or misleading, and once again GdV representatives are encouraged to point out any errors.

Wind Power

The GdV wind park consists of five 2.3MW Enercon turbines capable of generating up to 11.5MW, but during the first year of operation wind generation never exceeded 7.5MW. Wind has consistently been curtailed, usually but not always at or around the 7MW level. Figure 5, which shows wind generation in June 2016, is an example. Wind was curtailed at 7MW for much of the month:

Figure 5: GdV gross wind generation, 10-minute intervals, June 2016

Comments in previous posts have addressed the question of why wind output is curtailed at this level, but the reasons are secondary. The facts are a) that it is and b) that there has been no significant relaxation of curtailment thresholds in a year of operation. Curtailment of wind power at or around 7MW is obviously considered necessary, presumably because too much wind power compromises grid stability, and short of a system redesign we can be reasonably certain that it will continue at or around these levels.

In addition, wind power is GdV’s only primary generation source, meaning that the wind turbines must be capable of generating at least enough power to fill El Hierro’s annual electricity demand. But over the last year they filled barely more than half of it (45.1GWh demand versus 24.5GWh gross wind generation). Even with no curtailment wind generation would still have fallen short of demand. Clearly the GdV wind park is too small. (Why was it not built larger? The reasons are unclear, but there is evidence to suggest that a capacity factor of around 50% was assumed for design purposes. The actual capacity factor calculated using gross wind generation over the last year is 24%.)

Grid Stability

A 2012 study conducted before GdV started operations concluded that power generated by the wind turbines could be admitted to the El Hierro grid without compromising grid stability provided three of the Pelton turbines in the hydro plant were maintained as a spinning reserve:

The results show that, to ensure system stability in the worst network contingency, the best option is to hold three hydraulic units in spinning reserve mode

This approach has clearly not worked, and as a result GdV has had to resort to other measures. And it’s important to note here that GdV has been experimenting for not just one year but two. The just-completed year of full operation was preceded by a year of testing.

And what are these other measures? There are two basic approaches, both of which must have been developed during the testing period because they were applied as soon as GdV went into full operation:

  1. During lower-wind periods generation is matched to demand using mostly diesel for load-following, assisted or replaced by wind and hydro generation when available.
  2. During higher-wind periods diesel generation is used in baseload mode and held stable at levels of 1.6MW or higher. Load-following is performed by switching wind generation between the grid and the GdV pumping plant, which wastes the excess power by pumping water uphill from the lower to the upper reservoir and letting it flow down again without turning the hydro turbines. In short, the hydro system is being used as a dynamic resistor – a far cry from its intended purpose.

Figure 6 shows generation for July 2015, the first month of full operation and a good wind month. For most of the time diesel was run in a 1.6 or 3.2MW baseload mode and generation was matched to demand by sending excess wind power to pumping. During a few lower wind-days, such as July 7 and 8, demand was matched with variable combinations of diesel, wind and hydro. Overall, however, the plot is very similar to the June 2016 generation plot (Figure 2), confirming that there has been no significant change in operating procedures over the last year:

Figure 6: El Hierro generation by source, July 2015

A third approach was tried in May 2016, with wind and hydro used as baseload generation and diesel for load-following. Needless to say it failed to improve renewables output, and in fact probably chopped a point or two off GdV’s annual percent renewables number. The fact that it was even attempted suggests that desperation may have begun to set in:

Figure 7: El Hierro generation by source, May 2016

Two other factors bear on the question of grid stability. The first is grid outages. Since mid-February there have been five complete or partial grid crashes on El Hierro (February 18 at 0450 and 1040, February 19 at 0320, April 7 at 1220 and June 1 at 1420). The reasons for these outages have not been publicized, but the three February outages correlate with what appears to have been system-mandated shutdowns in wind generation, possibly caused by wind speeds exceeding the turbine cutout speed (wind speeds of up to 16m/s were recorded at the Airport over this period):

Figure 8: Gross 10-minute wind generation versus El Hierro demand during the February 2016 grid outages.

The second factor is 100% renewables testing. Since August 2015 GdV has conducted eleven tests, with durations ranging from 2 to 41 hours, when diesel generation was shut down and all GdV’s generation came from renewables. Two of these tests occurred in June (Figure 2).

The problem in evaluating the significance of these tests is that except for those run on Sundays, when demand is lowest and a grid outage will cause the least damage, there is no obvious reason why they started and stopped when they did. This is in fact a problem with all the GdV grid data, which show numerous changes in the generation mix that do not coincide with any obvious changes in wind conditions or demand. It seems that GdV’s operating protocols, which are reportedly handled by state-of-the-art computer technology, are too complex for the human mind to understand. If so it’s not surprising that GdV has failed to solve its grid stability problem. But the bottom line is that grid manager REE remains unwilling to allow these tests to continue indefinitely, and presumably it has good reasons for this.

Energy Storage

Here we come to GdV’s fundamental (and unsolvable) problem. GdV was built because of the existence of an inactive volcanic crater 700m up the hill, which it was believed would provide enough energy storage when filled with water and linked to a lower reservoir to smooth out fluctuations in wind generation. Unfortunately no one bothered to do the sums and check the wind records. Had they done so they would have found that the storage was adequate to fill El Hierro’s demand for only about two windless days and that low-wind periods on El Hierro can last for months. As a result the project now boasts a pumped hydro system that is totally inadequate and which to all intents and purposes might as well not be there. Here is what I had to say about it in the January/February update :

Now we will look at a specific example – October 2015, the worst wind month since operations began, although December wasn’t much better. The GdV reservoirs have an energy storage capacity of about 250MWh (limited by the 150,000 cu m capacity of the lower reservoir) and I start by assuming that they are fully charged at 0000 hours on October 1, although as a practical matter they won’t be because the second half of September was windless too. How long does the storage last? Figure 7 shows that it runs out at midnight on October 4, leaving a 3,000MWh deficit between demand and wind generation over the rest of the month that would have to be filled with diesel generation.

Figure 9: Figure 7 of the January/February update, showing the 3,000MWh energy storage deficit in October 2015.

A 3,000MWh deficit represents over ten times the storage capacity of the existing reservoirs. Add to it the deficits incurred during the windless periods in September and November and the existing storage capacity would have to be increased by a factor of at least twenty to provide adequate long-term storage. This is not a feasible option, nor is it ever likely to be.

The hydro system does not seem to be working as planned either. Hydro generation to date has been minimal, and the fact that the upper and lower reservoirs seem never to have been filled to more than 20% of their design capacity suggests that there is either a shortage of desalinated water or a problem with dam stability. These are, however, secondary issues.

Is GdV a failed project?

There are two aspects to this question; first, what exactly were GdV’s goals, and second, if they have not yet been met, is there any chance that GdV could still meet them.

As to what GdV’s goals were, there are three different perspectives. First we have the starry-eyed pronouncements of the mainstream media, who were never in any doubt that GdV was henceforth going to supply all of El Hierro’s energy needs with renewables. GdV is nowhere close to doing this, so the verdict here is FAIL.

Second are two engineering studies carried out before project startup, one of which estimated that GdV would supply 68.4% of El Hierro’s electricity demand  with renewables and the other 64.6%. With renewables supplying only 36.4% of El Hierro’s electricity in its first year of operation GdV is falling well short of these projections too. So the verdict up to this point is also FAIL.

Third is the one that counts – the official version of what GdV was supposed to achieve and the one on which the project was marketed and financed. This is set forth in GdV’s project description and reads as follows:

The operation’s philosophy is based on supplying the electrical demand of the island with renewable sources, thus guaranteeing the stability of the electrical network; the diesel engine plant will only operate in exceptional/emergency cases, when there is not enough windwater (sic) to produce the demanded energy.

This is another obvious FAIL. The wording clearly implies that GdV was expected to produce if not 100% renewable energy all the time then something very close to it. In addition, the stability of the electrical network is still not guaranteed and the diesel plant has so far operated for more than 97% of the time, not just in exceptional cases. I hasten to add, however, that I don’t think that GdV’s bloated expectations were an intentional attempt to defraud. They simply illustrate what happens when green energy enthusiasts get carried away with visionary concepts that they do not take the time to evaluate properly, and also the gullibility of the project’s backers, notably the Spanish government, who also never took the time to do their homework before signing the GdV contract. As a result the government paid through the nose for a very modest amount of GdV renewable electricity in 2015 – €12 million for the 8.7 GWh delivered works out to €1.38/kWh – while the El Hierro Island Council, which owns 67% of GdV, is laughing all the way to the bank.

The second aspect of the issue is whether GdV, given time, could ultimately meet its goals. In this context I am indebted to Hubert Flocard, who after carrying out a detailed analysis of GdV’s first-year operating data has concluded that the maximum achievable annual renewable fraction at GdV barely exceeds 50% even when all of the wind and hydro power the grid can accept is sent to the grid. This number is of course dependent on wind speeds over the last year being representative of a typical year, but Figure 10 suggests that they are not exceptional:

Figure 10: Smoothed daily average wind speeds at El Hierro airport since January 1, 2014

The details of Hubert’s analysis are provided in the Appendix at the end of the post.

Finally comes the $64,000 question:

What does GdV’s performance tell us about the potential of renewable energy?

The answer is simple. Intermittent renewable energy is not going to replace dispatchable fossil fuel generation without adequate energy storage backup, and since the amount of energy storage needed is almost always prohibitive it follows that an energy future based entirely on intermittent renewables is not a realistic prospect. As discussed at length in previous posts the only way to integrate significant amounts of intermittent renewable energy with the grid is by maintaining enough dispatchable capacity to cover demand when the wind doesn’t blow and the sun doesn’t shine. GdV has in fact already effectively defaulted into this operating mode.

The unexpected difficulties experienced in stabilizing the El Hierro grid at high wind penetration levels also come as an unpleasant surprise. It is not clear to what extent larger and more stable grids will experience similar problems, but the assumption that any problems of this type can be easily overcome with appropriate technology may require review.

Yet one would never know that anything was wrong from recent press releases. On July 8 GdV will host its first conference, which will be attended by representatives from other countries anxious to replicate GdV’s “success”. Here is an excerpt from the release (my translation):

Wind and solar are variable and fluctuating sources that by themselves are not capable of supplying constant energy, which results in generation limitations in vulnerable isolated systems, which in general do not cover more than 30% of demand*. GdV, which combines unstable wind generation with hydro generation, has been capable not only of making the maximum use of the available resource, substantially exceeding these generation limitations, but on numerous occasions has been the sole source of generation for the island.

*I have no idea which systems these are or where the 30% number comes from.

The second sentence stands out. It would in fact be difficult to cram more misrepresentations into a single short sentence. GdV has not made maximum use of the available resource – generation from the 11.5MW wind farm is routinely curtailed at 7MW and much of the wind power that remains is wasted pumping water uphill. The 11.3MW hydro system has generated an insignificant amount of electricity. The renewables penetration achieved in GdV’s first year of operation does not “substantially exceed” 30%. Renewables have been “the sole source of generation” for only 241 out of 8,880 operating hours, or less than 3% of the time. For 969 hours (11% of the time) renewables generated no energy at all. But of course we never get to read about that.

APPENDIX: Hubert Flocard’s Analysis

June 2016

Diesel 1793.33 MWh
Demand 3891.67 MWh
Renewable fraction 53.92 %
NB : On June 2 there are two missing lines which I have replaced by linear interpolation (my usual way of handling missing data)

From July 1st 2015 to June 30th 2016
Diesel 29768.48 MWh
Demand 45517.93 MWh
Renewable fraction 34.60 %
Wind 24257.93 MWh
Wind turbines load factor 24.01 %

Maximal achievable renewable fraction 51.33 %
(using wind or hydro as much as possible – no loss of wind energy – and diesel when either wind or hydro power is missing). The value decreases to 48.38 % if one asks that diesel never gets below 25 % of average demand. Then again there is no loss of wind energy (but a larger fraction is returned as hydro production with the associated 40 % loss)

Maximal achievable fraction without GdV hydro component and diesel never below 25 % of average demand : 41.01 %
Only 76.95 % of wind production can be used. The rest is lost.


Monthly renewable fraction (red line = yearly average)

Daily renewable fraction

Hourly renewable fraction

Fraction of demand covered by each production (52704 intervals of 10’ each) Diesel = grey, Wind to the grid= green, hydro to the grid ) blue.

Fraction of time in % (over 52704 intervals of 10’ each) with diesel covering a given fraction of the demand. The 00-05% bar corresponds always to 100 % renewable fraction. The 95-100 % bar to (almost) all the demand being covered by diesel production.

Wind power (MW) over 52704 intervals of 10’ each

Power (MW) Wind to the grid = dark green, Wind to pumping (lower bound) = light green, Hydro to the grid = blue.

Electric production (MW) Diesel = grey, Wind to the grid = green, Hydro to the grid = blue

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157 Responses to El Hierro completes a year of full operation

  1. Dave Rutledge says:

    Hi Roger,

    Wonderful work. I am getting the idea that hydro is not as dispatchable as I thought. Also, in California, the droughts that we have from time to time mean that the GWh that is available over the year can be reduced by a factor of two for several years. And finally, where we are the water is also used, which means that power is produced when people want water rather than the other way around.


    • Willem Post says:


      For pumped storage hydro plants to produce dispatchable energy, they must have large upper and lower reservoirs, especially if the pumps are to be powered with intermittent, variable wind and solar energy.

      It is clear from Roger’s analyses, the reservoir capacities, MWh, are much too small. They likely would need to be increased by at least a factor of three.

      What is also clear, eager-beaver folks built first, and analyzed later.

      By now, they likely are fully aware of short-comings, but are too embarrassed to own up to them and recommend a way forward.

  2. singletonengineer says:

    What a great place to have a conference. How I wish that I had been at the one on July 8.

    It would only take one Spanish speaking person person armed with the wonderful information from this site to wipe the smiles off some faces.

  3. Brian Turner says:

    Another case of not understanding adequately what Mother Nature can and can’t do. It also clearly demonstrates what benefits could be had from synchronous wind turbines which would add a lot to stability and load factors. A pity that the only workable sync solution of reasonable size is Dewind, effectively shut down by Daewoo (In difficulties of their own.) Again the sponsors of wind projects not understanding the benefits of sync and too focussed on up front costs.

    • Kees van der Pool says:

      Brian, type 1&2 synchronous wind turbines are obsolete and would be exactly the wrong kind for El Hierro for a bunch of reasons, one of them being poor reactive power control. They are being phased out wherever used.
      The type 4 turbines on El Hierro are exactly the right choice. There are no indications that any of the problems on El Hierro are/were caused by lack of spinning inertia.

      Here is excellent report on the various types and their advantages/drawbacks:


      • Kees van der Pool says:

        I guess the link went south. Here is a better way:


        and click on the “Wind Turbine Plant Capabilities Report” pdf.

      • Kees: You say “There are no indications that any of the problems on El Hierro are/were caused by lack of spinning inertia.” If this didn’t cause them, what did?

        • Kees van der Pool says:

          Hi Roger,

          If you refer to the mishaps earlier this year, it is obvious that the Peltons did not start up when they should have. One look at the ‘hydro’ graphs confirms that. My guess was insufficient diesels to compensate. RED Espana promised a report – I’m holding my breath. . . . .

          Whatever it was, its straightened out and everything seems to be working just fine lately.


          • Thanks Kees. I guess with 48 hours of 100% renewables generation GdV has now set a new record. But 100% renewables will last only as long as the wind does.

      • Brian Turner says:

        Kees, The D8.2 Dewind turbine does not fit into the labels types 1 – 4. This report you kindly referenced seems to be covering only these definitions. Obviously the D8.2 can provide inertia generated from drive train and blades, etc, with the Windrive in the system. They can provide reactive current capability in 60Hz system to 3 x pu. As far as i know there are no D8.2’s installed in Oz. most are in USA & Canada.
        The difficulties at Daewoo Shipbuilding currently does not help.
        Wind load % on grid as it increases, needs reactive capability, lots in fact. Why would Energienet be converting old thermal plant units into synchronous condensers.
        This report talks about synthetic inertia. I have yet to hear any favourable remarks from the grid guys on same?

        • Kees van der Pool says:

          Hi Brian,

          I’m not familiar with D8.2 Dewind turbines – if you have a link to a schematic/technical writeup it would help.

          Also, what are synchronous condensers and how do they relate to windmills? If you mean synchronous capacitors, yes, that is done and they are used here in California to compensate the tremendous reactive current when the big pumps of the aqueduct systems are started up. Judy Curry’s blog has some interesting insights from ‘a planning engineer’ on how that all works. I’ll send you the links when I get home later, fascinating reading, also of the comments.

          As far as ‘synthetic inertia’ is concerned, I’m sure the windmill inverters can be designed to supply 3 times nominal but still is not inertia.


          • Kees van der Pool says:

            Hi Brian,

            In that case, send me a schematic and I can tell you how it relates to the type 4 Enercons, also equipped with an alternator/rectifier/capacitor/inverter. No drivetrain, which would be unsuitable for the wind conditions on El Hierro.


          • Brian Turner says:


            Just Google DeWind. Wikipedia even. This is a standard synchronous machine in every way. except design mods for application and reliability. Voith “Windrive” is the variable speed element to keep generator at 60Hz fixed. Naturally produces Vars and can feed the inertia from blades directly. We even ran LVRT tests in factory, all satisfactory and have one in S America at Veladero-Barrick Gold mine at 4300m elevation. a world record for a 2 MW 6.6kV machine.

      • Brian Turner says:

        Kees, I should have added that I led the initial alternator design team working in close harmony with Dewind.for 8.2 at voltages up to 13.8 kV.

        • Brian Turner says:

          Kees, A synchronous condenser is another name for a standard synchronous machine running on the grid (no driver) taking a small % load from the grid and feeding back pure VArs to control volts. Energinet in Denmark have a couple of old plant generators adapted to motor on the grid of about 300MW origonal rating.

          • Kees van der Pool says:

            Brian, thanks for participating in the conversation. I looked up Dewind. Your earlier reference to Daewoo is now more clear clear.

            You are right, the D8.2 Dewind turbines do not fit in the Type 1-4 classifications and yes, the inertia of the whole assembly would be available to the grid. From the Wikipedia article it seems the company no longer exists. Is there any overriding technical reason for this or did Daewoo just give up?
            Do you know if there are any other turbine manufacturers that are considering a variable gearbox?

            Re: the synchronous condenser, I think they are also known as synchronous capacitors which seems to describe their function better. For obvious reasons, it is not surprising that they are used in Denmark.

            Below the link to the Judy Curry blog regarding wind+solar I mentioned earlier. The comment of aplanningengineer | May 7, 2015 at 6:59 pm | refers to synchronous condensors/capacitors and their possible function in wind/solar installations:



          • Brian Turner says:

            Kees, Dewind were reasonably successful in USA due to having to compete against GE who had patent blockers on DFIG in USA. So cost was not quite the same issue as elsewhere. as far as I am aware there is no technical reason they are where they are. Daewoo are great at building ships. No cross over skills I am afraid to power generation.
            There is a company in new Zealand who were making 1 MW synchronous machines using a 2 bladed turbine. They bought the alternators from my old company.


  4. Euan Mearns says:

    They simply illustrate what happens when green energy enthusiasts get carried away with visionary concepts that they do not take the time to evaluate properly, and also the gullibility of the project’s backers, notably the Spanish government, who also never took the time to do their homework before signing the GdV contract. As a result the government paid through the nose for a very modest amount of GdV renewable electricity in 2015 – €12 million for the 8.7 MWh delivered works out to €1.38/kWh – while the El Hierro Island Council, which owns 67% of GdV, is laughing all the way to the bank.

    Roger, I refuse to accept that they are so dumb. It is elementary engineering to model supply and demand. El Hierro appears to be one of the least prosperous of the Canary Islands. Tourism on the other islands has brought real prosperity. Loads and loads of jobs in construction, bars, restaurants, car rentals, airports, shops, you name it.

    This project appears to have brought some high level jobs to the island and is lining the coffers of the island council. What’s not to like from their perspective? Two electricity systems to run instead of one.

    So I think the project may in fact be a gigantic lie. They have the choice between that and being unimaginably dumb.

    • Mike Mellor says:

      As I pointed out in an earlier comment, the windfall (ahem) of generation payments made to the island work out at about €10,000 per capita, paid for by mainland Spanish consumers. I’m not at all against subsidies for poverty relief, but this seems an exceptionally wasteful way to go about it.

    • Euan: As far as I can tell there’s no one on the Island Council who has the technical background necessary to understand what’s happening at GdV. Their sole source of information is Juan Pedro Sanchez, the Council’s liaison with GdV. And Juan Pedro, who was involved in the early stages of the project and has an interest in seeing it do well (and I suspect also writes all the press releases) tells them only about the good things that have happened. So it’s quite possible that the Council genuinely believes that GdV is a success and sees nothing wrong with getting paid mucho dinero for it output.

    • My intervention is more a question than assertive.
      Utilities are not used to compute only energy, also the ETS and diesel substitution is very lucrative for wind.
      El-hierro belongs to Red Elettrica that certainly have to discount certificates.
      I’ve miss the reason you consider only one year to work out the €1.38/kWh .
      If you consider instead 20 years of life is 0.07/kWh plus maintenance other 0.07/kWh the cost is 0.14kWh and the green certificate is about .08kWh paid by all european. So a final cost for the island is 0.06 kWh that is a good deal compared to diesel.
      Perhaps this is the Council reason of such a satisfaction.

      • Massimo

        “If you consider instead 20 years of life”

        That cost was based on the payment made for electricity delivered this year, alone. This payment will remain failryl constant (+ inflation). The CaPex is on top.

        • as I understand it most of the 12 million euros paid to GdV in 2015 came from a clause in the contract which guarantees the project a minimum rate of return on investment. The amount paid for GdV power was probably only a small fraction of the total.

        • This means the CapEx is over €100M? right?
          So I’m curious to understand why you are analysing so deeply and so extensively a plant that is almost 20 times out the target. Are you just twisting the knife?
          I could suggest to open another topic focusing Ouarzazate solar or the Photo-voltaic in Italy that is declining of 12% year.

          Even with an old steam engine generator and a coal provision the economics would be at 0,06€/kWh without subsidies. Additionally 100M€ are enough to buy and stock,i.e. in a lake bed, 3 Mtons of coal and run such generator for 1000 years (with the same power) and with a very slow and diluted release of the emissions in atmosphere.
          What about the plant lifespan? 20 years?
          So considering the huge CapEx is now fully converted in CO2 with oil intensity and dispersed in atmosphere, I could assume the Coal would be 50 times (1000/20) greener than El Hierro plant.

          • “This means the CapEx is over €100M? right?
            So I’m curious to understand why you are analysing so deeply and so extensively a plant that is almost 20 times out the target. Are you just twisting the knife?”

            That is a fair point to an extent but why not analyse it? It is his blog.

            You could also ask why so much hullabaloo was generated in the media with no follow up analysis?

    • Kees van der Pool says:

      Hi Euan,

      Well, maybe not a gigantic lie but certainly wild green exuberance, coupled with unreasonable extrapolation of achievable numbers and many local and global stakeholders converging to justify this project. All the way from the engineering numbers of fifty or so percent RE to a full 100% and thus a shining example for the whole world. Roger’s reality turns out to be around thirty percent – a number that Belen (de-facto Chief of El Hierro) carefully avoids mentioning. Instead, she talks about the impressive amount of carbon dioxide saved – a number that won’t speak to many.

      Meanwhile, the island counsel is laughing all the way to the bank, El Hierro is firmly on the map with groups of visiting dignitaries and green pilgrims kicking extra euros into the local economy. El Hierro is ‘el fin del mundo’ without a great deal of tourism and this is all very welcome, as you mentioned.

      Technically, there is nothing wrong with the GdV plant. Apart from the mishaps earlier this year, where the hydro generators did not kick in when the wind flawed, everything seems to work just fine, with a good day yesterday and today at 100% RE. The blackout and semi-blackout were acknowledged by the Spanish grid authorities who promised an inquiry – who knows, maybe we’ll get to see an explicit report on the ‘why’.

      The design of GdV is IMHO not in question. The engineering studies by the Spanish engineers look as solid as any, Enercon designed the windfarm control unit and hydro plants are very well known entities as Spain has a huge installed base of hydro power. The diesel plant has been in operation for many decades – no mystery there either. Some points were raised earlier in this blog regarding spinning inertia or lack thereof with 100% RE. Julia Fernández paper, referred to many times earlier, explains this was solved with the synchronous hydro generators (‘Peltons’) spinning as flywheels in ‘dry’ mode. The megawatts they can instantaneously bring to bear on the grid in case of a malfunction is more than sufficient to keep the frequency long enough within the set levels to allow time for the primary regulation to kick in.

      The system is not optimal for two reasons: the curtailing of the windfarm to about 7 MW from the nominal 11.8MW due to excessive turbulence at the site and, as became clear thanks to the sleuthing of Roger, Hubert and Rainer, a limited amount of water in the reservoirs. Maximum water and ‘balls out’ on the windmills would extend the 100% RE intervals but desalinized water is expensive, especially on El Hierro, and I’m sure that Enercon wishes to avoid risk to the windmills as much as possible.

      These are ‘judgement calls’ – it would be nice if GdV would, one day, appear on this blog and explain their thinking.


      • The system is not optimal for two reasons: the curtailing of the windfarm to about 7 MW from the nominal 11.8MW due to excessive turbulence at the site and, as became clear thanks to the sleuthing of Roger, Hubert and Rainer, a limited amount of water in the reservoirs.

        Kees, Thanks, but you’re forgetting the two key defects: 1) even with no curtailment the wind farm still wouldn’t be able to fill El Hierro’s annual demand and 2) the pumped hydro storage would still be about twenty times too small even if the reservoirs could be filled to capacity.

        • Kees van der Pool says:

          You are absolutely correct Roger – I was referring to the system as currently designed not being optimized, not arguing that non-curtailment and more water would yield 100% RE.
          I don’t think it was ever dimensioned to supply 100% RE, although Googling ‘El Hierro Renewable’ yields enormous numbers of starry eyed articles about El Hierro’s 100% ‘energy independence’ (not even just ‘electricity supply’ independence).

          Whatever the design goal %, it’s not meeting it because of the curtailment of the windmills and lack of sufficient water in the reservoirs. I don’t know if the curtailment was something decided on from the beginning (I doubt it) but not filling the reservoirs is a conscious decision. Too expensive? Won’t materially increase the 100% RE intervals anyway? Who knows.

          Right now, the hydro plant is a very expensive power dump for excess windpower, occasionally assisting with a blast of hydro. Even as a demo project it stinks, but everybody concerned is now aboard the green train that left the station a year ago and it will be a while before reality about wind/solar sets in.

        • Willem Post says:


          “2) the pumped hydro storage would still be about twenty times too small even if the reservoirs could be filled to capacity.”

          How was the 20 times arrived at?

          How much is maximum capacity, MWh, and how much is the actual working capacity, MWh.

  5. Anteros says:

    Thanks for this comprehensive and thoughtful post, Roger. Impressive.

    I checked the Wikipedia article on El Hierro – specifically its section on energy generation – and it exceeded my expectations (my expectations were negative, and it exceeded them in that direction..)

    Here’s how the Wikipedian renewable energy enthusiasts like to portray the El Hierro experiment. An alternative (un)reality methinks!

    “According to the Ministry for Industry, Tourism and Commerce, El Hierro will become the first island in the world to be self-sufficient for electrical energy”

    “The closed-loop hybrid wind/hydro system is expected to save approximately US$4M per year (calculated with January 2011 oil prices) previously spent on about 40,000 barrels of crude oil imported annually, and makes the island completely self-sufficient for electrical energy

    “….five wind turbines with 2.5 MW each, which are the island’s only electricity supply”

  6. Diarmuid Foley says:

    My thoughts ” without grid-scale storage variable renewable energy is like a one-legged kangaroo dancing to the sound of the cash register “

  7. Diarmuid Foley says:

    The Canary Islands ( population 2.1 million ) are ideal for a small modular reactor, or series of reactors. I would be interested in en economic and technical feasibility study of same.

  8. Rainer says:

    thank you for this post. Think it says all.
    Please put this post also in the http://euanmearns.com/el-hierro-portal/.

    2016-07-10 23:30 diesel off till now

  9. OpenSourceElectricity says:

    Well, the problems all come down to the hydro plant, being the most expensive part of the system, being a complete failure till now. What we see so far, is what a wind farm of 10MW curtailed to about 70% of it’s output continuously can do to suport the grid, which would have cost alone maybe 20 Mio € on this island.
    Be aware that wind power often drops _past_ Diesel failures, if you take a close look into data.

  10. GdV back on 100% renewables generation since 2340 last night.

  11. Jose A. says:

    I think there’s a typo:

    “As a result the government paid through the nose for a very modest amount of GdV renewable electricity in 2015 – €12 million for the 8.7 MWh delivered works out to €1.38/kWh –”

    That should be 8.7 GWh.

  12. RDG says:

    The post from ‘Stuart’ two threads ago is completely wrong and scams like El Hierro and Energiewende will continue until people stop treating the word ‘Energy’ in the abstract.. Renewables is not just another “energy source” additive to our existing sources. Wood–>Coal–>Oil were new dense and ordered sources of ‘continuous burn’ (combustion) with novel chemical and physical properties that provided an increased multiplier effect allowing societal progression. Renewables are not additive in this context. Who in our industrial based civilization wants intermittency and unadjustability and nothing but electricity? The financial “industry” wants it for obvious reasons…nobody else…because the financial industry increasingly is living in an abstract world indifferent to the needs of people. Lords and Kings are not interested in our welfare.

    Whether renewables is cheap (from a naive and deliberately misleading price viewpoint) or ‘well designed’ is of no importance. Bottom line, It is not even modestly additive in our existing industrial context nor is it possible to run any kind of functional society on renewables alone. Ask the German and California commenters what they are “transitioning into”. I have no idea. But from the looks of it, with the core german banks in trouble, it would appear they are transitioning into chaos and economic ruin.

    I don’t know why everyone seems to obsessed with getting rid of something (fossil fuels) that is impossible to do? Why is controversial to say “El Hierro is a scam”?

    Stuart says:
    July 8, 2016 at 5:15 pm

    But demand for oil and gas continues to rise.

    In 2009 the world consumed 84 million barrels per day, this year we will consume 95 million barrels per day.

    Renewables are not replacing fossil fuels they are merely providing an additional energy source. If you look back over human history, no energy source has ever been replaced.

    Gas did not replace oil, oil did not replace coal, coal did not replace wood. Today we burn more gas, more oil, more coal and more wood than any year in human history.

    New energy sources are merely added to the mix, the truth is we have never replaced an energy source. New sources of energy just increase aggregate economic demand. Demand for energy is not capped.

    • Stuart says:

      You seem to have misinterpreted my point.

      My point is that renewables CANNOT replace fossil fuels. Indeed no primary energy source has ever been replaced by a new(er) energy source.

      Every new energy source that has ever been introduced has been accretive rather than displacive. We burn more wood today than the Romans, more coal than the Victorians.

      This is what I mean when I say “additive” new ways to harness energy do not displace old ways to harness energy, we continue using them all. New energy just leads to more demand.

      At the highest over view we cross over into ecology.

  13. ristvan says:

    Very nice analysis. Hyped hope meets grid reality. Reality wins. Hope is hopeless.
    GdV also demonstrates that renewables are severely uneconomic. Warmunist renewable cost comparisons never include the cost of intermittentcy backup. Here, that was to have been the missized pumped hydro. APlanningEngineer (senior utility exec with grid engineering background) and I posted The True Cost of Wind at Judy Curry’s some months ago. We corrected the several egregious ‘cheats’ in the official US EIA LCOE analysis published mid 2015. Result: CCGT ~$58/MWh, wind ~$144/MWh

  14. Leo Smith says:

    Obviously they should have installed kites….;-)

    • yes, they should…
      with €100M of CapEx we could offer:

      – 100 MW installed with 7000h of availability
      – Gold plated power wings and ropes
      – all pulleys in solid gold
      – an improved supercaps equipment to covers the erratic power interruption
      – full insurance covering safety, security, technological, production risks, and skeptics
      – a bunch of Italian girls as tour operators for the farm
      – colorful helmets for people too afraid to wings

  15. Stuart says:

    A more dispassionate article would be more powerful. There are so many superlatives and instances of feigned incredulity that it reads a bit like a political manifesto (not a criticism, just feedback).

    For balance perhaps mention some positives in the conclusion even if they are overshadowed by the negatives. Again adding some opposing points actually makes the case more powerful by making the case more objective.

    The conclusion that the storage/buffering requirements of a power grid based on intermittent primary energy are poorly understood and commercially untested is an extremely important point. On this conclusion I applaud the work.

    Empirical data from commercial scale operations is far more authoritative than any theoretical or prototype data. Here we see it laid bare.

    The $/kWh for renewable technologies, even though it is falling, is currently insulated from the cost of storage because the world still has a fossil fuel base load as our primary energy source.

    If you remove the fossil fuel base load you might expect the $/kWh of renewables to explode.

    This leads me to a further hypothesis, is there a glass ceiling for renewables as their market share of the energy mix? If so what is this figure?

    In light of this would a cleaner and more economic global power supply involve gas and carbon capture storage?

    Is gas+CCS cheaper than renewables+storage? Governments should stop mandating preferred technologies and let the markets decide which of these clean power solutions can address the world energy demands and our emissions problem.

    It’s time to end subsidies and introduce carbon pricing.

    • There are so many superlatives and instances of feigned incredulity that it reads a bit like a political manifesto

      Could you please provide some specific examples?

      • Stuart Ellison says:

        1). June started inauspiciously with a grid crash – remove the word inauspiciously.

        2). The “busts” in May 2016 were a result of a failed generation experiment discussed later – remove the word failed (experiments that are completed are not failed)

        3). *hopelessly* inadequate energy storage – remote the word hopelessly

        4). 7MW is obviously considered necessary, presumably because too much wind power compromises grid stability, and short of a system redesign we can be reasonably certain that it will continue – This is all subjective and you cannot be “reasonably certain”.

        5). filled barely more than half – remove the words “barely more than”

        6). Needless to say it failed to improve renewables output – no evidence to support the assumption that this was an attempt to improve renewables output.

        7). The fact that it was even attempted suggests that desperation may have begun to set in – Subjective, no evidence provided to support the assumed goal of improved renewables output.

        8). there is no obvious reason why they started and stopped when they did – contradicts earlier statements that it was “obvious” and “clear” what they were doing. In reality the data does not support the “reasonable certainty” of the assumed operating strategy.

        9). It seems that GdV’s operating protocols, which are reportedly handled by state-of-the-art computer technology, are too complex for the human mind to understand – hyperbole.

        10). First we have the starry-eyed pronouncements of the mainstream media – remove the term starry-eyed

        Another interesting note is the wind curtailment, they have 5 x 2.3MW turbines and they curtail the output at ~7MW. This indicates that only 3 of the 5 turbines can operate at a time. Is this down to placement of the turbines?

        • Stuart Ellison says:

          I really don’t want to bicker about semantics. Please feel free to delete the above post and the first two paragraphs of my original post.

          It just distracts from the discussion.

    • @Stuart

      Empirical data from commercial scale operations is far more authoritative than any theoretical or prototype data. Here we see it laid bare.

      This is one of the most harmful and dangerous and in the meantime shared/agreed statements I ever read. And isn’t a semantic issue, it is very philosophical.

      • Stuart says:

        Hi Massimo,

        Why do you believe it is dangerous to give more authority to empirical commercial scale data than to theoretical data?

        I find that rationale absurd.

        Theoretical or prototype data is by definition based on assumptions and is untested. Empirical data from a full scale system does not share these assumptions or the lack of physical scrutiny.

        • We all studied Math some engineering other economics; we cannot negate our ability of abstract thinking. My teachers said me that something have to run well first in mind, then mandatory on paper (computer /simulation) and only at the end real. The risk is to jump the paper phase and kicking mortal hit to the world economy like PV or commits bloody errors.
          The hydraulics of El-hierro is not Rocket/KiteGen science, everything is available in the schoolbooks and it is easy to figure out the overall behavior and performance on paper.
          You have to check in advance the resistance of the upper lake or the piping working pressure, because safety.
          You have, as well, to check in advance the energy balance and the economics, with a relative precision that cannot admitting uncertainties to the decision-making.

          • Euan Mearns says:

            Massimo, Roger has been following the El Hierro story for a year. If you check out the El Hierro portal. We agree that we could easily work out that it could never work on paper in advance. And yet those in charge were unable to do this. Instead it is advertised as a 100% renewables scheme. And despite the abject failure it is still hailed as a success. By design it could never have worked. But on top of that it is evident that the top reservoir, built in a volcanic vent, has failed. So it is an engineering disaster too. I can’t recall the exact cost, but its something like €80 million. A lot of it EU money. Spain is not exactly rolling in wealth. We are following the story to try and expose it for what it is.

            But I think we all agree that you begin with paper, brains, computer and ideas. Then tests. Then full scale testing.

    • robertok06 says:

      “This leads me to a further hypothesis, is there a glass ceiling for renewables as their market share of the energy mix? If so what is this figure?”

      The ceiling is their capacity factor relative to the country where they are installed (i.e. one cannot use the capacity factor of PV in California o Chile to make forecasts for PV in Sweden or UK).

      This, and more, is rather well explained in this paper…


      … which I keep permanently opened next to the the tab for this excellent blog. 🙂


    • gweberbv says:


      the glass ceiling is – in a very rough approximation – reached when the level of penetration is equal to the capacity factor (assuming that the capacity factor is related to the maximum achieveable output). For example solar PV in the northern part of Europe has a CF near 10%. In a naive way you can assume that it produces at nameplate capacity for 10% of the time and zero for the rest. If we assume that demand is flat all time, solar PV installations with a nameplate capacity equal to the demand could supply the system for 10% of the year. And each kWp installed on top of that fleet would produce excess power that goes to waste in absence of energy storage. So, here is your ceiling: penetration = CF (in this simplistic picture).

  16. Pingback: El Hierro, fiasko för ”förnybart” | KLIMATSANS

  17. Blackburn's with Darwin says:

    48hrs and counting since the last carbon-emitting compression stroke … and all against no out of the ordinary wind data.

  18. Pingback: YOU!: Fix the US Energy Crisis | Page 66 | Physics Forums - The Fusion of Science and Community

  19. Rainer says:

    2016-07-13 07:00 Diesel on

    • Kees van der Pool says:

      Hi Rainer,
      Maybe they were getting ready for the morning peak without having to use hydro and so allow further pumping. A roundabout way to pump with diesel power, prohibited by the GdV rules.

      • Kees van der Pool says:

        Um – it would be so nice to have a person ‘on the ground’ to take pictures of the reservoirs. . . . . .

        Knowing the levels would help a lot in trying to fathom GdV’s thinking.
        Three months and two weeks to go? Camera already packed?

  20. Rainer says:

    2016-07-13 15:30 and
    2016-07-13 16:00
    7.8 MW Eólica
    New max ???
    Still not 11.5 MW……

  21. Between 2330 on July 10 and 0650 on July 13 GdV completed 55 hours of 100% renewables generation, easily exceeding the previous record of 41 hours. All of the generation came from wind except for a few tiny squirts of hydro.

    But there was still significant loss of wind power because total wind generation exceeded demand for almost all of the time and had to be curtailed. The hydro system was evidently incapable of storing the surpluses.

    And once again, why did the test start and end when it did? There was no change in total wind generation that could account for it.

  22. http://www.eldiario.es/canariasahora/sociedad/Hierro-abastecerse-seguidas-energias-renovables_0_536846948.html

    El Hierro sets a new record by supplying itself with renewable energy for more than 55 consecutive hours.

    We have demonstrated that (100% renewables generation) is indeed possible with the technologic formula of GdV – Belén Allende, President of the Island Council.

    During the present year, GdV has supplied 54%* of the island’s electric energy, a very significant fact taking into account that until June the plant had not completed its first year of operation. The plant is technically capable of covering 75%** of annual electricity demand, but the first phases are subject to a gradual integration to determine how it handles new and continuously changing scenarios in resource availability and demand behavior. Juan Pedro Sanchez, Island Council represntative.

    * From January 1 through June 30, 2016 GdV supplied 38.6 percent of El Hierro’s electricity demand.

    ** Our best estimate is 51%.

    • sod says:

      Thanks for the link. It also says:

      “No risk to system stability

      “We can distinguish between two types of 100% renewable energy, on the one hand that refers to the moment, such as achieved today, which is to keep the grid only alternative energy without a risk to system stability , and that is already a proven reality and increasingly is given in El Hierro more frequently and for longer periods lasting, “says Allende.

      In this line, he said that achieving supply 100% of the annual electricity demand with renewable is a long-term goal but in which already works, “and proof of this is the new direction towards integrating sustainable mobility island, which will, surely, increase the threshold of 70% of annual demand supply which is technically capable of reaching the Central hydro-wind and that will be very soon when you have optimized system operation. ” “

    • sod says:

      Why is their percentage number off by such a large amount? Looking at the calculations above, even when looking in a positive way at this year, we get only close to 40% on average.

      Are we missing some hydro part? Strange!

      • If we include all the power generated by GdV, including the wind power wasted in pumping, the January-June renewables percentage increases from 38.6% to 50.3%. Adding in the first half of July could well increase this to 54%. But they wouldn’t do that, would they?

        Would they?

        • Rainer says:

          Even REE does it all time.
          Any 10 min 100% in REE is the produced electricity and not the demand.
          In other words: Base of 100%=demand + kids water world (water pumped round and around)
          source the graph in:
          A BIG system failure.
          REE should know better.
          GDV and the Cabildo de El Hierro do not want to know better.

  23. Kees van der Pool says:

    Roger, you wrote “The hydro system was evidently incapable of storing the surpluses”‘

    Another confirmation there is insufficient water in the system. Your graph shows vigorous pumping over the time period with just a few blasts of hydro, in no proportion to the amount of pumping.

    The 100% RE was cut short despite perfect wind conditions of 10m/s at the airport.
    Non-curtailment of the windmills would have made no difference – it just would have increased the volume of water being pumped around to dump the surplus energy.

    • Kees:

      Water is a much more precious resource than electricity on El Hierro, and I suspect what may have happened is that the farmers are taking everything they can get from the desal plants and leaving little or none for GdV. The alternative explanation that the reservoirs are beginning to fail is possible, but there’s no sign of impending liner failure in any of Rainer’s earlier pictures.

      Another possibility is simply that GdV has found that they get the best bang for the buck by using the hydro system as a dynamic resistor to balance win output against demand rather than to store energy. This allows them to keep going with a minimal amount of water in the reservoirs. All they need do is pump it around and around, adding a little now and then to make up for evaporation losses.

      You’re right about the wind. For the last month it’s been blowing from the north at speeds of between 6 and 10m/s at the airport – the longest stretch of sustained winds since January 2014, which is as far back as I’ve gone with the wind records. But GdV is still able to use only a fraction of the wind park’s output, and at some point the winds will die and El Hierro will be back to good ol’ diesel power again.

      • Kees van der Pool says:

        Roger, that about sums it up. The 50% (max calculated) – 30% (actual) = 20% “extra RE” time possible by purchasing 150,000 m^3 expensive desalinized water probably does not make any financial sense. The diesel supply ship has to sail anyway and 20% extra is just marginal costs.

        I wonder if the earlier blackout & semi-blackout were not simply caused by lack of water in the top reservoir and thus no hydro when it was needed. Hard to believe, one would hope that GdV would be like hawks on the reservoir levels.

  24. sod says:

    I have been looking at the july data over the last few days.


    Over the first half of the month so far, diesel was basically stuck at 1.5 MW output all the time, with a small period of higher diesel use on the 5./6. of July and the zero use around the 12th.

    If this keeps going, we might see a new highest percentage, possibly above 60% for July (or at least for a significant part of the month).

    And the wind speed forecast for the next couple of days is still pretty high.


    PS: On a seperate topic, this graph about wind direction is interesting.


    Could the reason for the horrible wind output from september to january be a problem with wind direction?

    • Roger Andrews says:

      The turbines at GdV are aligned EW along the crest of a ridge and designed to catch northerly winds. There is a correlation with wind direction, with wind production falling off when the wind turns east or west, but the correlation with wind speed is stronger. The low wind output in September through November last year was a result of low wind speeds, not wind direction.

      July 2016 will almost certainly set a new renewables record for GdV because of a period of unusually sustained winds. If the wind kept blowing like this year-round GdV would be capable of filling 70% or more of El Hierro’s electricity (although not energy) demand. But of course it won’t.

  25. Rainer says:

    2016-07-17 08:20 Diesel off

  26. ducdorleans says:

    As usual, I’m late to this party … 

    A big thanks to Roger, Euan, Rainer, Hubert, Damian, and all the others who are following the El Hierro experiment for us …

    From March 2007, when I first read about El Hierro in the “De Standaard” newspaper here, I promised to follow up on it … I then thought that about all engineering parameters were in favour (or even about as optimal as it could get) of “green” electricity … Low demand all residential, plenty of wind on an island, plenty of elevation difference, hardly any constraint of building reservoirs and windmills where needed, etc. etc. …

    You all saved me a lot of work !

    As to the results … Well, it is something … But with 35% we’re still a long way from 100% green electricity, let alone 100% green energy … ( FYI, that 100% green energy is foreseen, here in Belgium, for the year 2050 …)

    which publication only made 1 of my old engineering professors laugh loudly and publicly … that only 1 was, was a very sad moment for our profession, imho …

  27. Rainer says:

    2016-07-18 10:10 diesel on

    • Another Sunday test (25 hours long) but a very interesting one. Wind drops to near zero and is replaced by hydro before diesel kicks in even though the wind was still blowing strongly according to the airport records.

      • Kees van der Pool says:

        Roger, maybe I’m beating a dead horse but I think it is a consequence of the severe turbulence mentioned by Enercon regarding the windconditions at the site. The airport measures windspeed over a certain sample period (30 minutes?) but nothing about the instantaneous conditions facing the windmills.

        Looking at the graphs, I think the defensive mechanism of the windmills kicked in by constraining the output in successive increments until turned off at 15:50. Large swings before that with the pumps being turned on and off within a few sample periods.

        The airport has not posted 15:50 yet. It will be interesting to see if there might be an explanation there.

        • Kees van der Pool says:

          Airport @ 4:30 pm, average windspeed 9 m/s, windgusts 15 m/s, direction 350deg.

          • Rainer says:

            E70: Calculated power curve published up to 25m/s

          • Kees van der Pool says:

            Hi Rainer,

            Yes, I have the same calculated power curve. Consider that this is not only calculated but also assumes ideal, steady windconditions. When the wind is gusting to the tune of 15 m/s at the airport, you can be assured it is really gusting at higher windspeeds at the windfarm. In one of your reports of your visits to GdV you mentioned it was difficult to stand up.

            Right from the beginning, Enercon restricted the output by forty percent because of turbulence and there must be a very good reason for that, especially with a highly visible pilot project. Windshear and turbulence cause uneven loading on the hub/blade/bearing assembly with bearing failure the prime failure mode of windmills.

            I think the sequence ‘wind off’ and a little bit afterwards ‘diesel on’ points in the direction of an automatic shutdown. If it was done manually, I think it was an entirely logical decision to shut the windpark down and wait a bit until the conditions get better as the kWhrs are not really needed since there is no sense in just pumping water around.


        • Kees: That’s a plausible explanation. The turbines are sited on a ridgetop to maximize wind velocity but the topography in the area could well generate turbulence. To judge by the consistency of wind output at other times. however, it seems that turbulence at the scale necessary to force curtailment is a fairly rare occurrence.

          • Kees van der Pool says:

            Yes. I think its not so much curtailment which implies curtailment at all windspeeds in order to be able to regulate both down as well as up (= ‘more wind’), like the Irish windmill scheme.

            It is more constraining the output at a given level, beyond which the risk does not warrant the incremental power that can be generated, which will be mostly wasted anyway.
            Lacunae like this can be compensated with diesel and hydro without screwing up the overall RE percentages and general correlation with the airport numbers.

            Its either the wind or the ‘hfrik explanation’: ‘GdV operators have taken leave of their senses’ :).

          • Rainer says:

            lower storage empty……

          • Kees van der Pool says:

            Yes, that is also an explanation. There probably has to be a minimum quantity of water in the system to allow ‘pumping around’. Evaporation, due to the summer sun and lots of wind, may have dropped the levels too low.

            They are busy hydro generating @ 22:00 with some extra diesel for the evening peak so the lower reservoir is filling up.
            Still no windpower, even at 11m/s (all by itself odd), with a possible reason that they cannot pump yet. No pumping = no way to absorb excess energy from the windpark = turn off the windpark.
            Another manifestation of not enough hydro in the plant?

            We really need that ‘man on the ground’. . . . . .

          • It is more constraining the output at a given level, beyond which the risk does not warrant the incremental power that can be generated, which will be mostly wasted anyway.

            Because El Hierro demand hardly ever exceeds 7MW effectively all of the wind power generated above this threshold would be wasted.

          • Kees van der Pool says:

            Exactly, unless there is enough water available to do actual useful pumping.
            The windfarm started generating again @22:30. They will have to cut back either the hydro or the diesels soon, With this kind of wind, hydro should flip in the pumping mode shortly.

          • Greg Kaan says:

            So what’s the answer? More desalinators?
            Then they wouldn’t need to do so much pumping, either.

            Bravo to Rainer’s “kids water world” reference 😀

          • Greg: There is no solution. Even with unlimited desal water, no grid stability problems and an enlarged wind park GdV still won’t be capable of supplying 100% year-round renewable electricity to El Hierro because the storage capacity of the reservoirs is totally inadequate (see Figure 9). There’s nothing that can be done about this, which is the main reason I declared GdV to be a failed project.

          • Greg Kaan says:

            100% is ridiculous, I totally agree.
            But I was thinking in terms of GdV being able to better utilize the storage reservoirs/penstock/peltons that have been constructed so that diesel consumption could be further reduced.
            The ROI will always be miserable but an increase in the desalination capacity to allow the current storage capacity to be used would seem a reasonable expenditure in light of the vast sums already spent.

          • There’s a catch 22 here. More desal plants will need more electric power, and unless this comes from diesel – which defeats the purpose of the exercise – it will have to come from GdV. But GdV needs more water to get the hydro system working properly and produce the power.

            And then there are the island’s banana-growers, who never saw a cubic meter of fresh water they didn’t like.

  28. I’ve been wondering why GdV starts and stops its 100% renewable tests when it does. I’ve always assumed that these tests have been closely coordinated with grid operator REE, so yesterday I took the bull by the horns and emailed REE to ask them why. I got the following response:

    Estimado Sr. Andrews:

    En contestación a su petición, le informamos que nosotros somos transportistas en alta tensión y responsables del sistema eléctrico, pero no participamos en la generación de electricidad. La Comisión Nacional de la Energía y el Ministerio de Industria y Energía pueden disponer de información relevante. Le recomendamos, por tanto, que visite:

    Regarding your question, we inform you that we are high-tension distributors responsible for the electric system, but we do not participate in the the generation of electricity. The National Energy Commission and the the Ministry of Industry and Energy may have relevant information. We therefore recommend that you visit (their websites) ….

    Back to square one, it seems.

  29. sod says:

    Diesel on again? (10 am)

  30. Having thought about this a bit, it occurs to me that, based on the charts, that the main reason that this is not working as well is it could is that the backup power source (Diesel) is not flexible enough. This is probably the reason that wind is curtained at 7 MW although it is possible that the pumping capacity of the pumped storage might also be a factor.

    If they had a GT or CCGT (which can still be run on fuel oil) the backup power could be throttled down to zero with the turbine still running. I understand that a gas turbine idles at full speed but very little fuel since it has no load.

    It that problem were addressed a simple control algorithm should be possible with the GT doing the load following unless there was sufficient power from the wind turbines. In that case, load would be followed by diverting power to the pumps and if the upper reservoir filled, then water would need to be drained from it (power wasted) as is done now. When there was not sufficient power from the WTs, then some stored power from hydro could be used based according to an algorithm taking into account history of wind and possibly weather predictions. And if using hydor for spinning reserve works, this could be done when needed but I understand that it is best not to turn GTs on and off very often.

    It should then no longer be necessary to curtail the wind output except in extraordinary wind conditions because the GT should be flexible enough to simply turn down and any excess could be sent to the hydro storage pumps. If this still wouldn’t work, then more pumping capacity might still be needed.

    I would presume that the original designers didn’t consider that they needed a more flexible fossil fuel backup power source because this was going to work on 100% renewables.

    Also, as you suggested, with the low capacity factor of the wind farm, it would appear that installing at least One more wind turbine is needed.

    I do, however, agree that it was totally unrealistic to think that this would work out of the box or that it is possible to obtain over 50% of their power from renewables without a lot of storage capacity — a totally impractical amount of storage capacity. Perhaps they could add some solar PV.

    • “Having thought about this a bit, it occurs to me that, based on the charts, that the main reason that this is not working as well is it could is that the backup power source (Diesel) is not flexible enough.”

      I find that hard to believe. However if true, then surely there would be periods when the wind is not curtailed?

      • Greg Kaan says:

        It’s not true. The diesels ran by themselves to power the El Hierro grid prior to GdV and load following was not an issue. Most smallish island grids run with diesel (or gas) reciprocating generators.

        I still suspect that the “inertial emulation” feature of the Enercon E-70 turbines could be at the root of the instability issue since each of the turbines form a major portion of the generation capacity when the wind is blowing strongly. This means that as the inertial emulation adjusts the output of the turbine to suit the assessed active power and frequency requirement, the grid responds more than it would if the turbine capacity was lower. With 5 turbines, each independently assessing the grid condition and making adjustments, I can see the adjustments overshooting, causing the inertial emulation circuits to reassess and then adjust in the opposite direction. As all the turbine adjustments fall into sync it could topple the grid.

        There are those who have openly dismissed this as a possibility but I haven’t seen anything that discounts this.

        I also suspect that the Enercon was hoping GdV would be a proof of concept for their inertial emulation feature in small island grids

        • Kees van der Pool says:

          Greg, as one who ‘openly dismissed that possibility’, I can only hope that Enercon sees the light after a full year of causing (perceived) instabilities of the grid and fixes the defect in the operation of the windfarm.
          They should remove the ‘inertial emulation’ feature, which is, after all, an option that can be deleted with a simple software change.

          If you could point at a particular moment where you think the Enercons were guilty of crashing the grid, Rainer might be so kind as to look in his frequency logs, which would without doubt show the chaos cause by the windmills.

        • But how far down can the Diesels be throttled down?

          Look at Figure 6.

          The Diesel does not throttle down linearly to zero like a turbine would. In fact there appear to be Two steps in the low range of its output.

  31. 1saveenergy says:

    5yrs of Green self-sufficiency…… 58% powered by diesel !!!

    The project to bring energy self-sufficiency to South Korean’s Gapa Island was launched in 2011. The reason that the island was selected for the trial project is because of its small size (0.85 square kilometers), its plentiful wind power and solar energy.
    The population of the island is 178 people; the electricity powers the 97 households on the island, four electric cars and a desalination plant.

    After 5 yrs, the island is meeting 32% of its energy needs from wind power and 10% from solar power. The other 58% of energy is still supplied by 450kW diesel generators.

    A total of 14.3 billion won (US$12.49 million) was invested in the project. Two 250kW wind turbines were installed, along with 174kW solar panels in 49 locations, plus an energy storage device, a system control center, power conversion equipment and remotely controlled power meters.

    I think….
    Capital expenditure spread over 20 yr life is –
    $12.49 million / 178 = $70,168 / 20 = $3,508 per yr per capita
    $12.49 million / 97 = $128,763 / 20 = $6,438 per yr per household
    for just 42% green energy

    A 450kW 562kva Cummins GTA28, 2006 model Genset is $59,950….
    Lets allow a just a 10 yr life & lets buy 3 for ‘energy security’ – $180,000 / 178 / 10 = $101 per yr per capita
    for 100% energy

    But what about the fuel ???….
    Well, I doubt each single person is going to use $3,407 worth of diesel per yr.

    As the Americans say – “Go figure”

    • Greg Kaan says:

      Thankyou for this information – I had not heard of Gapa Island before.

      It just goes to show that Asian nations are just as capable of making the same mistakes as Western ones, especially as South Korea is extending the project to 2 larger islands.

    • ducdorleans says:

      probably through the magic of someone else picking up the tab, it seems that this has been very positive for the islanders …

      “Before the project began, electricity cost between 120,000 and 130,000 per month during the summer, but now, the price has fallen to one fifth of that, between 20,000 and 25,000 won. There has also been a major boost in the number of tourists, which rose from 10,000 in 2008 and 40,000 in 2011 to 110,000 in 2015.”

    • 1saveenergy: Thanks for the information and the link. I might do a post on some of these lesser-known renewables projects when time permits.

  32. At 1920 on July 18 diesel generation was upped from ~1.6MW to ~3MW again with no decrease in wind speed. What is going on?

    • Kees van der Pool says:

      It looks like they really wanted to maximize pumping, a high 4.6MW worth of water going uphill. Maybe the banana growers parted with some of their cubic meters.

      Again, the roundabout way to pump with diesel, 7.5 MW of wind would have been plenty to supply the grid, even for the evening demand.

      • Rainer says:

        What about this idea:
        A lot af pumping= a lot of electric production = a lot of REE % in generation.
        They do not calculate in electrical demand…………

    • sod says:

      Utterly strange behaviour. July numbers were looking too good, so they decided to curtail wind at zero MW?

      Please everyone look at this graph and try to find any explanation !!!


      • The REE graph:

        Is highly misleading because of the way they put it together. If you want to find out what’s going on you have to look at diesel, wind and hydro separately:

  33. Kees van der Pool says:

    Roger, if you are still awake, we have an event @ 2:00. Demand dropped suddenly from 4.8MW to 2.5MW, the system immediately cranked up pumping to 6.5 MW (= maximum of all eight pumps turned on) and decreased the diesels down to 1.8 MW from 3.1MW. Power from the windfarm steady @ 7.3 MW.

    It looks like about half the island was switched off but not for lack of power and the system (so far) reacted correctly. I don’t think I have ever seen all pumps turned on at the same time (two groups of one 1600 kW variable-speed pump (inverter driven) and three 600 kW fixed speed (synchonous) pumps each).

    No posting beyond 2:00, about 25 minutes ago.

  34. Kees van der Pool says:

    Updated to 5:10. It sure looks like a wild night. I don’t even want to guess what this is all about.

  35. sod says:

    Wind now curtailed down to 6MW.


    Wind speed is still high.


    It is utterly unclear what they are doing.

  36. Rainer says:

    “the max wind output is capped 40% below nominal for a very good reason”
    At least one time a heavy load test should have be run. Just to find out if the specs are true.
    And this test should have be run before last payment.
    But only possible if the line is build for 11,5MW……..
    Till now the max was 7.8 MW.

    • sod says:

      I agree.

      Can anyone explain, what they are doing.

      Yesterday output:


      and wind data:


      Today, output:


      and wind data:


      Are they afraid that a high renewable percentage in July could cause wrong expectations for other months? Are they trying to actively keep the percentage low?

      • Kees van der Pool says:

        Sod, since Enercon runs the windfarm with their ‘Windfarm Control Unit’ (FCU), I’m afraid the only one that can answer your questions is Eric Breckwoldt @ Enercon.
        Did you get the chance to contact him?

        The Enercon website has a neat feature for just such an inquiry:


    • Kees van der Pool says:

      Rainer, Enercon does not test the fully assembled windmills for rated power, the E-70 curve is calculated. I imagine they test the piece parts: for instance the generator for BEMF & resistance, the blades for stiffness, the bearings for the correct sound profile, the electronics over temperature etc.etc. Undoubtedly, lots of testing.

      Enercon also decided to restrict the maximum output to 60% of nominal and added a blade load control system due to turbulence. Testing to full specs, even if this were possible at all given the quality of the wind, would involve risk as the ‘self defense’ system of the windmills would have to be turned off.

      More power from the windfarm would be totally wasted anyway given the dimension of the GdV lower reservoir. Up to and including 7/24/16, a total of about 670,000 m^3 of water was pumped uphill, enough to empty the lower reservoir four times if filled to capacity, which it is not.
      Hydro used was about 60,000 m^3 so 610,000 m^3 water was pumped around without doing any useful work, other than dissipating an excess of 1,140 MWh wind energy.

      I’m not too sure what you mean by “But only possible if the line is build for 11,5MW……..”. Do you think the cabling between the windfarm and the hydro installation might be inadequate?

      • Rainer says:

        Yes sir

        • Kees van der Pool says:

          If that’s the case, somebody must have disregarded the Spanish code on the required cable cross section for the windfarm maximum current rating and the inspector missed it when inspecting.

          This means that the entire 500m+ connection between the windfarm and the hydro plant must be replaced. The company responsible will have to install new, correctly rated cables and will be penalized.

          I made a mistake: BEMF applies to motors. Generators are measured for volts out per unit of rotation (RPM, rad/sec etc).

  37. Rainer says:

    About inspectors and law at El Hierro:

    With or without inspector:
    An inspector and the bosses also have to run a test with 11.5MW -max cargo-. That is a really inspection.
    If GDV bought a 11.5MW plant and take the mouth full that it can make 11.5MW they have to prove it.
    As long as not one time -even only one 10 minute- measurement 11.5MW are reported by REE:
    The plant cannot do it or the line can not do it.
    So GDV bosses are only mouth heros like in all the press releases.

    • Kees van der Pool says:

      A lawless place El Hierro seems to be . . . . . .

      ‘The plant cannot do it or the line can not do it’

      Clearly, the plant cannot do it because Enercon capped the output at about 7.5MW so we’ll never know if the connection between the windfarm and the hydro plant is adequate or not.

      Maybe sod will come back with the word from Enercon as to what is really happening, I’m sort of counting on him.

      • Rainer says:

        “Clearly, the plant cannot do it because Enercon capped the output at about 7.5MW”
        Please give me the source of this…..

        Found this source 2016-01-31::
        “Con las condiciones meteorológicas de esta mañana, el Parque Eólico tiene la posibilidad de producir en torno a los 10MW, casi la totalidad de la potencia instalada, 11,5. El consejero de Gorona del Viento, Juan Pedro Sánchez,…”
        google translater:
        “With the weather this morning, the wind farm has the potential to produce around 10MW, almost all of the installed capacity, 11.5. The Minister of Gorona del Viento, Juan Pedro Sánchez..”

        My comment:
        Max reported by REE : 7.8MW.

  38. Rainer says:

    “That the windfarm is not limited in output?”
    I do not have any source that it is limited by Enercon.

    “That GdV is now a reliable source of hard information?”
    Exactly the opposite. Maybe he knows that the Enercons can make 11,5MW but also maybe he knows that the line can not handle it.

  39. Rainer says:

    This “gossip” of only 60% of the Enercons E70 i do not believe:

    source solo german,sorry:
    there page 6
    28 – 34 m/s
    mit ENERCON Sturmrege-

    Google Translator:
    “Speed regulation wind speed:
    28 – 34 m / s
    with ENERCON Sturmrege-
    ment * ”

    Do not remember 28 m/s wind speed…..
    Maybe you did watch closer.

    Still my thesis is:
    The line is to weak.
    Build at the end of the projecto and was not enough money left. Not think a German company will sell a 2,3 MW generator and than will cut it down to 60% of it. They never ever would sell a second!

    Sure i know the calculation of Hubert that it will not help to make a lot more % REE only.
    GDV total is managed till now at ca 60% of the possibilities and under 5% REE only.
    That is the really shame.

  40. Kees van der Pool says:

    Rainer, according to your ‘thesis’ it is not Enercon but the duplicitous GdV operators who are restricting the output of the windfarm. This is necessary because the power line between the windfarm and the hydro plant is ‘too weak’ because the project ran out of money.

    Did I get this right?

    • Rainer says:

      That is my opinion.

      • Kees van der Pool says:

        Enercon “Windblatt” of 01 2016:

        “In day-to-day operation, however, the WECs run at limited capacity
        because the variable power output triggers fluctuations of frequency
        and voltage in the grid that need to be compensated constantly. “The
        fact that we are able to perform this compensation and that the grid
        parameters do not go haywire, that is what makes this project so
        unique,“ says Breckwoldt [=ENERCON Sales Director for Spain & Portugal]”.

        Another interesting note, also from Eric Breckwoldt:

        “the wind conditions at the site also created problems for the project planners.
        In summer, the winds along the west coast of El Hierro are extremely
        strong, often with heavy turbulence. So the planners opted for the
        E-70 wind turbine on a 64-metre tubular steel tower. “This sturdy wind
        turbine is the ideal solution for this type of site,“ says Eric Breckwoldt.
        In addition, the E-70 wind turbines were equipped with a blade load
        control system that has been used successfully in the E-82 model”.

        Might this not be a better explanation for the things we see, rather than the ‘thesis’ of underhanded and unscrupulous behavior on the part of GdV?

        • Rainer says:

          Still missing at least one test with max power. That do not have to be in day-to-day operation but have to be to proof the abilities of the equipment.

  41. Pingback: Gorona del vent i la transició energètica: siguem realistes | Les CIÈNCIES en BLOC

  42. Blackburn's with Darwin says:

    Diesel switched off at 5:20 30/07/16

  43. Rainer says:

    really do not have a problem if GDV is capping wind at 7,xxMW in everyday use .
    There is really not enough water storage room and i think litarally not enough water to use any extra MW. Stiil is spoiled a lot.
    As long as the “Kids waterworld”, pumping up and running down without making energy, is not realized with diesel energy.
    Now at least GDV shows what it is able to do, if it would be run all possible time without diesel……

    • sod says:

      Still no diesel, 64 Hours now?

      Should be a new record or is my calculation wrong?


    • sod says:

      “really do not have a problem if GDV is capping wind at 7,xxMW in everyday use .”

      I am worried about it. And i am especially worried about them making no tests with higher output.

      As we can see i the analysis by Roger and Euan, there is not only a lack of daily percenatge, but a real lack of not enough wind output to run the island (hydro is just storage and can not provide anything on its own).

  44. Pingback: Gorona del Viento y la transición energética: ¿qué cabe esperar? – 15/1515

  45. Rainer says:

    2016-08-02 09:00 Diesel On again
    Wind at airport still 10m/s
    Why Diesel again?????
    A new press release with new record will be published without facts why diesel again bit a bunch of blob… blob…

    • OpenSourceElectricity says:

      Seems somebody loves the sound of the diesel engines too much to operate without them for a longer time. So the system is still not used as designed, and so the percentage of renewables is lower than designed. What the system could provide if operated as designed is still not possible to tell from outside, as well as the causes why it is not operated as designed. As it seems something with the hydropower-part seems not to persuade someone. Whatever and whoever this may be.

  46. Blackburn's with Darwin says:

    Has anybody ascertained how much of the pumped water is used for irrigation?

  47. OpenSourceElectricity says:

    As it seems none of the water in the upper reservoir is so far used for irrigation, although this would make perfect sense. But mabe they do creative book keeping, and calculate running other pumps all over the island as “hydropower consumtion” as well. With the hich differences in elevation on the island they can also consume in the MW-area. But this is a guess, not based on any data.

  48. jjdm says:

    Hi Roger,

    Wonderful work.

    Reading this I remembered a paper that I thought interesting (from a mathematical point of view, I’m a mathematician) that talks about this: “Unit Commitment in fully Renewable, Hydro-Wind Energy Systems”.


    At that time I thought it was great that mathematics could help build a system to manage a fully renewable electrical system. What most caught my attention in your analysis is the following:

    Wind and solar are variable and fluctuating sources that by themselves are not capable of supplying constant energy, which results in generation limitations in vulnerable isolated systems, which in general do not cover more than 30% of demand*

    *I have no idea which systems these are or where the 30% number comes from.

    There is no mention of this in the paper. It is absurd to think of a fully renewable system with this condition (constraint). Therefore, I think that the idea of the project doesn’t correspond its management.

  49. Thanks for all your comments.
    I write from Canary Island an It is very important for us (iceacan.org) to see your comments about GDV. We would like to share with you our point of view, beyond technical aspect.

    Tomas Padrón was the president of El Cabildo del Hierro at the same time he was the salesman of Endesa.

    If you put the fox to guard chickens…

    Regards form Gran Canaria and Thanks again.

  50. Alvaro: No hay de que. Yes, we would be interested in any information on GdV that you might be in a position to share with us.

    Tomas Padrón posted a comment (in Spanish) a while ago that mentioned potential problems with reservoir stability. I sent him an email requesting further information but never got a reply. Maybe there is something you could add.

Comments are closed.