[evan_au]

an unimaginable capital expenditure on electric transport

the lifetime cost of electric cars is becoming cheaper than petrol cars

I was very surprised recently when a colleague decided to replace his petrol car by a hybrid car, on economic grounds. Part of this was the observation that the hybrid has a higher resale value than a petrol car of the same age. I always thought that they carried a significant cost premium.

A move from petrol to hybrids brings a significant reduction in dinosaur consumption*, provided you don't use the airconditioning too much.

A major takeup of all-electric cars (and smartphones and smart watches) depends on further advances in battery technology; unfortunately, this is an area of technology which is not progressing particularly quickly.

* OK, according to current theories, most carbon-based fossil fuels come from the Carboniferous period, which predates the dinosaurs.

[wolfekeeper]

A major takeup of all-electric cars (and smartphones and smart watches) depends on further advances in battery technology; unfortunately, this is an area of technology which is not progressing particularly quickly.

No, that's false. The main problem that is stopping people buying the cars right now, is purchase price, but the cost of the battery (which is the primary cost item) is dropping 8% year on year due to economies of scale. The limited range is rarely the issue that people think it would be (some people really do regularly do long distances and they would be better off with a hybrid or a diesel.) The UK has a pretty good charging infrastructure now and it's likely to further improve.

[Scottish Scientist]

Thank you for your feedback wolfekeeper.

The only thing I disagree with in the model is that you're assuming only wind and pumped storage.

Well what is it about my model that you agree with then?

In the real world we have solar coming up. It's running behind wind because it's more expensive than it, and much more expensive than burning dinosaurs... but it's starting to be cheaper than metered electricity from the grid. When that happens the price of the metered electricity from the grid will start to go up; more of the electricity will be peaking electricity. This will push installation of solar ever harder, because it's cheaper to the end user, and the grid will get greener.

Also, wind and solar are anti-correlated.

During the summer, the wind is relatively low, but solar goes up. Vice versa in the winter.

Which very strongly suggests to me that I should extend my model to include power from solar as well.

Solar power in the United Kingdom
"In 2014, the almost 650,000 solar installations had a total capacity of over 5,000 MW of solar power."
http://en.wikipedia.org/wiki/Solar_power_in_the_United_Kingdom

Which makes me disappointed indeed that the Gridwatch site, http://www.gridwatch.templar.co.uk/ from where I downloaded the demand and wind power data http://www.gridwatch.templar.co.uk/download.php does not include any data relating to solar power.  []

Does anyone know where data for solar-generated MW with time for the UK can be found? I mean like how much every 5 minutes like Gridwatch -

How Gridwatch data is downloaded, in a format that can be uploaded by a spreadsheet ...

id, timestamp, demand, wind
403446, 2015-04-01 00:05:03, 26774, 5590
403447, 2015-04-01 00:10:02, 26993, 5571
403448, 2015-04-01 00:15:02, 27252, 5566

- or how much every hour would be excellent too, but how much every week is no good for simulating how it interacts with wind intermittency. Daily values might be of marginal interest.

Anyone? Who knows where UK solar-generation data can be had? Come on! Speak up!  [?]

So, electric cars; the pumped storage stuff may not be needed.

The Scottish government has approved a plan to build a pumped-storage hydro scheme at Coire Glas, Scotland, proposed by the SSE, http://sse.com/whatwedo/ourprojectsandassets/renewables/CoireGlas/

but, frustratingly, has not been given financial incentives from UK policy.
I'm not the only Scot who is pointing this glaring omission out.

"Scottish Renewables – Pumped Storage – Position Paper"
http://www.scottishrenewables.com/media/uploads/140529_scottish_renewables_pumped_storage_position_paper.pdf

So I really need to accuse UK Secretary of State for Energy and Climate Change Ed Davey, and the UK government of Cameron & Clegg for really failing Scotland and Britain very badly on pumped-storage hydro.  [!]

I can't really in any way agree with any kind of statement which lets that lot of rubbish UK politicians off the hook for not incentivizing or bankrolling the urgently-needed pumped-storage hydro.

If I am to be expected to discuss electric cars for energy storage, it needs to be after said politicians have been thoroughly named, shamed and turfed out of office, a better government is elected and all planned pumped-storage hydro plans are fully funded and going ahead to construction.

The fundamental point is that the more you add different types of sources and other storage to the mix, the more the variations even out. So the full 290 GW may not be needed; that gives on average maybe 70 GW or a little less, but to the extent other sources provide power, this can be reduced.

A very interesting fundamental point and if I can source solar generation data with time, I'll see what I can do to extend my model to investigate it.

Thanks again for your feedback wolfekeeper.  []

[wolfekeeper]

National grid do a far g(r)eekier version:

http://www.bmreports.com/bsp/bsp_home.htm

From there I managed to find this:

https://www2.bmreports.com/bmrs/?q=actgenration/actualorestimated

That might only be today's though, I didn't look at it too carefully, but if you hunt around you might find more.

edit: no you can select any day over a wide range and get the data.

[Scottish Scientist]

National grid do a far g(r)eekier version:

http://www.bmreports.com/bsp/bsp_home.htm

From there I managed to find this:

https://www2.bmreports.com/bmrs/?q=actgenration/actualorestimated

That might only be today's though, I didn't look at it too carefully, but if you hunt around you might find more.

edit: no you can select any day over a wide range and get the data.

Great find wolfekeeper!  [8]
Even the guy from gridwatch didn't seem to know about any solar data available. I will investigate further later and report back but the BM Reports site seems to be unresponsive right now.

[wolfekeeper]

I imagine the solar figures are estimates based on weather and PV installation data: the national grid need a model of it to improve their demand estimates.

[alancalverd]

The Scottish government has approved a plan to build a pumped-storage hydro scheme at Coire Glas, Scotland, proposed by the SSE, http://sse.com/whatwedo/ourprojectsandassets/renewables/CoireGlas/

but, frustratingly, has not been given financial incentives from UK policy.
I'm not the only Scot who is pointing this glaring omission out.

It's not an omission. It's called "preparing for independence". For as long as SNP policy is to appropriate UK-owned energy sources and sell the product to the remainder of the Kingdom, you will have to fund your own capital projects.   

The UK has a pretty good charging infrastructure now and it's likely to further improve.

Reading Motorway Services has parking space for about 600 cars and 100 trucks, with two recharging points. OK for "early adopters" (I've never seen either charging point occupied!) but a long way short of providing an adequate replacement for liquid fuels. And as I am sure SS will agree, if you replace all road transport with electric vehicles, you will need to double your entire grid capacity: generation, distribution and storage. No problem, as long as the cost only falls on the users of electric vehicles (why  not? Petrol companies are not charities and not subsidised by the taxpayer - the entire extraction, refinement and distribution system is paid for by the user, who also pays 120% tax to support "alternatives"!)

[Scottish Scientist]

National grid do a far g(r)eekier version:

http://www.bmreports.com/bsp/bsp_home.htm

From there I managed to find this:

https://www2.bmreports.com/bmrs/?q=actgenration/actualorestimated

"Actual Or Estimated Wind And Solar Power Generation (B1630)"

That might only be today's though, I didn't look at it too carefully, but if you hunt around you might find more.

edit: no you can select any day over a wide range and get the data.

You can select the year back to "1999" but get "No results" for selected dates earlier than about Christmas holidays 2014. The data doesn't look reliable. Highly corrupt or random data in places.

There's also "solar" data included here -
"Actual Aggregated Generation Per Type (B1620)"
https://www2.bmreports.com/bmrs/?q=actgenration/actualaggregated

I imagine the solar figures are estimates based on weather and PV installation data: the national grid need a model of it to improve their demand estimates.

The guy from Gridwatch says "that is estimated and its not real time. ..Its the guess for a days worth".

I asked him if he knew where to find solar data but he didn't offer much hope.

It doesn't exist. I've been looking for years. Its all small scale stuff and no one knows until people send in their bills how much it has generated.  Or how much fraud is going on.

How can you collect real-time data from a million rooftop solar panels? Even if you could,. how could you tell if it was really solar energy or someone driving an inverter from next doors supply, or from a diesel generator?

You can guess at how much is being generated by looking at the midday dip in the 'demand' figures. But its only a guess.

Hmmm. []

The Scottish government has approved a plan to build a pumped-storage hydro scheme at Coire Glas, Scotland, proposed by the SSE, http://sse.com/whatwedo/ourprojectsandassets/renewables/CoireGlas/

but, frustratingly, has not been given financial incentives from UK policy.
I'm not the only Scot who is pointing this glaring omission out.

It's not an omission. It's called "preparing for independence". For as long as SNP policy is to appropriate UK-owned energy sources and sell the product to the remainder of the Kingdom, you will have to fund your own capital projects.

Well we can still co-operate on joint projects even if Scotland goes independent, as per the Channel Tunnel which was a British - French venture, as was Concorde, as is Airbus. The fact that the UK and France are independent countries didn't stop us co-operating on a joint ventures for mutual benefit.

So let's co-operate, as Britons, but also as Europeans.

I was thinking, if we are needing to use solar then let's do it right.


"Solar power in the United Kingdom"
http://en.wikipedia.org/wiki/Solar_power_in_the_United_Kingdom

What Europe needs is a whole lot of mass-arrays of solar photo-voltaic panels somewhere near the south of Spain, either on land, or if the Spanish need their land for growing grapes or whatever, how about on artificial floating islands somewhere off Gibraltar?

Maybe north Africa wants in too? There's a lot of sun in Morocco across the Gibraltar Strait. Maybe Morocco would like to sign a 50- or 100-year lease to the European Union for some land in Morocco to put solar photovoltaic arrays on? We could make it worth their while. Guarantee the deal by deploying a European military force to guard our solar PV arrays and the interconnector carrying the power back to Europe. [O8)]

So the Mediterranean or thereabouts for solar, everywhere for wind, Scotland for pumped-storage hydro.

If we pull together as Europeans, we can take advantage of the best renewable resources and share the spoils amongst us all. Everyone wins if we co-operate. If we retreat into our bunkers, everybody loses.

We need to be co-operating and national independence should be not be viewed as "a barrier" to co-operation on joint projects for mutual benefit. The multi-national companies have figured that out years ago so here and now we all also need the independent national public sectors to remember the benefits of working together, right?

[wolfekeeper]

The UK has a pretty good charging infrastructure now and it's likely to further improve.

Reading Motorway Services has parking space for about 600 cars and 100 trucks, with two recharging points. OK for "early adopters" (I've never seen either charging point occupied!) but a long way short of providing an adequate replacement for liquid fuels.

Right.... so you've never seen either of them occupied, but you "know" that it's not adequate? Do you have these 'intuitions' often???

And as I am sure SS will agree, if you replace all road transport with electric vehicles, you will need to double your entire grid capacity: generation, distribution and storage. No problem, as long as the cost only falls on the users of electric vehicles (why  not? Petrol companies are not charities and not subsidised by the taxpayer - the entire extraction, refinement and distribution system is paid for by the user, who also pays 120% tax to support "alternatives"!)

Right.... it's a 'funny' thing, none of the electric car adopters have reported their electricity bill doubling. It's almost like you're talking bullshit, but you would never do that, right?

Electric cars do, on average 25 miles per day. They use 0.15-0.25kWh per mile. So let's take the upper of those two figures. That's about 6.25kWh/day.

Let's further assume that all of the cars in the UK become electric. There's 35 million cars in the UK.

So that's 6.25 * 35,000,000 * 365 = 79 billion kWh.

Meanwhile the UK grids output in (say) 2012 was 375 TWh.

If you divide one by the other you get 21%; most of which would be done at night, when the grid is quiet, and that's assuming worst case 0.25 kWh per mile. More normally electric cars get more like 0.15 kWh/mile.

So nothing like doubling.

And that's going to take a decade or two to achieve.

Meanwhile, people are installing solar panels... currently at a faster rate than they're buying electric cars.

A 1kW (peak) solar panel in London makes very roughly 3kWh of electricity per day, on average. That's about 5 square metres. The car uses 4kWh.

[alancalverd]

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.

Yes, electric transport is great for urban use. I am all in favour of electric taxis, trolleybuses, trams and underground trains, but quoting "average daily mileage" does not make the electric car practicable for intercity use, or desirable in town.

[wolfekeeper]

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.

[alancalverd]

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.

[wolfekeeper]

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.

[alancalverd]

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.

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?     

[wolfekeeper]

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.

[alancalverd]

Really, this is not hard.

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

[wolfekeeper]

No, but buying shares in services stations might be profitable.

[alancalverd]

Chicken! This is, apparently, a self-financing no-brainer, led by an acknowledged expert. You should be selling shares, not buying them!

[Scottish Scientist]

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

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

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/

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

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.

[Scottish Scientist]

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

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/
 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
 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
 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/
 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
 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!