Renewables North of the Border...

[DaveS]

They do something similar from a Loch above Loch Ness. (However the power that stores is tiny. I remember being amazed that it was even enough for smoothing.)

Foyers is rated at 300 MW (2 X 150 MW sets) which, while not huge, is approaching half the rating of a standard 660 MW thermal generating set, so can't in fairness be described as tiny either. Cruachan was originally rated at 400 MW (4 X 100 MW sets) but was uprated recently to (I think) 440 MW.

To put this in context the aggregate capacity of Scotland's conventional hydro electric generation is around 1200 MW.

However a pump storage scheme stores energy rather than power (obviously ), and since running continuously the upper reservoir can be emptied or filled in about 20 hours, the energy storage capacities of Foyers and Cruachan are about 6 GWh and 9 GWh respectively.

[DaveS]

Hydrogen has this usefull ability to go straight up when it leaks.

Indeed.

Not a rhetorical question, but does anyone know where hydrogen lies on the spectrum of greenhouse gas effectiveness?

[Nick]

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From Greenhouse Gas Online:

Hydrogen (H2) is similar to carbon monoxide in that it acts as an indirect greenhouse gas through its effect on hydroxyl (OH) radicals. By reducing the levels of OH in the atmosphere, hydrogen increases the lifetime of some direct greenhouse gases, such as methane.

Much hydrogen is itself produced in the atmopshere by the oxidation of methane, with total global emisssions estimated to be about 70 million tonnes each year. As well as removal in the atmopshere by its reaction with OH, significant amounts of hydrogen are also taken up by soil microorganisms.

Human Impact
Currently man is responsible for around half of total hydrogen emissions, with the most important man-made source being fossil fuel burning. Overall, the indirect action of hydrogen as a greenhouse gas, through its reaction with OH radicals, is not currently of huge importance. However, future developments in hydrogen based power supplies could lead to substantial increases in hydrogen emissions.

Potential for control
Future development of hydrogen based fuel sources should include an awareness of hydrogen as an indirect greenhouse gas.

[Nick]

They do something similar from a Loch above Loch Ness. (However the power that stores is tiny. I remember being amazed that it was even enough for smoothing.)

Foyers is rated at 300 MW (2 X 150 MW sets) which, while not huge, is approaching half the rating of a standard 660 MW thermal generating set, so can't in fairness be described as tiny either. Cruachan was originally rated at 400 MW (4 X 100 MW sets) but was uprated recently to (I think) 440 MW.

To put this in context the aggregate capacity of Scotland's conventional hydro electric generation is around 1200 MW.

However a pump storage scheme stores energy rather than power (obviously ), and since running continuously the upper reservoir can be emptied or filled in about 20 hours, the energy storage capacities of Foyers and Cruachan are about 6 GWh and 9 GWh respectively.

Today's blog entry is about Pumped Storage Hydro In Scotland .

[Arghiro]

I don't understand your problem. There is so much hot air up there that air capture heat pumps must be highly cost effective.

[Rowana]

I don't understand your problem. There is so much hot air up there that air capture heat pumps must be highly cost effective.

I agree! Put a few in that expensive monstrosity in Edinburgh. That's all it's good for, and they produce enough hot air for the lot of us!

{/rant}

[ParaHandy]

... can be emptied or filled in about 20 hours, the energy storage capacities of Foyers and Cruachan are about 6 GWh and 9 GWh respectively.

My own experience of the Hydro pumped schemes was being dragged round a damp and smelly cavern and, upon being asked whether I had a question, I blethered on about cost of filling the loch up again. Geezer snorted and asked what kind of idiot d'you think we are, we wait until it pisses down. From this insight 40 years ago I presume that recharging the batteries still costs an awful lot more than what you get back in charge.

For what its worth you can make a reasonable stab at how you might organise large scale energy storage using last month's consumption data. January is typically the peak demand month of the year. If you had 45GW of capacity you would need an average of 42GWHr stored capacity which would require the application of 77GWHr of energy over 12 hours to achieve and, of that 42GWHr, at least 8GWHr has to be capable of being released in 1 hour - equivalent to 4 very big power stations. I chose a base of 45GW because demand is "equidistant" in terms of time about that value in a 24hr cycle. Demand itself was a max of 53GW and minimum of 34GW. If you drop the base to 40GW then the energy cycle is unbalanced; there would be less time for regeneration than generation which would be, I think, untenable, and the stored energy soars threefold to 120GWHr.

The first observation about storage is that whatever system you adopt, it can not be simplex ie working in only one direction at a time; it has to be duplex which effectively rules out any pumped storage system. The reason for this is you will most likely be a net consumer or generator of your stored power for 12 hours in a 24 hour cycle; you would simply not have the time to regenerate a 24 hour cycle system in less than 12 hour. Its a quite sublime application of Newton's law of energy conservation (with a dab of modern logic flung in). If you were to extend the cycle, say 48 hours, then the stored energy requirement becomes an unimaginably large figure and the cost soars. Cost can only be controlled if you regenerate during the offpeak hours.

Its quite obvious that you have to site the stored energy facility close to where it is consumed. A lot of power has to be delivered very quickly and the further it is away, the greater are friction losses.

A further observation is that this only works with non-intermittent variables; at least, that is true of such a mathematical model as I propose and which would thus rule out wind power.

[DaveS]

... can be emptied or filled in about 20 hours, the energy storage capacities of Foyers and Cruachan are about 6 GWh and 9 GWh respectively.

My own experience of the Hydro pumped schemes was being dragged round a damp and smelly cavern and, upon being asked whether I had a question, I blethered on about cost of filling the loch up again. Geezer snorted and asked what kind of idiot d'you think we are, we wait until it pisses down. From this insight 40 years ago I presume that recharging the batteries still costs an awful lot more than what you get back in charge.

For what its worth you can make a reasonable stab at how you might organise large scale energy storage using last month's consumption data. January is typically the peak demand month of the year. If you had 45GW of capacity you would need an average of 42GWHr stored capacity which would require the application of 77GWHr of energy over 12 hours to achieve and, of that 42GWHr, at least 8GWHr has to be capable of being released in 1 hour - equivalent to 4 very big power stations. I chose a base of 45GW because demand is "equidistant" in terms of time about that value in a 24hr cycle. Demand itself was a max of 53GW and minimum of 34GW. If you drop the base to 40GW then the energy cycle is unbalanced; there would be less time for regeneration than generation which would be, I think, untenable, and the stored energy soars threefold to 120GWHr.

The first observation about storage is that whatever system you adopt, it can not be simplex ie working in only one direction at a time; it has to be duplex which effectively rules out any pumped storage system. The reason for this is you will most likely be a net consumer or generator of your stored power for 12 hours in a 24 hour cycle; you would simply not have the time to regenerate a 24 hour cycle system in less than 12 hour. Its a quite sublime application of Newton's law of energy conservation (with a dab of modern logic flung in). If you were to extend the cycle, say 48 hours, then the stored energy requirement becomes an unimaginably large figure and the cost soars. Cost can only be controlled if you regenerate during the offpeak hours.

Its quite obvious that you have to site the stored energy facility close to where it is consumed. A lot of power has to be delivered very quickly and the further it is away, the greater are friction losses.

A further observation is that this only works with non-intermittent variables; at least, that is true of such a mathematical model as I propose and which would thus rule out wind power.

Well, where to start?

Firstly, I'm glad that my energy storage figures of about 6 GWh & 9 GWh based on memory agree with Webbie's quoted 6.3 GWh & 8.8 GWh.

There is some truth in your man's remark. In round numbers both generating and pumping is about 90% efficient, giving a storage cycle efficiency of 81%. However, captured rainfall adds to the upper reservoir - and a network of pipes captures burns further afield to increase the overall catchment area - so more water goes down the hill than is pumped up. The net result is an average storage cycle efficiency of around 90%, and more when there's heavy rain.

Your demand figures are, I presume, for GB (excluding? interconnectors). I must say that the idea of using storage to entirely balance the entire daily GB demand is heroic, and beyond anything I've ever seen previously considered. I would seriously question the practicability of this. IMHO there will always be the need for some load following generation which, combined with dynamically scheduled load, can go a long way towards achieving what's wanted. On a smaller scale this is certainly so. Prior to introduction of the current NETA / BETA trading system, and using these techniques, the South of Scotland winter load curve was essentially flat, with a peak around 1800 and a dip at around 0500 of similar energy volumes. Cruachan was used to transfer one into the other leaving a virtually flat generation steam line, i.e. a single set could be used for (quite limited) load following, the rest running flat out or stopped. In efficiency terms it really doesn't get much better. All gone now, of course, for the "benefits" of unrestrained market competition.

I think I understand your point re. balancing pumping & generation, but would point out that that is one reason why Cruachan & Foyers were designed with lower MW capacity than the dams could theoretically support: the margin means that there is no need to achieve perfect daily balance, so e.g. it is possible to deplete the upper reservoir Monday to Friday then fill it up again over the weekend.

I disagree with your point re. siting of storage to avoid friction. Despite persistent rumours to the contrary, electricity transmission is actually quite efficient - around 98% on average. This is why most of the big English coal burners were sited in Yorkshire - it's cheaper to move electricty by wires than coal by trains.

There is scope for increasing storage capacity through the installation of pumps at conventional hydro stations. Webcraft's source mentions Hydro's plans for Sloy. For bulk energy storage (as opposed to short term stability response) there is no requirement for the sophistication of reversible pump storage systems - a big industrial pump is quite good enough.

[ParaHandy]

[Your demand figures are, I presume, for GB (excluding? interconnectors). I must say that the idea of using storage to entirely balance the entire daily GB demand is heroic, and beyond anything I've ever seen previously considered. I would seriously question the practicability of this.

Scotland never signed up to OFGEM's reporting regime, I can't find any data after 2001, but divide my data by 10 and you'll be about right for Scotland and the storage numbers work if you're prepared to risk not having load following generation. My data attempts to show the quantum of a UK storage scheme and probably not very well judging by your reaction. If a storage system had any advantage then we'd have had more of them irrespective of whether renewables are contributing. What data there is coming out of the Scottish Parliament indicates that facilities like Cruachan consumed in 2001 as much power as they generated (5,000GWhr) and were operating then probably to full capacity.

The "Scottish question" is one that I was attempting to address which is if Salmon's plans come to fruition there will be a substantial surplus of (renewable) power which he hopes the rest of the UK will buy off him. He's ramming through a new power line from the north to the central belt which is a mark of his intent. His problem is a simple commercial one: have the power available at 1800 and he'll get over 8p a kwhr, any other time and its worth less than 4p. To hit that timing with an intermittent power source requires storage and I can't see how the power delivered will ever cost less than what he'll be paid. (Or is this just to offset his non-nuclear policy?)

[Nick]

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The other interesting storage technology is underwater compressed air - big bags on the seabed around offshore windfarms which will be filled in times of windy plenty then released to (presumably) run through turbines of some sort when the wind stops. Problem with all these things is we already have the technology and the political agenda to put up thousands of turbines long before the interconnectors or any methods of dealing with the intermittency are deployed.

Will the fuses blow? Can she tak it Cap'n Eck?

BTW, if anyone knowledgeable (basicly I think that's Para and Dave, the rest of you one step back please) would care to comment on any article in the Scots Renewables blog it would at least help make it look as though someone was reading it.

[DaveS]

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The other interesting storage technology is underwater compressed air - big bags on the seabed around offshore windfarms which will be filled in times of windy plenty then released to (presumably) run through turbines of some sort when the wind stops. Problem with all these things is we already have the technology and the political agenda to put up thousands of turbines long before the interconnectors or any methods of dealing with the intermittency are deployed.

Will the fuses blow? Can she tak it Cap'n Eck?

BTW, if anyone knowledgeable (basicly I think that's Para and Dave, the rest of you one step back please) would care to comment on any article in the Scots Renewables blog it would at least help make it look as though someone was reading it.

Compressed air storage has intrinsic problems. Consider that compressing the air requires a rising pressure and a diminishing flow rate as the reservoir fills. It is very difficult to optimise a pump (or any other machine) for such a varying load. Similarly with generating, although recent developments in maximum power point tracking can help a bit. I would be surprised, however, if an overall cycle efficiency of much above 60% could be achieved. There is, of course, no equivalent of pump storage technology's "free lunch" of precipitation capture. Similar considerations apply to flywheel storage, phase change, and the various other techniques which get re-invented every 10 years or so.

Cap'n Eck has a problem. If he could put aside his appallingly blinkered negative view of nuclear (currently supplying about 50% of Scotland's electricity from 2 power stations), and agree to the replacement on life expiry of the current nuclear capacity as a pragmatic medium term fix, he would buy ample time to properly and economically develop the renewable technologies which could, in principle and given realistic development time, supply all Scotland's electricity needs. By discounting nuclear, even for the medium term, he makes this process much dearer as money is thrown with increasing desparation at all sorts of projects, sensible and otherwise. And there is absolutely no guarantee that the gamble will succeed and the lights will stay on.

I, personally, would quite like to see an independent Scotland, but not at the expense of becoming a third world country. I resigned my membership of the SNP many years ago when they adopted their puerile "Nuclear free with SNP" stance.

[Nick]

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The other interesting storage technology is underwater compressed air - big bags on the seabed around offshore windfarms which will be filled in times of windy plenty then released to (presumably) run through turbines of some sort when the wind stops. Problem with all these things is we already have the technology and the political agenda to put up thousands of turbines long before the interconnectors or any methods of dealing with the intermittency are deployed.

Will the fuses blow? Can she tak it Cap'n Eck?

BTW, if anyone knowledgeable (basicly I think that's Para and Dave, the rest of you one step back please) would care to comment on any article in the Scots Renewables blog it would at least help make it look as though someone was reading it.

Compressed air storage has intrinsic problems. Consider that compressing the air requires a rising pressure and a diminishing flow rate as the reservoir fills. It is very difficult to optimise a pump (or any other machine) for such a varying load. Similarly with generating, although recent developments in maximum power point tracking can help a bit. I would be surprised, however, if an overall cycle efficiency of much above 60% could be achieved. There is, of course, no equivalent of pump storage technology's "free lunch" of precipitation capture. Similar considerations apply to flywheel storage, phase change, and the various other techniques which get re-invented every 10 years or so.

Cap'n Eck has a problem. If he could put aside his appallingly blinkered negative view of nuclear (currently supplying about 50% of Scotland's electricity from 2 power stations), and agree to the replacement on life expiry of the current nuclear capacity as a pragmatic medium term fix, he would buy ample time to properly and economically develop the renewable technologies which could, in principle and given realistic development time, supply all Scotland's electricity needs. By discounting nuclear, even for the medium term, he makes this process much dearer as money is thrown with increasing desparation at all sorts of projects, sensible and otherwise. And there is absolutely no guarantee that the gamble will succeed and the lights will stay on.

I, personally, would quite like to see an independent Scotland, but not at the expense of becoming a third world country. I resigned my membership of the SNP many years ago when they adopted their puerile "Nuclear free with SNP" stance.

If Scotland is going to put up the insane forest of windmills currently on the drawing board then inefficencies of storage technogies won't matter as we will have a ludicrously huge surplus generating capacity and 60% efficiency - or even less - will do nicely. My main worry is that we are going to put in all this intermittent generating capacity long before any storage technology - efficient or otherwise - is ready to cope with the load. Where is all ths juice going to go?

IF - and it's a big if - the storage problem is addressed at the same time as we erect these damn windmills then maybe wee Eck isn't as mad as he at first seems. I don't think he is necessarily leading us into the generating wilderness, but time will tell. Looking at the shenanigans at Olkiluoto and Flamanville I think the UK government has left a new nukes programme far too late anyway, and Scotland may well be keeping the lights on doon sooth with windpower through the interconnector in six years time.

Keep the faith!

[Arghiro]

My main worry is that we are going to put in all this intermittent generating capacity long before any storage technology - efficient or otherwise - is ready to cope with the load. Where is all ths juice going to go?

I expect that they plan to sell it to England/ France et al, after all, the wind blows in different places at different times. It is probable that you will have too much when we don't have enough & maybe even vice versa on odd occasions. It is not unusual for Channel gales to occur at the same time as Scottish calms.

In my view (from one pace backwards following Nick's offensive comment ) the issue is one of antiquated oil fired stations that were designed for base load & can't easily be shut down quickly. At least the Nukes can be switched on & off in reasonable time scales.

With variable loads AND variable supplies matching NEEDS a flexible set of base supply stations that can be shut down (reducing running costs - which probably isn't true of Nukes) at will. I can see that the Scottish Hydro stations with remote auto controls might be a good way of interfacing with variable wind power gennys. Hydro may not be reduced cost when shut down, but the stored water is easily held for the days when it is needed which means that both the Hydro & wind are more cost effective when they work together. Or is that too obvious for you experts?

I await your comments with interest.

[Nick]

In my view (from one pace backwards following Nick's offensive comment ) the issue is one of antiquated oil fired stations that were designed for base load & can't easily be shut down quickly. At least the Nukes can be switched on & off in reasonable time scales.

With variable loads AND variable supplies matching NEEDS a flexible set of base supply stations that can be shut down (reducing running costs - which probably isn't true of Nukes) at will. I can see that the Scottish Hydro stations with remote auto controls might be a good way of interfacing with variable wind power gennys. Hydro may not be reduced cost when shut down, but the stored water is easily held for the days when it is needed which means that both the Hydro & wind are more cost effective when they work together. Or is that too obvious for you experts?

The Scottish hydro staions already have remote controls and can be brought onstream in about two minutes. At the moment this is largely done in response to price fluctuations rather than to ensure continuity of supply. There is insufficient standby hydro capacity to deal with the introduction of even the 6GW of extra windpower planned for Scotland, let alone the 30GW on the UK drawing board, which is why we need either storage or some form of renewable that can supply base load (or nukes . . . )

What offensive comment btw? Shirley shome mishtake . . .

[Arghiro]

So the Nukes & Hydro together (as relatively quick response units) will do nicely then?

BTW, why is Hydro no longer considered a good option? I doubt it is lack of suitable sites, could it be the escalation of labour costs on the capital works required, or the perceived eco-impact of flooding valleys? I would have thought that building a few more Hydros would be a relatively quick way of filling gaps in the supply.

But what do I know?