El Hierro, January/February 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.

The low-wind conditions that dominated during the last four months of 2015 continued into January 2016, leading to only 22% renewables generation in that month. Much of February, however, was characterized by strong winds, and combined with the 100% renewables tests that were performed this resulted in renewable energy supplying 54% of El Hierro’s grid demand in that month, exceeding the 52% achieved in June/July 2015.

El Hierro monthly grid statistics are summarized in the Table below. Note that wind and hydro generation sent to the grid are now combined into a single “renewables” category. The reasons for this are discussed later:

Figure 1 plots average daily diesel and renewables (wind + hydro) generation since full operations began on June 27, 2015:

Figure 1: Average daily generation since project startup 

Figure 2 plots the 10-minute Red Eléctrica de España (REE) grid data for January and February 2016. Features of interest include the four periods of 100% renewables generation (16 hours between 0540 and 2140 on January 31, 41 hours between 0100 on February 14 and 1740 on February 15, 24 hours between 0110 on February 20 and 0120 on February 21 and 35 hours between 0020 on February 28 and 1050 on February 29) and the two grid “crashes” around 5 am on February 18 and between 3 and 5 am on February 19, which were probably triggered by high winds and rain:

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

In previous updates I’ve found that I repeat myself a lot, so in this one I will discuss the January and February results relative to some of the questions and observations that arose in the recent “16 hour” and “41 hour” posts, which so far have generated almost 300 comments between them:

1. Segregating wind and hydro

The Red Eléctrica de España (REE) 10-minute grid data (accessible via the “El Hierro Live Grid” sidebar) provide three numbers for the El Hierro grid – diesel, wind and hydro. REE has confimed that the diesel and wind numbers show actual generation from the Llanos Blancos diesel plant and the GdV wind farm. The hydro number, however, shows net generation from the GdV hydro plant less power consumed in the pumping plant and doesn’t distinguish between the two. Moreover, according to REE the pumping station and the hydro plant are both often working at the same time. As a result the hydro numbers are ambiguous. A value of minus 1MW could, for example, represent 1MW of pumping and no hydro generation, or 1.5MW of pumping and 0.5MW of hydro generation, or 2MW of pumping and 1MW of hydro generation. There’s no way of knowing which.

The graphs in previous posts that segregated wind and hydro into green and blue bars assumed that the negative hydro values represented pumping and the positive values hydro generation. This assumption was broadly in line with GdV’s operating scheme, which is to send as much wind power as possible directly to the grid to avoid the 40% energy losses incurred in the hydro circuit. But when grid stability is factored into the equation GdV may well have a preference for hydro over wind despite these losses, and consequently it’s likely that previous analyses will have overestimated wind sent to the El Hierro grid and underestimated hydro. For this reason wind and hydro are now combined into a single “renewables” category, although how much of the renewable energy is wind and how much hydro makes no difference to the total amount of renewable energy sent to the grid.

2. “Windy Sunday” tests and grid stability

100% renewables tests have been conducted on four of five Sundays since the wind began to pick up in late January (Figure 3), with Sunday selected presumably because it’s the day a grid outage would have the least impact. The tests have continued either until the wind dropped, which was the case during the January 31 and February 14/15 test, or until the diesels were restarted even though wind generation still exceeded demand, which was the case with the February 15/16 and 28/29 tests. This has prompted the question “why weren’t the February 15/16 and 28/29 tests allowed to continue?”

Well, REE hasn’t told me why, but clearly there was something about the tests which suggested to REE that GdV wind still isn’t quite ready for prime time. Here it’s important to recognize that the stability of the El Hierro grid is REE’s responsibility, and that in deciding what the grid can and can’t accept REE has to meet the Spanish codes for island grids set forth in the Boletín Oficial del Estado 2006 – which according to Merino et al “are among the most demanding international codes currently in force for wind power integration in electrical systems” – and also has to conform with various other Spanish and EU directives governing the management of grids. REE also isn’t performing the tests to see how long 100% renewables generation can be stretched out before something breaks. The purpose is to evaluate the grid’s ability to recover promptly from a major fault, such as a busbar short-circuit, when 100% of the generation is coming from renewables. And the fact that the El Hierro grid took 24 hours to recover from the unscheduled outages that began around 5 am on February 18 suggest that it isn’t very good.

The way in which GdV’s output is being handled, particularly the curtailment of wind at around 7MW (discussed later), has been described as “insane” by some commenters, but there’s really nothing insane about it. What GdV has done is adopt effectively the same solutions to the wind instability problem as has King Island, Tasmania, a closely comparable project with battery storage instead of hydro. So if GdV is insane Hydro Tasmania is too. But this is nevertheless an important issue because it tells us what other high-penetration renewables systems will probably have to do to ensure grid stability. The two key ingredients are:

  • A dynamic resistor to control frequency fluctuations caused by variable wind output. King Island’s resistor does this by converting excess wind to heat. GdV does it by sending excess wind to pumping.
  • A means of adding inertia to the system. King Island does this with a flywheel. GdV does it by keeping at least three of the 2.83MW Pelton hydro turbines spinning.

A dynamic resistor, however, inevitably involves some wastage of wind power. An example of wastage at King Island is shown in Figure 3 below, reproduced from the King Island Renewable Energy Integration Project document . Maybe 15-20% of the available wind energy is curtailed:

Figure 3: Generation mix for King Island, Tasmania, showing wind wastage

As shown in Figure 4 wastage at GdV is higher – an eyeball estimate suggests about 30% during the 41-hour period of 100% renewables generation during February 15 and 16 even when wind farm output is curtailed at around 7MW, about which more later:

Figure 4: Generation during February 14/15 renewables test, 10 minute REE data

But what we are left with is a case where grid demand has been met with 100% renewables for 41 hours simply by switching wind output between the grid and pumping and without having to adjust generation. At the cost of the wastage of wind power that couldn’t have been used anyway GdV’s intermittent wind output has been converted into dispatchable power. And if wind (or solar) energy can’t be made dispatchable there is no way a high-penetration renewables project will ever succeed.

Figure 4 also reveals some details of the test. Once every 13 or 14 hours wind farm output was abruptly reduced for an hour or two presumably to see how the grid responded, and during the second and third tests wind was briefly “spiked” back on again towards the end of the test. The responses to the first and second tests were evidently acceptable but the diesels were turned back on immediately after the third. This may have been because the response in this case was unacceptable or simply because REE had obtained all the information it had planned on getting from the test.

Another feature of Figure 4 is the flat-topped wind output, which shows that wind was deliberately curtailed at around the 7MW level. Why, asked some commenters, curtail wind at this level? GdV has 11.5MW of installed wind capacity, why not use all of it? In this particular case the reason is obvious – all the additional wind power would be wasted, so there’s no point generating it, and the unconstrained wind surges would probably have a destabilizing influence anyway. The question is really why GdV can use only some of the wind power it’s capable of generating, and we’ll get to that later.

3. Irrigation and water supply impacts

Because GdV and the El Hierro Island water council have not responded to requests for data we have had to resort to detective work to estimate two important numbers – how much desalinated water has been delivered to the GdV lower reservoir and how much has been extracted from the upper reservoir for irrigation or other uses.

There is general agreement that there are three desalination plants on El Hierro:

  1. El Golfo: One plant, capacity 4,000 cu m/day
  2. Tamaduste (also known as El Cangrejo): Two plants each of 1,200 cu m/day capacity, total 2,400 cu m/day
  3. La Restinga: Two plants of 1,200 and 500 cu m/day capacity, total 1,700 cu m/day

These plants have a total production capacity of 8,100 cu m/day assuming that all operate continously.

Figure 5 is a map of El Hierro showing the locations of the three plants relative to the GdV reservoirs and the island water pipeline network (for a closer look at the pipeline network this map from the Consejo Insular de Aguas de El Hierro can be enlarged to almost any scale). The tabulation of plant specifications at the bottom of the Figure is from the Official List of Canary Island Desalination Plants, dated 2013. Note that the expansion of the El Golfo plant from 1,350 to 4,000 cu m/day in 2012 isn’t shown on the list.

Figure 5: El Hierro’s desalination plants and water pipeline network. Red pipelines are pumped and blue pipelines gravity-fed.

Let’s now see how these three plants are positioned to deliver water to GdV:

First El Golfo. The El Golfo area is the only respectably flat piece of land of any size on El Hierro and it’s here that effectively all of the irrigated crops (mostly bananas) are grown. El Golfo’s water has historically come from water wells but now it will come from the El Golfo plant to avoid further groundwater depletion. The plan is to use all of the plant’s output in the El Golfo area.

But let’s assume that some of El Golfo’s water does get sent to GdV. How does it get there? By a tortuous pipeline route that requires pumping up to an elevation of 770m close to the island capital of Valverde. And shortly after this the water arrives at a point immediately above the upper reservoir, whereupon the logical solution if the upper reservoir is to be used for fresh water storage is to drain it down into to the upper reservoir. It certainly makes no sense to let the water drain all the way down to the lower reservoir and then pump it back up again.

But why send water to GdV at all when it can be used locally?

La Restinga has the same problem, only worse. Any water sent from here to GdV will have to negotiate about 20km of winding pipeline, will have to be pumped up to an elevation of 1,130m and will eventually arrive at the same point above the upper reservoir as the El Golfo water did.

Tamaduste is the only desaladora that is realistically positioned to deliver water to GdV, but at a rate of only 2,400 cu m/day even if it operates at full capacity for 100% of the time, which it probably doesn’t, and if there are no other demands on its production, which there almost certainly are. But we will nevertheless assume that Tamaduste ran flat out during July and August 2015 and that all of its output was delivered to the GdV lower reservoir. This gives 62 days times 2,400 cu m/day for a total of 148,800 cubic meters delivered.

And how much water was pumped from the lower reservoir to the upper reservoir during July and August? The REE “hydro” grid values show that 2,743 MWh was consumed in pumping during these months, enough to pump over a million cubic meters of water from the lower to the upper reservoir.

So we have 150,000 cubic meters entering the lower reservoir in July and August and over a million cubic meters leaving it. The only possible explanation for this imbalance is that the water pumped from the lower to the upper reservoir was allowed to flow straight back down again. Why was so much water pumped uphill in the first place? Because GdV has been using pumping as a dynamic resistor during high-wind periods ever since the project went into full operation in late June, 2015. As shown in Figure 6, the July 2015 generation mix was in fact very similar to February 2016 generation mix (Figure 2) except that no 100% renewables tests were performed during the month:

Figure 6: July 2015 generation, 10-minute REE data

And if almost all the water pumped uphill came straight back down again we can reasonably assume that very little water was extracted from the upper reservoir for irrigation or other purposes.

4. Why GdV will never achieve full-time 100% renewables generation.

One reason GdV will never achieve 100% renewables generation as currently set up is the use of the GdV reservoirs as a dynamic resistor, which as discussed above will lead to the curtailment of a significant amount of wind generation and probably leave the existing 11.5MW wind farm incapable of generating enough electricity to fill annual island demand. It’s important to note here that a dynamic resistor was not part of the original operating plan, which assumed that grid stability at high levels of wind penetration could be achieved simply by keeping three Peltons as a spinning reserve (see Merino et al, link above). But it’s clearly a requirement if the system is to function, and GdV has to live with it, as does King Island 11,000 miles away on the other side of the Earth. And the stability problem at GdV still hasn’t been solved, although it’s clearly moving closer to solution.

But that isn’t the main obstacle.

We will now assume that grid stability isn’t a problem and that all the wind power the 11.5MW wind farm is capable of generating can be sent directly to the grid or to storage. Assuming an optimistic 40% capacity factor this gives a total wind farm output of 40GWh/year, just about enough to cover El Hierro’s annual demand. But there will of course be periods when wind generation exceeds demand and the surplus wind must be stored for reuse, and other periods when wind generation is lower than demand and the energy in storage must be released to cover the deficit. And if GdV’s reservoirs don’t have the capacity to handle these storage and release requirements, well, it’s back to diesel power.

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 7: Duration of energy storage, September 2015, current design

Is there anything that can be done to beef up the storage capacity of the reservoirs? An obvious option would be to use the ocean as the lower reservoir, which would increase storage from 250MWh to about 630MWh, limited by the 380,000 cu m capacity of the upper reservoir. But this does not greatly improve matters. Storage runs out around 6pm on October 7 and we are still left with a demand shortfall of 2,600MWh over the rest of the month:

Figure 8: Duration of energy storage, September 2015, storage increased to 630MWh by using the ocean as the lower reservoir

The only other practicable option would be to increase the size of the wind farm. Figure 9 shows the impacts of doubling its capacity from 11.5MW to 23MW while keeping the ocean as the lower reservoir. They are again not very large. The storage now runs out at midnight on October 8 and we are still left with a 2,200MWh demand shortfall over the remaining 23 days of the month:

Figure 9: Duration of energy storage, September 2015, storage increased to 630MWh by using the ocean as the lower reservoir, wind farm capacity doubled to 23 MW

And if we were to allow for the fact that low-wind conditions were common between mid-September 2015 and late January 2016 the demand shortfalls would increase substantially.

The same thing happens in reverse, although in this case there’s no way of doing an analysis because we don’t know what the wind generation profile would have looked like without curtailment. But there were certainly occasions in July and August when surplus wind generation could have charged the reservoirs from empty within a few days, leaving no room for any surplus generation that came after.

Clearly the storage capacity of the GdV reservoirs is at least an order of magnitude too small to allow the project to supply El Hierro with 100% year-round renewable energy or anything close to it. The question is, why wasn’t this recognized earlier? Well, it almost certainly was. But the “innovative” GdV reservoirs had received such overwhelming international acclaim that it would have been a brave person indeed who dared to tell the project’s backers that their baby was ugly. As a result GdV is still widely touted as a 24/365 100% renewables project, or something very close to it, even though it has no chance of becoming one. Here’s the official line from Gorona del Viento:

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 wind (or) water to fill energy demand.

How often do exceptional/emergency conditions occur? Five percent of the time? Two percent? One? Sorry, but the diesel engine plant is going to operate a lot more often than that. Based on results to date Hubert Flocard and I in fact estimate that diesel generation will be supplying island demand for about 50% of the time.

The fact of the matter is that GdV’s performance will be hostage to the wind for the rest of its operating life. During high-wind periods such as occurred in July, August and early September last year and in the second half of February this year we can expect that the plant will ultimately be capable of supplying 100% of El Hierro’s electricity with renewable energy for extended periods. But during low-wind periods such as occurred between mid-September last year and mid-February this year diesel generation will have to provide the bulk of the island’s needs. The basic problem is that GdV has every conceivable kind of smart gadget in its control room except for the one it really needs – a gadget that makes the wind blow to order.

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111 Responses to El Hierro, January/February 2016 update:

  1. Joe Public says:

    Thanks for the update.

  2. Euan Mearns says:

    Roger, thanks for update. With 8 months in we have 32% renewable instead of 100% – that’s quite a deficit. Do we know if the calm conditions of Sep-Jan are normal or may they be in some way anomalous? Or were some of the wind turbines perhaps broken? But even with windy conditions they are just getting 50%. And this is a system where installed wind is more than double peak demand.

    I wonder if GdV get paid for all the wind they produce and waste?

    If this is normal then there was never any way this facility could provide 100% renewables with the amount of storage installed. And it would never be economic to expand the storage unless they go a chemical route like hydrogen or methane.

    It would be interesting to calculate a ratio of synchronous to non-synchronous supply if that was possible? Am I right to say that they only go 100% when there is a large surplus and they can run the water pumps flat out to stabilise the load?

    • Do we know if the calm conditions of Sep-Jan are normal or may they be in some way anomalous?

      Here’s a plot of daily wind speeds at El Hierro airport, 2014 versus 2015. There are some divergences but some remarkable similarities too (June 2014 and June 2015 wind speeds were almost identical) and September and October were low-wind months in both years. Mean annual wind speeds are the same (6.7m/s in both years) and standard deviations effectively the same (2.2m/s in 2014 and 2.1m/s in 2015). In short, 2015 looks like a fairly typical year, although it would be nice to have more data to go on.

      Or were some of the wind turbines perhaps broken?

      No way of knowing, but the correlation between airport wind speeds and wind generation suggests that turbine outages aren’t common:

      It would be interesting to calculate a ratio of synchronous to non-synchronous supply if that was possible?

      It will be possible if we can get the REE “hydro” values segregated into “generation” and “pumping”.

      Am I right to say that they only go 100% when there is a large surplus and they can run the water pumps flat out to stabilise the load?

      Pretty much, although the pumps don’t have to run flat out to do it. Another consideration is that 7MW of wind generates only 4.2MW of hydro, not enough to fill demand, if the need arises to convert it all to synchronous generation.

  3. Stuart Brown says:

    Thirded, I’m fascinated by this stuff 🙂 You’ve led me to wonder if they had any possibility of building a tidal lagoon like the thing proposed for Swansea, and to realise the coast falls dramatically into the sea to a depth of 3km! Bit of an engineering challenge that. Given El Hierro is practically sat on a volcano, is there no scope for geothermal energy? There was lava bubbling out of the sea bed a couple of kilometres away (Bimbache) in 2011.

    Roger, in an earlier post you linked to the splendidly named HydroWorld.com, with a piece by some of the IDOM engineers involved in 2012. One of the authors was head of GdV, too. It says-

    “Realistically, however, about 65% of island’s total annual energy demand will be covered by the hybrid hydro-wind plant.”

    So it seems they did recognize it wouldn’t do 100% in advance, even if they may still have been somewhat optimistic…

    • Willem Post says:


      Sometimes people like to have projects, even, upon close inspection, these projects are marginal, or worse.

      Hence not too much analysis is wanted. Just give us the money and let us play.

      If it falls short, we’ll do better next time (still without too much analysis), and the next time,….

      The part about synchronous rotational inertia is interesting, as wind turbines provide rotational inertia, but it is not synchronous and not steady, i.e., worse than useless, as it disturbs the grid.

      Another issue is real and reactive power.

      The real and reactive power, and frequency and voltage of the energy of wind turbine plants are variable. These very short-term variations are due to a blade passing the mast*, about once per second, and the various wind speed velocities and directions entering the plane swept by the rotor. A plant with multiple wind turbines would have a “fuzzy”, low-quality, unsteady output. These short-term variations are separate from those due to the weather, and usually need to be reduced, such as by reactive power compensation with synchronous-condenser systems, before feeding into a grid, especially “weak” grids, to avoid excessive grid disturbances.

      * This passing creates a burst of audible and inaudible sound of various frequencies; the base frequency is about 1 Hz, similar to a person’s heart beat, and the harmonics at 2, 4 and 8 Hz are similar to the natural frequencies of other human organs. Inaudible sound, a.k.a. infrasound (less than 20 Hz), likely causes adverse health impacts on nearby people and animals, including DNA damage to nearby pregnant animals, and their fetuses and newborn offspring. Because infrasound travels long distances, a buffer zone of at least one mile would be required to sufficiently reduce these adverse impacts on people; roaming animals would continue to be exposed. See wcfn.org URL.


      • Greg Kaan says:

        Thanks for the link to that NREL paper, Willem. The voltage, phase and frequency noise added by the multiplicity of small, quasi independent generators that comprise a windfarm is rarely mentioned by either proponents or supporters.

        The only truly effective filter would seem to be to use the combined output of a windfarm to drive a single large synchronous generator which then feeds the main grid. The cost of such a filter would be add greatly to a windfarm’s cost however, and would be a limiting factor in expanding a windfarm (either by adding additional turbines or by repowering with larger turbines)

      • gubelu says:

        Please inform yourself a bit deeper about the inertia of the wind power generators, this topic was analysed in detail at previous discussions, I do not want to repeat this here.
        The E70 used here provide synteticc inertia – so inertia comming from the rotating masses of the turbine, bur with the fixed frequency of the inverter, which exceeds the capabilities of the diesel generators or the hydropower per MW installed.
        This can most likely also be seen on the graphs of the grid failures during storm, where Diesel power died first, wind power died later.

        • Greg Kaan says:

          I was referring to the majority of wind turbines that have the synchronous generator linked directly to the grid.These FACT equipped Enercons may be rather better behaved in this respect.

          Do you have any source indicating the comparative cost of an Enercon turbine vs an equivalent output Vestas? It would be interesting to see how much the elimination of the gearbox compensates for the inverter cost.

          You think the graphs produced by Roger can display the 10 second interval (or thereabouts depending on how much shortfall the turbines are trying to make up for) for which the turbines may have tried to cover the loss of the diesel generators? I suggest that you look at the source of the data from the El Hierro Live Grid link – the data is in 10 minute intervals which is far beyond the inertial emulation capabilities of the turbines.

          • gubelu says:

            Well directly connected synchronus generators are not in the market any more for some years. There are either double fed asynchronus generators + partly inverters which transfor the variable frequency output of the Asynchronus generator to a fixed frequency output (sometimes called G3 wind turbines) as Vestas uses it, or the full inverter systems as Enercon uses them. (sometimes calls G4 wind turbines) . (directly connected synchronus generators have been generation 1 &2)
            double fed generators are e.g. explained here in english: http://www.elforsk.se/Rapporter/?download=report&rid=13_02_ rapport_screen-1.pdf as can be seen from market shares, both solutions are competitive.

          • Greg Kaan says:

            Thankyou for that link – the document is quite informative. although a lot of the content mirrors the paper linked by Stuart Brown further down.

            These newer turbines do seem likely to reduce the noise mentioned in Willem’s linked document. They still do not have the capability of doing more than to smooth out a fluctuation over a few seconds, however, and the need for reduced output while recovering means that they although they may reduce the amplitude of a fluctuation, they actually extend the effects.

          • gubelu says:

            This is correct for a G3 turbine running at maximum output. A G4 turbine like the E70 does not need to reduce power, as can be seen from other documents , and if the wind turbine isoperated below maximum possible output, it is always possible to increase output to maximum (defined by wind). This isless important in big grids where usually all pssible output fromthe wind turbine is wanted, but in a island grid like el Hierroit is reasonable to remain some percent below maximum, like a power station providing regulation power to the grid.

    • Given El Hierro is practically sat on a volcano, is there no scope for geothermal energy?

      Stuart, go to the top of the class. Why they elected to go for wind instead of geothermal on an island that’s sitting over a magma chamber surpasses my comprehension. A couple of 5MW geothermal plants could easily supply the island’s needs for the foreseeable future and the GdV hydro plant would be more than large enough to handle load-following. And there would be no problems with grid stability because all the power would be synchronous.

  4. Flocard says:

    This is just a quick comment.
    (which has also the side interest of letting me to follow the discussion using the “notify me of new comments via e mail” button)

    The uncertainty on the meaning of the column “hidraulica” that you describe in Sect.1 of your post
    has two consequences
    1) only the knowledge of the volume of water in at least one reservoir (for a study over a short time period) and preferably the two reservoirs (for a study over a longer time period) will allow us to resolve the ambiguity described in this sect.1(given that we get a clue also on the injection from the desalination plants)

    2) resolving as we have often been doing the ambiguity by saying (contrary to REE statement as you point out) that pumping and hydro turbining DO NOToccur at the same time, that is by using positive ‘hidraulica’ to calculate contributions of the hydraulic turbines and negative ‘hydraulica’ to estimate the amount of water which is pumped necessarily provides a LOWER BOUND on the volume of water which is being pumped from the lower reservoir. The more one deviates from this extreme way of resolving the ambiguity the more the hydraulic turbines are used to waste wind energy according to the global efficiency of the hydraulic installation (pumps, pipelines, turbines). This waste of wind energy is then traded for a positive contribution to grid stability..


    • Hubert:

      On your point 1). GdV certainly has all the data we need to resolve this question but I doubt they would release it. This leaves us with the option of approaching the question indirectly by analyzing reservoir volumes. But we have no information on reservoir volumes either, and neither GdV nor the Island Water Council seem willing to give us any. One thing we could do, however, is have Rainer, if he’s willing, begin to take periodic photos of the upper and lower reservoirs (daily would be best, but weekly would be better than nothing). These would allow us to make estimates of reservoir water volumes and changes in water volumes that we could reconcile with the REE hydro values.

      On your point 2): You’re quite correct. Our estimates of the volume of water pumped uphill could be too low. But this doesn’t change our conclusion that almost all of the water pumped uphill was allowed to run back down again. It just means that more water than we thought was circulated between the reservoirs without generating any electricity.

      • Willem Post says:

        “But this doesn’t change our conclusion that almost all of the water pumped uphill was allowed to run back down again. It just means that more water than we thought was circulated between the reservoirs without generating any electricity.”

        A nice way waste energy; pump water up, let it flow down!

        How much subsidies did it take to create this folly?

        • Kees van der Pool says:

          Nothing new about wasting windpower. The Germans, also lacking large scale storage, dump their excess wind/solar gigawatthours on their neighbors, often at negative prices.

          • gubelu says:

            …. negative prices which are so low, that the average proice for each kWh exported is significant above wholesale market price in germany, and also higher or not significant below the price of imported power… So much about rumors.

          • Paul AUBRIN says:

            Gubelu says: March 3, 2016 at 1:31 pm
            “…. negative prices which are so low, that the average proice for each kWh exported is significant above wholesale market price in germany, and also higher or not significant below the price of imported power… So much about rumors.”
            A page, on the web site of the EPEX spot market, explains that those “rumours” are not groundless.
            How often do they occur?
            Negative prices are a comparably rare phenomenon, as several factors have to happen at the same time. However, they are nothing unusual. In Germany, where inflexible power generation from renewables is increasing, 56 hours on 15 days with negative prices were observed on the Day-Ahead market in 2012. On the Intraday market there were 41 hours on 10 days. If these markets were not coupled, negative prices would occur more often, and price peaks would be more acute.

  5. Stuart Brown says:

    Willem, I quite agree about the rationale for funding, or lack of it!

    However, it seems the Enercon wind turbines along with their control systems are not quite that unsophisticated. What is fed into the grid comes from the output of the inverter(s) for the whole wind farm, with the individual turbines being isolated from the grid and each other. So, the wind farm has no real inertia to offer at all, is synchronised to the grid, and can provide whatever real/reactive proportion of power is required. Presumably synchronisation for El Hierro means synchronised to the Pelham hydro turbines since they are turning continuously.

    If they include the same techniques as described for a much bigger system in Quebec (same 2.3M turbines), then they are capable of adding a few percent extra power from the rotational energy of the machine to help steady the frequency variations due to a sudden drop in generation elsewhere:

    Adds 10% extra power in about a second, only lasts 10 seconds, and stuffs the efficiency of the wind turbine for a while, but the hydro is capable of adding about 1MW/s in normal operation too.

    As an aside the Hydro-Québec TransÉnergie system appears to be an island grid in itself, so might be worth a study in its own right?

    Like you, I’m no fan of this wind generation, but I can respect the engineering to try and make it work in a real grid!

    • Greg Kaan says:

      That’s a very interesting paper. Too bad it does not mention how much it costs to add the inverter (to provide the inertial emulation) to each turbine. The added ability to smooth out a fluctuation, in the absence of meaningful energy storage, is better than nothing but not by much.

      I’m not sure how Hydro-Québec TransÉnergie system would qualify as an island grid, though, as they provide significant interconnections to 4 other large grids

      • gubelu says:

        If the inverters are designed for fault ride threw, and the according higher currents (which is standard today) this is a software question.
        And if the wind turbines are curtailed at 7MW while ther is enough wind for 11,5MW, they can sacle up within seconds to a output of 11,5MW, they just have to turn the blades in the right position. No mass needed to accelerate, no machine parts to heat up carefully, etc.

      • Stuart Brown says:

        Greg, bad phrasing on my part – I’m sure you are right about the interconnections, but in the paper it mentions that the system has no AC synchronisation with other grids. Since the discussion was mainly about frequency variations, power factors and the effect of having so much wind in the mix, I wondered if the Quebec project shed any light on the subject – I’ll admit I’ve not looked at all.

        • Greg Kaan says:

          The article does state “HQT’s power system is not synchronously connected to any other AC network ” yet the company’s system map clearly shows only one HVDC interconnector (to Vermont) while all the others are unlabelled so they are presumably HVAC.
          Very odd.

          As an island grid case, though (assuming it was, in fact, isolated), Hydro-Québec TransÉnergie is on the large side and if 3.5GW (nameplate) of wind turbines were to represent 10% of its peak load and 25% of its low summer load, there must be plenty of traditional synchronous generation available despite the concerns of the study.

  6. Stuart Brown says:

    Sorry – was meant to be a reply to Willem above.

  7. gubelu says:

    Biggest problem is that we know too little to know what happens with the water.
    The pipe connection to the upper reservoir also does not exist in the maps as they are available.
    Also the pipe connection to the lower reservoir is missing. It is also know that el Hierro uses several million m³ of water for irrigation every year. (Rainer provided a link to this Data)
    So it remains unknown if they use the water to mhave some fun with pumping instead of simply adjusting the pitch regulation of the wind turbines, or are there simply some more pipelines missing in the map which have been added to connect the hydropowersystem to the irrigation system at sea level. If the later would be the case, also the bigger volume of the upper reservoir makes sense, which would then provide 150.000m³ combined space for pumping and irrigation, and 200.000m³ for irrigation only.
    If the system design would work logically, the existing pumping stations would have been retrofited to work as generators too (there are some texts on the KSB-Homepage how this can be done), so a constant flow of water from the upper reservoir to the irrigated areas below 700m would result in a constant power generation fed into the el Hierro Grid by the pumping stations not showing up in any statistics beside a according drop in demand.
    If the system would work like this, all statistic data would make sense beside the curtailing at 7MW.

    • The pipe connection to the upper reservoir also does not exist in the maps as they are available.

      But it exists. All you have to do is look for it. This Google Earth street view image has been shown a number of times before but you don’t appear to have seen it, so here it is again:

      It shows a pipeline emerging from the upper reservoir and heading off towards Valverde, the island’s capital. (The photo was taken in June 2013 when construction activity was still ongoing, hence the temporary flexible connection.)

      The next image shows where the pipeline goes. It continues north for about 400m, buried under white-painted concrete in the drainage ditch, and then a white stripe shows where it crosses the road. The pipeline is clearly heading for Valverde, now less than a kilometer away, where it can link up with the island’s water pipeline network.

      The next image shows work in progress on the other side of the road crossing. The pipeline is clearly a permanent installation constructed to meet code. The sign in the background confirms that the work is being done by the Canary Island government, so we can further assume that it’s part of the 2002 Plan Hidrológico Insular de El Hierro which governs the future development and use of water resources on the island:

      image hosting 15mb

      And if the government is going to go to the trouble of digging a hole, laying a pipeline and covering it with carefully-manicured concrete several inches thick we can assume two things:

      1. This is the only pipeline to the upper reservoir that the 2002 plan calls for.
      2. The government will have made the pipeline large enough.

      And how large is the pipeline? It’s hard to judge exactly what the diameter of the buried portion is from the photos, but it looks like six or eight inches (150-200mm) tops. How much water could a pipeline of this size transport between the upper reservoir and the closest point of hookup to the island pipeline network, which is about 1km away and 50-100m lower in elevation ? I would guess not very much at all, but it would be nice to have an informed estimate.

      Also the pipe connection to the lower reservoir is missing.

      Here it is under construction in July 2013:

      This pipeline is heading for the lower reservoir, which is off the image to the left and 50m up the hill. It has a diameter of maybe ten inches, or 250mm, and it probably links with the gravity-fed pipeline leading south from the Tamaduste desalination plants 5km to the north. As to how much water it could transport, one assumption would be a maximum of 2,400 cu m/day, equal to the production capacity of Tamaduste’s two desaladoras. Again, however, it would be nice to have an informed estimate.

      The bottom line is that we have one modest-sized pipeline feeding the lower reservoir and one very modest-sized pipeline extracting water from the upper reservoir. We don’t know exactly how much water these pipelines are capable of transporting, but it’s clearly nowhere close to the plus-one-million cubic meters that according to the REE data was pumped up the hill in July and August last year.

      Finally, am I correct in assuming that gubelu is another one of the noms-de-plume, like guber and gweberbv, that Gunther Weber is submitting comments under?

      • gubelu says:

        No, or do I have to asume that Roger Andrewa is the same a euan Means?
        What I wanted to say is that the map of the pipelines is obviously not complete. So we do not know where else it in incomplete or not. So basing assumptions of the operation on this map is not on a very solid base.

        Calculating flows and pressure losses in a pipeline is a easy task for a engineer with the right software.
        The pipeline connecting the upper reservoir below ground seems to be much bigger than the provisoric black pipe over the road. To have in 2 Months the 10.000m³ loss per day of irrrigation water from the upper reservoir, it is 416m³/hour. With 200mm inner diameter, and 20°C of the water the pressure loss of the pipeline is 4,43 bar/km, so 44,3m of height so to say. Which is pretty much but not impossible with the steep environment.
        With 250mm it becomes 1,48bar, per km, with 300mm it becomes 0,67bar/km.
        If somewhere a second pipeline si burried which we don’t se, it becomes 200mm:1,2 bar/km 250mm: 0,41 bar, 300mm: 0,17bar

        So there are no giant pipelines neccesary to handle the amount of water in question. So what we do not know is, if the map of the water is not correct in other pipelines, too, but the operation of the system is reasonable, so the additionally pumped water is going to irrigation, or if the operation of the system behaves as if there is a irrgation, but instead of sending the water to irrigation it goes back to the lower reservoir without being used for power generation.

        • Roger Andrews says:

          Gubelu: Thanks for your estimates of pipeline capacity, which are the first I’ve received from anybody. I’m not going to dispute them, I’m going to assume they’re correct, and that the upper pipeline could indeed have extracted a million cubic meters of water from the upper reservoir during July and August. This raises the following questions:

          * Where did all this water go? Total annual water consumption on El Hierro is only about 3 million cubic meters, and most of that goes to irrigation in the El Golfo area, which is self-sufficient in water and doesn’t need any help from GdV.

          * If a million cubic meters was extracted from the upper reservoir then a million cubic meters must have been fed into the lower reservoir. Where did all this water come from? It’s twice as much as the island’s desalination plants could have supplied working 24/7/365.

          Maybe you could supply us with some numbers showing how all this fits together.

          If somewhere a second pipeline si burried which we don’t see

          Having assumed that the existing pipeline is large enough it doesn’t matter whether another pipeline exists or not. But I’ve been looking at the upper reservoir trying to find another pipeline route that would make sense. I can’t find one. Can you?

          • guber says:

            Well, Rainer put some link in here with data from the el Hierro water system it shows two points: 1) Water consumption in summer is nmuch higher than in winter 2) Water demand is rising fast.
            So the question is in which direction do we assume – are mr. SancheZ from el Hierro and his team reasonable and try to do a good job, or are they running the system like maniacs?
            I prefere to be optimistic about their intentions, although some System parameters in operation like curtailment of wind power generation remain queer.
            So if we assume a reasonable operation, in a irrigation system where the water comes from a top reservoir now instead of comming from sea level, the pumping stations of the island would be operated as generation systems, with a expected efficiency of about 80% for a pump runing in reverse mode.
            To get Water to el golfo , it is neccesary to get it up another 200m or go the way around the northeast. It is possible that they use some of the electric power in times when there is Wind to pump water over the mountains to the other side, (so via Tinor and then down via a new pipe and turbines to the other coast, the irrigated areas at el golfo seem to start somewhere around 300-400m above sealevel)
            It could also be that irrigatiion in the northern part of the island, so 400-600m above sealevel was extended in the recent times. a few km² irrigated land can consume this amount of water.
            It is unknown how much production of desalination can be increased when power consumption is not a cost factor. As far as I could find out the desalination systems are usually designed to operate at 50-60 bar pressure, but with pumps being able to provide 80 bar pressure to keep the system fully operational if by some cause the permeability of the membranes is reduced. How far the output rises if 80 bar are applied on clean membranes I do not know. I would expect with laminar flow and a fix reverse pressure from the salt concentration something above 25%. If such a operation has other negative side effects beside higher power consumption is not known (just that the systems are designed to work with higher pressure to be able to deliver the full output with partly closed membranes)
            So a lot of factors remain unknown, also if some parts of the systems which are part of the idea of the system are not built yet, e.g. additional desalination capacity.
            I would also like to know from Euan Means, where exaktly he found a link taht the designer of the systems intended to have 100% of renewables of the time for 100% of the time during the year. So far the papers I saw tolt that the system should allow extensions to reach 100% of renewable supply in further steps, and allow temprorary running on 100% renewable supply as it is now. What newspapers made of this information is a totally different question, and not in the hands of the ones who designed the systems. If you had press reports about systems you designed yourself sometimes, you will know that the connection between what was told to the journalist, and what he understood while not understanding technology at all, is frightening loose.
            Which is a problem for nuclear, for renewables, and for conventional power, as well as all other kinds of technology.

          • Guber: I took your comment off moderation so that I could explain to you why you were on moderation to begin with. It’s because you have made no effort whatever to familiarize yourself with the details of the GdV operation and as a result you are posting a lot of ignorant comments:

            So if we assume a reasonable operation, in a irrigation system where the water comes from a top reservoir now instead of comming from sea level ….

            The water doesn’t come from a “top reservoir”. It’s desalinated sea water. It comes from the sea level, and according to your vision of how things work it gets pumped from sea level through pipelines to the GdV upper reservoir and then gets released back down again through the same pipelines. Is this “reasonable”? Well, there may be some cases where it makes sense to do this but right now I can’t think of any.

            To get Water to el golfo ….

            If El Hierro’s water is now distributed from the GdV upper reservoir, as you seem to think, then a lot of the water in the upper reservoir would have come from the El Golfo desal plant. Is it “reasonable” to pump this water 700m uphill through a long, winding pipeline to the upper reservoir and then release it through the same pipeline back down to El Golfo? “Insane” would probably be a better word.

            So a lot of factors remain unknown, also if some parts of the systems which are part of the idea of the system are not built yet, e.g. additional desalination capacity.

            Once more you haven’t done your homework. The systems that are part of the “idea” are all in place, including the desal plants. Numerous references confirm this. All you have to do is read them.

            Here on Energy Matters we encourage comments that make a positive contribution to the discussion. Yours do not.

      • @ Roger
        “How much water could a pipeline of this size transport between the upper reservoir and the closest point of hookup to the island pipeline network, which is about 1km away and 50-100m lower in elevation ? I would guess not very much at all, but it would be nice to have an informed estimate.”

        You would be surprised. Just doing a very simple calculation on a reservoir with a 200 mm plastic pipe (I reckon that is the size you got but could be a tad bigger) out to an open point @ an elevation 50 m lower than the reservoir, you could get over 2000 m3/h.

        However you would not design to that. For a 200 mm pipe with sensible velocities, you would be controlling the flow to around 250-450 m3/h. Higher velocities run the rise of hydraulic hammer and noise – 450 already pushing that limit.

        • Sorry that 2000 m3/h was considering a pipe length of 10m.

          For 1 km, the flow would be in line with the design velocities that you would want. ie between 250-450m3/h.

          All depends on the control though.

        • Donough. Useful information! Thank you.

          Would you now care to have a go at my pipeline route?

          A couple of things to note: Once water from the upper reservoir gets to the existing pipeline network it’s all downhill going to the east (note that north is pointing NE on the map) but uphill to the west, at least to begin with. To the west is where all the irrigation demand is.

          I came across this Google Earth street view of a couple of existing (pumped) water pipelines. I would guess that the UR pipeline is probably the same size.

          • Euan Mearns says:

            The pipes from hydro schemes in Scotland are MUCH fatter than that. But this is a baby scheme – right?

            TGV for scale.


          • The penstocks at GdV are 1m in diameter too.

            The Pelton turbines are rated at 2 cu m/sec maximum flow each, or 7,200 cu m/hour for all four. A rough calculation based on turbine capacity (11.2MW), reservoir storage capacity (270MWh) and reservoir volume (150,000 cu m) gives 1.74 cu m/sec, or 6,250 cu m/hour. The head is 650m and penstock length is 2,350m. Maybe someone could scale these numbers down to 200mm diameter.

          • Roger


            From the reservoir towards v.verde we go uphill? That means pumping.

            Looking at the pictures you seem to have a mix of pipe sizes that I do not understand. Certainly I think the large red ones in your first post pic 4 are in the 200mm or so category.

            On your response post the second pic looks like 50 – 75mm (2-3″ in old speak). If all the pipes from the reservoir to the existing pipework are that size, you are talking about 10-60m3/h.

            I would suggest is that since the length of the pipe is so long, most of the fractional losses will be due to that. Bends and fittings and curves etc will not have a huge effect on the final result. So modeling this as a straight pipe will give a decent ballpark.*

            It is likely that it is controlled to do much less on average over a week or a month probably via a variable speed pump controlled by the demand.

            I could do a more detailed calculation but the diameter confusion I have is key.

            Feel free to follow up by email. Possibly a conversation will clear up the confusion.

            *A simple but fairly accurate calc is here.

          • @ Roger

            Try again post.

            I am confused about the pipe diameter. Most of your pictures including the second picture on your response are small; guessing around 50-75mm. That would put you in the region of 10-50m3/h. A rule of thumb is that for most water pipelines, you would use 1-2m/s velocity (flowrate=velocity/Xsection area) though with gravity you can sometimes get up to 4 but probably not this application.

            I used a 200 mm pipe based on the fourth photo of your first photo; the larger orange pipes. So we need to sort the pipe diameter.

            Once that is done, with regard to the pipe run as it is so long, the layout does not need to be so accurate. Surely bends and fittings will make an affect but the main friction losses will be due to the pipe length and the outlet pressure (If the existing pipework is at pressure, then at the very least we need to fed in higher at a higher pressure and the smaller the pressure difference, the less flow). Thus it is fairly OK to model the system for our purposes as a straight pipe with a straight elevation drop (just for simplicity). I have the capability to make it as complicated as you like but we are not designing the system here.

            A simple calculator is below and you can account for outlet pressure (converted to meters) by subtracting from the overall drop. So if the reservoir is at 50m and it is pumping into a system at 1 bar, your overall drop just a touch under 40m. It is not too bad.

            Also your map shot seems to state that on this pipe run we are going up hill to the tune of circa 50m at the start? That means a pump.

            My guess is that the system supplies a variable flowrate controlled by a variable speed pump and a pressure vessel on the existing pipework. The pump speed is matched with demand and for these sorts of flowrates, that can be fairly accurate (especially at 50 m3/h if that is correct).

            Feel free to email etc. Conversations can often clear up confusion better than online.

          • Roger Andrews says:

            Donough: Thanks for your responses. I’m busy doing something else right now but will be back later.

  8. sod says:

    Thanks for this update. I disagree with many aspects but i really appreciate the effort you make to form a strong base for the debate. Thanks a lot!

    I will only comment o two points for the moment. The first one being the comparison with the King Island grid.

    I do not see a wind curtailment in the (few) King island data points that we have.
    These provide multiple points with wind at 2 MW output in a 2.45Mw system. At worst, the curtailment would be at about 80%, not at about 60% (7 MW of 11.5) in el Hierro.

    (page 13 has wind above 2MW)

    To me, it looks like they are using the resistor INSTEAD of curtailment, and not in addition.

    My second point is criticism of the analysis of the past months, as if we would see a a working system at top performance. The reality is the opposite. We know that wind is curtailed to 7MW all the time, often also to 5MW. And this is only the curtailment that we can easily see. We do not know how many tests with limited wind they did and whether they are curtailing ramp rates of the wind output as well. The wind output looks horrible to me and without any further facts i do not accept this as the maximum output that is possible (so calculations based on this output are mostly futile).

    final question: I would like to hear some real estimates about that “permanent water power output” being hidden by pumping up. 1MW? 2 MW?

    • Sod: Thank you for your kind words. A few responses:

      I do not see a wind curtailment in the (few) King island data points that we have.

      If you click on the King Island Live Grid box when the wind is blowing strongly (which it isn’t at the moment) I think you will find that a significant fraction of the wind power generated is being absorbed by the dynamic resistor and wasted as heat.

      To me, it looks like they are using the resistor INSTEAD of curtailment, and not in addition.

      GdV curtails wind by imposing a threshold on wind farm output. Then it curtails it some more by sending any remaining surplus wind to pumping.

      My second point is criticism of the analysis of the past months, as if we would see a a working system at top performance.

      I’ve no idea how you came up with that interpretation. The project is still feeling its way forward and is obviously still not at “top performance”. As to what its top performance might be, this was made clear in the text:

      During high-wind periods such as occurred in July, August and early September last year and in the second half of February this year we can expect that the plant will ultimately be capable of supplying 100% of El Hierro’s electricity with renewable energy for extended periods. But during low-wind periods such as occurred between mid-September last year and mid-February this year diesel generation will have to provide the bulk of the island’s needs.

      Based on results to date We (Hubert Flocard and I) have estimated that renewable energy from GdV will ultimately supply about half of El Hierro’s electricity needs. This is well short of expectations but still a considerable improvement over the 32% achieved to date.

  9. ducdorleans says:

    Roger, a tiny request …

    would it be possible to alter fig. 1 that it shows days/months, instead of “days since beginning” .. ? … for, most probably, these data and graphs will be a yearly pattern …

    (I have read only up to there …)

    anyway and already, thanks a lot for these updates …

  10. gweberbv says:

    Another 10 million investment for something like 10 MW PV capacity would bring them close to 80% renewables, I suppose. I wonder why they installed the wind turbines instead.
    The average insolation looks like paradied for solar: https://en.wikipedia.org/wiki/El_Hierro#Climate

  11. Some earlier commenters have wondered how much GdV cost and how large a subsidy it has received. Here are some numbers.

    Capital cost: Estimates vary depending on the source, but the most commonly-quoted number is 82 million euros.

    Subsidy: 35 million euros from the “General State Budget” – presumably the Spanish government.

    Guaranteed payment for power delivered: 236 euros/MWh. Repeat, 236 euros/MWh.

    Payments to guarantee an acceptable return on investment: Not known, but add them to the revenues from sales of power and GdV expects to earn 7 million euros in 2015, which works out to 0.81 euros for each kWh of renewable energy supplied to the El Hierro grid during the year.

    Price paid by El Hierro residents for this electricity: 0.23 euros/kWh

    Subsidy per kWh: 0.58 euros, paid presumably by the Spanish taxpayer.

    • sod says:

      “Price paid by El Hierro residents for this electricity: 0.23 euros/kWh

      Subsidy per kWh: 0.58 euros, paid presumably by the Spanish taxpayer.”

      There is a problem with this kind of numbers. The comparison here is between constantly paying for diesel and a one-off investment (that pump storage lakes are there to stay for ever).

      I also still do not accept the weird idea that they filled those reservoirs once and now pump in circles, with no water being added or leaving (rain, irrigation, desalination, …). As the graphs in the original post show, this use of the system does not make the slightest sense at all, at least they should have gone for upper and lower pools of the same size.

      It is also utterly unclear why they are not pumping sea water, if this was the purpose. So either we are missing an important point or a central part of the project is a failure of epic proportions.

      The same is also true for curtailing a 11.5 MW wind system at 7 MW. If you are planning to not use the upper 40% at all, you would have a possible solution with much lower maximum output and much steadier/higher output at slower windspeeds.

      Looking at the way the site is designed and at the tests, i have to admit that the epic mess up is a not too unlikely option.

      • gweberbv says:


        as the upper reservoir is needed also for water supply/irrigation, pumping sea water into it would not make much sense. Moreoever, working is with salt water seems to be a really ugly business in the long term. To my knowledge there is a single hydro storage system using salt water (located in Japan) and they need to use special materials that can survive the salt water.

        Again: If one wants to look for strange/stupid ideas in this scheme, I would start asking why they are using wind turbines instead of solar panels. From the data present in this blog we have learnt that El Hierro has months with very poor wind conditions. And the storage capacitiy only last for a few days even with optimum conditions (which still is a huge storage capacity when you compare it to European countries).
        I wonder if this island ever experienced a month with poor insolation. Probably not. So, why not installing 10 MW of PV modules, storing during peak time and using the energy during the following night? If you really want to, you could still include maybe 2 or 3 MW of wind capacitiy just for the fun of it.

        But instead they chose to build 11 MW of wind and no PV at all. Strange!

        • gubelu says:

          As far as I have heared, this has simply historic reasons. The system design was made in the second half of 1990*s, and was since then on it’s way to get threw the red tape in spain.
          So when the disign was finally approved it was technically outdated in many ways, but could not be changed any more.
          If the system would be designed today, it would be reasonabl to use a mix of wind and solar (wind delivers power at night), which would allow the system to provide 100% of the power really most of the time. It would also be reasonable to use PV-inverters with (really) synthetic inertia, which would include some battery or supercapacitor storage, or output limitations, or both.
          Also nobody today would plavce all 5 turbines so close to each other, but would distribute them along the 20kV grid over the island, to remove the short time variations, because then the output on the cale of seconds up tp 5 minutes would be uncolrrelated, which provides a significant smoothing with 5 Turbines already, which makes life much more easy.
          But now the system is as it is, and they have to make the best of it, until in a few years it is politically possible again to add changes and install some MW of Solar additionally. And maybe a wind turbine on the other side of the island, along with more desalination capacity.

      • Euan Mearns says:

        Sod, peak demand is about 5 MW, so what is the sense in producing 11.5 MW even if the wind conditions allowed? What are you going to do with the extra 6.5 MW?

        The answer is pretty simple. GdV can never work because it does not have any where close to adequate storage.

        • sod says:

          “Sod, peak demand is about 5 MW,”

          peak demand is about 6.5MW and demand seems to be above 6MW for multiple 10 minute periods basically every weekday.


          It is utterly clear to me, that the wind output above 7MW would go to pumping. That should be the idea behind this system. and you could offer it for cheap money, desalination jumps to mind as a process, that might use lots of power on demand!

          As i said above, a different system with less peak wind output and more output at lower wind speeds would have been a great benefit.

          I totally agree with gubelu, that historic reasons might explain this extreme mess up. And a combination of wind turbines at different paces and solar would make a 100% renewables at (about) 100% of the time much eassier.

          But to be fair to the project, this was not the plan either. (more like 60% and 100% sometimes).

          Just to be clear, most people would have said that this is impossible some years ago and i am just waiting for people to dispute the fact, that el hierro is running on 100% wind for days!

          • Roger Andrews says:

            In an attempt to shed some light on the growing darkness here, 11.5MW was selected because it’s what would be needed to cover El Hierro’s demand (about 40GWh/year at the time) with wind power, assuming a) a 40% capacity factor, b) that wind power could be admitted directly to the grid without destabilizing it and c) that the hydro plant would allow all of the wind power to be used. Assumptions b) and c) were the big misconceptions.

    • Euan Mearns says:

      Roger, you need to put these numbers at the top of your next update and make the point that all this buys you 32% capacity.

  12. REE has just awarded GdV its annual innovation prize:

    Con motivo de la celebración del Día Mundial de la Eficiencia Energética, el día 5, el presidente de Red Eléctrica, José Folgado, ha entregado las distinciones que concede anualmente su empresa para impulsar las iniciativas que persiguen reducir los consumos de recursos naturales y las emisiones de dióxido de carbono (CO2). La gestión automática en tiempo real de la central hidroeólica de El Hierro ha sido seleccionada dentro de la categoría de innovación. Se trata de un sistema de monitorización y de apoyo al operador del centro de control de Red Eléctrica en Canarias, que acorta el tiempo de respuesta y mejora la integración de las energías renovables “no gestionables” en el mix energético de la isla.

    “To celebrate World Energy Efficiency Day, March 5, the president of REE, José Folgado, has issued the awards that REE gives each year to stimulate initiatives that seek to reduce the consumption of natural resources and CO2 emissions. The real-time automatic management of the central hidroeólica de El Hierro has been selected in the innovation category. It consists of a system of monitoring and of support to the operator of the REE control center in the Canary Islands that shortens the response time and improves the integration of “unmanageable” renewable energy in the island’s energy mix.”


  13. jacobress says:

    The El Hierro system is complicated, It is and integrated system of water and electricity. The desal plants consume electricity so the “grid demand” includes desalination use, and water pumping from beach plants to higher located users. And this use can be intermittent – the desal plants and pumping can accommodate themselves to electricity availability.

    I have no data, but here are some guesses: The water grid is interconnected, and all desal plants can deliver water, at least to the lower reservoir, which serves also as water reserve. The upper reservoir is used to supply water (under gravity pressure) to the whole island.
    The water you deduce is just pumped up then released back down, is actually released into the water supply system of the island.

    The unused capacity of the wind turbines is, maybe, destined for future use. maybe not all desal plants are yet operational, or maybe they don’t yet run at full capacity. Maybe they reckon (and planned for ) higher water usage in the future, once desal water is available. More water means more electricity needed.

    The water and electricity systems are inter-dependent, you can;t consider them separately.

    • sod says:

      “The El Hierro system is complicated, It is and integrated system of water and electricity. The desal plants consume electricity so the “grid demand” includes desalination use, and water pumping from beach plants to higher located users”

      I think that you are right. But from an analytic perspective, we are having a problem here.

      in his analysis, Roger basically assumes no water is taken out of the system.

      so we basically are discussing two different systems:

      1. A closed system with water being nearly entirely used for electricity production, hidden in the background. Water is simultaniously pumped up and running down, stabilising the system. No new water is added,no water is taken from the system. Basically a close loop between upper and lower reservoir, with nearly constant flow in both directions.

      2. a combined irrigation system. a majority of the water is not used to generate electricity, but for irrigation purpose. Water is constantly added by desalination and constantly taken out of both (?) reservoirs for irrigation purpose. While pumping up, there is little or no water coming down for electricity purpose, only to keep the turbines spinning.

      To move on, we either need more information or someone has to bring forward good arguments, supporting his position. For a start, i would begin with the assumption that there is a numerical value to the hidden water flow down (for electricity production). Let us say about 2 MW for version 1 and 0.3 MW for version 2. Shouldn t we be able to spot the difference somewhere? for example when the hydro system changes from net pumping to net electricity production?

  14. Rainer says:


    Statement of „Consejero de Gorona, Juan Pedro Sánchez“

    Very interesting also the comments.

    I still have the question:
    Why GDV do not answer the questions of us?

    • jacobress says:

      Thanks for the interesting link.
      It says there that the water system (desalination and pumping) consumes 45% of the total electricity consumed on El-Hierro.
      It also says that up to 1 Sept 2015, the price of electricity was the same in all Spain, which clearly means that the mainland was subsidizing the expensive electricity produced on El-Hierro by diesel-generators.
      From now on, each island pays its own expenses, and the GoV plant will reduce the consume of diesel-oil, and therefore reduce the price of electricity in El-Hierro. (But the price of diesel also fell…)
      I think that biggest contribution to lower electricity price is the fact that the plant, especially the wind turbines were paid (in big part) for by the European Union and the Madrid government.

      • gweberbv says:

        Proving infrastructure that is compareable to mainland standards for an isolated and small community like an island can only work via subsidies. This does not only apply for electricity supply.

    • sanches says:

      I think this is simple to answer – this is a anti renewabls site, where everything which tries to overcome the limitations of renewables and makes a renewable system fly is “grren piss” and “geen diarhoe”, and everybody who makes useful proposals gets blocked – or “put on moderation” as it is said here euphemistic, and then no contibution ever shows up again. Only Oil gas and nuclear are allowed to be praised as the holy gral.
      So if anybody checks the site before answering, or looks for those people writing here with the same name they use in the email, it is obvious why they don’t answer. I doesn’t seem to make any sense, since anything positive about the system in el Hierro is likely to be ignored, anything negative will be published over dozends of pages.

      • Euan Mearns says:

        This project was sold as a 100% renewables enterprise and is currently delivering 32%. And it cost a reported €82 million. Those in charge are either dishonest or incompetent. It is noted that you evidently support this form of conduct and struggle with polite discourse so I have put you straight to moderation. Come up with technically sound and polite comments and they will be published.

        Much of Europe (especially Spain) is bankrupt and we simply cannot afford to piss money away like this – IMHO. I see the same thing on a lesser scale where I live in Scotland. We have hydrogen powered busses. They cost about double, are normally broken down and the H2 is probably sourced mainly from FF.

        • Rainer says:

          if this Mr Sanches in fact is “Consejero de Girona, Juan Pedro Sánchez” of GDV, please publish any comment of him. I am very curious to get more looks in his “competent thinking”. In this case a phrase will be true: “Got him on the balls”.
          Thank you.

          • Euan Mearns says:

            I did some checking. I don’t think it is the same guy. Why do GdV not answer emails or participate on the blog? Well, if you spend €82 million promising 100% renewables (which is already dreadfully expensive) and deliver only 32% you have nowhere to hide. A few years ago I’d have been inclined to begin reporting this up the chain of responsibility. But that goes Spanish Government, EU and then the UN. The system as it is now is totally bankrupt – intellectually, scientifically and financially. This has happened before in the 1930s.

          • No, it definitely isn’t Juan Pedro Sánchez. He’s far too busy leading El Hierro and the world into a bright green sustainable energy future to post vulgar comments on a blog.

            And Señor Sanchez has just made another interesting prediction. He notes that beginning on September 1 2015 consumers living on Spanish islands will no longer pay the same for electricity as consumers on the Spanish mainland or even on the next island over. Because of this he is confident that “in a few months El Hierro’s electricity will be the cheapest in the Canaries.” It will be interesting to see how this prediction pans out.

            http://www.diarioelhierro.es/t26496/ab02.asp?idweb=26496&idrg=159311 (h/t Rainer).

          • Euan Mearns says:

            I think this may be Mr Sanchez admiring the virtual reality €82 million creates. I’m sure he is a very nice man unaware of the tsunami bearing down on him as Roger’s posts generate increasing volumes of traffic.

          • I doubt it has anything to do with us, but the article starts out: “In the street there are still many doubts relative to the famous central Hidroeólica de El Hierro. Many doubts that those who live on this island would rather not have. This is why we have gone into the bowels of the plant to find out up close the answers to the questions many of you have been asking.”

      • Rainer says:

        Dear Mr. Sanchez,
        Thank you for your contribution. Certainly there are in this forum different settings. Also I do not like the very naive opinion to be able to solve all energy problems with nuclear energy only. But that is really no reason to use swear words. This is simply a discussion of technically interested people. Also, I think it quite normal not to hide behind some anonymous email addresses. They prefer just to wrong facts around the world. That really hurts me.It makes a bad picture not only to GDV but to El Hierro. However, you did meet another point perfectly. GDV is simply unwilling to publish technical data.
        GDV is build by public money so the data is owned by the public.
        Source: Ley de transparencia
        GDV do not understand that: “Transparencia gana confianza”
        As optimistic solar and wind crazy person I still look forward to further contributions possibly with published real data. Nowadays it is common to put in online in real time. Maybee even from a journalist if not from GDV. In which media ever. Maybee a link in a local online paper?

      • @ Sanches

        So what you are saying is that we should turn a blind eye to failure. Even if that failure could potentially prevent us from reducing CO2 emissions. You are not very green are you?

      • Rainer says:

        Dear mr Sanchez,
        You are the “Consejero de Girona, Juan Pedro Sánchez” of GDV?
        If so, then the level of your comment is unsustainable. My heart bleeds for GDV and El Hierro.

  15. Roger Andrews says:

    No test this Sunday. Not enough wind.

    • Rainer says:

      Do not agree.
      Enough combination of wind an hydro to hit demand.
      But not enough wind to spoil 40% like in the last tests.
      Not enough guts or finacial pressure, the same management problem…….
      Everybody get paid even if diesel is spoiled.

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  17. botwid says:

    Well, I came to the same conclusion. 100% renewable is a just dream. One must remove at least 50% of the population of El Hierro to make it fossil-free.

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  19. sod says:

    “Well, I came to the same conclusion. 100% renewable is a just dream. One must remove at least 50% of the population of El Hierro to make it fossil-free.”

    I think there is a major misunderstanding here.

    The El Hierro system was not build do provide 100% renewables all the time. The target was saving diesel with a high renewables percentage (60+%?), achieving 100% at some times.

    It is obvious by now, that El Hierro can provide 100% renewables over extended periods of time.


    We also know that the system can provide 50+% over months (it did so over the first two month in service).


    But we also know, that they are not using the system to maximum effect:

    Wind is curtailed at 7MW of 11.5, basically wasting up to 40% of the output.

    The majority of pumped hydro is NOT used to produce electricity. In my opinion, there are convincing hints, pointing to a massive use of water for irrigation purpose.

    • Euan Mearns says:

      The El Hierro system was not build do provide 100% renewables all the time. The target was saving diesel with a high renewables percentage (60+%?), achieving 100% at some times.

      Reference please Sod. My finger is hovering over the moderation button. Never ending babble is quite simply not tolerated. And in any case, 32% is barely half of 60%.

      • botwid says:

        I have followed the project for a long time and officially the system was built to provide 100% renovables.

        (start at 3:39)

      • sod says:

        “Reference please Sod.”

        my spanish is not very good, so there will be other people who have better access to sources.

        But the main project flyer is pretty straight forward: “El Hierro, towards 100% renewables” is the titel, and on electricity it says:

        “With great ascents and high wind energy potential (Trade Winds),
        El Hierro proves to be a very suitable place for the implementation
        of a Wind-Hydro power station; it is also the fi rst Wind-Hydro
        power station that will be providing close to 80% of the electricity
        demand of a totally isolated area.”


        And this scientific source is also speaking about 80%, and it names a spanish source that admits that 100% remain “utopia”:

        “The tests that are being submitted to the plant are basically
        setting communications with Red Eléctrica. At Gorona
        was explained that until the opening of the plant – all the
        tests that had been made were internal and it had not been
        provided a single kilowatt to the network, now it has an
        input to the grid of 10% at first, then 20%, 30%, etc. –
        everything it is being adjusted. The goal for the first year
        is to make sure that 80% of the energy provided annually
        to the grid would be renewable. Gorona recognizes
        though, that 100% remains a utopia [9].”


        I am curious, has anyone an official statement about 100% renewables, 100% of the time?

        “And in any case, 32% is barely half of 60%.”

        As i said before, the system is obviously not working properly. And there obviously was some false optimistic assessment before, while we now see exactly the opposite: An extremely cautious approach to the integration of wind and hydro into the grid.

        Basically there is an enormous amount of pumping but nearly no output from the hydro plant. I simply disagree with the idea that the water is just flowing back down for grid stabilisation, because the diesel is nearly constantly running at 1.5 MW and we know that the system can be kept stable with wind alone (so there would be much less need for hydro backup while the diesel is running).

        To judge the system, we would need to look at successful months (like the first two, which had 50% renewables). And we need to look at the potential of the system, not at the real output during an obvious testing phase.

        • Euan Mearns says:

          I am curious, has anyone an official statement about 100% renewables, 100% of the time?


          • Roger Andrews says:

            I think I mentioned this somewhere upthread, but probably the closest you’re going to get to an official statement is this. It appears in both the GdV and the Endesa project writeups, and in bold:

            La filosofía de funcionamiento se basa en el abastecimiento de la demanda eléctrica de la isla con fuentes renovables, garantizando la estabilidad de la red eléctrica; la central de motores diesel solamente entrará en casos excepcionales/emergencia cuando no haya ni viento ni agua suficiente para producir la energía demandada.

            “The operating philosophy is based on supplying the island’s electricity demand with renewable sources, guaranteeing the stability of the electrical grid; the diesel plant will be operated only in exceptional/emergency cases when there is insufficient wind and/or water to fill energy demand.”

            I think this is close enough to 24/7/365 renewables as to make no difference.

          • Rainer says:

            Homepage of GDV:
            “La empresa
            Gorona del Viento El Hierro, S.A., es la empresa encargada de desarrollar la promoción de un proyecto denominado “Central Hidroeólica de El Hierro”, mediante el cual, se pretende cubrir el 100% de la demanda eléctrica de la isla utilizando exclusivamente energías renovables.
            The company”
            Gorona del Viento El Hierro, S.A., is the company responsible for developing the promotion of a project called “Central hydro-wind of El Hierro”, by which it is intended to cover 100% of the electricity demand of the island using only renewable energy.

            Reality right now of GDV:
            16 + 41 + 2 + 35 = 94 hours supplied completely the island. These are 1.08% and not 100%!

          • The Spanish verb “pretender” connotes uncertainty. A more correct interpretation of “se pretende” would be “aspires to” or “seeks to” or “aims to”.

          • sod says:

            ““The operating philosophy is based on supplying the island’s electricity demand with renewable sources, guaranteeing the stability of the electrical grid; the diesel plant will be operated only in exceptional/emergency cases when there is insufficient wind and/or water to fill energy demand.” ”

            Emergency obviously sounds like it basically never gets used. and i am with you (as it is obvious in multiple sources), that in public statements the performance and plans have been overstated by a big margin.

            But the second part of the description (“cases when there is insufficient wind”) basically allows for no renewables at all.

            So this simply is not a good definition/prediction of the expected renewable output. There must be some numbers somewhere! In Germany you would most likely find this in a “Planfeststellung” (the presentation of project plans to officials), which should be public.

            It is utterly obvious that the system as it is now can not produce even close to 100% for 100% of the time (my 60% might be more realistic, i think i confused the number with those from King Island).

            But i think that things will change soon. Such a secret can not be kept very long. I assume that people are reading this very topics and that it will be only a matter of time until more sources pick this up.

            At the same time, those responsible for the project keep making optimistic statements (now about el Hierro paying a lower price!).

            Either these guys are totally insane or there is a reasonable explanation. The only one i can think of, is this:

            Nobody is paying for the current problems. It is a testing phase, while in a parallel process there are discussion about future cost/benefit sharing of the project/output. This gives a rational explanation for the current situation, as a high output would not be beneficial for the island (and those running the project). So i would not be al suprised, to see the system working in a completely different way, the very moment that it is going into real production mode (beginning of next year?) with a different paying scheme.

          • Rainer says:

            Other Source
            “Central Hidro-Eólica para la isla de El Hierro. Objetivo: 100 % energías

    • Rainer says:

      curtailed at 7M????
      Since 2016.03.01 20:50 curtailed by 5.3 to 5.6. Like the most time of staying in service….
      Where is the sense of that????
      The answer of GDV i would like to get….

  20. sod says:

    I also think the results from the el Hierro project make it possible, to revisit the chira-soria Project, which also got a rather bad assessment by Roger here:


    From what we know now, i think we can get a rather different picture. While the system will of course still fail on a “100% renewable for 100% of the time” scale (measured against the worst period of lack of wind that ever could be imagined), other aspects look more positive by now.

    A very positive point by now, is the size of both reservoirs. It is a huge advantage, that the lower reservoir is much bigger than the upper one.

    We know from El Hierro, that there is basically unlimited wind supply for pumping (if we stop curtailment, of course), so the numbers will look completely different for Chira-Soria.

    Another point of critisism of the project was the idea to build the hydro part first. This will be an advantage now, as we see on El Hierro the new critisism is, that the focus on wind power and on similar wind mills (with curtailment instead of a different setup) was problematic.
    So Chira-Soria can avoid this error and go for a more diverse set up, with a high percentage of solar and with much lower system costs.

    • Euan Mearns says:

      It is a huge advantage, that the lower reservoir is much bigger than the upper one.

      This is rubbish. In pumped hydro, having upper and lower reservoirs abut the same size makes most sense (if you have to build the lower reservoir). You pump all the water up the hill and the let it flow down again.

      We know from El Hierro, that there is basically unlimited wind supply for pumping

      This is irrelevant because it is the size of the upper reservoir that determines how much surplus power can be diverted to pumping. I’ve told you this already but you seem incapable of learning.

      So Chira-Soria can avoid this error and go for a more diverse set up, with a high percentage of solar and with much lower system costs.

      Solar PV is much more expensive than wind. But its true that using solar + storage is likely far more sensible than using wind. A smart teenager could have worked that out a decade ago.

      • gweberbv says:


        solar PV on El Hierro is for sure not ‘more expensive as wind’. Probably you are drawing conclusions from the situation in Scotland. Just think about the following:

        – PV and onshore wind have roughly the same to install costs per nameplate capacity.
        – In Scotland, good offshore wind locations offer a capacity factor near 30%. Solar PV may reach 10%. On El Hierro, you can expect between two and three times more solar yield.
        – While it will be possible to store nearly 100% of excess PV production during daytime and use it during the following night, you have to curtail a lot of wind because the reservoir is to small for weeks of continous excess production (followed by weeks on undersupply from wind).
        – To maintain/repair the five wind turbines on El Hierro you need a team of experts, special tools and spare parts that you need to ship from Europe. To maintain/repair a PV installation, you can hire a local electrician and the spare parts can be delievered by UPS, Fedex, etc.

        The El Hierro project was designed maybe ten years too early. When PV was expensive and wind looked like the only way to go.

        • Euan Mearns says:

          Gunter, are you the same commenter as Guber? You really ought to comment under your own name. I’ve suggested to Roger he should look into El Hierro designed on solar and geothermal. Solar looks like a no-brainer to me here. The pumped upper reservoir is more than adequate to cover diurnal storage. And El Hierro is nearly in the tropics. They couldn’t get rid of the diesels completely, but I’d guess they could have had a 90% renewable system based on solar and hydro. Don’t know what the cost comparisons would look like.

          • gweberbv says:

            No, I am not guber. But it is obvious that he is also a German speaker. Probably I know him from German energy-related forums, but with a different name.

      • sod says:

        “This is rubbish. In pumped hydro, having upper and lower reservoirs abut the same size makes most sense (if you have to build the lower reservoir). You pump all the water up the hill and the let it flow down again.”

        That is a good start, as this article notes.


        They assume that it will double the output capacity.

        But your idea of similar size reservoirs is based on multiple assumptions. For example that water is only used to produce electricity and that emptying a reservoir is a good idea.

        In the real world, you would never want either reservoir to be empty ever.

        “This is irrelevant because it is the size of the upper reservoir that determines how much surplus power can be diverted to pumping. I’ve told you this already but you seem incapable of learning.”

        You assume that the main use of the hydro is to produce electricity. That is simply not true on El Hierro today (basically the hydro output is close to nil). The main advantage of the hydro so far seems to be not output but input. the majority of work being done is smoothing the output of wind and lack of demand by sending wind(or diesel) power to pumping. so you want a big lower reservoir to keep pumping if their is good wind and you will want to use the water in another way, apart from producing electricity (irrigation jumps to mind).

  21. Euan Mearns says:

    Roger, I’ve been reading a lot about the capital costs of various energy technologies recently. From memory you said that GdV cost €82 million. And it provides about 7 MW peak demand. So this works out at a stonking €11.7 billion per GW of installed capacity. Compare with gas at €1 billion per GW. But GdV so far has only produced 32% of expected performance. Factor that in and the cost is €36.6 billion per GW installed effective capacity.

    I’m increasingly convinced that mis-allocation of capital in inefficiency underpins Europe’s economic decline – combined with Greenthinking that seems to permeate the whole of political media.

  22. Donoughshanahan:

    Replying to your earlier comments and questions on pipeline size with a little more room to spare.

    Here are some more Google Earth street view pictures of pipelines:

    Photo 1 you’ve already seen. The larger pipeline is probably the one that pumps water uphill from the Tamaduste desalination plant to Valverde, which I’m using as the central point because of its closeness to GdV.

    Photo 2 is the same pipeline farther down the hill, The building in the right background may in fact be one of the 1,200 cu m/day Tamaduste desal plants. It’s right where the island pipeline network map puts it.

    I couldn’t find a place where the Valverde-El Golfo pipeline was exposed, but the “fenceposts” in photo 3 show the remains of a section of it that was replaced where it went under a road. It’s a six, maybe eight inch concrete pipe. The rest of the pipeline is presumably the same size. (Note that this is close to the high point of the El Golfo pipeline at 780m, or 80m above the upper reservoir intake. Note also that it’s next to a dried-up reservoir that I estimate has a capacity of 15,000-20,000 cu m. Could this be where the water from GdV is scheduled to go?)

    Photo 4 shows the La Restinga – Valverde pipeline. It’s a little hard to see but it’s clearly mickey mouse. I think we can forget about any significant amount of water being transported along it.

    So how large are these pipelines? I think we can assume six or eight inches, or 150-200mm, for the Valverde-Tamaduste and Valverde-El Golfo lines and for the upper reservoir line, and maybe ten inches, or 250mm, for the line going to the GdV lower reservoir. I think we can also assume that the island pipeline network is not designed to transport large volumes of water.

    Thanks, incidentally, for the link to the calculator. It’s the only one I’ve come across that I can do anything with.

    • Sorry for the delay of reply.

      The pipes in the photos are for the water supply system as opposed to the generator system.

      “Photo 2 is the same pipeline farther down the hill, The building in the right background may in fact be one of the 1,200 cu m/day Tamaduste desal plants. It’s right where the island pipeline network map puts it.”

      This pipe is feeding this plant right. So that is your first clue. 1200/24 = 50m3/h. Assuming you loose 20% or so of the water due to the desal process then you are looking at a supply requirement if 75m3/h. 3″ inlet pipe.

      Photo 1 looks to me to be a small pipe 2-3″ fits. Also there is a visual clue in that the pipe is no thicker than the road wooden bollards which AFAIK are usually not very thick.

      Photo 2; harder to tell but the same.

      Photo 3: Pipe trench of about 0.2-0.3m. A 200mm pipe would need at least 550m pipe trench. Again the posts offer a visual clue.

      To me all of these photos suggest a sub 100 m3/h pipeline. Obviously all of this is far inferior to a tape measure.

      I think the larger pipes are for the generation system.

      Regarding the calculators there are quite a few on line but most do require at least a slope estimation and some require more.

      The first leg of the water supply system from the reservoir up hill is pumped. If being clever, then there would be a resevoir i.e. water tower but already on the hill so… Then your drop provides the pressure head.

  23. botwid says:

    The upper reservoir may contain up to 380.000 m3. If one of the desalination plants in La Restinga was producing (1.200 m3/day) and at the same time was pumping water to the upper reservoir, it would take almost a year to fill up the upper reservoir. I have not been able to find any proof that desalination water is used in the GdV plant. What do you think?

  24. sod says:

    Thanks for the BBC article. Good information!

    “But the goal is to go further than the 50-50 mix of renewables and diesel generation achieved over the summer.

    The station should already be able to cover 70% or 80% of total consumption, according to some of those involved.

    Juan Pedro Sanchez, an industrial engineer who works as an adviser to Gorona del Viento, foresees steadily increasing the length of time the plant is used to cover 100% of the island’s needs. This was done for two hours on 9 August, the next step will be to try it for 24 hours and ultimately it should be possible for weeks on end, he thinks.

    “I think that in a year or so, the plant could supply all the electricity the island needs for about 200, 250 days,” Sanchez says.”


    70% to 80% seems to be what we expect from the system as it is now. That is about what i thought, but might still be a little positive thinking. so 60+% should be a reasonable estimate.

  25. Rainer has just sent me some pictures of the upper reservoir pipeline, taken today (March 10), which I think put to rest the question of how much water has been extracted from the upper reservoir for irrigation purposes since GdV started operations:


    Top left: A Google Earth street view image taken in June 2013 showed a flexible connection strung on poles between the pipeline in the road and the reservoir. I had assumed this connection was temporary, but almost three years later it’s still there.

    Top right: A closer view of the coupling outlined in the circle in the top left photo.

    Bottom left: A close-up of the coupling. It’s a little difficult to read the tape measure but the outside diameter of the pipe looks to be about 10cm, or four inches. The pipe is constricted to an even smaller diameter where it passes through the coupling.

    Bottom right. Again it’s difficult to read the tape measure, but the outside diameter of the buried part of the pipeline looks to be about 20cm, or eight inches.

    Obviously the flexible pipe isn’t capable of transporting more than a small volume of water, particularly when the water has to be pumped 60m uphill before it can go anywhere. From this we can conclude:

    1. That no large volume of water has been extracted from the upper reservoir since GdV commenced operations.
    2. That extracting water from the UR has not been a high priority anyway. Otherwise they wouldn’t have left the UR connected to an 8 inch pipeline buried under the road with a 4 inch (or less) plastic pipeline perched on poles.

    • sod says:

      OK: Strong information. Hm.

      Roger, could you please add up the plus and minus hydro data seperately for each month (or did you do that already and i missed it?).
      Basically this would mean that there is water flowing down while the turbine is not running at full output.

      Do we know if there is drinking water taken from the upper reservoir? the intake should be in the middle of the lake, so it would be hidden most of the time (but should have been visible during the building period).

    • Thanks for the photos.

      Plastic looks like it is a 100 mm outside diameter pipe. It is funny but the information will all be there on the pipe to give you the exact size, if you know what to look for. I am at a loss to explain the expansion joint in the bottom right as it enters the ground. I would still wager based on the trenches that the underground pipe is not much bigger than the plastic. Who knows?

      Always hard to tell from photos but that does not look like a flexi connection to me. It looks more like the plastic pipe has warped under the weight of the fluid passing through it over time. Common when the pipe is not supported properly and does not take much time. If that assessment is true, it could possibly break soon.

      Flexi pipes in generally will carry less water than fixed but not that much less. It is not a good indication of capacity.

  26. sod says:

    Extremely weird diesel behaviour, starting at 13:40.


    They have been pumping diesel today, that is at least now a point that nobody can deny.

    Stable wind output, stable demand, increase in diesel and increase in pumping hydro. Strange.

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