How to make El Hierro 100% renewable

Euan suggested that I explore other renewable options for El Hierro to see how they compare with the existing Gorona del Viento (GdV) hybrid wind/pumped hydro plant that cost €82 million to install. But the GdV plant, which has been widely acclaimed as a 100% renewables system, has so far delivered only 32% renewables and will probably never be capable of delivering much more than 50%. It is found that a solar photo voltaic (PV) + diurnal storage system could deliver 100% renewables provided grid stability concerns can be overcome and provided there are no prolonged cloudy periods, but at a price tag of $US150 to 200 million. Concentrated solar power (CSP) switches off completely when it is cloudy and is not a viable option. Geothermal could provide a reliable 365day/24hour electricity supply for a fraction of the solar costs provided an exploitable geothermal resource exists, but geothermal potential appears never to have been explored even though El Hierro is an active volcanic island sitting on top of a magma (molten rock) chamber.

Those of you who are getting bored with El Hierro will be pleased to learn that this post isn’t like the previous ones. Instead of presenting graphs and analyses showing how the GdV wind/hydro plant operates and why it will never supply El Hierro with 365/7/24 renewable energy we look here into the question of whether there is an alternative approach that might. Three options are considered:

  1. Solar PV
  2. Concentrated solar power (CSP)
  3. Geothermal

The conclusions are:

1.  50MW of solar PV plus overnight storage could deliver 365/7/24 energy at a capital cost of $US150-200 million and with 75% of the solar energy wasted, but there is still no guarantee that the system would always be capable of filling 100% of demand (extended cloudy periods are not unknown on El Hierro). Another unresolved question is whether  100% solar generation can be made to work without comprising grid stability.

2.  CSP is not a viable option.

3.  Three ~4MW geothermal plants could deliver 365/7/24 dispatchable energy with no grid stability problems and no need for energy storage or diesel backup at a capital cost of – well, it’s impossible to say without more data, but almost certainly less than the $150-$200 million the solar plant would cost. The problem is that no geothermal resource has yet been identified on El Hierro, largely because no one has bothered to look for one. The chances that such a resource exists are, however, good.

Initial state conditions

The evaluation assumes that El Hierro is starting its quest for 100% renewable energy from scratch. The ~13MW Llanos Blancos diesel plant is in existence but the GdV plant is not.


Estimating monthly PV generation:

The first step is to establish how much electricity a solar PV plant on El Hierro will generate during each month over the course of a year. To do this I consulted the sunny portal data base looking for operating data for solar PV installations in the Canary Islands. I found four – Canapaplas (93 kW), Dias El Sabadal (46 kW) and Siemens Maquinaria (20kW) on the island of Gran Canaria, which is about 250km east of El Hierro, and P. Tenerife (95kW) on Tenerife, which is about 150km east of El Hierro. Figure 1 plots monthly generation from these systems since 2008, expressed as the monthly capacity factor:

Figure 1: Monthly generation from four PV systems in the Canary Islands, expressed as capacity factors

Averaging these results gives the monthly plot shown in Figure 2. The annual capacity factor is 17.6% which is about right for the latitude (28 degrees) but there is a factor-of-two seasonal swing from about 22% in summer to about 11% in winter. Monthly El Hierro electricity demand (2015/16 data from REE) changes little through the year:

Figure 2: Average monthly capacity factors for the four systems shown in Figure 1 and El Hierro monthly electricity demand (MW)

The two approaches to achieving 100% solar generation:

These are:

1. Install enough solar capacity to generate 44GWh in a year (El Hierro’s present annual consumption) and handle the seasonal swings by storing the summer surplus for re-use in the winter.

2. Install enough solar capacity to handle winter demand and curtail the excess power generated in summer.

Approach 1 has been discussed in a number of previous posts, all of which have concluded that it isn’t going to work because the amount of storage needed is prohibitive. As shown in Figure 3 El Hierro is no different. To store the summer surplus for winter re-use over 4 GWh of storage would be needed –fifteen times the ~270 MWh capacity of the existing GdV reservoirs:

Figure 3: El Hierro monthly PV generation compared to El Hierro monthly demand, Approach 1

Approach 2, which was discussed in this post, expands solar capacity to the point where it can fill demand in December, when solar output is lowest, which in the case of El Hierro is around 50MW. The results are summarized in Figure 4. The approach wastes a lot of energy (75% of the energy generated in this example gets curtailed) but it will work, at least in theory. It will still be necessary to store solar energy generated during the day for re-use at night, but we need only 60-70MWh of storage to do this, or about a quarter of the capacity of the existing GdV reservoirs. The approach therefore assumes that a pumped hydro facility similar to the existing one will be installed at GdV.

Figure 4: El Hierro monthly PV generation compared to El Hierro monthly demand, Approach 2

We therefore proceed with Approach 2.

The Solar PV Scenario:

Because of the wastage of power associated with 100% renewables I expanded the scenario to include progressively less solar generation and progressively more diesel generation, with the idea being to see whether a high percentage of solar generation – although not 100% – could be achieved with significantly less wastage and at significantly lower cost. Procedures and assumptions were:

Monthly generation is calculated from installed capacity and the monthly capacity factors shown in Figure 2.

All solar generation that can be sent to the grid is sent to the grid

Solar generation that exceeds demand is sent to storage.

Surplus solar generation left over after grid and storage demands are filled is wasted

Diesel generation makes up the shortfall when solar generation is insufficent to fill grid and storage demands.

Solar energy is stored in and released from the GdV upper and lower reservoirs, which along with the hydro plant and pumping station will be constructed from scratch.

Nighttime storage requirements are calculated assuming that the day and night are 12 hours long and that energy demand during the night is the same as during the day (an oversimplification, but this is an approximate analysis). The storage requirement is set equal to the highest storage requirement in any month.


These are summarized in Figure 5

Figure 5: Solar generation (%), diesel generation (%), solar generation wasted (%) and diurnal energy storage requirement (MWh) as a function of installed PV capacity.

Supplying El Hierro with 100% solar electricity year-round would require 46.2 MW of solar capacity, which I’ve rounded up to 50MW. To this we can add the ~10MW of pumped hydro storage capacity that must be installed at GdV and also the 13MW Llanos Blancos diesel plant. So once the solar panels are in El Hierro would have over 70MW of installed generating capacity to service an average demand of 5MW. One gets the impression that there has to be a better way.

Well, if we insist on 100% solar PV generation there isn’t. But if we don’t there are some options that probably make more sense. For example, Figure 5 shows that 30MW of solar PV capacity gives 92% solar generation and only 14% energy wastage while 22.5MW gives 79% solar generation and no wastage. In these scenarios the diesel plant would of course have to be kept in operation, but it’s questionable whether the 50MW scenario could operate without diesel backup 100% of the time anyway. There is such a thing as cloud cover on El Hierro, and the possibility of an extended cloudy period that cuts solar generation and exhausts the storage capacity of the reservoirs can’t be discounted.

A final concern related to solar PV is grid stability. GdV has been trying since the plant started its test period in June 2014 to come up with a means of integrating all the wind power it produces with the El Hierro grid but still hasn’t succeeded, and the problems with solar PV could be as bad if not worse. And if this problem can’t be solved the 100% solar PV option won’t work no matter how many MW(p) are thrown at it.

Capital Costs:

(Estimating levelized costs of electricity is beyond the scope of this post.)

IRENA gives 2014 capital costs of $2,000/kW for utility-scale solar PV systems in Europe, which with 50MW of installed capacity gives a total capital cost of $100 million. The actual capital cost would be higher than this because of El Hierro’s remote location. I can make no exact estimate of how much, but I’m going to guess 50%, which increases the solar capital cost to $150 million.

Then we have to add the cost of constructing the reservoirs, hydro plant and pumping plant at GdV, which is a critical part of the installation because it handles diurnal load, because it can supply island demand for up to a week in the event of a long cloudy spell, because the hydro turbines can be used as spinning reserve to maximize grid stability and because hydro pumping can be used as a dynamic resistor to match solar generation to demand in the same way as it is currently being used to match wind generation to demand. How much will this cost? The total installation cost of GdV was around $100 million and I would guess that at least half of this went to the hydro side of the operation, so I’m going to say $50 million. Adding this to the $100-150 million cost of the solar system gives an all-up cost of $150-200 million.

However, the 30MW option that delivers 92% solar will cost only $110-165 million and the 22.5MW option that delivers 79% solar only $95-140 million. Unless one is totally fixated on a 100% renewables future these options would probably make a good deal more sense.


CSP has two advantages over solar PV which on the face of it would make it appear to be the obvious solution for going 100% solar:

  1. It stores solar energy as heat in working fluids like molten salt, so it has built-in storage capability. With enough storage it can deliver full-time dispatchable solar power to the grid.
  2. It uses the stored heat to produce steam that drives turbines, so it has the inertia needed for grid stability that solar PV lacks. Grid stability should therefore not be a problem.

It does however, have one disadvantage. It needs to be jump-started with natural gas in the morning (Spain allows natural gas to contribute up to 15% of total generation). So even in its pure state CSP won’t deliver 100% renewable energy.

I began the analysis by estimating how much power a CSP plan would generate on El Hierro. The closest plants I could find were in Spain, which has 49 CSP plants aggregating 2.3GW, and Figure 6 shows the daily capacity factors achieved by these plants since REE started segregating CSP and PV in its grid data on May 1, 2015. Generation from Spanish PV plants is also shown for reference:

Figure 6: Daily generation at Spanish CSP and PV plants expressed as capacity factors, May 1 2015 to March 11 2016. The month designations are based on the 30-day intervals shown on the X-axis and are approximate 

CSP plants cost roughly three times as much as PV plants yet their capacity factor over this period is only 40% higher (24.5% vs 17.8%). CSP output is also subject to wild short-term fluctuations that are muted in the PV data and which are probably caused by clouds ( PV panels continue to generate at a reduced level when clouds cover the sun but CSP plants don’t). The feature of most concern, however, is that for much of last winter Spain’s CSP plants generated effectively no electricity at all, which makes them essentially useless as a source of year-round power. Based on these results it is in fact legitimate to question whether CSP has any advantages at all over solar PV.

I gave up on CSP at this point and moved on to geothermal.


Geothermal delivers year-round dispatchable baseload power at capacity factors of around 90% and creates no grid stability problems. It could also be used in a load-following mode, although no one has yet done this because so far there has been no need to do so.

The system I envisage would consist of three 4MW dual-flash or binary units, with the idea being that two units would be capable of supplying El Hierro demand when the third was down for maintenance. Assuming they could be adapted for load-following the three units would be able to supply El Hierro’s demand with 365/7/24 renewable energy all by themselves with no ifs, buts or probables.

How much would these units cost? I don’t know, but $10,000/kW, which is probably the upper limit, gives a total cost of $120 million, significantly less than the $150-200 million cost of the 50MW PV option. (Note that with geothermal there is no need for hydro storage). And if the geothermal resource is good enough the cost could be half this. But all this is speculation because no geothermal resource has as yet been found. What are the chances that one exists on El Hierro? Let’s look at the evidence.

El Hierro is a volcanic island that began to form about a million years ago – the blink of an eye in terms of geologic time. Volcanic activity on the island continues. Tanganasoga, a semi-active volcano in the center of the island reportedly throws out rocks from time to time and a submarine eruption off the southern tip of the island has been continuing on-and-off since 2011. And underlying the island is an active magma chamber defined by microseismic activity, as shown in Figure 7:

Figure 7. Microseismic activity on and around El Hierro between 19 July 2011 and 29 March 2013. Colors define the date (blue in 2011 grading to red/brown in 2013).  Image from the Spanish Instituto Geográfico Nacional

Most interesting is the east-west section at the bottom, which indicates that magma is present below the center of the island at a depth of less than 10km. The magma temperature is probably around 1,100°C, so even if we assume a purely conductive gradient between the magma chamber and the surface we would still expect to encounter “commercial” temperatures of 200°C at depths of around 1,500m, which is well within drilling range. The hope, however, would be that a convective geothermal system would bring high-temperature fluids closer to the surface than that.

It surpasses my comprehension why no one has ever looked into the geothermal potential of El Hierro (a web search for “El Hierro geothermal potential” draws a complete blank) but it’s never too late to start.

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68 Responses to How to make El Hierro 100% renewable

  1. Rainer says:

    Thank you Roger
    Only can agree that a 100% by renewables is a really challange.
    It is really a good idea to lean back from time to time to get a new overview.
    What about making a mix of the existing GDV and this new overview?
    El Hierro got to lean back and think about options and make the best out of the existing situation.
    But very first GDV got to be run in a optimal way.
    Then look what can be done.

    Made some researches to the actual situation in three looks of different working situation to lift a little the fog from GDV.:
    – Diesel + Hydro
    – Diesel + Wind
    – Wind + Hydro
    German comments, but graph is graph

    • Ampere says:

      So if I read the comments correct, the grid stability is reduced when hydro kicks in, so they might have a problem to gegulate the hydro plant properly. Which would explain why they don’t like to use it for power generation.

  2. Joe Public says:

    Thanks for sharing that link to Sunny Portal, it has a wealth of information that is local for most readers here.

    Intrigued by the observation


    …… does however, have one disadvantage. It needs to be jump-started with natural gas in the morning (Spain allows natural gas to contribute up to 15% of total generation). So even in its pure state CSP won’t deliver 100% renewable energy.”

    I was aware the Ivanpah solar plant near Nevada burns a lot of natural gas, making it a greenhouse gas emitter under state law.

    Morocco’s Noor1, the first phase of world’s largest solar plant has recently opened. The Grauniad proclaims power will be generated from dawn until three hours after sunset, but strangely makes no mention of the need for fossil fuels to kick-start it every morning.

    • Roger Andrews says:

      Joe: I don’t know whether Noor uses gas or not, but if it does it isn’t strange they should fail to mention it. After all, CSP is supposed to be a 100% renewable source and you shoot yourself in the foot if you admit up front that it’s actually 15% fossil fuels.

      But there is a solution. Use biomass instead of gas. This is what the Borges plant in northern Spain does:

      The facility combines solar power generation with biomass-fired power generation in a system that allows for continuous electrical production of renewable energy 24/7, even when the sun isn’t shining. The plant peak capacity of 22.5 MWe is obtained when there is sufficient solar power. At night, when only the biomass power is available, the plant power capacity is 12 MWe.

      • Joe Public says:

        Thanks Roger.

        Morocco’s Ain Beni Mathar facility is a thermo-solar combined-cycle power plant fired by Nat Gas from the Maghreb-Europe pipeline 13km away.

        Its total capacity is 472 MWe, of which up to 20 MWe may be delivered from solar, which simply reduces gas consumption at full power, rather than providing additional power.

      • Willem Post says:


        The capital cost of the first solar power station (510 MW of CSP plants, plus a 70 MW PV solar plant; total land area 6,178 acres, 10.7 acres/MW) is estimated at about $3.2 billion for the CSP plants (about $6.3 million/MW), plus about $250 million for the PV solar plant. Financing of about $1.2 billion at near-zero interest from the World Bank, et al., and about $2.0 billion from private sources, which with accelerated depreciation to reduce taxes of investors, reduces the effective cost of capital for the project to about 2 – 3%, which enables the energy to be sold at reduced costs/kWh under 25-y power purchase agreements, PPAs.

        Noor 1, commissioned Feb, 2016; 500,000 single-axis, tracking parabolic mirrors; output 160 MW gross, 143 MW to grid; 3-h molten salt storage; fossil-fired boiler plant for CSP start-up and supplementary energy, as needed; wet cooling with water from a nearby reservoir; Dowtherm A at 293 C into solar field, 393 C out of solar field; capital cost $1.15 b; energy will be sold at 18.9 c/kWh.

        Noor 2; single-axis, tracking parabolic mirrors; output 200 MW, estimated 180 MW to grid; 7-h molten salt; dry cooling; energy will be sold at 14 c/kWh.

        Noor 3; mirrors focused on a tower; output 150 MW, estimated 135 MW to grid; 7 – 8 h molten salt storage; dry cooling; energy will be sold at 15 c/kWh. This configuration was included for comparison purposes.

        Noor 4; PV solar systems; output 70 MW. This configuration is included for comparison purposes, because the cost of utility-scale PV systems has declined to enable energy generation at an LCOE of less than 50% of CSP!!

      • Willem Post says:


        Do you have the REE URL do get data similar to the CSP graph? I looked for it, but could not find it.

        The winter performance of CSP in Spain is dismal. How much is storage, on average? 3 hours?

        Before embarking on expensive CSP, did folks not know it often gets cloudy in Spain during the winter?

        2300 MW x $5,000,000 = $11.5 billion “invested” over the years in systems that produce a LITTLE of VERY EXPENSIVE energy. What has been the production, MWh, over those years?

        Spain has good winds which often blow day AND night, winter AND summer, especially near Gibraltar.

        With more pumped storage, Spain could augment its hydro power CF, which would provide steady energy, 24/7/365, that is dispatchable.

        The misguided, political RE concept of “we need to do it all” is wasteful; somewhat similar to Germany going into PV. Germany should have built those PV systems where it IS sunny.

        • Willem Post says:

          Had Spain invested the $11.5 billion in nuclear plants, it would be having 2300 x 8760 x 0.90 = 18.13 TWh/y of STEADY energy, 24/7/365, at a cost of about 10 c/kWh, instead of creating a lot of distraction (which costs money), and throwing money into a dead-end black hole.

  3. A C Osborn says:

    Roger, Iceland could not only supply El Hierro with the costs for Geothermal but also the expertise in it’s construction and use.

  4. michael hamilton says:

    It’s good to see an article moving towards understanding what are the best overall solutions to particular problems. You clearly highlights the high cost inherent in trying to get to 100% renewables, perhaps that should not be the goal?

    Regarding Solar costs, 2m/MW is on the high end of cost estimates. There are PPA agreements coming in where power is being contracted (excluding subsidy) at around $50/MWh, price levels that become interesting for many (most?) countries.

    Fully agree with you regarding geothermal, could have been a nice solution.

  5. Euan Mearns says:

    Roger, Figure 5 is key. Following on from what Michael Hamilton says, I think pursuing 100% renewables without indigenous hydro or geothermal is rather foolish. The goal should be some form of cost-optimised renewables. Given that they now have the pumped hydro in place, what would 25 GW of solar PV cost to install?

    The absence of geothermal anywhere on The Canaries is a bit of a mystery. I visited this place on Lanzarote a couple of times, rocks glowing red hot just below the surface.

    • Roger Andrews says:

      The goal should be some form of cost-optimised renewables.

      This is clearly the way to go. Spending vast sums of money and wasting vast amounts of energy to get the last squeal out of the pig makes no sense.

      Installing 25MW of solar PV on El Hierro would cost about $75 million according to my estimates and somewhat less if Michael Hamilton is correct in saying that $2,000/kW is too high. But installing it would be an admission that the much-touted GdV wind/hydro plant is a failure, so I don’t see it happening. I haven’t done the sums but I’d be willing to bet that a combination of wind and solar wouldn’t supply El Hierro with 365/24 renewables either.

      • michael hamilton says:

        FYI, Here is a link for the US PPA that is net $50 (after ITC $38)

        El Hierro is indeed very interesting, but as you demonstrate, to reach 100% is too expensive. This 100% idea/goal is effectively an expensive intellectual excercise that becomes distracting and confuses the fact that some degree of renewable power can be incorporated cost effectively into many power systems.

        It’s as interesting to follow what is going on in remote mining sites in places like Chile and Australia. It seems that there are plenty of power auctions there, and a decent volume are being won by solar and/or battery systems.

        There is a cost effective place (which may be growing) for these technologies, it’s just that they are often deployed sub optimally. But hey, that’s politics.

        • Roger Andrews says:

          Michael: Thanks for the data you are supplying, but I’m working with capital costs, and cents/kWh don’t tell us what the capital cost was.

          • michael hamilton says:

            Roger: Talking to some friends in the solar industry in the UK, they are looking at capital cost sub £1m/MW (min 5mw, ground mounted). I can’t give you a reference for this i’m afraid but I’m sure you could validate that with your own sources.

            The cents/kwh is interesting (I would contend more useful than capital costs) as it shows you a number that already accounts for variables such as solar irradiance, lifetime, installation costs etc.

    • Ampere says:

      Yes, storing energy not in form of electricity but in form of “manufactured” simple but energy intensive product can also be a tool in the toolbox In this case a cheaper, but maybe a bit less efficient desalination plant run with a capacity factor of 0,5 or so, and a simple water pool somewhere on the island storing desailnated water for times with little wind or sunshine. As far as I rmember most of the power si used for desalination so far, if this could be switched away for some weeks without running short of water, this would allow the hydropuwer to buffer for much longer times, and also for low solar/low wind to supply much bigger shares of demand. The existing upper reservoir can store 400MWh in the form of desalinated water along with the pumped hydro functioality.

    • Roger Andrews says:

      nukie and Ampere.

      I would suggest you spend some time learning something about the project before posting any more comments.

      • Golf says:

        Rolf, did you look at page 45, and see that the curve of agricultural use of water (irrigation) whis is the mayor part of water use in el hierro is very close to the solar power production?
        And you know that each m³ of desalinated water produced at times when power production is high stores 2-3kWh of electric power (+2kWh /m³ when it is stored 700m above theplace of use)?
        If you have critics about the point, please put them in numbers. As far as I can see the point they make is valid for the system of el Hierro.
        So increasing desalinationcapacity is another possibility to store energy in el Hierro.

      • nukie says:

        Well, what should be learned in your opinion?
        Water consumption is equivalent to a constant load of a bit above 1,5 MW in el Hierro.
        Detailed calculation derived from public data I placed here:
        Water consumption is varying from between 140,917m³/month to 454,735m³/month in August.
        Your Figure 4 does not show any variation of demand of the desalination, so obviously desalination is so far running as baseload all around the year.
        How they store the water from january till august I could not find in the documents, but overall desalination capacity in 365/24 operation fits to the demand of the island, maybee they fill up groundwater in January, and retrive in again in August.
        Storing about 200,000m³ for water demand in January and December (and a bit November) would allow to reduce demand in el Hierro in this time to 3,5MW, so allows to install 42% less PV capacity.
        Here the resulting demand and supply curves:
        This variant would require 33% more desalination capacity, and a bit less than 200,000m³ storage, which actually exists in the upper reservoir, so far unusable by hydropower production.
        Desalination costs about 1600$/m³/day in San Diego, El Hierro is more expensive, on the other hand overall cost for desalination is sinking.
        Additional 3300m³/day in el Hierro would so cost 5.3 Million €, whle reducing costs for PV by a higher amount of money.

        • I’ll try one last time.

          What should be learned in my opinion:

          1. That the subject of this post is how El Hierro might achieve 100% renewables generation. The conclusion is that the only option that can be guaranteed to work 365/24 is geothermal, provided a suitable resource exists. The obvious next step is therefore to evaluate the island’s geothermal potential, which is something that should have been done years ago.

          2. That wind and solar or any combination thereof will probably never be able to supply 365/24 renewable energy. There will always be periods when the wind doesn’t blow strongly enough and the sun doesn’t shine brightly enough to keep the power coming. Some level of diesel backup will therefore always be necessary.

          3. That high-penetration wind and solar scenarios may in fact never work at all. After almost two years of testing and operation, and despite a control room full of state-of-the-art smart gadgets specifically designed to manage the problem, GdV and REE still haven’t figured out how to integrate all of the wind energy produced into the grid without compromising stability. Even if this problem is solved GdV will probably never be able to supply much more than 50% renewables to the El Hierro grid. (Why? because of extended low-wind periods. Check out the September and November generation plots).

          4. That your fixation on water use and desalination plants is what’s known as “bikeshedding”. Look it up.

          • nukie says:

            Well that geothermic production is also a good idea, os obvious, once someone finds the idea – but often seemingly obvoius points go unnoticed. The price tag for a geothemal system would neet to be found out.
            That from today point of view the system in el Hierro is not opitmal designed is obvious.
            Including desalination which makes up a large part of consumption (the assumed consumption as stated above is about thee lowest possible, higher consumption per m³ is possible) is also seemingly obvious, but it was skipped in your fast draft for a solar – only system.
            It allows in parallel to extend the time the grid can run from storage by 30%.
            Having a Diesel as backup where a diesel plant already exists is not a serios cost question. I have had enogh mothballed Diesels kept alive for decades at low costs in projects.
            So the question is also: how close is it neccesary to get to 100% – is i90% enough, 99%, 99,9%? Conventional power (+ existing renewables) reaches 99,99% today.
            From Rainers description I conclude that the dieselplant reaches 99,5-99,9%.
            Which is by far out of scope of the system as it is today.
            A cloudy period between february and October in the solar only version (relevant for islands without active vulcano but located somewhere in the sun belt) would just result in a reduced amount of desalinated water or remain without effect. Cloudy periods in December and January, assumed with 50% of generation at average days, would be allowed to last 80 hours without use of Diesel, if before there was sufficient sun.
            Since Rainer has a solar power station, maybe he records his production and can tell how often this situation has happened – just for curiosity.

  6. Flocard says:

    Thanks for this analysis.
    Here is just a comment outside the scope of your post which will allow me to follow the discussion.

    When one analyzes world CO2 emissions, one notes that 60 % is emitted by six countries (China, USA, India, Russia, Japan, Germany) and 75 % by the first 15 emitting countries. In these countries, CO2 emissions is predominantly associated with electricity generation and one is mostly using coal (or lignite) to produce electricity.

    Suppose these 6 or 15 countries make an effort to reduce globally by 5% their CO2 emissions, certainly it would not be sufficient from the point of view of IPCC but it would be visible on world graphs of emissions.

    On the other hand, the same analysis of world CO2 emissions shows that all the small islands of the world which mostly rely on fuel for their production of electricity only emit together 0.5 % at most of the total.

    If it was decided that instead bothering these small (generally poor and technically understaffed islands) with complicated renewable systems one would say that they were the only place in the world allowed to burn coal for their electricity, afuel which is plenty and cheap, their emissions would move from 0.5 % of the total to may be 0.75 % thus still remain essentially invisible. One would have solved their problem from both technical and economic points of view and there would be no detectable impact on the world CO2 emissions.

    I have nothing against the fact that rich nations such as Spain play with -as we would say in French – a “danseuse” of their choosing by defining systems such as GdV so that can make their engineers have some fun or any other replacement system of their choosing except the geothermal line when it is a viable option (that when if it does not get into the same problems that were encountered with the “La Soufrière’ volvcano on the island of Guadeloupe (geothermal plant at the well named village “Bouillante”).

    Engineers know that it is more efficient to put efforts on the main components of the problem before bothering dealing with those which are minuscule.
    Everything that is being described will never solve the energy problems of these islands. It is just a game for rich countries masquerading as ecology.

    • Willem post says:

      That would be much too practical to enter the minds of the greenies.

      Far greater, and even less excusable idiocy, is Germany’s helter skelter turn towards SOLAR energy

      • gweberbv says:


        somebody simply had to spend about 100 billion bucks to get PV prices where they are now. If Germany had not done it, maybe PV would still be at 5000 Euros/kWp. Instead at best locations PV is now winning auctions for less than 50 Euros/MWh and prices are still dropping.

        100 billions are also needed to accomodate a million refugees for 5 years. And 100 billions are saved by German treasury within two years when interest rates are at 1% instead of 3%. In other words: these 100 billions are just peanuts.

        • Willem Post says:


          No wonder Germany is less of an economic engine of Europe, causing the rest of Europe to have near-zero economic growth or worse.

          More of such decisions, such as welcoming 1,000,000 culturally different refugees a year, will make it a lot worse.

      • Willem Post says:

        Sorry about mis-spelling your name.
        My spell-checker keeps changing what I type, including your name.

        • Rainer says:

          forgot to say:
          my solar power i have in Berlin, Germany. And i just use the Grid as Battery. At the time it was build storage really not was the problem. And to be honest: in winter time in Berlin the production is far under demand. And in summer time of course during daytime only good production. But still: In Berlin all year between 60% and 90% of demand.

          • Greg Kaan says:

            Rainer, would you be able provide the capacity of your solar installation?

            And when you say the system provides between 60% and 90% of demand, is this net (ie when the meter runs backwards, do you subtract that from your consumption) or only as applied to your consumption?

            Finally, is the 60-90% of demand met by your PV system the financial or energy return (since your feed in rate won’t be the same as your consumption rate)

            I’d just like to get some perspective on your figures.

      • Rainer says:

        it is NOT helter shelter. On my house i have since more than 25 yeras photovoltaic runnung. No one hour work with it. No 1 buck paid for technical support. No one hour cleaning job. Since this 25 years it makes between 60% and 90% of my annual electric demand.
        OOOHHH, did spend a lot of hours in the basement looking to the meter running reverse direction……

    • Roger Andrews says:

      Hubert: You say Engineers know that it is more efficient to put efforts on the main components of the problem before bothering dealing with those which are minuscule.

      When dealing with new technologies it’s common practice – and this is certainly the case in the mining industry – to build a pilot plant that may be only a hundredth the size of the planned commercial plant but which is large enough to show whether the technology will work as planned.

      We can think of GdV as the world’s first 100% renewables pilot plant (except for King Island, Tasmania, which we can’t evaluate because they won’t send us their grid data). It’s often assumed that GdV won’t tell us anything about the prospects for ultimate 100% renewables generation in places like China, Europe and the US because El Hierro is a small, isolated island, but this isn’t exactly true. Big energy consumers will face the same intermittency and grid integration problem as GdV, just on a much larger scale.

    • sod says:

      “On the other hand, the same analysis of world CO2 emissions shows that all the small islands of the world which mostly rely on fuel for their production of electricity only emit together 0.5 % at most of the total.

      If it was decided that instead bothering these small (generally poor and technically understaffed islands) with complicated renewable systems one would say that they were the only place in the world allowed to burn coal for their electricity, afuel which is plenty and cheap, their emissions would move from 0.5 % of the total to may be 0.75 % thus still remain essentially invisible.”

      Your analysis leaves out the two most important points:

      It is the big polluters, that have abundant coal, while those small islands do not and instead rely on expensive diesel imports.

      So it simply makes economic sense to start the move towards renewables on those islands (and it is actually really shocking that most of them did not start decades ago. They could have saved fortunes!).

      It si much harder to introduce renewables in the high coal use countries, as renewables there have to compete with 50 years old dead cheap coal plants running on their own cheap coal.

      On the other hand, it makes much more sense to test high penetration of renewables in a small closed grid. And those basically only exist on islands.

  7. Rainer says:

    GDV back in Carbon age:100% diesel
    2016-03-14 14:10 diesel only
    2016-03-14 17:00 diesel + 0,2 MW Wind
    2016-03-14 17:10 diesel only
    2016-03-14 18:50 Hydro Back, wind follows

  8. gweberbv says:


    maybe I am stupid, but from Fig. 4 I would not expect a curtailment fraction of 75%, but maybe 30%. Even in June/July ‘only’ about 50% of the generated electricity is useless.

  9. I visited El Hierro and GdV in June 2015 and their storage is for about 5 days. But when you add the storage of desalinated water, it gets up to 10-15 days. Adding solar to the mix may increase the renewable factor a bit, if there is ample sun during the low-wind months.
    Michael Sterner from Germany wrote the bible on energy storage. Germany needs to store energy throughout 4-5 winter months, so they are on a whole different level. Sterner’s answer is methanization, where you sore hydrogen in the form of methane. The Navy can make jet fuel for $4 a gallon from the carbon in seawater. I have not figured it out yet, but making carbon fuel from excess energy at a 30% roundtrip efficiency is the only choice to get to 100%.
    I live on another island, Maui, and you can see a plan for a 100% Maui at

  10. Rainer says:

    GDV yesterday gave the change to look at the situation only Diesel.
    Here the frequency and the Fourier graph:
    – Diesel

  11. sod says:

    “Well, if we insist on 100% solar PV generation there isn’t. But if we don’t there are some options that probably make more sense. For example, Figure 5 shows that 30MW of solar PV capacity gives 92% solar generation and only 14% energy wastage while 22.5MW gives 79% solar generation and no wastage. In these scenarios the diesel plant would of course have to be kept in operation, but it’s questionable whether the 50MW scenario could operate without diesel backup 100% of the time anyway. There is such a thing as cloud cover on El Hierro, and the possibility of an extended cloudy period that cuts solar generation and exhausts the storage capacity of the reservoirs can’t be discounted.

    A final concern related to solar PV is grid stability. GdV has been trying since the plant started its test period in June 2014 to come up with a means of integrating all the wind power it produces with the El Hierro grid but still hasn’t succeeded, and the problems with solar PV could be as bad if not worse. And if this problem can’t be solved the 100% solar PV option won’t work no matter how many MW(p) are thrown at it.”

    I totally agree with these two paragraphs.

    25MW of solar looks like the best deal to me. With a realistic price, this would not have been too expensive and a lot of the money would have ended on the island (installation).

    The single argument against this, are the grid stability issues you mention. I agree that these would be bigger than with the current set up and i also believe, that some battery storage would be necessary to help with small changes.

    It would be so much better, if El Hierro was doing something similar to King Island, as it is obvious that the best solution would be a mix of technologies.

    So does anybody see a good combination of solar added to the current system? How would geothermal help? why no flywheels to keep the diesel spinning? Why no massive demand management with desalination? What could battery storage do to stabilise the grid?

    • gweberbv says:


      I expect that solar will be on the table as soon as the wind turbines need a lot of repairs. Keeping them alive for decades will be very expensive as El Hierro is a remote place and there is probably no local infrastructure for wind turbines.
      In contrast, a PV installation can be maintained by a local electrician and the whole installation only consists of parts that are trivial and can be delievered by Fedex.

  12. Can anyone convert this information into a pipeline flow rate?

    • nukie says:

      Well the flow meter is measuring exactly up to a flow of 60m³/h from the pipe into the reservoir. The way it is built the black pipe is obviously for temporary use, and to bring water (or air) from the pipe to the basin. the main connection to brin water from the basin into the pipe network would be underground connectiong to the upper end of the penstock which should run somwhere like the red line: A logical way allowing a continuous flow from the basin into the pipe network would follow the way along the blue line or something similar.

    • nukie says:

      There is a pipe crossing the HI-1 road in a line approximately from the storage? to the wind park, oly visible in google maps / earth, but not on street view since it starts to be above ground just a few meters north of the street.

    • Take the meter

      DN100 refers to the diameter of the meter and unless there are reduction either side, a good reference to the size of the pipe.

      Qn is the nominal flowrate of the meter.

      The black numbers on the white dials is giving you the total m3 that has passed through the meter since installed or reset.

      The smaller red dials are not clear but usually indicate instantaneous flow.

      In light of that info I do not think you need to mess around with the chart. I do not think you have enough info to do so anyway.

      • I have not had time to model the system but in light of the above, I do not think it necessary. Let me know if you concur Rodger.

        “Well the flow meter is measuring exactly up to a flow of 60m³/h”#
        Not quite. The nominal flowrate specifies where the flowmeter is at its most accurate. The Qmax can be much much higher but obviously not that much higher than the Qn. For this application you could take a quick rule of thumb of 1.5 times larger but it is hard to say.

        Further the flow can even be higher if the meter head is set up to report it as opposed to flat lining at the max value.

        By and large this meter when active, was expecting to see flows of 60 m3/h. Not all the time mind.

        • nukie says:

          To be correct the meausurement equipment should be used in design from Qmin to Qn, but must work according to standard till Qmax=2*Qn. But a pipe along the other road would just make sens if it is running towards Tinor (so to bring water from the basin with a pump towards the south), and the black pipe makes just sense to fill water from this pipe into the basin. A pipe bringing water from the basin elsewhere would have to be connected to the penstock comming from the lowest point of the basin.
          Having a pipe the way Andrew proposes would mean in both directions to pump water up 50m and let it run down in vaccum on the other side 50m, so loosing a lot of energy. (or needing a turbine and generator on the other side to recover the energy.
          Running the Pipe in a “U” is much more reasonable, having always positive pressure and about zero need to pump between basin and the proposed reservoir.
          So a reasonable design would have two branches, one running along the lower road, and maye running from this road again uphill to the reservoir, ending at about the same level as it starts in the basin. So this pipe could bring water to the east and north of the island inclunding el Golfo. But water would not flow from the reservoir to fill the basin higher than 1 or 2 meters.
          The other branch would require a pump at the basin, and be connected to the pipe valverde – Tinor (910m) and this pipe would have more than enough pressure to bring water in the upper basin.
          The black prvisoric pipe with the meter would then be there to fill the basin initially, if the main direction of this pipe is basin->Tinor, and the main meters are also running in this direction, and not reverse. The 57300m³ on the meter would not be unreasonable to fill Penstock and upper basin to a minnimum to start operation. It would be unused later on, water would be brought to the lower basin then and pumped up for further distribution (and metered at the lower basin).
          Nothing to proove this, but this would be a reasonable construction.

          • nukie says:

            Possible way of pipe with the structure looking like a pipe in google Maps :

          • I don’t see it. If so that is one expensive pipe and if you are tasked with filling the basin, why meter it?

            Further it would not be necessarily inefficient to pump the water up the hill an then use the potential energy to let it fall.

            If you routed the pipe around the hill, you get a much longer pipe run which adds a lot of expense especially considering the trenches. It also means a bigger pump.

            Essentially it is a trade off

        • nukie says:

          Arrgh – sorry, misused Roger Andrews name unintentionally Very Sorry!

  13. Rainer says:

    @Greg Kaan
    the solar in Berlin is not really the topic of this blog. But to make it a round thing:
    Talking about electric demand, no financial aspects. The other 25 year old tec dates are not exactly in my mind. The time i build it was paper time and the dates are still on paper in Berlin. When i did build it for sure was not a economic thing like all the man toys like new stereos, cars, boats, etc….

  14. nukie says:

    @donoughshanahan :Well 50 m up and letting it fall is quite a lot of energy, compared to 400m Pipe or so, when running a System for many years. 136 MWH* 1/pump efficiency per million m³ (if used for irrigation) e.g. with 26ct/kWh and 100% pump efficiency would be 36.425€/4month of observaion when 1 Mio m³ aproximately vanished from the upper reservoir. So the 400m extra pipe pay off in a few months.
    Pump becomes much smaller, since given a big enough pipe water would run by itself, or with just a tiny extra pressure, far below 5 bar pressur to bring it up to 751m. Also with two pipes of 8-10 Inches pressure losses per km with the calculated flows come into reasonable areas (pressure loss per km)

    • The exact economic size of a flowrate in this region of 60 m3/h nominal is not going to 400mm.

      “Well 50 m up and letting it fall is quite a lot of energy, ”
      To pump the water uphill 50 m at 60 m3/h would require a pump in the region of 10 kW. However the totaliser makes it clear that 60 m3/h is not maintained at all times.

      And then letting it fall from a height is free i.e. gravity. As it is an intermittent feed, your inlet pressure is always maintained.

      Anyway we are not designing this system. There is a trade off with the cost of a longer pipe run and the shorter up 50m with a pump. I don’t think we should get into that discussion.

      • nukie says:

        Well, I do not see any place where at this black pipe piece ther would be the place where the pump is located which would have to be less then 10m above water level if it should pump water from basin to reservoir.
        This is why I guess this black pipe is to do the reverse flow, and from the provisoric design this is not done on regular base according my guess.
        For reverse flow water would be coming from the pipe which leads from the reservoir further up passing north of the basin higher up the hill, and so be under continuous pressure, with usual flow direction uphill.
        Problem is that there are not enough informations about the system available, so some reverse engineering must be done.

  15. nukie says:

    About metering: as far as I can see the Hydroelecric system is owned by local gouvernent and spanish utility, water supply system most likely owned by lokal gouvernment (to be verified) so when water changes from one side to the other it must be metered, since there are different owners juristically.
    (a general agreement would make things much more easy, but is not always possible)

  16. nukie says:

    Here for google Earth the pipe-like structure which I see:

  17. To Nukie, Donough, Rainer and others who are now contributing valuable data and comments on the question of pipelines and reservoir flows, thank you. However, new information that greatly complicates the picture has come to my attention and we are not going to get much farther until this issue is resolved. Consequently my next step will be to send emails to REE, GdV and the Island Water Council in an attempt to find out what’s going on. As soon as I do – if I do – I’ll put up a new post. Until then comments are closed on this one.

Comments are closed.