Pumped-storage hydro dam schemes to store wind energy (Scotland)

[Peter Dow]

This begins with a statement of the obvious as far as Scottish electrical power-generation engineers and scientists are concerned I expect but I am making this introductory statement anyway, not for the benefit of our scientists or engineers but to inform the political debate about the potential of the Scottish economy "after the North Sea oil runs out" because political debate involves mostly non-scientists and non-engineers who need to have such things explained to them.

The Scottish economy has a profitable living to make in future in the business of electrical energy import/export from/to English electrical power suppliers and perhaps even to countries further away one day.

The tried and tested engineering technology we Scots can use in future to make money is pumped-storage hydroelectricity.

Wikipedia: Pumped-storage hydroelectricity

The technique is currently the most cost-effective means of storing large amounts of electrical energy on an operating basis, but capital costs and the presence of appropriate geography are critical decision factors.

In Scotland, the Cruachan Dam pumped-storage hydroelectric power station was first operational in 1966 and was built there to take advantage of Scotland's appropriate geography and available capital.

So Scotland has the appropriate geography for pumped-storage hydroelectric power and we have the capital particularly if we invest some of the taxes on North Sea oil before it all runs out and it is all spent.

Investment in wind-power energy generation is proceeding apace, in Scotland, in England, on and offshore, and that's very "green" and quite clever, though wind power is not as dependable as tidal power, but unless and until sufficient capacity to store energy becomes available to supply needs when the wind isn't blowing then conventional, and perhaps increasingly expensive, coal, gas or oil burning or nuclear energy power will still be needed to keep the lights on when the wind doesn't blow.

Scottish opportunity
Here is the opportunity for the Scottish economy in a future where wind-power generation is increasingly rampant: if we Scots build a large capacity of new pumped-storage hydroelectric power stations, not only can we supply all our own Scottish energy needs from "green" renewable energy schemes, but we could provide energy storage capacity for customers outside Scotland, particularly in England, who live in a land not so well endowed with appropriate geography for hydroelectric power.

In future, a Scotland with investment in a massive pumped-storage hydroelectric capacity could buy cheap English wind-power while the wind is blowing then sell the same energy back to English power suppliers, at a profit, when the wind isn't blowing and the English will pay more for energy.

So everyone wins, the energy is all green, the electricity supply is always available when it is needed and that is how the Scottish energy economy does very well after the North Sea oil runs out.

So problem solved but not job done as yet. We Scots do actually need to get busy investing and building pumped-storage hydroelectric power generation and supply capacity in Scotland now.

My vision for a LARGER hydro dam at Coire Glas, Scotland than SSE's

I am presenting here my vision for a large pumped storage hydroelectric 2-square kilometres surface-area reservoir and 300+ metre tall dam which I have designed for the Coire Glas site, Scotland.

(View site using Google Earth where the convenient label is "Loch a' Choire Ghlais" - or, http://tinyurl.com/coireglas)

I was inspired to conceive and to publish my vision by learning of the Scottish and Southern Energy (SSE) proposal to build a smaller hydroelectric pumped-storage scheme at Coire Glas which has been presented to the Scottish government for public consultation.

I have not long been aware of the SSE plan for the Coire Glas scheme, not being a follower of such matters routinely, but I was prompted by an earlier tangentially-related news story (about energy storage technology for renewable energy generators such as wind farms) to write to Members of the Scottish Parliament on the merits and urgency of new pumped storage hydroelectric power for Scotland on 14th February and a reply from Ian Anderson, the parliamentary manager for Dave Thomson MSP received the next day, the 15th February informed me about the SSE plan and Ian added "initially scoped at 600MW but, to quote SSE, could be bigger!"

I replied to Ian "So the schemes proposed by the SSE are welcome and ought to be green-lighted and fast-tracked, but I am really proposing that Scots start thinking long term about an order of magnitude and more greater investment in pumped storage hydroelectric capacity than those SSE plans."

So I had in mind "bigger would be better" but it was not until the next day on the 16th February when a news story informed me that the SSE plans had been submitted to the Scottish government for public consultation that I thought "this needs consideration now".

So starting late on the night of the 17th, early 18th February and all through the weekend, I got busy, outlining my alternative vision for a far bigger dam and reservoir at the same location.

So this is my vision as inspired by the SSE plan. If my vision is flawed then the fault is mine alone. If my vision is brilliant, then the brilliance too is mine.




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The black contour line at 550 metres elevation shows the outline of the SSE proposed reservoir of about 1 square kilometre surface-area and the grey thick line shows the position of the proposed SSE dam which would stand 92 metres tall and would be the tallest dam in Scotland and indeed Britain to date though it seems our dams are several times smaller than the tallest dams elsewhere in the world these days.

Part of the red contour line at 775 metres elevation, where the red line surrounds a blue shaded area, blue representing water, shows the outline of my larger reservoir of about 2 square kilometres surface-area and the thicker brown line shows the position of my proposed dam which would stand 317 metres tall which would be one of the tallest man-made dams in the world, 1475 metres long and about 72 million cubic metres in volume.

Enhanced satellite photograph




Image also hosted on PostImage.Org

[Peter Dow]

Cross section of the Dow-dam
The Dow-dam would be more than 3 times higher than the proposed SSE-dam. In this diagram, a horizontal line one third of the way up the Dow-dam indicates the relative height of the SSE dam although it is not aligned with this cross-section.




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Maps showing the line of cross-section viewed from each side




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Image also hosted on PostImage.Org

Cross section of the Dow-dam reservoir



Cross section along the major diameter of the elliptical excavation of the reservoir bed


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The Upper Reservoir

The green ellipse of major diameter of 1.5 kilometres and minor diameter of 1 kilometre represents an excavated reservoir bed, as flat and as horizontal as practical, at an elevation of 463 metres.

Since an excavated reservoir bed is not, that I can see, part of the SSE plan, at any size, I will provide some more information about my vision for that now.

The basic idea of excavating a flat or flattish reservoir bed is to increase the volume of the water stored in the reservoir because more water means more energy can be stored.

Capacity of the reservoir, energy stored and power supplied

Excavating around 138 million cubic metres of rock increases the volume of the reservoir so created to about 400 million cubic metres, achieving a theoretical energy storage capacity of more than 600 GigaWatt-Hours and it ought to be possible to excavate enough rock to achieve a practical 600GW.Hrs electrical energy supplied.

Accordingly, I envision it would be appropriate and useful to install the required turbine-pumps to supply up to 12 GigaWatts of electrical power to the grid for up to 50 hours before the energy store would be exhausted.

Excavation details

Depending on the geology and strength of the rock of Coire Glas the walls of the reservoir bed perimeter could be as steep as vertical from the reservoir bed up to the natural elevation of the existing rock surface which would mean, presumably, blasting out rock to create a cliff which at places could be as much as about 290 metres tall.

Near the dam, the reservoir bed perimeter wall would be only 40 metres or less tall. The further from the dam, the higher the wall will be and the more rock needs to be excavated.

A vertical reservoir bed perimeter wall would be ideal to maximise reservoir volume wherever the geology provides a strong stone which can maintain a vertical wall face without collapse, (a stone such as granite perhaps). Ideally this would allow about 138 million cubic metres to be excavated to flatten the reservoir bed.

Where the geology only provides a weaker stone then a sloping perimeter wall at a suitable angle of repose for reliable stability would be constructed.

So the reservoir perimeter wall could be as sloped as shallow as 45 degrees from the natural elevation at the perimeter of the eclipse sloping down to the reservoir bed at 463 metres elevation in the case of the weakest and most prone to collapse kinds of stone.

Exactly how strong the stone is at each location I guess we'll only find out absolutely for sure if and when engineers start blasting it and testing the revealed rock wall face for strength.

The shape of the perimeter of the excavated reservoir bed is not absolutely critical. So long as it ends up as a stable wall or slope, however it is shaped by the blasting, it will be fine. There is no need to have stone masons chip the perimeter smooth and flat! The ellipse is simply the easiest approximate mathematical shape to describe and to draw. If the end result is not a perfect ellipse, don't worry, it will be fine!

Loch Lochy and vicinity water flow control works

Here is an annotated satellite photograph of the land south from Coire Glas showing Loch Lochy, Loch Arkaig, the isthmus between the lochs, Mucomir where Loch Lochy empties into the River Spean before it flows on as the River Lochy, the Caledonian Canal and Fort William where the river flows into a sea loch.




Click to see larger image

New waterway

Loch Lochy is separated from a neighbouring loch, Loch Arkaig, by a 2 km wide isthmus, which I have identified on this map as "the Achnacarry Bunarkaig isthmus", after the local place names.

It ought to be quite straight forward to build a canal or culvert, to connect those two lochs. The idea is that the new waterway would be wide and deep enough, enough of a cross section area under water, perhaps hundreds of square metres, so as to allow free flow from one loch to the other, so as to equalise the surface elevations of the two lochs, so as to increase the effective surface area of Loch Lochy so as to decrease the depth changes to Loch Lochy when water flows in from the Coire Glas reservoir when it discharges water when supplying power.

Now, Loch Arkaig has a natural surface elevation of 43 metres and this would be lowered to that of Loch Lochy. The surface area of Loch Arkaig is given by wikipedia as 16 km^2 also, (though it looks to me somewhat smaller than Loch Lochy). In addition, partially draining Loch Arkaig to bring its level down to that of Loch Lochy will also reduce its surface area.

If say, the additional surface area of Loch Arkaig is about 10 km^2 added to Loch Lochy's 16 km^2 this would give an effective surface area of 26 km^2 and reduce the potential depth variation to

Potential depth variation of Loch Lochy + Loch Arkaig = 400 000 000 m^3 / 26 000 000 m^2 = 15.3 metres.

Without equalising the loch levels, the depth changes to Loch Lochy that would require to be managed may be potentially more like 25 metres than 15 metres. So the new waterway is an important part of the new water flow control works that Coire Glas/Dow requires to be constructed.

[Peter Dow]

Additional Loch Lochy water level control measures

When the Coire Glas reservoir is full, then the water level of Loch Lochy should be prevented, by new water works - drains, dams, flood barriers etc. - from rising due to rainfall and natural flow into the loch above a safe level which allows for the reservoir to empty into the loch without overflowing and flooding.

The safe "upper-reservoir-full" loch level will likely turn out to be around about 15 metres below the maximum loch level.

The next diagram showing the new loch drain and the reservoir pump inlets indicates how this might be achieved.




Click to see larger image

The drain from Loch Lochy to the sea which goes underground from the 14 m elevation level in the loch would need capacity for the usual outflow from Loch Lochy which currently goes through the Mucomir hydroelectric station.

I have estimated the flow through Mucomir from its maximum power of 2MegaWatts and its head of 7m as somewhere near 0.2 Mega-cubic-metres-per-hour and compared that value using a spreadsheet I have written to predict the capacity of water flow through different sizes of drains using the empirical Manning formula and this is also useful for determining the appropriate size of the new water channel between the lochs.


Ease my quantity

To construct Coire Glas/Dow/600GW.Hrs/12GW may cost of the order of around £20 billion, but that would be my order of magnitude educated guess more than a professional cost estimate.

In other words, I'm only really confident at this early "vision" stage that the cost would be closer to £20 billion than it would be to £2 billion or to £200 billion but I'm not claiming to be able to quote an accurate cost estimate at this stage.

I have not itemised my costs - how much for land, how much for labour, how much for trucks, how much for diggers, how much for cement, how much to install the generators etc. and the SSE have not published itemised costs for theirs either so I can't calculate my costs in a proportion to the SSE's costs.

Although my version offers 600 GigaWatt-Hours energy and 12 GigaWatts power (or 20 times the capacity and performance) some of the items in my version would cost more than "in proportion", in other words more than 20 times the SSE's cost.

For example, the cost of my dam will be more like 27 times the cost of the SSE's dam. (3.44 times higher and thicker and 2.27 times longer).

For example, the cost of excavating 400 million tonnes of rock from the reservoir bed to increase the capacity of the reservoir to hold water (and energy) in my version won't be in proportion to the SSE costs for excavating their reservoir bed because, as far as I know, they don't plan to excavate their reservoir bed at all.

On the other hand, my land costs are about the same as the SSE's - much less than in proportion. I may well need to use more land to dispose of the additional excavated rock spoil but perhaps when that additional land has been landscaped over it could be resold?

So it depends how much the land is as a proportion of the SSE's costs. If land is a small part of their costs, if 20 similar sites to build on are just as cheap and easy to buy then my costs will be much more than proportional, since saving land won't save much money.

If land is scarce and valuable and the cost to purchase suitable land with a good chance to get permission to build on it is a significant proportion of the SSE's or anyone's costs to build 20 of their size of hydro dam schemes then my costs may be better than proportional. Sometimes securing suitable land for development can be very problematic, very expensive. Sometimes people won't sell their land. Sometimes the authorities won't agree that the land can be used in this way.

The SSE say that suitable sites for such pumped storage schemes are rare indeed, so land costs may be very significant and my scheme good value for money.

If indeed the cost of my scheme is somewhere around £20 billion it is likely to cost far more than the SSE or any electrical power supply company looking to their annual profits for the next few years could possibly afford.

Something like £20 billion I expect could only be found as a national public infrastructure project, spending government money, like the building of a large bridge or motorway would be.

A £20 billion government project would require Treasury approval, at least while Scotland is ruled as part of the UK.

I have suggested funding my much larger hydro dam scheme by re-allocating of some of the Bank of England's "Quantitative Easing" funds which amount to some £300 billion of new money printed with not much to show for it.

Any Questions?

OK, well I guess that's the vision part over. The rest is fairly straight-forward engineering I hope. Oh, and there is always getting the permission and the funding to build it of course which is never easy for anything this big.

OK, well if anyone has any questions or points to make about my vision or can say why they think the SSE plan is better than mine, or if you don't see why we need any pumped storage hydroelectric scheme at Coire Glas, whatever your point of view, if you have something to add in reply, please do.

[Dan]

Hello Peter & welcome ,.... thats a fair bit to digest there !

[Wee Jim]

Wow!! Hello and welcome! i will have to have a read through that sometime i have more time!

[Peter Dow]

Hello Dan and Wee Jim. Thanks for the welcome.

Yes it is a lot to read but it is way more construction work to do if it ever gets the go-ahead and funding. One of the biggest, if not the actual biggest ever construction jobs in Britain.

[Muz]

Hi Peter & welcome

I can see some real problems with either project SSE or yours, but more yours, thats perhaps why they kept it to the size they did

Firstly .. in order to gather the volume of water you envisage, you propose significantly altering the geology of the landscape, and to this effect the problem of doing that to any great degree is that rock is porous. So you have no way of knowing how much volume of water you might lose, which would alter the water table of the surrounding area and cause springs galore for example for miles around the site.

.. on other schemes I have seen, they are usually natural holding areas, where a valley or glen is simply flooded and the natural bottom, seals the vast quantities of water involved, or if it doesent, the natural elements are present to start the process of decay, and growth of plant or marine life to add more organic matter to the bottom to strenghten the tank effect.

Secondly, I am dubious that there would be enough volume of water to keep the reservoir topped up, naturally the balance is maintained by how much is let out, and pumped back, but the margins of viability could be reduced should enough volume not be present to allow the flows you envisage.

Thirdly .. the environmentalists will not allow it .. that doesnt need much expansion !! look at the carry on with the super pylons (so ok, .. they went ahead) but I dont think they would stand for more desecration of our beutiful country .. me .. Ive an open mind, as I realise the benefits of your proposal.

[Wee Jim]

How much of the cash are you planning on stumping up for it yourself?? I mean SSE will be looking for handouts but they will be using their own cash too!

[Peter Dow]

Hi Peter & welcome

Hi Muz and thanks for the welcome.

I can see some real problems with either project SSE or yours, but more yours, thats perhaps why they kept it to the size they did

The real problem is the cost and my much bigger project would cost a lot more. The SSE could not afford to fund a project of the size I propose therefore I also propose that it be funded by government as an infrastructure project, like a big bridge or motorway would be funded.

Firstly .. in order to gather the volume of water you envisage, you propose significantly altering the geology of the landscape, and to this effect the problem of doing that to any great degree is that rock is porous.

Some rocks are porous but other rocks are impermeable.

So you have no way of knowing how much volume of water you might lose, which would alter the water table of the surrounding area and cause springs galore for example for miles around the site.

Well the SSE have probably had a geological survey of the site done and so they'll probably have an idea of how much porous rock and how much impermeable rock is there.

Likewise for my bigger scheme I'd expect a full geological survey so as to anticipate what to expect in construction so as to come to a final decision on whether this is the best site to build something as big.

.. on other schemes I have seen, they are usually natural holding areas, where a valley or glen is simply flooded and the natural bottom, seals the vast quantities of water involved, or if it doesent, the natural elements are present to start the process of decay, and growth of plant or marine life to add more organic matter to the bottom to strenghten the tank effect.

Well the point you make is a good one - porous rock can be sealed naturally but that's also true for a man-made reservoir - it can be sealed artificially if needs be.

Wikipedia: Ludington Pumped Storage Power Plant

Because impervious bedrock is more than 800 feet (240 m) below the reservoir, the builders had to line the reservoir with a layer of asphalt and clay to prevent water seeping into the ground.

Secondly, I am dubious that there would be enough volume of water to keep the reservoir topped up, naturally the balance is maintained by how much is let out, and pumped back, but the margins of viability could be reduced should enough volume not be present to allow the flows you envisage.

Assuming any leaks get sealed then the system is designed so that the same volume of water is circulated up and down between the upper and lower reservoirs. The normal operation of a pumped-hydro scheme does not require a significant flow of water into the scheme.

Thirdly .. the environmentalists will not allow it .. that doesnt need much expansion !! look at the carry on with the super pylons (so ok, .. they went ahead) but I dont think they would stand for more desecration of our beutiful country .. me .. Ive an open mind, as I realise the benefits of your proposal.

Well the smart well-informed environmentalists should allow it because it offers a chance to move towards 100% of our energy supplied from clean, pollution-free, renewable energy sources - and that's got to be good for the environment.

It means more pylons to carry the power to and from the scheme and more wind farms to power it so it means more changes in the appearance of the landscape but that is a price worth paying, a necessary sacrifice for the greater good. Well I think so anyway.

[Peter Dow]

How much of the cash are you planning on stumping up for it yourself?? I mean SSE will be looking for handouts but they will be using their own cash too!

I'm not Sir Mervyn King, Governor of the Bank of England, who can print £325 billion in new money to give to his pals in the city who went broke because of their bad investments so they can continue with more reckless casino banking on the money markets.

Wikipedia: Quantitative easing

In October 2011, the Bank of England announced it would undertake another round of QE, creating an additional £75 billion, and in February 2012 it announced an additional £50 billion, bringing the total amount to £325 billion.

So unlike Sir Mervyn I don't have personal control of the billions of pounds that would be needed for something like this.

Every time Sir Mervyn eases his pals' quantity by printing new money that's the country's currency he is printing, our wealth he is spending.

So instead of wondering what I am spending my income support on you'd be better asking yourself whether Sir Mervyn should be allowed to hand out all those billions of the country's currency to his city pals or whether the same new money would be better spent on infrastructure that the country needs, that the people need, like pumped-storage hydro dam schemes like the one I have described here.

[Wee Jim]

Thanks for the reply. I did not ask about merv and his mates. I asked about you and what cash you would put to it. What are you as an individual looking to get out of this dare i say dream? As to get something like this on the go then you will have to put alot of time and your own money into it before you even get to a planning stage.

I know you are an educated man, But from what i see here you need to do alot of groundwork/surveys/tests etc etc which will probably have to be paid for out your own pocket. Anyone with time on their hands like you can come up with drawings and quotes but what experience in Hydro Dams or Electricity Production do you have?? To be fair what experience in any construction have you got?

I also think its easier to say these things from your one bedroomed flat in Aberdeen as you wont have to look at this Hydro Dam and all the works if (i very much doubt) it got the go ahead.

[FrankB]

It means more pylons to carry the power to and from the scheme and more wind farms to power it so it means more changes in the appearance of the landscape but that is a price worth paying, a necessary sacrifice for the greater good. Well I think so anyway.

I dont follow this logic. ? I thought the idea was that this is a green solution, not one that makes even more pylons, and sacrefices evn more of our countryside.

One of Scotlands biggest industries is tourism, whos going to want to look at wind turbines, massive lochs, andeven more pylons ? come on

[Stock]

Firstly welcome to the forum Peter and thank you for sharing you thoughts. This is an interesting project you propose but I haven't found anything in the proposal to deal with the serious concentrated weight of 400,000,000 tons of water. The next item I raise is the levelling of the floor of the basin, would the additional capacity be cost effective?. Material for the construction of the dam?
Now this type of project was proposed here two years ago but the .5billion of an inter connector to start with helped to put paid to it, then the sale of the electricity are people or industry going to pay a premium because it is green?

What would the payback projection be for such a project? the other thing needed to be considered is " if this level of investment was put in to biogeneration ie willow,straw, biomass or timber then it will generate the need for a workforce labour this creates local economies and increases the tax take. buildings will be put up, equipment purchased etc, etc.

Your project will only create a labour demand for the construction stage but very little afterwards..............
Just my thoughts on the subject.

Stock

[Peter Dow]

Dam foundations and height of the dam above the bedrock
The top of the Dow-Dam has an elevation of 780 metres by design.




Image also hosted here

The lowest elevation of the current ground surface of Coire Glas along the line of the proposed dam is 463 metres and subtracting 463 from 780 is how the initial value of 317 metres for the nominal height of the dam above the existing surface used in previous diagrams was arrived at.

However, the glacial deposit of as yet unknown thickness is to be removed before building the foundations of the dam within and upon the bedrock.

Although the lowest surface elevation along the line of the dam of the bedrock too is unknown a formula relating the Height of the Dam Above the Bedrock (HDAB) to the Glacial Deposit Depth (GDD) can be easily stated.

HDAB = 317 + GDD

Examples.

If the GDD turns out to be 13 metres then the dam will be 330 metres tall.
If the GDD turns out ot be 83 metres then the dam will be 400 metres tall.




Image also hosted here

I propose that the height of the Dow-Dam be as tall above the bedrock as it needs to be to keep the top of the dam at an elevation of 780 metres no matter how deep the removed glacial deposit layer turns out to be.

My approach may well differ from the SSE's approach. The SSE have said that their dam will be "92 metres" high and they may stick to that without having any goal for the elevation of the top of their dam.

As the diagram indicates, I propose to secure the Dow-Dam to the bedrock by massive piles inserted and secured into shafts which would be drilled into the bedrock.

[Wee Jim]

Come on now Peter you seem to be avoiding some of the questions.

What i dont get is its all you propose this you propse that etc but how can 1 man who lives on benifits in a flat in Torry really think that he has a shot at producing something of this scale? even with the best crisis loan in the world you'd maybe get a mini digger hired for a day!!

Maybe its just me but i am very very doubtfull over this 'vision'. It appears to me to be a case of bullshit baffles brains!!