[RD]

It needn't be a balloon. A steel can will do quite nicely, and it doesn't need to be very deep under the ocean: the domestic gas supply pressure is only a meter of water gauge or less. The deeper it is, the more efficient, but large steel cans are very cheap and easy to make.

Scottish Scientist was suggesting storing the hydrogen at depth (~100m)

Deeper seas are better because the water pressure is proportional to the depth allowing the hydrogen to be compressed more densely, so that more hydrogen and more energy can be stored in an inflatable gas-bag.

Building a heavy-duty "gasometer" made of steel, on the sea-floor, 100m below the surface of the salty-sea, sounds very-expensive and impractical to me : It will be bigger than a military submarine , and they cost over a billion dollars each.

[alancalverd]

Hence the reason for a low-pressure steel tank  - far simpler, and the weight of the tank provides the driving force to pump the gas.

[Scottish Scientist]

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

But (a) you state we only need an average of about 60 GW

No I didn't. In the context of "60 GW" I was not talking about "we" but "the UK" and not "an average" but "peak".

Also I wasn't talking about anyone "needing" a peak demand.

Peak demand is a given and you use that given to model how much energy storage capacity you need to match up with and back up that given peak demand.

Alternatively, if one has a energy storage capacity available one can predict how much of a peak demand one can offer to use the energy storage to back up.

However peak demand is not something one, or my plan, "needs" per se.

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.

and (b) wind currently produces rather less than one third of its peak capacity

True enough. Is your point intended to be along the lines of your previous comment?

Diplodocus 2. We use electricity because it is cheapish and reliable. Given that you will need to install at least 3 times overcapacity (possibly 7 times on my assumptions)

I've recommended nameplate maximum wind power = 5.5 times peak demand.

The figures I gave were very clear - for Scotland 33GW/6GW = 5.5, for UK 290GW/52.5GW = 5.5

I'm not sure where you get "3" or "7" from?

My "5.5 x peak demand" recommendation is based on my modelling of a wind power & pumped-storage hydro only renewables system.

For such a wind & pumped-storage system, I also recommended matching peak power in GW equal to energy storage in GW-days divided by 1.11.

So for a wind & pumped-storage hydro only system with

• 280 GW-days energy storage,

I recommend being able to back up only

• a peak demand power of only 280/1.11 = 252 GW,
• an average demand power of only 252/1.6 = 157 GW

and commensurate with those figures,

• a nameplate wind turbine maximum power capacity of 252 x 5.5 = 1386 GW

would be required to complete that system - a system which could span multiple countries in Europe, not just the UK.

To put this in perspective, in the whole of Europe there was (2013/4) only about 213 GW of wind and solar power generating capacity installed (though it increases every year) -

Wikipedia - Renewable energy in the European Union
http://en.wikipedia.org/wiki/Renewable_energy_in_the_European_Union

 - which would use up only 213/1390 = 15% of the balancing and backing-up capacity of this scheme.

So this "biggest-ever" scheme could meet all of Europe's future needs for balancing and backing up intermittent renewables even when intermittent renewable power generating capacity grows to more than 6 times what it is today.

The "264 GW" peak power and the 264/1.6 = 165 GW average power was not based on the computer modelling of wind & pumped-storage hydro systems but purely from the somewhat arbitrary maximum canal design flow rate of being able to empty my plan for a Strathdearn reservoir in a day and estimating what peak power could be generated from turbines for that particular maximum flow rate.

I used that 264 GW peak power generation to predict carbon dioxide saving without claiming I had a modelled system to demonstrate such a peak power production.

I've made no prediction as to how much nameplate wind power, solar power, biomass power or whatever renewable power might be required to help supply such a "264 GW" peak power or "165 GW" average power from this hydro-scheme plan as yet.

- and the best sites have already been used.

I just don't agree. I don't even agree with wind "farms" as such because I think huddling wind turbines together where they shelter each other from the wind is inefficient.

I would recommend instead deploying wind turbines in lines, more like the way pylons are deployed, but siting wind turbines on land on exposed high points or along ridges and for off-shore, in circular formations.

Note that your dam won't save (i.e. generate or reduce the need for) electricity, only embarrassment.

The hydro turbines generate electricity. The dam holds the water in the reservoir. I manage to generate my own embarrassment without the assistance of any dam.  [:I]

http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html

Calculated deaths per Terawatt hour

Wind power proponent and author Paul Gipe estimated in Wind Energy Comes of Age that the mortality rate for wind power from 1980–1994 was 0.4 deaths per terawatt-hour. Paul Gipe's estimate as of end 2000 was 0.15 deaths per TWh, a decline attributed to greater total cumulative generation.

Hydroelectric power was found to to have a fatality rate of 0.10 per TWh (883 fatalities for every TW·yr) in the period 1969–1996

Nuclear power is about 0.04 deaths/TWh.

So if we add hydropower storage to wind, it's altogether about 6 times more dangerous than nuclear.

That's good to know for new portable nuclear power which I support but not convincing enough for me to support new-build nuclear power stations for the grid.

[RD]

Back to the gas-bags ...

Approximately 1 m³ of air at ambient pressure is required per tonne of lift.

http://en.wikipedia.org/wiki/Lifting_bag#Filling_lift_bags

So if your hydrogen gas-bag was 300 m³, (approximately as big as a house), the buoyancy force would be around 300 tonnes. If the bag was a cube the [5] surface area would be 224 square meters, so the pressure would be 1.34* tons per square meter. 

 * I'd throw in a factor of ten to be on the safe side, so you're looking for fabric/membrane for your gas-bag which can withstand a pressure of around 13 tonnes per square meter, indefinitely. Does such a thing exist ?  [ that pressure is about the same as for a car-tyre, which is reinforced with steel & nylon/kevlar ].

If the gas-bag was even bigger, the required strength per square meter for the envelope would have to increase. So the properties of materials currently available will set an upper-limit on the maximum size of such a gas-bag. A house-sized bag would only contain enough gas to heat A house for about a week in winter.

[wolfekeeper]

1.3 tonnes per square metre is only a fraction of 1 atmosphere.

The highest pressures I can think of off-hand from a flexible fabric would be the Bigelow space stations. They're pressurised to around 70 kPa- about 7 tonnes per square metre.

And I don't think there's a maximum diameter- you just put more layers of material down.

[RD]

1.3 tonnes per square metre is only a fraction of 1 atmosphere.

You haven't added in the 10x safety-margin , which would make it "only" around atmospheric pressure ...

And I don't think there's a maximum diameter- you just put more layers of material down.

You're agreeing with me that you would have to increase the strength per square meter the bigger the envelope got. So as it gets larger at some point it's going to get impractical / unaffordable.

Building an envelope the size of a house to store a weeks worth of gas for one house seems uneconomic : there would have to be one per house. How much would a tyre the size of a house cost ? , then add the cost of making the floating platform with the solar cells and turbines , installing them and maintaining them at sea & under the sea. [ Oh and energy conversion losses of ~50% x1 or x3].

[alancalverd]

Building an envelope the size of a house to store a weeks worth of gas for one house seems uneconomic : there would have to be one per house. How much would a tyre the size of a house cost ?

...and yet, remarkably, hot air balloons fly quite well (I've flown them with a deadweight up to 5 tonnes, then packed them into the back of a Transit van) hydrogen balloons fly even better (Graf Zeppelin had a grand piano and nearly 100 tonnes of static lift) and half of the UK's power consumption already derives from gas. In fact within living memory, nearly all that gas was stored above ground as gaseous hydrogen and methane at less than 2 atmospheres pressure, and those gas tanks survived two world wars - as indeed did most of those around Europe.

[wolfekeeper]

1.3 tonnes per square metre is only a fraction of 1 atmosphere.

You haven't added in the 10x safety-margin , which would make it "only" around atmospheric pressure ...

Nope, there's already a safety margin. It's a pressure vessel. Pressure vessels are potentially insanely dangerous, that's why there's ALWAYS a safety margin.

And I don't think there's a maximum diameter- you just put more layers of material down.

You're agreeing with me that you would have to increase the strength per square meter the bigger the envelope got. So as it gets larger at some point it's going to get impractical / unaffordable.

Nope. Again, it's a pressure vessel. Pressure vessels for gases have a mass that is strictly proportional to the mass of gas they can hold. So if it's cost effective at some size, it's cost effective at all proportionately bigger sizes.

edit: see

https://en.wikipedia.org/wiki/Pressure_vessel#Gas_storage

edit2: submarines are similar, but they're designed for much high pressures, some of them can take thousands of atmospheres. That's also different because it's a compression, for compressive loads, steel works well. For tensile loads, kevlar is much lighter, stronger cheaper.

edit3: another example is fizzy drink bottles. A 2 litre, 6 atmosphere bottle weighs a few tens of grams and costs pence. A 2 litre, 1 atmosphere, compressive vacuum chamber would cost tens of pounds, and be made of glass or steel and be much, much heavier. It's a completely different thing.

[RD]

... it's a pressure vessel. Pressure vessels for gases have a mass that is strictly proportional to the mass of gas they can hold. So if it's cost effective at some size, it's cost effective at all proportionately bigger sizes.

We're agreed that the wall-strength will have to increase as the size of the envelope is is scaled-up. So the cost per unit area will increase as the envelope gets bigger if same material is used increasingly thickly.  My point was a fabric adequate for a lift-bag the size of a suitcase would not be adequate for a gas-bag the size of a house : the bigger version would have to be a better-specification to withstand the higher pressure, e.g. it would have to be thicker or reinforced or completely-different material.

In Scottish-Scientist's diagram the gas-bag resembles a hot-air balloon which are made of lightweight nylon, in practice the gas-bag will have to be more like the wall of a car-tyre.  A hot air-balloon costs about £10K ,  what will a car-tyre the size of house cost ?  $100K  ?, and each household would need one. It seems uneconomic.

... (Graf Zeppelin had a grand piano and nearly 100 tonnes of static lift) ... gas was stored above ground as gaseous hydrogen and methane at less than 2 atmospheres pressure, and those gas tanks survived two world wars - as indeed did most of those around Europe.

If you tried to sink a Zeppelin, or a gasometer, underwater they would burst before they were completely submerged because of the increased buoyancy force by [attempting to]  surround them with water, rather than the air they are usually surrounded by.

[alancalverd]

But if you inflate it deep under water, it stays compressed, like the swim bladder of a fish. Some deep-sea fish lead happy and useful lives at great depth but explode when brought to the surface.

[RD]

... like the swim bladder of a fish ...

Biomimicry : an excellent idea. What would a fish-bladder scaled-up to the size of a hot-air balloon cost to make ? , ( bear in mind the wall-strength of the bladder would have to increase proportionately ).   

( no pun intended :¬)

[alancalverd]

You seem to be under some misapprehension regarding the required wall strength of a vessel iin equilibrium. The pressure of the gas inside equals the pressure of the water outside, so there is no stretching or bending force in the wall. The only reason bathyscaphes and submarines have such thick walls is to keep the pressure inside much lower than the pressure outside.

If you ignore the mass of gas, the buoyancy force equals the weight of water displaced, which is fairly independent of depth. In the case of air balloons, we transmit the lift force to the load by enclosing the (hydrogen) balloon in a net or stitching load tapes into the fabric of a hot-air balloon. A big fishing net would do the job here.

[RD]

... the buoyancy force equals the weight of water displaced ...

Or to put that another way : the gas-bag would have to be strong enough to contain the same amount of water as it displaced, when on land, like those above-ground temporary back-yard swimming pools ...

 [ Invalid Attachment ]

... In the case of air balloons, we transmit the lift force to the load by enclosing the (hydrogen) balloon in a net or stitching load tapes into the fabric of a hot-air balloon. A big fishing net would do the job here.

Agreed : mesh-reinforcement is a solution, as exists in a car-tyre , which brings us back to the cost of making something similar to a car-tyre , but as big as a house, or hot-air balloon.

[Scottish Scientist]

Back to square one: it's 21 April, and so far only 4.5 days this unexceptional month with wind sufficient to generate 2 GW - the running mean is less than 10% of capacity. Time, I think, to review the statistics: as I suggested a few pages back, you need at least 14 days' storage at mean demand if you are going to use electricity as a reliable power source.

Interestingly, governments get upset and start putting emergency schemes into play when at-plant fossil fuel reserves fall below 5 days' worth. One can't help feeling that they know something about it.

The challenge was met on 9th April.

today is the seventh consecutive day with wind power at less than 2GW. In fact the running average is less than 1 GW for the past week.

As I say, I love a challenge and the low wind period just now is such a challenge, so I've run it through my model - normalised for a case study of the UK this time - and here's the results.


Click for full size image - https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_april2015.jpg

So there would still be some water left at this time in the 1400 GWh reservoirs with 290 GW installed wind power, but it is running low admittedly, so we'll have to wait to see if the wind can pick up to save the day or whether I will need to rethink my 1400 GWh / 290 GW recommendation.

I think you - or at least your customers - will find 24 hours' storage rather inadequate, even in a mild spring.

Remember I have tested these the equivalent of these 1400 GWh / 290 GW specifications (normalised for the case study of Scotland) on the spring of 2014 and it worked.

As you can see for this period in early April 2015, the design specifications of 1400 GWh / 290 GW have managed this period of low wind (so far) for longer than 24 hours of low wind.

This is because 1400GWh is 58.33 GW-days but the daily average of power demand is less than the peak demand of 52.5GW. Demand from April 1 to 9 2015 has varied between a minimum of  25649 MW and a maximum of 43069 MW.

This is because 1400GWh is 58.33 GW-days

Fine. But average demand for the last 8 days has been over 30 GW so you needed 240 GW-days to supply it. I don't think a 300% shortfall (and the wind is only just now picking up to 3 GW) is "nitpicking"!

It seems nitpicking when you don't acknowledge the graph I posted shows acceptable performance for the data available when I downloaded it which was up to the 9th April.

Your graph appears to show 60 GW of wind power on 7 April.

My graph is the result from a computer simulation of what wind power the UK would generate if the UK had installed 290GW of maximum wind power rather than just the 12GW we have installed just now.

So the grey line plots gridwatch data for wind power multiplied by a normalisation factor to indicate what wind power would have been produced had we 290 GW's worth of wind turbines installed. Understand?

Imagine 7 April is Groundhog Day but what Phil Connors (Bill Murray) does different this time is he installs 290 GW of wind turbines and 1400 GWh of pumped-storage hydro.

So the challenge was met from 1st to 9th April but Alan wanted to see more.

So I have run the Gridwatch data for the 1st to today 26th April through my model to see.


Click to view a larger image - https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_april_1_26_2015.jpg

So the configuration of 290GW nameplate of maximum wind turbine power and 1400 GWh maximum pumped-storage energy capacity would have performed well.  [8D]

Time for this Groundhog Day movie to end because the solution works. Phil Connors has got the girl.

[alancalverd]

Pretty good calculations, SS. Assuming 100% availability of your 290 GW installed wind power, you had 8 hours' reserve at the worst point in the last month. Given the usual standards for offshore (100-year) and nuclear (1000-year) adverse events, I wonder how much statistical data you would need to meet an acceptable criterion of confidence?

All we need do now is to find a substitute for the other 70% of the UK's energy consumption, and you will be a hero.

But most significantly, you have robustly shown that by adding 5.5 times more generating capacity than is required to meet actual demand, then (or preferably before then) building the world's largest hydroelectric scheme in the hope of never using it, and doubling the carrying capacity of the grid, we might, with luck, get back to where we are now, except that the rest of the UK will be beholden to Scotland.

I have never seen a more thorough and elegant demonstration of the political economic and practical futility of wind power. The physics seems impeccable, the statistics are sound, and I hope your papers get the publicity they deserve.

[alancalverd]

Or to put that another way : the gas-bag would have to be strong enough to contain the same amount of water as it displaced, when on land, like those above-ground temporary back-yard swimming pools ...

Not at all! The swimming pool has to be strong enough to carry the water because there's nothing supporting it outside. But a bubble of gas under water needs no container to stop it dissipating, only something to stop it rising. And at significant depth, the assembly will actually become less buoyant

Wetsuits are made from neoprene, impregnated with tiny air bubbles. When divers descend, these air bubbles are compressed and lose buoyancy. Wetsuits that provide 11 pounds/5 kilograms of buoyancy at the surface will only provide about 2.5 kg of buoyancy at 33 feet/10 meters where the ambient pressure is two atmospheres (ata). At an ambient pressure of five ata, which occurs at 130 feet/40 meters, its buoyancy will be reduced to about one kilogram. In addition to wetsuit compression, the gas spaces within a diver's body compress at depth, further reducing your buoyancy.

That's the problem that fish have to overcome: if they dive too deeply, the swim bladder gets compressed so they can't return to shallower water.

So no problem with an underwater gasbag: as long as it's deep enough, its buoyancy will be limited by the external pressure.

At 100 m depth, the ambient pressure is about 150 psi - a fairly convenient working pressure for gas transmission to the grid (though the main arteries work at about 1200 psi - say 800 m depth. - so you'd need boost pumps from most UK waters). The density of hydrogen at 100 m is about the same as atmospheric air, so no great problem with buoyancy, particularly if you use steel tanks rather than balloons.   

[wolfekeeper]

Presumably quite a lot of the primary energy for the UK is used to make electricity; if we get 1kWh of electricity from a fossil fuel that would have taken 2-3kWh of primary energy. Using wind changes that equation.

A lot of the rest of the energy will be things like heating in buildings and transportation. But heating energy can be reduced using heat pumps/air conditioners. They can make ~3 kWh of heat from 1 kWh of electricity.

And electric cars, again, a factor of ~3 improvement from going the electrical route. And they have built-in batteries. Sure, they're not as easy to use for long distances, but building a fast recharging infrastructure is better or worse than the equivalent amount of pumped storage??? Fast recharging is probably easier. And you could power them from (mostly unmetered) solar.

[RD]

...  a bubble of gas under water needs no container to stop it dissipating, only something to stop it rising ...

The fabric of the gas-bag will experience the buoyancy force, that force won't just exist in the tether anchoring the bag to the sea-floor.

... use steel tanks rather than balloons

Re-creating steel gas-holders, (aka gasometers), at the bottom of the sea would be hugely-expensive, even if made to the same specifications as the original land versions ...

 
http://en.wikipedia.org/wiki/Gas_holder

Guesstimate : around the same cost as an offshore oil-rig , hundreds of millions of pounds ?


http://en.wikipedia.org/wiki/File:Types_of_offshore_oil_and_gas_structures.jpg

[alancalverd]

Guesstimate : around the same cost as an offshore oil-rig , hundreds of millions of pounds ?

Why? The tank shouldn't cost much more than a tank of the same size on shore, and it doesn't need to be in particularly deep water, or indeed under water at all - as your photograph shows, we have a 200 year history of storing hydrogen in big tanks on the ground - as long as it is near a supply of water and bulk electricity.

[Scottish Scientist]

Careful here.

The measured wind output is 0.77 GW. That's about 1.5GW, because half is unmetered. This is coming from 12 GW of nameplate wind power.

Meanwhile Scottish Scientist called for 290GW of nameplate wind power.

So, if we had 290GW we would be getting 290/12 * 1.5 = 37 GW of power right now.

Hmm. That's not what I meant by "nameplate" which I meant interchangeably with "maximum wind power" as in proportion to the maximum wind power as metered by Gridwatch.

I've tried to avoid any comparison to unmetered or claimed installed capacity but which is never measured or metered.

The figure I am multiplying-by depends on this statistic.

The maximum wind power in 2014 measured by Gridwatch in 2014 was 6835 MW on 2014-12-09 19:50:02.

So if my modelled "290 GW maximum wind power" had been installed it would have produced 290,000 MW on 2014-12-09 19:50:02.

"nameplates" of wind turbines which are unmetered I ignore.
"nameplates" of wind turbines which are out of commission I ignore.
"nameplates" whose operator forgot to turn them on I ignore.
"nameplates" which are just nameplates but don't deliver that power I ignore.

So I'm strictly only referring by "nameplate" to the actual real measured power - nameplates which "do what they say on the nameplate" so to speak. "Ronseal" (it does what it says on the tin) nameplates, if you like.

So don't compare what I would describe as the UK's 6.8 GW "nameplate" maximum wind power which was actually metered on 9th December 2014 with the "12 GW" as allegedly installed wind turbines capacity in the UK, which I've ignored for the most part.

So the way I would do the conversion from a "measured wind output is 0.77 GW" is as follows

0.77 x 290,000/6835 = 0.77 x 42.42 = 32.7 GW which is closer to 33 GW than the "37 GW" you got doing the calculation your way.

Now maybe with the fact that wind turbines like everything else are not 100% reliable this would mean to get to a maximum wind power of 290 GW, there would need to be 290 GW of working turbines plus another percentage of wind turbines which are down for maintenance etc.

I'm only really modelling performing capacity. The actual number of turbines needed and adding up all the values including what's on the nameplates of the turbines which are not working at any time would be a different figure and higher than 290 GW, but I'm not getting in to how much that might be at this stage.

By the time a system like Scottish Scientist's would be up, how many GW of solar power will be on the grid?

Solar is definitely in the mix of very promising renewable generators and I propose future systems with solar too.

I've only modelled wind but not solar because Gridwatch has wind data but no solar data to model with.

So the model is not intended to be a blue print for a system in future to be "up" but to give us an idea of things like - well how much energy storage might we need and how much renewable generating capacity might we need?

So think of the "290 GW" solution as an approximate guide to how much wind + solar + wave + tidal might the "UK" (meaning the electricity consumers of Britain or of the sum of the home nations now part of the UK) need, rather than me proposing that we do actually do the Groundhog Day thing and install 290 GW of wind for real.