[Scottish Scientist]

You can't assume that metered demand is being met by unmetered input - that would be ridiculously generous of the suppliers, and anyway, as Gridwatch states, unmetered supply is already shown as a reduction in demand, so you mustn't double-count it! Furthermore it is generally the case that unmetered wind is small power for local consumption and therefore will not contribute significantly more to the grid as large windfarms are built to absorb your taxes.

Thus using conventional arithmetic, if we had 290 GW of installed wind power  right now, we would be getting  290/12 =  24.16 GW

Incorrect. I've not used the "12 GW" figure in my modelling so it has no place in any such sum.

I did use the "12 GW" and "12" factor in my first post -

Today in the UK we have about 12GW of wind power installed.

So I estimate we'd need a factor of 290/12 = 24 times more wind turbine power than we have today.

- but that "12" has not been a factor in any of the modelling I have done.

[Scottish Scientist]

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

You really want to have your cake and eat it! Every watt of car battery is another load on the grid, so if you want to replace road vehicles with electric ones, you will need 580 GW of installed wind power and twice the storage capacity that SS is proposing. Plus, of course, twice the grid carrying capacity and a whole lot of infrastructure to deliver the juice to the cars.

And that will still leave you with 50% of current UK fossil fuel consumption for heating, cooking and direct use in industry....

I should point out that whereas my model indicates that present UK electricity needs could be met by 1400 GWh of energy storage capacity, even twice that or 2800 GWh would only be 41% of the 6800 GWh provided by my Strathdearn pumped-storage hydro scheme.

So my plan for Strathdearn PSH offers energy storage capacity for

* the present needs of the UK
* + some needs of other countries
* + British future needs after we have electrified all our transport

[Scottish Scientist]

SS, you are so beautiful, as your science!

Aw shucks!  [:I]

[Scottish Scientist]

Presumably with 290 GW of peak wind, you'd have spare energy a lot of the time. I mean the standard capacity factor is about 25-35%, so you'd be averaging more power than you actually need- it's sized for the periods when the wind is a bit anemic. So at 25% CF, that's 72GW average, whereas the normal demand is 35-55.

But that's actually probably good; things like electric cars don't usually care as much about having to have power every single day; you could potentially just set the minimum charging point for what you need day-to-day, and if there's spare electricity going because it's particularly windy, it would charge it up further and save money; also electric water heaters could be switched on.

Absolutely right there wolfekeeper.

My modelling identifies surplus power with the "export" legend and graph lines coloured turquoise.

The area under the export power curve represents power x time or energy, as does the area under the demand power red line.

So compare the area under the export curve with the area under the demand curve and I think you can estimate that there seems to be the same again surplus energy available as there was energy supplied for electricity demand.


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

This surplus power could actually be exported to other countries or used for power-to-gas to make hydrogen to be added to consumer gas supplies for example.

[Scottish Scientist]

Presumably with 290 GW of peak wind, you'd have spare energy a lot of the time. I mean the standard capacity factor is about 25-35%,

I entered this discussion with a guesstimate that an installed capacity of 6 times average demand and 5 days' storage would do the trick, but events have shown otherwise,. My apologies.

So far this month, 20 out of 24 days the capacity factor of wind has been less than 10%, and for the last 2 days, zero. The mean capacity factor for the last 24 days has been about 14% and tomorrow isn't looking any better. So in order not to lose too many lives, destroy too much food, bring industry to a halt, or generally inconvenience the population, it seems on current evidence that you need at least to install at least 7 times average demand and one month's storage capacity.

Well as my modelling of April 1st to 26th has demonstrated, 5.5 times peak demand [5.5 x 52.5 ≈ 290 GW] was enough (which by the way is equal to 5.5 x 1.6 = 8.8 times average demand) and 1.11 days of peak demand power energy storage capacity (which by the way is equal to 1.11 x 1.6 = 1.78 days of average power energy storage capacity).

Note you are under-estimating the power required. Your "7 times average demand" would be only 52.5/1.6 x 7 = 230 GW.

So there I am saying - "Hey Alan, the UK would need 290 GW of wind power maximum. But there you are saying, "oh no SS, the UK can get away with only 230 GW".

Sorry but a mere "7 times average demand" or 230 GW would not be enough, at least not with only 1400 GWh of energy storage it wouldn't.

But of course you'd make your mere 230 GW work with a massive "one month's storage capacity" which would be 52.5/1.6 GW-months = 32.8 GW-months = 998 GW-days = 23953 GW-hours but just call that 24,000 GW-hours.

At a cost estimate of £26.7 million per GW-hour, your one month's storage capacity would cost 24,000 x 26.7 = £640,000 million or £640 billion, 53 channel tunnels worth and the best part of one year's government spending.

So it's cheaper to do it my way.

And that's just to meet the present need for electricity. If you want a wholly wind-powered economy you will need a generating capacity of 20 times present electrical demand, and a month's storage capacity at 150GW, otherwise people will surely die or find themselves stranded far from home.

I don't "want" a wholly wind-powered economy. I was modelling a wind & pumped-storage generation system because that's easier to model because the data is available and offers useful for pointers towards a renewables-only energy system.

Your figures are speculative at this stage and I won't speculate with figures of my own in reply except to say that your notion of "one month's storage capacity" is inappropriately high.

But here's a trick - sell electricity on a live market. When supply is low, prices are high. That will regulate demand and ensure that it is always exactly matched to supply. Because there is no significant lag between supply and consumption, and consumption can be monitored at every point of use, the unit price can be varied every second or less. The poor will have to learn to make choices instead of profligately cooking and keeping warm at the same time, and they will have to trade in their huge plasma screen TVs for neater LED models (everyone knows that the poor have ENORMOUS televisions - the Daily Mail says so). My private patients will continue to enjoy the fruits of their crimes, whilst honest peasants will be told that the waiting list for radiotherapy is due to factors beyond human control, not politics or incompetence.   

Well I think with wind power's increasing penetration into the electricity market we will be seeing the widespread adoption of off-peak electricity rates set automatically according to wind supply and relayed to smart meters to alert customers when they can save money by heating water, storage heaters, charging up electric cars and so on.

Everyone loves a bargain Alan and wind power can offer very cheap rate electricity at windy times.

[alancalverd]

Everyone loves a bargain Alan and wind power can offer very cheap rate electricity at windy times.

It's a sad fact that only the wealthy can afford a bargain. I would like to have an electric car for nipping out to the shops, but I only have the capital for one car so it has to be the one that will also do 300 miles at 70 mph without stopping, so I can get to work and back on the same day - not some time in the distant future when we have 20-second charging points all over the country, but tomorrow. I would like to buy bulk electricity for a storage heater but having just spent a fortune on an underfloor heat pump system, I can't adapt to that brave new world without destroying half the house. Fortunately I can afford to buy heating oil (for the other half!) in bulk when it's cheap, but the poor never seem able to fill a big tank, or to buy a whole case of wine  (I pay 25% less than someone who can only afford a bottle at a time). And so it goes on. Sure, rip out your 50 gallon hot water tank and replace it with an intelligent offpeak 200 gallon unit - it will only cost you £1000 and you will save £100 per year: try that on a pensioner!

And if we all started using offpeak electricity, wouldn't that just create a new peak, or at least even out demand?  The offpeak boom was in the 1950s and 60s when common sense ruled and the trend was to build more nuclear power stations, which work best when feeding a constant load at 90% capacity, so you could match load to supply over the long term by pricing. With wind it's the other way around - you have to use the stuff when it's available or get involved in expensive storage schemes.   

Seriously, I think your hydrogen store is a runner, because it can be introduced gradually and with no significant change in infrastructure or consumer hardware (changing from town gas to methane just involved changing the final jets on cookers and furnaces) but pumped water is a nonstarter in the big race.

[wolfekeeper]

It's a sad fact that I don't have a car that can go at 150 mph for 300 miles without stopping.

When will this conspiracy against poor people like me end??? When?

[alancalverd]

It's a sad fact that I don't have a car that can go at 150 mph for 300 miles without stopping.

That's why I use an aeroplane. Or, if I'm in a real hurry, a telephone.

When will this conspiracy against poor people like me end??? When?

When we have ground the last peasant into the dust and rid the world of poverty by the simple expedient of ridding it of poor people, of course. Really, why do the working class ask such stupid questions? Qu'ils mangeant de brioche, mon ami.

[Scottish Scientist]

Deep Sea Hydrogen Storage

Very sensible idea.

Thanks Alan.  []

Worth also investigating the use of the existing UK gas grid to store and distribute low-pressure hydrogen or manufactured methane,

Methane is harder to make from power-to-gas but easier to pipe into the existing gas grid with no conversion issues.

thus obviating the need for an electricity store,

Well hydrogen needs storing somewhere too.

Also pumped-storage hydro offers a higher energy efficiency energy store. You lose at least half of the energy converting to hydrogen then back to electricity. So a power-to-gas only energy store would not be the most efficient in the long run.

So I recommend what's most appropriate where and when

• pumped-storage hydro for land storage up to a limit of 1.11 peak-electricity-demand-days for the intermittent renewables,
• power-to-gas and gas-storage for surplus power after the pumped-storage hydro reservoirs have been topped up
  
• undersea hydrogen stores for off-shore when there's no or less demand for electricity from land than is being generated

major construction works or any novel generating plant: use the gas to run the existing gas power stations when the wind fails, just as now.

But for renewables-only generation, even using gas-energy-stores only, we'd need to build more novel gas-fired power stations. There's not enough gas-fired plant to provide the full electricity demand as yet. We'd also need either lots of hydrogen to methane conversion plant and / or additional hydrogen storage. Hydrogen is not a zero-build option.

http://www.technologyreview.com/news/510066/audi-to-make-fuel-using-solar-power/

Existing petrol-engined road vehicles can run on methane with very little conversion, or you could synthesise higher hydrocarbons for better energy density: pure synthetic diesel produces less NOx than biodiesel. And of course methane is already the preferred source of domestic and industrial heating in the UK, whilst hydrogen and oxygen are extremely useful industrial gases.

I'm not sure if it is worth collecting the oxygen from the undersea electrolysis situation. I had in mind the option of just letting the oxygen gas bubble away.

One reason to store the oxygen would be to increase the efficiency and reduce the nitrogen oxide combustion by-products of hydrogen-fired generators. Whether that advantage is worth the cost of collecting the oxygen, I'm not sure.

Be aware that for undersea electrolysis in order to produce oxygen as the anode gas, a custom electrolyte solution will have to be used. If you try electrolysing sea water directly you get chlorine gas off at the anode, which is not so easy to dispose of and can be poisonous.

So the technique will be to separate the custom more-concentrated electrolyte solution from the sea water by a semi-permeable membrane and allow pure water to pass through it by osmosis from the relatively dilute sea water.

It's worth pointing out that whereas we might describe this process as undersea "high-pressure" electrolysis, it is only so, "high-pressure", because of the ambient high-pressure resulting from being under water at depth.

So there's no high-pressure-vessel containment required for the electrolyte solution - as is required for high-pressure electrolysis which operates on the surface - and so undersea, a semi-permeable membrane is all that is required to keep the electrolyte solution contained.

This approach might actually make wind power economically viable and socially useful.

Hmm. I still think we need to build more pumped-storage hydro for best results.

[alancalverd]

Hydrogen storage isn't a problem, or at least it has been solved, used and abandoned in living memory (mine!). The oldfashioned town "gasometers" contained 50% hydrogen at final delivery pressure, above ground in water tanks, and worked for well over 100 years.

Rather than electrolyse seawater, my preference would be to bring the electricity ashore (as is already done, so no new technology required) and electrolyse fresh water inside the gasometer, either using "high pressure" electrolysis at the bottom of a lake or near-atmospheric pressure in a river or pond.

Gas-fired power stations already supply about half the UK demand, and are much cheaper and easier to build than coal or nuclear. The principal reason that gas has not taken over completely from coal is the rising cost of gas, so I don't foresee any great problem in expanding the gas-to-electric capability if electrolytic hydrogen becomes as cheap as wind enthusiasts would have us believe.

Thermal inefficiency isn't a problem either.We already tolerate a 50% energy loss in converting fossil or biofuel to electricity, but as I have pointed out a few times above, electricity is not the most important energy source anyway: we burn 70% of our fossil fuel either for direct heat or for transport, and hydrogen or synthetic liquid fuel would be perfectly acceptable in these roles, with minimal modifications to the burners, as distinct from ripping out industrial furnaces wholesale and replacing them with electric ones.

The organic growth of a wind-to-hydrogen economy is the least disruptive path to sustainable, secure, zero-carbon energy for the UK - it's the next best thing to Icelandic geothermal power, without the attendant earthquakes and volcanic deserts.     

[wolfekeeper]

I forget whether I already posted this:

(basically Texas has shed-loads of wind)

[wolfekeeper]

Interesting and related news from Elon Musk.

So he's selling 10kWh of battery for around $3500.

That's an average of $350 for 1kWh. If the batteries last 10 years, and they get cycled once a day; that's 3650 cycles, i.e. 9.6 c = ~ 6p for storage. The current cost difference on economy 7 is about 10p. So it's cheaper to buy all of your electricity at night and use it during the day storing it in these batteries.

Now, you might say- oh well, the economy 7 will smooth out then, because everyone will buy the batteries and then there won't be such a big price differential. This isn't actually a bad thing, because the day price will go down even if you haven't got a battery.

But this also misses the point that as more wind comes into the network, the natural variations in supply can be eaten up by the batteries also; the suppliers just need to create a new super 'economy' rate that is related to the wind supply.

edit: reading the small print, the 7kWh battery is suitable for daily cycling, and costs $3000 and is guaranteed for 10 years. So that's $428/kWh. So that's 11.7c per kWh; which is still 7p/kWh average per day.

edit2: OK, so it's only 92% efficient, so that makes it 8.1p/kWh.

[alancalverd]

10 kWh will run a house for most of a day, so it's a sensible starting point.

Lead-acid traction batteries cost about $30 per kWh, generally last about 5 years, and are easy to maintain and recycle. Why pay more? 

All modern domestic appliances work on 50 or 60 Hz AC, so in addition to the battery you will need a charger/inverter unless you want to completely re-equip your house. Add another £2000 and at least £500 installation charge to estimate the payback period.

[Scottish Scientist]

... Deep Sea Hydrogen Storage ...
 [ Invalid Attachment ]

How big is this gas-bag ?,  and how deep will it be under the sea ? .
Do flexible materials exist to make such a bag which can withstand the buoyancy forces ?


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

The biggest air-lifting bags available to buy now off-the-shelf hold a volume of 50 metres-cubed and they have a diameter of 5 metres and a height of 7.5 metres.



Presumably they could be custom-made much bigger for storing hydrogen but are not yet available to buy off-the-shelf because any bigger would not be useful for air-lifting bag purposes.

In any case, it will always be possible to increase the volume by rigging multiple gas-bags together as shown in this diagram.


As for depth, as I mentioned earlier

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.

the deeper the better because the density of hydrogen increases with depth, as per these graphs.


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

Consider how many 50 m³ gas-bags we'd need to store the energy required to provide 1 MW of electrical power for 1 day - a useful amount of back-up energy to store to serve one floating platform.

1 MW for 1 day = 1 MJ/s x 60 x 60 x 24 = 86.4 GJ of electrical energy which can be generated from 86.4/e GJ of hydrogen energy of combustion where "e" is the efficiency of the hydrogen-to-power generator and can vary from 30% to 60% depending on the complexity and expense of the generator.

The combustion energy from 1 gram of hydrogen is 143 kJ.

So the mass of hydrogen with 86.4/e GJ of energy is
mass = 86.4 x 10⁹ J / (143 x 10³ J/gram x e)
mass = 604/e Kg of hydrogen to provide 1 MW of power for 1 day

Consider three scenarios - 50 m³ gas-bags floating on the surface, at 200 metres depth and at 2000 metres depth.

Surface
Surface density of hydrogen 0.1g/L
Volume = 604,000g / (0.1g/L x e) = 6,040,000/e L = 6040/e m³
= 121/e x 50 m³ gas-bags
for efficiency of 30% that's 121/0.3 = 403 x 50m³ gas-bags  [V]

200m
200m density of hydrogen 1.8g/L
Volume = 604,000g / (1.8g/L x e) - 335/e m³ = 6.7/e x 50 m³ gas-bags
for efficiency of 30% that's 6.7/0.3 = 23 x 50m³ gas-bags  []

2000m
2000m density of hydrogen 16 g/L
V = 604,000g / (16 g/L x e ) = 37.75/e m³ = 0.755/e x 50 m³ gas-bags
for efficiency of 30% that's only 0.755/0.3 = 3 x 50 m³ gas-bags  []

So the advantage of depth in reducing the volume and therefore the number of gas-bags required to store a given mass and energy content of hydrogen is clear.

How deep you actually want to put the bags depends on -

a) the depths available of the sea where floating platforms can be operating at - consult a sea depths map, like the ones I posted earlier

Deeper seas, which are better for storing hydrogen in, can be found from an atlas of the oceans, such as this one.

Sea Atlas - https://scottishscientist.files.wordpress.com/2015/04/6004-050-e076d00f.gif

Looking at a close-up of the map for the area of sea closest to Scotland, Britain and Western Europe –



Click to view a larger image - https://scottishscientist.files.wordpress.com/2015/04/seas_euro_n_africa-200.jpg

– this shows that deep sea water most suitable for hydrogen storage is not to be found around the coast of the British Isles but depths greater than 4,000 metres can be found in vast areas of the Atlantic beginning a few hundred miles to the south-west in the Bay of Biscay.

So one area of sea which looks suitable for both solar and hydrogen powered electricity generation appears to be just to the west and south-west of the Canary Islands and to the north of the Cape Verde Islands. Whether this area is near enough to western Europe to be the best choice to supply western Europe considering the additional costs of longer interconnection cables remains to be estimated.

- and how deep you actually want to put the gas-bags depends on -

b) how deep the high pressure electrolyser can be made to work. High-pressure electrolysers can be made to work (in pressure vessels on the surface) at pressures corresponding to the pressures at depths of 1000 metres (about 100 bar) but higher pressures maybe up to 300 bar may be possible (corresponding to a depth of 3000 metres).

Since, as far as I know, the electrolysers required for this application have neither been designed, prototyped nor tested experimentally at sea depths, it is impossible at this stage to say with any certainty or proof at what precise sea depth high pressure electrolysers can be made to work, at all, or economically.

There seems to be an opportunity from this concept but only speculative answers to certain questions can be given at this time.

[wolfekeeper]

10 kWh will run a house for most of a day, so it's a sensible starting point.

Lead-acid traction batteries cost about $30 per kWh, generally last about 5 years, and are easy to maintain and recycle. Why pay more? 

Because they only last 5 years, because they can only be discharged halfway, because they're not very efficient, and because $30/kWh is highly over optimistic?

[RD]

2000m
2000m density of hydrogen 16 g/L
V = 604,000g / (16 g/L x e ) = 37.75/e m³ = 0.755/e x 50 m³ gas-bags
for efficiency of 30% that's only 0.755/0.3 = 3 x 50 m³ gas-bags  []

What does 4000*m of [copper] underwater power-cable cost ?, and how much does 4km of power-cable weigh ? , ( weight will have a bearing on the size of the floating-platform necessary ).

Divers can only work at 200m , so if it's 2000m forget about maintenance.
Putting stuff in 2km of water is what people do if they never want to see it again.
 [ the Titanic is at 3.8 km ].


[*Two 2km power-cables according to your diagram ,
 and 2 or3 anchor cable$ also each 2km long ].

[alancalverd]

Rather than work 2000 m below the sea, Why not compress hydrogen to 200 atmospheres in standard industrial bottles? It's already available off the shelf and used in huge quantities every day.

Bring the electricity ashore, electrolyse fresh water, and use the existing gas grid to store and distribute energy as previously.

Audi announced this week that they are now running a car on synthetic hydrocarbon fuel made from atmospheric CO2 and electrolytic hydrogen - LPG and liquid fuels are a lot more convenient and require very little conversion of existing vehicles.

As for the notion of siting windmills in a circle, the reason it isn't done is because half of them will then be in downwind of the other half, regardless of the wind direction.

Optimum siting is obviously in a line perpendicular to the prevailing wind. In the UK the wind rose generally has two maxima, one southwest and the other, rather smaller, northwest, so a staggered phalanx works pretty well.   

[wolfekeeper]

Looks like organic flow batteries are going to start to be available from 2017.

http://www.greentechmedia.com/articles/read/harvards-organic-flow-battery-under-development-in-europe

The previous estimates I've seen were that the chemicals for storing a kWh cost about $30; the current chemistries appear to be able to handle 5000 reuses; which is about $0.006 per kWh of usage.

If this is successful, it would appear to be a total game changer.

[alancalverd]

http://www.greentechmedia.com/articles/read/harvards-organic-flow-battery-under-development-in-europe

First, the company plans to attack the domestic storage market with systems of 5- to 20-kilowatt-hours, designed to hold around four hours of electricity.

Some elementary physics missing here.

He also cites the fact that quinones are natural, organic products that present little or no health risk.

Bullshit

http://pubs.acs.org/doi/abs/10.1021/tx9902082Quinones represent a class of toxicological intermediates which can create a variety of hazardous effects in vivo, including acute cytotoxicity, immunotoxicity, and carcinogenesis.

So, apart from some duff science and a few barefaced lies, it seems like a good idea!

[chiralSPO]

Looks like organic flow batteries are going to start to be available from 2017.

http://www.greentechmedia.com/articles/read/harvards-organic-flow-battery-under-development-in-europe

The previous estimates I've seen were that the chemicals for storing a kWh cost about $30; the current chemistries appear to be able to handle 5000 reuses; which is about $0.006 per kWh of usage.

If this is successful, it would appear to be a total game changer.

I am familiar with this from the primary literature, it's nice to see that the tech is going from academia to application, though I'm not sure that quinone-based flow batteries are ultimately the most exciting development. Flow batteries can store effectively unlimited amounts of energy (as big as you want the electrolyte reservoirs to be), which is nice, but both the energy density and power density are quite low compared to other energy storage methods. Flow batteries will be very useful for some applications, but I don't think it will be a "total game changer."

Also, there is no reason to say that quinones are benign! Sure there are natural quinones (like those involved in photosynthesis, and what bombardier beetles blast their enemies with, and the myriad cytotoxic quinones deployed by bacteria in their perpetual chemical warfare)...