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Author Topic: How can renewable energy farms provide 24-hour power?  (Read 74082 times)

Offline wolfekeeper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #50 on: 12/04/2015 15:21:54 »
Part of the problem for electric car users is the distance between filling stations. If you take the M25 and M4 from South Mimms to Reading, it's "only" 50 miles, with no service stations in between. The next station westwards is a further 20 miles, out of reach for most hybrids on "battery only" and marginal for medium 100% electrics. So if we have 500 electric cars parked at either station (not unusual) we will need 500 charging points, not 2. If you have slowmoving traffic in winter you can expect to find a fair number of automotive corpses around the motorways.
Everything you're saying is such complete and utter bullshit.

If you have a hybrid, do you want me to draw you a picture? They have a hole for petrol? You see the word 'hybrid' means hybrid electric-fossil fuel engine, and you can put fuel in it, or you can charge it from the wall. It's MAGIC.

And the economics of fast chargers is bloody simple, even for you. Each charger cost about US$60,000, about £40,000:

http://cleantechnica.com/2014/05/03/ev-charging-station-infrastructure-costs/

So if you charge (say) £40 for a recharge, then to repay for the charger infrastructure costs in a year each charger has to charge £40,000/£40 = 1000 cars per year = ~3 cars per day. After that, it's gravy. Of course you could charge less, say £20, and take longer to repay the loan, but the economics are simple; if you have cars queueing, add more chargers, unless you're a complete moron they make you money. (n.b. they're not charging at the moment, that's not a permanent thing, and they are already in some parts of America).

So if they really need 500 fast chargers, they would be ecstatic, they're making money.

edit: so what you're saying is that they may have to make multistory car parks, with fast chargers, so they can make EVEN MORE MONEY. Oh dear, they will be so sad.
« Last Edit: 12/04/2015 15:45:03 by wolfekeeper »
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #51 on: 12/04/2015 17:39:59 »
No need for a drawing, thanks. I first drew a hybrid car (actually it was a bus) 60 years ago and would very much like to own one, preferably with a gas turbine rather than a reciprocating engine as prime mover.

But this thread is about the replacement of fossil fuels by wind, not just better ways of using them.

The engineering of recharging stations isn't a problem. All you need to do is deliver an additional 20MW to every motorway service station. There are just over 100, so using your figures for a charging point and assuming there is adequate grid capacity and every station is within 30 m of an 11 kV supply, we need an infrastructure investment of about £1.5 - 2bn for the motorways alone. Probably the same again for A roads and again for city stations.

This leads to a chicken and egg problem. Even if I could afford the cost and inconveniece of an electric car, I couldn't go anywhere with it until there were enough charging points along the way, and it would be difficult to persuade anyone to invest £2bn in the hope that everyone will buy an electric car the next day. I think you would be looking at about 10 years for 50% market penetration. That sort of investment requires government intervention (not guarantees - they just end up with a tax bill and no product) and a nationalised electricity supply. I'm all in favour of that, but it doesn't seem very likely to happen in the UK.

 

Offline wolfekeeper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #52 on: 12/04/2015 17:53:36 »
I have no idea why you think the government would need to pay for this.

At the service station, they get money from the punters, and they use this to pay for the equipment.

If it costs them more, they charge more. They have (pretty much) a captive audience, and the equipment has a long life- they can probably easily borrow money for this, it's capital investment, and the users effectively pay them to build it.

It's self financing. It's money that would otherwise have gone to pay for petrol, often in another countries, instead it's spent on jobs within the UK.

On the contrary, the government could tax it, just like they tax petrol.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #53 on: 12/04/2015 20:12:26 »
The revenue argument is clear, but how are you going to raise £3billion capital for a venture that depends on everyone else buying an electric car before your hardware is obsolete? Market penetration (outside of the urban weekend ecowarrior clique) will be poor until the recharge network is complete.

Quote
they can probably easily borrow money for this,
Just try it! Private venture capital expects a 20% return in the second year of investment. Banks expect to see 50% equity funding for a new venture and are unlikely to lend at less than 10% in the foreseeable future. So you install £3billion capital equipment in, say , a year, then have to repay at least £300,000,000 in year 2 (half capital repayment, half interest, on the £1.5bn you borrowed). But how many people will have bought electric cars in the first year?

As I pointed out earlier, incremental growth (say 2 recharge points per station) is fairly easy to accomplish, but at some stage you are going to have to bite the bullet and undertake a massive refit to bring 20MW to each service station. If you are too slow, people will complain about having to wait for hours to recharge, if you are too quick you won't realise the expected (or required) return on investment.

Be sure the government will find a way to tax it, whatever you do, because whilst personal transport is obviously essential for politicians, it's an undeserved luxury for the plebs who vote for them. I'd prefer it if the grid were run as a profitable national asset, with a 20 year planning horizon. But I don't see any rightwing government nationalising the grid, or any leftwing government promoting private transport. And whilst businessmen can work with 20 or 50 year plans, politicians can't.

Any thoughts about electric HGVs? Obviously feasible, but what recharging facilities can you offer?     
« Last Edit: 12/04/2015 20:23:03 by alancalverd »
 

Offline wolfekeeper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #54 on: 12/04/2015 20:39:35 »
Look, none of this is rocket science; apparently it is for you, but I think everyone else reading this thread will understand that there's no fundamental problem, and I haven't even mentioned that you can order backup generators up to 250 megawatts, off-the-shelf items, to power recharging points during peak time if you're a bit shy on grid connection. The electricity itself is not even the expensive bit, it's installing the plug-in points, and as I say, they're self financing; and it's good to have a backup generator anyway, in case the grid goes down.

Really, this is not hard.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #55 on: 13/04/2015 08:25:02 »
Quote
Really, this is not hard.

I look forward to your becoming the first UK electric car billionaire.
 

Offline wolfekeeper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #56 on: 13/04/2015 17:44:41 »
No, but buying shares in services stations might be profitable.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #57 on: 14/04/2015 11:15:49 »
Chicken! This is, apparently, a self-financing no-brainer, led by an acknowledged expert. You should be selling shares, not buying them!
 

Offline Scottish Scientist

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Hi chiralSPO and thanks for your feedback.

1400 GWh (5.04x1015 J)
Check.
1400 GWh = 1.4TWh = 58.33 GW-days

of pumped hydro storage would be quite an engineering feat!
This is 1960s technology. Technically, it is very easy to do and not such a big a job either. £37 billion or 3 channel tunnels' worth of work.

Now the wind turbines are more work. 290GW with 12GW installed already leaves 278GW to build and install and at £1.6 billion per GigaWatt (on land) that comes to £445 billion worth of turbines or 37 channel tunnels' worth.

So the wind turbines are far more of an engineering feat.

Even assuming 100% efficiency (not a terrible approximation) you would have to have about 1010 m3 (1013 kg) of water pumped up 50 meters. That volume is slightly larger than the average volume of Loch Ness, which is the largest Loch in Scotland (7.4 km3 = 7.4x109 m3)*.

Perhaps we could use an elevation of 300 meters (the height of the Shard, in London) and only 1.67x109 m3 of water (somewhere between the size of Loch Tay and Loch Morar)*.
David JC MacKay in his book "Sustainable Energy - Without the Hot Air" considers finding sites for 1200GWh and reckons it would be tough.
http://www.withouthotair.com/c26/page_192.shtml [nofollow]

David cleverly managed to think of not putting all the water at one site though which makes it a lot less tough.

300 metres of head is typical for pumped-storage though 500 metres is possible too.
http://www.withouthotair.com/c26/page_191.shtml [nofollow]

The pumped-storage hydro scheme at the Cortes-La Muela, Spain hydroelectric power plant has a head of 524m and impounds a water of volume of 23Hm3 = 23 x 106m3 with a mass of 23 x 109Kg.



Which represents a stored energy maximum of mgh = 23 x 109 x 9.81 x 523 = 1.18 x 1014J or 32.8 GWh. A similar amount of energy is planned by the SSE for their pumped-storage hydro scheme for Coire Glas, Scotland.
http://sse.com/whatwedo/ourprojectsandassets/renewables/CoireGlas/ [nofollow]

So only 1400/32.8 = 43 Cortes-La Muelas or 1400/30 47 Coire Glases. I should point out that unlike Cortes La Muela which is pretty much maxed out, the site at Coire Glas - if the design was maxed out in the same fashion - could host a much bigger reservoir there - not 1400 GWh certainly - but 1/3rd of that possibly.

So if three sites like Coire Glas could site our needs for pumped-storage, I don't think it is as tough as David MacKay claims.

Time for the tough to get going.

On the other hand, 1400 GWh of electrochemical energy could be stored in 1.4x105 m3 of zinc metal (and the air needed to react with it). Not a small volume, certainly, but four or five orders of magnitude smaller than for pumped hydro.

Well pumped-storage hydro is the method of choice for electricity grid energy storage.

Thanks again for your feedback chiralSPO!

Intro please ...

Billy Ocean - When the Going Gets Tough, the Tough Get Going -



Click for a larger image - https://scottishscientist.files.wordpress.com/2015/04/strathdearn_pumped-storage.jpg [nofollow]

The map shows how and where the biggest-ever pumped-storage hydro-scheme could be built – Strathdearn in the Scottish Highlands.

The scheme requires a massive dam about 300 metres high and 2,000 metres long to impound billions of metres-cubed of water in the upper glen of the River Findhorn. The surface elevation of the reservoir so impounded would be as much as 650 metres when full and the surface area would be as much as 40 square-kilometres.

There would need to be two pumping stations at different locations – one by the sea at Inverness which pumps sea-water uphill via a pressurised pipe to 350 metres of elevation to a water well head which feeds an unpressurised canal in which water flows to and from the other pumping station at the base of the dam which pumps water up into the reservoir impounded by the dam.

The potential energy which could be stored by such a scheme is colossal – thousands of Gigawatt-hours – a minimum of 100 GigaWatt-days, perhaps 200 GW-days or more.

This represents enough energy-storage capacity to serve all of Britain’s electrical grid storage needs for backing-up and balancing intermittent renewable-energy electricity generators, such as wind turbines and solar photovoltaic arrays for the foreseeable future.

The geography of Scotland is ideal for siting pumped-storage hydro schemes to serve a European energy network infrastructure, with benefits for Scots, Britons and Europeans alike.
« Last Edit: 16/04/2015 07:40:12 by Scottish Scientist »
 

Offline Scottish Scientist

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Quote from: David MacKay
When the facility is generating, will there be problems maintaining the required flow along the canal to maintain the head in the Inverness pipe/generator? Assuming the goal would be to be able to generate a few GW, I wonder if the design would need to include a quite-large holding pool at the Inverness end of the canal?

https://scottishscientist.wordpress.com/2015/04/15/worlds-biggest-ever-pumped-storage-hydro-scheme-for-scotland/comment-page-1/#comment-5 [nofollow]

David,

I’m honoured to welcome your first comment on my blog – the first of many I hope. Your book – “Sustainable Energy – without the hot air” by David JC MacKay
http://www.withouthotair.com/ [nofollow]
 is the 2nd-most quoted reference source (after Wikipedia) in the online discussions I have been party to regarding renewable energy, especially your Chapter 26 “Fluctuations and storage”
http://www.withouthotair.com/c26/page_186.shtml [nofollow]
 in the context of pumped-storage hydro.

I rushed this post out in the early hours of this morning because I am keen to share my design concept at the earliest opportunity regardless that many key details of my proposal remain unspecified in the post at this time (15 April 2015). I intend to update this post on my own initiative and in answer to comments such as yours.

The most important missing detail in the first draft of this post is (was) any estimate for the power capacity. Whilst we may agree that power capacity should be in proportion to the energy storage capacity, we may differ on precisely what constant of proportionality to recommend.

On page 189 of your book,
http://www.withouthotair.com/c26/page_189.shtml [nofollow]
 you recommend storage capacity equivalent to 5 days of average power. Attempting to follow the guidance in your book, from an energy storage capacity of 100 GW-days, would not your book’s recommendation for power capacity be the peak power equivalent of 20 GW average power (1.6 x 20 = 32 GW peak power) or for 200 GW-days energy storage then the peak power equivalent of 40 GW average power (1.6 x 40 GW = 64 GW peak power), which is a lot more than “a few GW”?

Peak-power is the more relevant nameplate specification for a pumped-storage hydro-scheme because pumps and turbines must be able to handle peak power, not only average power.

In my blog post “Modelling of wind and pumped-storage power”
https://scottishscientist.wordpress.com/2015/04/03/scientific-computer-modelling-of-wind-pumped-storage-hydro/ [nofollow]
 I modelled a smaller constant of proportionality for energy storage capacity of only 1.11 peak-demand-days (equivalent to 1.6 x 1.11 = 1.77 average power-days), with satisfactory results. So, as of now, I’m recommending only “1.77 days” equivalently compared to your “5 days”, a constant of proportionality of about a third of yours.

Accordingly, I’d recommend for 100 GW-days, a nameplate peak power capacity of 100 / 1.11 = 90 GW, and for 200 GW-days, 180 GW. As you can see this is considerably in excess of UK peak demand of 60 GW, opening up the possibility to provide grid energy storage services to Europe as well.

Those figures had to be discussed first before turning to the requirements for water flow through the pumps, the pipe and the canal because all of the features of the hydro scheme must be scaled appropriately.

The required flow rate of water can be calculated, as you know, from the head and the power capacity and the empirical Manning formula
http://en.wikipedia.org/wiki/Manning_formula [nofollow]
 may be used to design the cross-sectional area of a canal to achieve the required flow rate.

So to get to your question David, yes there would indeed be problems in maintaining the required flow along the canal to maintain the head – at both ends because flow is in both directions – but a holding pool at either end, however large, would not solve those problems. Only a canal of a sufficient cross section with additional design features as required could hope to do so.

I’ve not done any estimates for the required minimum cross section of the canal as yet but that’s of interest certainly.

Once again, David, I must tell you how ‘fair chuffed’ I am that you commented on my post!
« Last Edit: 15/04/2015 13:48:42 by Scottish Scientist »
 

Offline David Cooper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #60 on: 15/04/2015 17:15:43 »
You think you could get planning permission for that massive salt-water tank? There are better technologies on the way which will wipe out the point of it before it could be built.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #61 on: 16/04/2015 00:01:37 »
The scale of this 64 GW dam project can best be appreciated by comparison with the Hoover Dam with a peak output of 1.4GW, and Drax power station (4GW). The largest hydroelectric station in the UK is 0.3GW at present. Admittedly these are fairly historic structures, so a fair comparison would be with the 22 GW Three Gorges Dam

Quote
......the dam flooded archaeological and cultural sites and displaced some 1.3 million people, and is causing significant ecological changes, including an increased risk of landslides. The dam has been a controversial topic both domestically and abroad.

except that both Hoover and Three Gorges are freshwater systems. Having overcome the minor technical problem of pumping seawater back and forth, raised enough money to build a power station three times larger than any other on the planet, and installed a distribution system to carry the entire national demand to and from one station instead of 600 with sufficient redundancy, you may find just the teensiest hint of concern from the occasional treehugger!

I think it is an inspiring project, which should be started immediately and funded entirely by the windpower industry. As the Hoover Dam was completed in 5 years and the Three Gorges in 12, it should be possible to complete this project before wind generation exceeds 20% of grid capacity - the point at which grid stability would be seriously compromised. The only pity is that it is in the wrong place:

Quote
Because of the power loss associated with this north to south flow, the effectiveness and efficiency of new generation capacity is significantly affected by its location. For example new generating capacity on the south coast has about 12% greater effectiveness due to reduced transmission system power losses compared to new generating capacity in north England, and about 20% greater effectiveness than northern Scotland.

but you can't have everything!
« Last Edit: 16/04/2015 00:03:55 by alancalverd »
 

Offline wolfekeeper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #62 on: 17/04/2015 01:56:22 »
Mere scale is virtually never a reason not to do something. You should look at stuff like cost per person, and the timescale over which it would be built instead.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #63 on: 17/04/2015 13:03:45 »
Scale is important because this project requires capital input. There is obviously no physical reason why it can't be done but the practicality is that you need enough money up front to start the work, with a sufficient promise that it will be funded to completion. Failing that, a project will run into the sand as lack of continuing funding means delay, which increases costs and makes further funding less attractive.   

Whilst Scottish independence remains a serious possibility, it won't be funded by the UK government, so the money has to be raised either by private investors or by taxing the Scots for long enough to build up the required capital reserve (and not spending it on something else, which politicians are bound to do).   

So, let's have some cost estimates, please!
 

Offline Scottish Scientist

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... and now the world's biggest-ever canal!
« Reply #64 on: 17/04/2015 17:11:12 »
I’ve updated my post to include more detailed estimates for the reservoir volume, maximum flow rate, energy storage and power capacity.

The volume of water impounded by the dam - about 4.4 billion metres-cubed of water.

The maximum potential energy which could be stored – about 6800 Gigawatt-hours – or 280 Gigawatt-days.

To fill or empty the reservoir in a day would require a flow rate of  51,000 metres-cubed per second, the equivalent of the discharge flow from the Congo River, only surpassed by the Amazon!

When nearly empty and powering only the lower turbines by the sea, then about 132 GW could be produced. When nearly full and the upper turbines at the base of the dam fully powered too then about 264 GW could be produced.

I’ve also used the Manning formula to estimate a canal size to cope with the maximum flow rate.

Canal

The empirical Manning formula relates the properties, such as volume rate, gradient, velocity and depth of a one-directional steady-state water flow in a canal.



Click to view a larger image - https://scottishscientist.files.wordpress.com/2015/04/manning_power_canal_200.jpg [nofollow]

For 2-way flow, the canal must support the gradient in both directions and contain the stationary water at a height to allow for efficient starting and stopping of the flow.



Click to view a larger image - https://scottishscientist.files.wordpress.com/2015/04/2-way_power_canal1.jpg [nofollow]

The “2-way Power Canal” diagram charts from a spreadsheet model for a 51,000 m3/s flow how the width of the water surface in a 45-degree V-shaped canal varies with the designed maximum flow velocity. The lines graphed are

Moving width – from simple geometry, for a constant volume flow, the faster the flow velocity, the narrower the water surface width

Static width – the width of the surface of the stationary water with enough height and gravitational potential energy to convert to the kinetic energy of the flow velocity

30km 2-way wider by – using the Manning formula, the hydraulic slope can be calculated and therefore how much higher and deeper the water must begin at one end of a 30km long canal to have sufficient depth at the end of the canal and therefore by how much wider the canal must be

Canal width – adding the 30km-2-way-wider-by value to the static-width determines the maximum design width of the water surface.

The equation thus derived,

y = 2 √ ( 51000/x) + 0.1529 x2 + x8/3/40

where y is the maximum surface water width in the canal and x is the designed maximum flow velocity

predicts a minimum value for the canal width of about 170 metres (plus whatever additional above the waterline freeboard width is added to complete the design of the canal) at a design maximum flow velocity between 10 and 11 metres per second.

Guinness World Records states that the widest canal in the world is the Cape Cod Canal which is “only” 165 metres wide.

So the canal, too, would be the biggest ever!

You think you could get planning permission for that massive salt-water tank?
Well the SSE got planning permission for their plans for a pumped-storage hydro-scheme at Coire Glas.

BBC: "Scottish government approves £800m Lochaber hydro scheme" - http://www.bbc.co.uk/news/uk-scotland-highlands-islands-25365786 [nofollow]

Admittedly, the SSE plan is only for a 30GWh reservoir and mine is some 226 times bigger.

There are better technologies on the way which will wipe out the point of it before it could be built.
Well the "long-life" electrical battery has been such a favourite topic for marketing hyperbole for so many decades that scientists are naturally sceptical of any such new claims.

The scale of this 64 GW dam project
I've increased the estimate for the storage capacity up from "200 GW-days or more" to "280 GW-days", so even assuming David MacKay's very conservative requirements for 5-days of average power that estimate goes up to 280/5 x 1.6 = 90 GW.

can best be appreciated by comparison with the Hoover Dam with a peak output of 1.4GW, and Drax power station (4GW). The largest hydroelectric station in the UK is 0.3GW at present. Admittedly these are fairly historic structures, so a fair comparison would be with the 22 GW Three Gorges Dam

Quote
......the dam flooded archaeological and cultural sites and displaced some 1.3 million people, and is causing significant ecological changes, including an increased risk of landslides. The dam has been a controversial topic both domestically and abroad.
The population density of the Highlands of Scotland is 9 people /km2. The scheme could be easily contained within 4 squares each of 10km x 10 km. So tops only 400km2 x 9 = 3600 people might be displaced (with generous compensation I trust).

except that both Hoover and Three Gorges are freshwater systems. Having overcome the minor technical problem of pumping seawater back and forth,
The Okinawa pumped-storage hydro scheme uses the sea as a lower reservoir.
http://en.wikipedia.org/wiki/Okinawa_Yanbaru_Seawater_Pumped_Storage_Power_Station [nofollow]


raised enough money to build a power station three times larger than any other on the planet,
Even the SSE has not raised the £800 million for their 226 times smaller scheme, so the 226 x £0.8 billion = £180 billion for this scheme is a big ask.

and installed a distribution system to carry the entire national demand to and from one station instead of 600 with sufficient redundancy,
It all adds to the cost, for sure.

you may find just the teensiest hint of concern from the occasional treehugger!
We can easily plant more trees than we have to uproot for this scheme.

I think it is an inspiring project, which should be started immediately and funded entirely by the windpower industry.
No for this, I was thinking some of the European Central Bank quantitative easing money would come in handy.
http://www.bbc.co.uk/news/business-30933515 [nofollow]
The ECB has only created 60 billion Euros because, after all, governments don't tend to trust bankers all that much these days but for a sound investment like this, with overwhelming benefits for Europe's renewable energy goals, perhaps the ECB can be persuaded to chip-in a good deal more than 60 billion Euros. Then of course the UK can chip-in with some Q.E. or deficit-spending likewise.

It's a big ask but it is worth it.

As the Hoover Dam was completed in 5 years and the Three Gorges in 12, it should be possible to complete this project before wind generation exceeds 20% of grid capacity - the point at which grid stability would be seriously compromised. The only pity is that it is in the wrong place:
Well this scheme's full power output from 130 GW up to 230 GW of power available is 20% of 650 GW to 1150 GW or 20% of the entire generation capacity of Europe.
http://www.eia.gov/cfapps/ipdbproject/IEDIndex3.cfm?tid=2&pid=2&aid=7 [nofollow]

Quote
Because of the power loss associated with this north to south flow, the effectiveness and efficiency of new generation capacity is significantly affected by its location. For example new generating capacity on the south coast has about 12% greater effectiveness due to reduced transmission system power losses compared to new generating capacity in north England, and about 20% greater effectiveness than northern Scotland.

but you can't have everything!
Direct current is more efficient for long distance power transmission.
http://en.wikipedia.org/wiki/High-voltage_direct_current [nofollow]

Mere scale is virtually never a reason not to do something. You should look at stuff like cost per person, and the timescale over which it would be built instead.
Agreed.

Scale is important because this project requires capital input. There is obviously no physical reason why it can't be done but the practicality is that you need enough money up front to start the work, with a sufficient promise that it will be funded to completion. Failing that, a project will run into the sand as lack of continuing funding means delay, which increases costs and makes further funding less attractive.   

Whilst Scottish independence remains a serious possibility, it won't be funded by the UK government, so the money has to be raised either by private investors or by taxing the Scots for long enough to build up the required capital reserve (and not spending it on something else, which politicians are bound to do).   

I think the way to build this is not all at once but first to build part of the sea-side scheme, using a length of canal as an upper reservoir.

Get a system working for Scottish 2020 renewables-only needs then once the team which has done that has a working scheme in place, hopefully the investment to complete the rest of the sea-side scheme and the reservoir and dam-base pumps would become available.

That way at least we'd have working pumped-storage to show for any investment if the money ran out before final completion.

So, let's have some cost estimates, please!

8 GW / 8.5 GW-days - £5.4 billion (Scottish needs demonstrator project, using about 20km of canal as the upper reservoir)
264 GW / 280 GW-days- £180 billion
« Last Edit: 22/04/2015 22:39:26 by Scottish Scientist »
 

Offline David Cooper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #65 on: 17/04/2015 18:30:14 »
There are better technologies on the way which will wipe out the point of it before it could be built.
Well the "long-life" electrical battery has been such a favourite topic for marketing hyperbole for so many decades that scientists are naturally sceptical of any such new claims.

I was thinking about two things: nuclear fusion power stations, and battery storage optimised not for power to weight ratio but for low cost bulk storage (there are promising noises coming from people working on that). Both of these will be in place before you can build your monster.

What is certain is that your giant fish tank would meet with enormous opposition for a variety of obvious reasons. You're talking about a dam 300m high and 2km long - an earthquake of 6 on the Richter scale is not an impossibility in that location, so I wouldn't want to live downhill from there.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #66 on: 18/04/2015 18:42:17 »
The production of concrete generates 410 kg of CO2 per m3.

A dam is roughly triangular in section with base width equal to its height, so we are looking at a carbon footprint of 37 million tonnes of carbon dioxide for the dam, plus probably twice as much to line the canal. plus whatever it takes to get the concrete to site. I guess at least 150 megatonnes. How much wind energy is required to offset this?

Remember that this project doesn't generate any energy, it merely stores energy generated elswhwere, so there's no "carbon offset" involved.

Nuclear power has the lowest carbon footprint of all energy sources, at about 4 gram per kWh so you would need 37,500 GWh of additional free wind energy to repay the carbon cost of building the project. Except that wind actually has a higher carbon footprint than nuclear, so if you wanted to reduce the overall carbon emission of the electricity grid you would do better to replace all the fossil plant with nuclear: no storage problem, no additional land requirement, and no additional transmission grid capacity.

But the SNP is pledged to a non-nuclear Scotland!
 

Offline chiralSPO

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Re: How can renewable energy farms provide 24-hour power?
« Reply #67 on: 18/04/2015 19:40:53 »
I agree that nuclear power is an excellent, low carbon energy source that should be taken better advantage of. However, that doesn't get you completely away from the energy storage problem. Nuclear plants have a very constant output, that can only be modulated a little bit, and quite slowly (as far as I know). While this can be used to provide a large portion of the base load, it is ill-adapted to the variability in consumer demand for electricity. Energy storage technology is still required for peak shaving and peak shifting, if you don't want to have some gas- or coal-fired powerplants that get cycled on and off as needed...
 

Offline David Cooper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #68 on: 18/04/2015 22:07:08 »
We could get rid of a lot of the sudden peaks in energy demand by getting rid of soap operas.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #69 on: 19/04/2015 10:02:44 »
There is certainly a place for pumped energy storage in an all-nuclear system, but as the ramp-up time for a nuke is a matter of minutes (the trick is never to shut the reactor down completely, and baseload is about half peak in the UK), you don't need to store the entire grid demand for 5 days, just half the demand for an hour or two. This was the philosophy behind Dinorwig, and it works very well.   

As I recall, the largest peak demand was during the Queen's coronation. as the procession left the Abbey, the entire nation switched the kettle on and went for a pee.
 

Offline wolfekeeper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #70 on: 19/04/2015 14:19:42 »
Nuclear is a non starter; renewables are growing far faster and that's not changing any time soon.

Although nuclear reactors can and are built to load follow, running a nuclear reactor at partial power makes it even less economic; the cost of the electricity is inversely proportional to its production.

Indeed that's why Dinorwig was built, it looked like they would need a whole bunch of pumped storage because the plan was to produce lots of nuclear power plants and they didn't want to have to make them load follow; in the end nuclear got scaled wayyyy back.

Apart from the huge economic risks of a major meltdown, nuclear power also has the waste problems, which have never really had any good solutions, only least bad ones; which still weren't very good.
 

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Re: How can renewable energy farms provide 24-hour power?
« Reply #71 on: 19/04/2015 14:44:00 »
At the moment I can't remember who to attribute this to, but there is a quote or saying out there along the lines of:

"I am a firm believer that nuclear fusion will ultimately be the only source of power used by the people of Earth--after all, we already have the reactor!"


In all seriousness, with the exception of radioactive materials and geothermal power, all of our energy is originally solar. We just need to develop more efficient ways of capturing, storing and distributing that energy, and we would have access to an almost unlimited  supply of energy (several orders of magnitude more than our current demands.)
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #72 on: 19/04/2015 18:35:40 »
Quote
In all seriousness, with the exception of radioactive materials and geothermal power, all of our energy is originally solar. We just need to develop more efficient ways of capturing, storing and distributing that energy, and we would have access to an almost unlimited  supply of energy (several orders of magnitude more than our current demands.)

Plants do it very well, and you can eat them too. The problem is that there are too many people. But that problem can be solved by simply doing nothing - make fewer people. Alas, however, there is no profit to be made by such a simple solution, and a world with a small population of well-fed, contented people would have no need of priests, politicians, and other parasites, so it won't happen because people are individually clever but collectively stupid.
 

Offline wolfekeeper

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Re: How can renewable energy farms provide 24-hour power?
« Reply #73 on: 19/04/2015 20:11:00 »
Plants are actually not that good at photosynthesis; their conversion efficiency for solar energy to plant energy is only about 1-3% or so, whereas solar panels are ~15-45% or more. Some of that is probably because they need the energy for metabolism; but the end result is the same; they suck for what we as humans want from them.
 

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Canal lining, boulder trap and main dam
« Reply #74 on: 20/04/2015 16:25:40 »
Canal lining and boulder trap



To maximise the water flow velocity, canals are lined to slow erosion. Concrete is one lining material often used to allow for the highest water flow velocities, though engineering guidelines commonly recommend designing for significantly slower maximum flow velocities than 10 m/s, even with concrete lining.

Designing for a slower maximum flow velocity requires a wider canal to maintain the maximum volume flow rate and is expensive in construction costs.

Water flowing at 10 m/s has the power to drag large – in excess of 10 tonnes – boulders along the bottom of a canal with the potential of eroding even concrete, so I suggest that the bottom 6 metres width of the lining, (3 m either side of the corner of the V) may be specially armoured with an even tougher lining material than concrete and/or include bottom transverse barriers of 2 metres depth to impede the flow along the corner of the V and trap boulders, smaller stones and gravel, in which case the water flow is more precisely modelled for Manning formula calculations as a trapezoidal canal with a bed width equal to the 4 metre width of the top of bottom transverse barrier (“boulder trap”) and a 2-metre smaller depth from the top of the boulder trap to the water surface.

Main Dam


Click to view a larger image -  https://scottishscientist.files.wordpress.com/2015/04/strathdearndam.jpg [nofollow]

The image shows the location of the main dam at latitude 57°15’16.2″N, decimal 57.254501°, longitude 4°05’25.8″W, decimal -4.090506°.

Click to view location on Google Maps -

NOPE - MY LINK TO GOOGLE MAPS IS BEING BLACKLISTED
but I've got a work-around via tinyurl
http://tinyurl.com/StrathdearmDamGoogleMaps [nofollow]

Assuming the dam would be twice as wide as its height below the dam top elevation of 650 metres, the superficial volume is estimated at 80 million cubic metres, not including the subterranean dam foundations which would be built on the bedrock after clearing away the fluvial sediment.

There are better technologies on the way which will wipe out the point of it before it could be built.
Well the "long-life" electrical battery has been such a favourite topic for marketing hyperbole for so many decades that scientists are naturally sceptical of any such new claims.

I was thinking about two things: nuclear fusion power stations,
So impractical as to not even be worth discussing. In my opinion, that will never be in place. I regret that Prof Brian Cox has been allowed air time on the BBC to mislead popular science viewers about this topic. Well I suppose he is more entertaining than a lot of the other rubbish on the box, but still - there's no substitute for practical applied science.


and battery storage optimised not for power to weight ratio but for low cost bulk storage (there are promising noises coming from people working on that). Both of these will be in place before you can build your monster.
Well we've heard promising noises for decades about this. I'm not getting my hopes up.

What is certain is that your giant fish tank would meet with enormous opposition for a variety of obvious reasons. You're talking about a dam 300m high and 2km long - an earthquake of 6 on the Richter scale is not an impossibility in that location, so I wouldn't want to live downhill from there.
It should be possible to build a dam as strong as the surrounding mountains, to withstand any earthquake which the mountains endure.

Admittedly, for people living near such big dams, repeated minor earthquakes arising from reservoir induced seismicity
http://en.wikipedia.org/wiki/Induced_seismicity#Artificial_lakes [nofollow]
may cause fear and alarm, at least until such time as the locals get used to it.

The production of concrete generates 410 kg of CO2 per m3.

A dam is roughly triangular in section with base width equal to its height,
I would place that configuration on the experimental side of the experimental-versus-conservative design boundary for dam footprints, which I would place at the ratio of base width equal to twice its height, which is how I've drawn my dam's footprint in my above diagram.

The issue is blast waves normal to the dam wall - with the 
"width = 2 x height"
or wider configurations, the normal shock is directed into the ground, harmlessly and foiling any sabotage of the dam.

Any narrower than w=2h and the normal shock wave reaches the opposite dam wall above the ground which can fail in tension as the shock wave is reflected from opposite wall, as was demonstrated in the WW2 Dam Busters raid.



so we are looking at a carbon footprint of 37 million tonnes of carbon dioxide for the dam,
You appear to have assumed a dam volume of 90 million cubic metres, which is closer to my estimate than expected because
a) the dam is effectively smaller near its edges because the geography is higher
b) my 80 million cubic metres doesn't include dam foundations so the total including foundations could easily exceed your 90 million cubic metres.

plus probably twice as much to line the canal.
Well I can't agree with this estimate. What did you assume for the canal length, lining area and thickness?

If the depth of the canal water is 88 metres and ignoring any freeboard above the waterline.

Length of lining of canal up the 45 degree slope = √( 2 x 88 x 88) = one slope 124.45 m
Two slopes = 248.9 call that 249m
Canal length 30km = 30,000 metres
Lining area = 30,000 x 249 = 7.47 x 10^6 m^2

Volume of lining per metre thickness is about 7.5 million metres cubed

So even if the lining were 1 metre thick - more than it needs to be I think - that would only be 7.5 million metres cubed, less than 1/10th of the dam volume.

Yet you estimate the canal needs twice the concrete for the dam. Why? Does the canal lining have to be 20 metres thick? Or has one of us got our sums wrong?

plus whatever it takes to get the concrete to site.
Plus fuel for the construction equipment and explosives to blast rock.

I guess at least 150 megatonnes.
Really?


How much wind energy is required to offset this?
Well it is your figure so you work it out. This link
http://www.electricityinfo.org/co2emissions.php [nofollow]
suggests that the average CO2 emission is 470g/kWh of electricity generated.

I'll work out how much CO2 my dam will save if used as part of a renewable-only generation system for the equivalent peak-power of 264 GW which equates to an average power capacity of 264/1.6 = 165GW

Annual CO2-free energy produced is 165 x 24 x 365 = 1.445 x 10^6 GW-hours = 1,445 TerraWatt-hours = 1.445 PetaWatt-Hours (PW-hours)

CO2 emissions 470g/kWh
= 470Kg/MWh
= 470 tonnes / GWh

So that's an annual CO2 saving of 470 x 1.445 x 10^6 tonnes CO2 = 679 million tonnes CO2


Remember that this project doesn't generate any energy, it merely stores energy generated elswhwere, so there's no "carbon offset" involved.
This pumped-storage hydro scheme would allow intermittent renewables to supply power 24/7 so it should get part of the credit for the carbon dioxide not emitted.

Nuclear power has the lowest carbon footprint of all energy sources, at about 4 gram per kWh so you would need 37,500 GWh of additional free wind energy to repay the carbon cost of building the project. Except that wind actually has a higher carbon footprint than nuclear, so if you wanted to reduce the overall carbon emission of the electricity grid you would do better to replace all the fossil plant with nuclear: no storage problem, no additional land requirement, and no additional transmission grid capacity.
What is the carbon footprint of Chernobyl or Fukushima and who is wasting time counting that when the radiation poisoning footprint of a nuclear disaster is what matters most anyway?

But the SNP is pledged to a non-nuclear Scotland!
I favour retention of the British nuclear deterrent on the Clyde.


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