El Hierro, March/April 2016 update:

The Gorona del Viento (GdV) plant on the Canary Island of El Hierro is a flagship project designed ultimately to provide the island with 100% renewable electricity and to demonstrate that hybrid wind/pumped hydro systems can be used to generate 100% renewable electricity in other parts of the world. GdV comprises a wind park with 11.5 MW capacity and a pumped hydro storage plant with 11.3MW capacity, installed at a total cost of €84 million. This is the fifth in a series of operational updates that began in September last year. 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.
March and April were better-than-average wind months at GdV, with renewable energy supplying 50.6% of El Hierro’s grid demand in March and 47.3% in April. As a result the percentage of renewable energy delivered to the El Hierro grid since full operations began in late June 2015 increased from 32.2% at the end of February to 36.2% at the end of April. El Hierro monthly grid statistics since full operations began are summarized in the Table below.

Figure 1 plots average daily diesel and renewables (wind + hydro) generation since project startup. Of particular note is the week from April 13 through April 19, during which wind generated no energy at all for 76% of the time (127 of 168 hours) and renewables supplied only 3.6% of EL Hierro’s grid demand.

Figure 1: Average daily percent renewables delivered to El Hierro grid

Figure 2 plots the 10-minute Red Eléctrica de España (REE) grid data for January and February 2016. Zero-diesel tests lasting for a total of 42 hours were performed without apparent incident on April 6th, 9th and 26th but do not seem to have led to any increase in the amount of wind power being integrated with the grid, so we can assume that the results were not entirely satisfactory. Load-matching is still being done by switching wind output between the grid and the hydro pumping station with the diesel generators operating in baseload mode when the wind is blowing strongly and by using the diesel generators in load-following mode during wind lulls.

Figure 2: January and February 2016 generation, 10-minute REE data

Another planned test on April 7 may have been aborted because it caused a partial grid outage. Between 1210 and 1220 a reduction in diesel generation from 1.8 to 1.1MW was accompanied by an abrupt 2.2MW decrease in demand – usually a sure sign that something has dropped off the grid. The grid was, however, back up and functioning within an hour (Figure 3):

Figure 3: April 7 zero-diesel test (?)

Over the last couple of months other information has come to light regarding the status of the GdV reservoirs. Reservoir balances estimated from water level photographs show that over time some 50,000 m3 of desalinated water is routinely pumped from the lower reservoir to the upper reservoir and allowed to flow back down again in order to balance generation with grid demand. But the total volume of water in the two reservoirs presently amounts to only about 90,000 m3, or about 17% of combined reservoir capacity. (150,000m3, the capacity of the lower reservoir, must be present in the upper reservoir and the lower reservoir must be empty to fully “charge” the pumped hydro system.) Moreover, historic photos suggest that the reservoirs have never contained any more water than this. As shown in Figure 4, the level of water in the upper reservoir has remained more or less the same for the last three years. There is also no evidence to suggest that a substantial amount of water has been extracted from the upper reservoir for irrigation. The ~100mm flexible pipe that was installed apparently for this purpose has now in fact been disconnected.

Figure 4: Photographic record of water level in GdV upper reservoir.

One possible explanation for this is a shortage of desalinated water. There is evidence to suggest that GdV is served by only one desalination plant (Tamaduste) and that other demands on this plant severely restrict the delivery of water to GdV.

Another is reservoir stability. In April 2011 the Barlovento reservoir on the island of La Palma to the north of El Hierro suffered a liner failure which caused a large volume of water to drain out of it:

Figure 5: Failure of Barlovento Reservoir, April 2011

Barlovento was also constructed in an extinct volcanic crater underlain by weak rock, as are the GdV reservoirs, and it’s possible that as a result GdV is unwilling to load the reservoirs any more than is necessary to support ongoing operations. A local perspective on the question was provided in this comment in an earlier post, English translation here.

I have read all the comments and see with astonishment that no one has mentioned the hydraulic and structural problems that the reservoirs can have, in particular the upper reservoir, which might explain why they don’t fill it.

Barring unforeseen events the next GdV update will be at the end of June when the plant completes its first year of full operation.

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25 Responses to El Hierro, March/April 2016 update:

  1. Joe Public says:

    A fascinating update, thanks Roger.

  2. Gunslinger says:

    During my research for “natural electricity storage Gaildorf” (Germany, Google search: “Naturstromspeicher Gaildorf) I ended a few weeks ago on this blog. Very, very, very interesting …
    What can I say. El Hierro is everywhere, or vice versa.
    Thank you very much for this blog.

    (This comment was created using the Google translator. So …)

    • Gunslinger: I’m glad you find the blog interesting. Come back and visit us any time.

      And Google translate seems to have worked fine. 🙂

  3. Rainer says:

    this post till now do not show up in:

  4. singletonengineer says:

    This is shaping as a classic example of Murphy’s Law:

    “If anything can go wrong, it will.”

    • Murphy was involved in the initial project design. He’s the one who came up with the idea of converting wind to hydro (soon abandoned), the one who said that wind power could be readily admitted to the grid with the help of synchronous Pelton turbines (it clearly can’t), the one who grossly overestimated wind generation (there’s evidence to suggest he assumed a 50% capacity factor) and the one who failed to recognize that the reservoirs were twenty times too small. Nothing went wrong that wasn’t bound to go wrong.

  5. Stuart Brown says:


    Slightly OT, sorry, but did you catch this about the Cobrador island solar and battery system? A bit more pragmatic than El Hierro perhaps given that the diesel is definitely the bigger part of the generating capacity?


    “Hybridizing the existing diesel power plant is financially viable due to subsidies and cash incentives provided by government”

    Nuff said, but undoubtedly good for the islanders!

  6. I just received this by email from Hubert Flocard, who has given his permission to post it as a comment.


    Attached you will find my results for the cumulated renewable fraction (33.38 % same as yours).
    (This is for just 10 month since I start my analysis on July 1st 2015.)

    As usual I calculate
    % time with P diesel 99 % = 12.73 %


    the maximal achievable renewable fraction given the wind power production and the demand power. After two months with reasonably strong winds It is now close to 50 %.

    If the wind curves at the airport you published for last year are confirmed with strong winds in May and June, I suspect it can reach 55 % for a full year just as the Spanish engineers predicted a long time ago.

    I also believe that the actually achieved renewable fraction can reach 37 % for a full year. (I note that the 1st of May was used for another test with few hours 100 % renewable)

    Note that if I enforce that at least 25 % of P demand should at any time come from inertia associated electric production (diesel or hydro) this maximal renewable fraction decreases to 47 %

    In both cases (0% or 25 %) there is not a kWh of wind production that is lost.

    Now on the other hand if I consider a situation in which the reservoirs and the hydro systems have not been built (only wind and diesel turbines) if I assume that there is a resistor immersed into the sea used only to waste wind power in excess (22 % of total wind energy production has to be wasted) and if I assume that at any time 25 % of P demand at least should come from diesel (stability reason) I find that the maximal renewable fraction can nevertheless be as high as 40 %.

    In other words as long as the achieved renewable fraction with the present complete system (wind + hydro) stays below 40 % one can affirm that all the money spent on the hydro system (reservoir, penstocks, pumps and turbines) is simply wasted money.One could have done better for much cheaper with only the wind turbines (and a resistor) added to to the diesel plant. I am sure the Spanish engineers also knew it all along.

    • Kees van der Pool says:

      An 8-9MW synchronous generator with a 25MJ flywheel could be added at trivial cost compared to the hydro plant. This would reduce the number of diesels that need to run to supply inertial response.

      • Roger Andrews says:

        Hi Kees: You’re getting closer to the King Island setup, which includes a dynamic resistor, battery storage and a smart grid too. Unfortunately we’re unlikely ever to find out how well King Island is doing because the operator (Hydro Tasmania) tells me that the grid data are commercially sensitive and not available to the public.

        • Kees van der Pool says:

          Good morning Roger,
          Indeed – any setup with windgeneration needs this ingredient, from El Hierro to Ireland to Germany. King island has the flywheel integrated into the diesel backup unit.

          At least El Hierro’s grid data are very much available, as opposed to King Island:

          “Unfortunately we’re unlikely ever to find out how well King Island is doing because the operator (Hydro Tasmania) tells me that the grid data are commercially sensitive and not available to the public”
          Translation: “our grid data does not look all that great and we’d rather not tell you”.

          • Have you ever looked at the real-time King Island grid output to see if you can figure out how their operating system ties all their whizz-bang smart gadgets together? I’ve tried a few times without much success.

  7. Rainer says:

    Well done translation.
    Lets ask Google translater for the Pinocchio language.
    May help also to read GDV press releases.

  8. Rainer says:

    Other “100%” project.
    Located on Azorean island of Graciosa. Do not mix up with Graciosa, a canary island.
    Did not find live grid data till now…

  9. sod says:

    A pretty optimistic article about El Hierro in a german paper today:


    “currently only achieves 50%”. No problems with the pumping mentioned at all.

  10. The Graciosa article is almost funny. It begins:

    The World’s First “100 percent” Renewable Grid

    Younicos has just announced that construction of the World’s first “100 percent” renewable grid is underway. This will be the first time a one megawatt-scale power system is being stabilized using batteries – without the need for thermal generators.

    And continues:

    100% Penetration Of The Grid

    This 100% renewable penetration of the grid will not occur 100% of the time

    A third of the Azorean island of Graciosa’s existing fossil fuel generation will remain as back-up power and to be employed during prolonged periods of unfavorable weather.

    Younicos software and controls will balance short-term power fluctuations, enabling wind and solar to provide 100% of Graciosa’s electricity most of the time.

    It’s already beginning to sound familiar and the plant’s not even built yet.

  11. Rainer says:

    2016-05-15 German Grid: 99,83% REE
    Do not see any “Resistor” or “Disney water world” sending energy in the orbit….
    Only see 17% extra conventional energy. Sure will be exported also.
    True: it is not a island grid…..
    Should be the goal in GDV too and no incompetent press releases.

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