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Author Topic: How can renewable energy farms provide 24-hour power?  (Read 74072 times)

Offline thedoc

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Renewable energy farms can only produce power when the sun shines or the wind blows, but new cheaper batteries allow them to store energy.
Read a transcript of the interview by clicking here

or Listen to it now or [download as MP3]
« Last Edit: 27/08/2013 14:04:01 by _system »


 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #1 on: 28/08/2013 10:13:03 »
Excellent technology, with serious economic consequences.

The problem with unreliable energy sources is that if they account for more than about 10% of the maximum grid capacity, they make the entire system uneconomic. If the wind blew at rated speed for 90% of the time, you would need 10% of your reliable sources to be switched off for 90% of the time in order to cover the gaps. This might be tolerable, but idle machines need space and maintenance, so they represent a financial loss (and the wind generally only blows at 10% of rated speed). Above 10% of unreliables, it is difficult  to persuade anyone to invest in conventional plant: big nukes and clean coal take a long time to fire up, small ones are expensive; gas plant costs less to install but is at the mercy of suppliers on the other side of the world; and whilst oil can be stockpiled, it is horrendously expensive to run. The sensible investment is in nuclear and big coal plant, but the prospect of at least 20% overcapacity or underutilisation will not attract shareholders.

So rather than impose levies on conventional power in order to subsidise unreliables, government should require windfarmers and the like to subsidise conventional standby plant, or require them to install at least 5 days' storage capacity at rated power, and insist that the store is full before allowing them to supply the grid directly.   
 

Offline syhprum

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Re: How can renewable energy farms provide 24-hour power?
« Reply #2 on: 28/08/2013 13:18:13 »
But look how terribly dangerous nuclear power is probably as many as 100 people have died as a result of nuclear mishaps since 1940
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #3 on: 28/08/2013 15:09:54 »
My goodness! That's almost a whole day's toll of coal miners, or ten minutes at Aberfan.

Now you could argue that wind electricity hasn't killed many people to date, but that is taking a very short-term view of windmills, which have been killing people on and off for thousands of years. And ignoring the lifecritical nature of a continuous electricity supply in the modern world.   
 

Offline CliffordK

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Re: How can renewable energy farms provide 24-hour power?
« Reply #4 on: 28/08/2013 19:04:16 »
Many of the "wind farms" are being built in places that get quite regular wind such as at the coast, or the Columbia gorge, although undoubtedly it varies somewhat with weather. 

Building a battery system with several megawatt-days, or gigawatt-days capacity, as well as high peak power flow, and low losses is undoubtedly expensive, as well as replacement expenses.  Some UPS type batteries may last over a decade, but only with occasional power drains.

It is my belief that hydroelectric power plants need to be redesigned to have a portion of the generation with quick reacting grid buffers.  While one might not want to vary the dam output from 0% to 100%, one could certainly fairly rapidly vary the flow by 10% or 20% or so.

In some cases, the reservoirs are back to back as on the Columbia River, or paired as the Lookout Point / Dexter Reservoir pairs in which the upper reservoir could go through huge production surges with little environmental impact.

In designing a "grid", one should consider each energy resource for its strengths and weaknesses.

Solar: Strong diurnal patterns.  Also affected by seasons and clouds.  Perhaps helped by an East/West or North/South power grid, but long distance grid links are also expensive.  Unused power is "wasted".

Wind:   Variable, 24 hrs/day.  Unused power is "wasted"

Nuclear, I believe power output can be varied somewhat on a diurnal basis, but to a large part slow reacting.  Also, one has to plan on shutdowns and recharge cycles.

Coal/Steam, also slow reacting, but can vary with diurnal usage.  UNUSED POWER IS CONSERVED.

Internal Combustion fuels including biogas, can be quick reacting, Unused power is conserved, depending on supply and storage.

Hydroelectric.  Generally seasonal.  Should have a couple of days partial storage capacity depending on the design, but certainly must use 100% of the water supply.  I believe many plants are designed to be slow reacting, but that isn't necessarily a requirement.  They should be able to be designed to be quick reacting, at least in part, especially if designed to buffer water flow.

Tides.  Diurnal, no storage capacity beyond perhaps a few hours.

Underwater Ocean Currents.  Are these fairly constant?  No Storage.

Anyway, it is my thought that rather than investing in expensive batteries, to design the grid to utilize the natural capabilities of each power generation system. 

Any use of fossil fuels should be incorporated only to buffer other systems considering essentially infinite storage capacity of the fossil fuels, and expense of the fuels.
« Last Edit: 28/08/2013 19:13:14 by CliffordK »
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #5 on: 28/08/2013 19:52:33 »
The big problem with wind is that power output depends on the cube of the wind speed, so a windmill with a nominal rating of 100 kW at its optimum wind speed tends to produce less than 15 kW averaged over a year, even in the best UK onshore locations. Offshore you can get about 20% of rated power but the maintenance costs are ridiculous. You can't make it go much faster than its optimum because the blade speed is limited to the speed of sound at the tip, so if you use big wings to squeeze the last drop out of a gentle breeze, you have to feather it in a gale (drag force increases with v^2, so you need to minimise the angle of attack to prevent damage), and a small fan will only produce useful power on the few days when it gets really windy.

All the best UK locations have been taken, so future wind plant is unlikely to exceed 10% of its rated capacity.  And even if we covered the entire country with windmills, we couldn't generate all the power we need (less than 30% of our energy consumption is electricity).   

Windmills are very effective where you can use power opportunistically. Grinding corn is possibly the only large scale example.

Scottish Hydro have already built pretty much everything that might possibly be economic for hydroelectricity in the UK.

Tidal power is hugely attractive in theory, and has been for the last 150 years or so. But only three large plants have ever been built because there really aren't many suitable locations.

My vote is for biofuel, and an 80% reduction in energy use.
 

Offline evan_au

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Re: How can renewable energy farms provide 24-hour power?
« Reply #6 on: 28/08/2013 22:30:01 »
Storage of electricity has always been problematic. Liquid and gaseous/liquified fuels store much more densely and safely (because the atmosphere is a vast, omnipresent "free" repository of the other energy-producing ingredient: oxygen; it also doubles as a toxic waste dump - it's a pity we have to breathe the stuff!).

For solar-thermal generators, molten-salt thermal storage seems more promising than lithium-ion electric batteries. The thermal storage can shift generation capacity from the daytime (when the sun shines best) into the evening peak, when solar heating is fairly ineffective.

Most of the discussion so far has been about "Supply-Side" energy management, where you manage how much power is produced from different sources, and when.

However, an equally important aspect is "Demand-Side" management, where you manage how and when energy is consumed.
  • In some countries, there is a long history of using off-peak electricity for hot water and slab heating. The electricity company signals when it is to turn on and off, typically using tones on the power line to select one of dozens or hundreds of "channels". If power is short that night, they can leave it on for less time.
  • New buildings are often built from better insulating materials (less air conditioning load), are pre-configured so the power consumption in office blocks is reduced at night and weekends, and can often sense when rooms are unoccupied and turn off the lights
  • Extending this to other applications like air conditioning, dishwashers, clothes dryers etc is effectively a problem in communication, computing and economics.
  • In the end, what we spend on electricity is a tradeoff with what we spend on health, communication, transport, entertainment, food, etc. You only really discover how much you value something when it stops for a while...
« Last Edit: 28/08/2013 22:38:44 by evan_au »
 

Offline CliffordK

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Re: How can renewable energy farms provide 24-hour power?
« Reply #7 on: 28/08/2013 22:46:07 »
Another thing to consider.
Most of the "developed world" is based on grid power.

An alternative is distributed off-grid power.  In a sense, it is inefficient because excess power is wasted, and it can be difficult to plan for peak needs. 

However, there are some advantages such as lower line losses, and it shifts the storage needs from the producer to the consumers.  The consumer also becomes much more aware of actual power usage.

Anyway, one might consider encouraging distributed generation/storage in cases where the "grid" is unavailable such as the developing world, new developments, and places where the grid suffers massive failures such as after Hurricane Katrina.
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #8 on: 29/08/2013 08:10:13 »
Using primary electricity for space heating is insane. It is the most expensive and most flexible form of energy we have, and really shouldn't be squandered. A properly insulated and correctly sited new build, even in the British Isles and the northern US states, doesn't require any space heating at all. A school in Chester, built some 50 years ago with airspaced double glazing, has never used space heating, and modern insulators are a lot better.

Right now I'm converting a 150-year-old stable  block into domestic accommodation. Despite having all-north-facing picture windows, and being shaded by trees on the south so negligible solar input, we calculate that an airsource heat pump will provide all the hot water and space heating for a 120 square meter single storey building - possibly the worst case starting specification for a single elderly occupant - for around £1.50 per day. With a family of four, it shouldn't need any space heating at all.

I never understood why commuter trains are heated in winter. You stand on the platform in the snow, wearing several layers of clothing, then cram into a small space with lots of other people, take off your coat, and sweat. Why not turn the heating off keep your coat on for the journey?     

Grid power actually accounts for very little of our energy needs. What matters is that it is instantly available at all times, and extremely flexible - hence the electricity grid, and with rather less flexibility, the gas grid.  I guess the most common example of distributed off-grid energy is road fuel. Reliable old technology, no problem dealing with peak demand, and no waste! And the consumer is acutely aware of power usage. Indeed that is true in any case where you have to pay for it, surely?
 

Offline peppercorn

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Re: How can renewable energy farms provide 24-hour power?
« Reply #9 on: 29/08/2013 14:03:07 »
Using primary electricity for space heating is insane. It is the most expensive and most flexible form of energy we have, and really shouldn't be squandered.

"In 1979 the Danish government unveiled the “Heat Supply Law for Denmark,” dividing the country into regions that would be supplied with domestically produced natural gas, and those that would be supplied with CHP produced district heating. Furthermore, the government created an “obligation to connect law” which required citizens to connect to district heating or natural gas if it was available, and outlawed the use of electric heating for new building construction. This acted as a reinforcing loop - creating a strong domestic demand for the new Danish gas, and also for the continued expansion of district heating"- Source: Danish Energy Agency, 2010

And why not here?
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #10 on: 29/08/2013 18:45:31 »
Creeping socialism, dammit.
 

Offline CliffordK

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Re: How can renewable energy farms provide 24-hour power?
« Reply #11 on: 30/08/2013 15:43:10 »
Here, rainfall is strongly seasonal.  And, thus river flow also is seasonal.  Thus, more hydroelectric energy is generated during the winter.    Therefore, there are actually benefits of using electric heating when there is more electricity being generated.

However, I agree it is ludicrous to keep the house at 70° year around.  Let it get a bit warmer in the summer and save on the AC bill, and a bit cooler in the winter. 

Much more could be done to incorporate geothermal heating/cooling in home design.
 

Offline grizelda

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Re: How can renewable energy farms provide 24-hour power?
« Reply #12 on: 01/09/2013 18:41:39 »
In Quebec, the provincial hydroelectricity agency prices electricity so cheaply everyone uses it to heat their houses. The government then declares a loss which is made up by billions in equalization payments from the rest of Canada. No creeping socialism there, it's rampant.
 

Offline peppercorn

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Re: How can renewable energy farms provide 24-hour power?
« Reply #13 on: 02/09/2013 12:30:36 »
No creeping socialism there, it's rampant.

I don't we should confuse mismanagement with socialism (of whatever flavour).

However, it would seem a great shame in places where hydroelectric is seasonal, that there may turn out to be far too little incentive to improve the housing stock to make it thermally efficient.  This outcome has not exactly been uncommon over the years in a 'free market' economy either; power has been cheap (relatively speaking) for a very long time.
 

Offline FunkyWorm

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Re: How can renewable energy farms provide 24-hour power?
« Reply #14 on: 04/09/2013 11:13:17 »
Talking of socialism...

The Chinese government have identified the batteries in electric cars as being the perfect reservoir for the country's electrical storage requirements.  Imagine a whole population of electric vehicles with maybe a third of them plugged in and charging from the grid at any moment. Some of them will be pretty close to being fully charged and so they can be used to buffer the supply. Presumably you'd get some financial inducement to leave your car plugged in as much as possible.

Seems like an interesting idea.
 

Offline CliffordK

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Re: How can renewable energy farms provide 24-hour power?
« Reply #15 on: 04/09/2013 11:28:19 »
Yes,
Plug-In cars may serve as a power reservoir, unless you are planning on a trip that requires a 100% charge, and find your car is only 75% charged.

Battery life is also affected by depth of discharge and the number of cycles.  So, extra power cycles during the day may adversely affect one's car battery life, and having the batteries partly charged when one expects them to be fully charged could be bad.

On the other hand, some power companies are charging different rates depending on the time of day, so it may make sense to use a smart charger to recharge after midnight when the rates are lowest. 
 

Offline Scottish Scientist

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Well yes obviously renewable energy can provide 24-hour power with an energy store back-up but there's no need to re-invent the wheel here folks.

Pumped-storage hydroelectricity
http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity [nofollow]
works well to back-up intermittent wind turbine power, if you build enough energy storage capacity to service your electricity grid's needs when the wind isn't blowing much.

The more difficult question, which I now have an answer for all you naked scientists to check my figures and peer-review for me please is -

How much nameplate or maximum wind power generation capacity in GigaWatts (GW) and pumped-storage hydro-electricity energy storage capacity in GigaWatt-hours (GWh) ONLY would it take to provide all the electrical power needs for the UK grid, 24-hours a day, 7 days a week?

My estimate for the UK grid's requirements is -
  • Wind Turbine maximum power 290GW
  • Pumped-storage hydro energy capacity 1400GWh
That's a LOT more of both needed than we have installed already.

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.

Today in the UK we have about 27GWh of pumped-storage hydro installed.

So I estimate we'd need a factor of 1400/27 = 52 times more pumped-storage hydro than we have today.

I initially worked out figures for the energy requirements of Scotland only, or a peak demand of 6GW or 11.4% of the UK peak power demand of 52.5GW.

Scotland Electricity Generation – my plan for 2020
https://scottishscientist.wordpress.com/2015/03/08/scotland-electricity-generation-my-plan-for-2020/ [nofollow]



I've created a spreadsheet model to determine how much wind power and pumped-storage hydro energy capacity would be required for Scottish needs.

So remember to multiply the figures in my diagrams by 52.5/6 or 8.75 to get the appropriate numbers for the UK.

Modelling of wind and pumped-storage power
https://scottishscientist.wordpress.com/2015/04/03/scientific-computer-modelling-of-wind-pumped-storage-hydro/ [nofollow]


Click for full size image - https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_june.jpg [nofollow]


Click for full size image - https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_january_b1.jpg [nofollow]

My cost estimate for Scotland was £50 billion for wind turbines and pumped-storage not counting grid infrastructure upgrades.

So say maybe £480 billion for the UK.

The annual government budget for the UK is something over £700 billion so a project of the size of £480 billion or the cost of 40 channel tunnels would clearly take a number of years to afford and to build.

So renewables-only electricity generation is indeed possible but it is not cheap and it is not easy, if my figures are anything like correct.

« Last Edit: 08/04/2015 19:22:06 by Scottish Scientist »
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #17 on: 08/04/2015 17:13:32 »
Present UK grid capacity is about 80 GW. It is sensible to plan for 100 GW in the foreseeable future.

Nameplate capacity of a windfarm is of no importance: what matters is actual mean performance. Currently it is about 30% of rated capacity and is unlikely to improve as all the best sites have, of course, already been taken. So the current input from wind is about 4 GW averaged over the entire year.

http://www.gridwatch.templar.co.uk  shows today's wind contribution to be 0.68 GW as I write, about 1.9% of present consumption. The amount is likely to decrease in the next 3 hours as he sun goes down, and this will coincide with rising demand for rush-hour trains and domestic cooking. Today is fairly typical of the hottest and coldest days in the UK, which are the days when there is maximum demand and no wind. These anticyclonic conditions can last up to 14 days at a time, so if you want to rely entirely on wind you need at least 14 days' storage capacity, and 100% overcapacity in your generating system so that you can recharge the batteries when the wind blows, whilst continuing to supply the immediate load.

If you can site the storage units next to the windmills, that's entirely sensible and indeed should be a planning condition for every windmill. Unfortunately you probably can't do so for offshore windmills, and would create a huge visual nightmare and an additional maintenance problem if you did so for onshore wind. So you probably need to site your storage units somewhere near the distribution stations. Problem is that you now need to double the power capacity of the grid cables so they can carry both the demand current and the recharging current. You need to factor that cost into your calculation. 

Present pumped storage capacity is 30 GWh, installed on the best available sites. 14 days' storage is almost 27,000 GWh. Given the very small amount of ground above 1000ft amsl in the UK, I suspect that this cannot be achieved without substantial damage to upland farming. Remember that a PSU needs two ponds, one at the top of the hill and one at the bottom. And of course the pump/generators need to have the same running capacity as the maximum grid demand.

Thus, if you are prepared to flood  most of the Highlands and Snowdonia, you need to install 300 GW of windmills to meet peak demand, plus 300 GW to recharge the storage units, plus 100 GW of pump/generators, plus 100 GW of additional grid cabling and switchgear.   

The cost of doing so is left as an exercise for the reader, but I think you will find nuclear power a lot cheaper, more reliable, and less environmentally damaging.
« Last Edit: 08/04/2015 17:17:56 by alancalverd »
 

Offline Scottish Scientist

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Re: How can renewable energy farms provide 24-hour power?
« Reply #18 on: 08/04/2015 18:48:23 »
Hi Alan and thanks for your feedback.

Present UK grid capacity is about 80 GW. It is sensible to plan for 100 GW in the foreseeable future.
Data statistics show a trend of decreasing maximum power demand.

Wikipedia
http://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#Network_size [nofollow]
2005/6 63GW

Digest of UK Energy Statistics
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/337649/chapter_5.pdf [nofollow]
Table 5.9 page 143

2009 60,231 MW
2010 60,893 MW
2011 57,086 MW
2012 57,490 MW
2013 53,420 MW

Gridwatch
23/01/2014 17:30:03 52477 MW

I am no expert but my guess would be the energy trend is caused by the deindustrialization of the UK with our previous heavy industry being done in China increasingly?

So I don't foresee a need for 100GW total capacity on present trends.

Also I don't see an urgent need to build additional renewable reserves since it would be acceptable at least initially to use other types of capacity - such as biomass fuel burning or even fossil-fuel burning power stations as a reserve.

For the academic interest in looking at the figures, to calculate a capacity where peak demand = 70% of total capacity including reserves.

52.5 GW / 0.7 for a 75GW total renewable capacity.

maximum wind power + reserve = 290GW / 0.7 = 414 GW
pumped-storage hydro + reserve = 1400 GW / 0.7 = 2000 GWh


Nameplate capacity of a windfarm is of no importance: what matters is actual mean performance. Currently it is about 30% of rated capacity and is unlikely to improve as all the best sites have, of course, already been taken. So the current input from wind is about 4 GW averaged over the entire year.

http://www.gridwatch.templar.co.uk [nofollow]  shows today's wind contribution to be 0.68 GW as I write, about 1.9% of present consumption. The amount is likely to decrease in the next 3 hours as he sun goes down, and this will coincide with rising demand for rush-hour trains and domestic cooking. Today is fairly typical of the hottest and coldest days in the UK, which are the days when there is maximum demand and no wind. These anticyclonic conditions can last up to 14 days at a time, so if you want to rely entirely on wind you need at least 14 days' storage capacity, and 100% overcapacity in your generating system so that you can recharge the batteries when the wind blows, whilst continuing to supply the immediate load.

Present pumped storage capacity is 30 GWh, installed on the best available sites. 14 days' storage is almost 27,000 GWh. Given the very small amount of ground above 1000ft amsl in the UK, I suspect that this cannot be achieved without substantial damage to upland farming.

Thus, if you are prepared to flood  most of the Highlands and Snowdonia,

I've taken all those factors into account in my modelling. Did you not even notice that I recommend installing 290GW of wind turbines which makes peak demand of 52.5GW only 18% of installed nameplate wind turbine capacity?

My model has been tested on real gridwatch data for 2014 and the more cost effective solution is not "14 days' of storage capacity" but only a bit more than 1 day of storage and more wind power.

Alan you are doing what I was doing before I did the numerical modelling using real demand and wind power data from gridwatch -  guessing and going on hunches.

There's no substitute for running a computer model on real data and plotting graphs to prove your solution works. I did that. My solution works, I think. Certainly you are not disproving my model by quoting your hunch that 14 days storage is needed. No it's not.


If you can site the storage units next to the windmills, that's entirely sensible and indeed should be a planning condition for every windmill. Unfortunately you probably can't do so for offshore windmills, and would create a huge visual nightmare and an additional maintenance problem if you did so for onshore wind.
Pumped-storage can be built in a very low profile way. Admittedly 52 times more pumped-storage than we have now, would have a higher profile but nothing like the profile of the existing wind turbines we have never mind the 24 times more we'll need.

So you probably need to site your storage units somewhere near the distribution stations. Problem is that you now need to double the power capacity of the grid cables so they can carry both the demand current and the recharging current. You need to factor that cost into your calculation. 
Well I've just not factored the cost of grid into my cost estimates, sorry.


Remember that a PSU needs two ponds, one at the top of the hill and one at the bottom. And of course the pump/generators need to have the same running capacity as the maximum grid demand.
Already remembered, thanks.

you need to install 300 GW of windmills to meet peak demand, 
290GW of wind turbines. Only more if we opt for a wind turbine reserve.

  plus 300 GW to recharge the storage units, plus 100 GW of pump/generators,
No peak demand is 52.5 GW so I only need 52.5 GW of hydro-generators. The same 52.5 GW for pumps is plenty too and has no problem in filling the reservoirs from empty in a little over a day.

  plus 100 GW of additional grid cabling and switchgear.   
The additional grid infrastructure is needed to connect up all the new turbines which can be supplying up to 290GW of power, but not all to the pumped-storage and demand. Anything in surplus above 2 x peak demand needs new grid for export only or to power-to-gas to generate hydrogen for the gas grid.

The cost of doing so is left as an exercise for the reader, but I think you will find nuclear power a lot cheaper, more reliable, and less environmentally damaging.
Aside from the grid costs which are complicated to calculate and depend on the length of new grid between plants whose location is not yet known, I've already estimated costs of about £480 billion for 290GW of wind turbine and 1400GWh of pumped-storage.

Well thanks again for your feedback Alan!
« Last Edit: 25/04/2015 19:18:55 by Scottish Scientist »
 

Offline chiralSPO

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Re: How can renewable energy farms provide 24-hour power?
« Reply #19 on: 08/04/2015 20:24:28 »
1400 GWh (5.04x1015 J) of pumped hydro storage would be quite 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)*.

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.

*Loch volumes found here: http://en.wikipedia.org/wiki/List_of_lochs_of_Scotland
 

Offline Scottish Scientist

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Re: How can renewable energy farms provide 24-hour power?
« Reply #20 on: 08/04/2015 22:46:23 »
Hi chiralSPO and thanks for your feedback.

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

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

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

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

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

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

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

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

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



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

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

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

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

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

Thanks again for your feedback chiralSPO!


 
« Last Edit: 08/04/2015 23:20:24 by Scottish Scientist »
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #21 on: 09/04/2015 00:13:39 »
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My model has been tested on real gridwatch data for 2014 and the more cost effective solution is not "14 days' of storage capacity" but only a bit more than 1 day of storage and more wind power.

and that, I think, is the fatal flaw in all proposals for wind power. During a winter anticyclone, the whole of the UK (and most of Europe) can be covered by a high pressure zone with average winds of 5 kt or less, for at least a week at a time. "More wind power" won't deliver any power when there's no wind! You need to consider a supply that, in effect, can go to zero for several days at a time, and when it recovers, you need to supply all the present demand plus enough power to recharge your storage system before the next shutdown. Thus your installed primary generating capacity needs to be about 6 times average demand, plus 1 x peak demand for the pumped storage units. Ignoring the cost of building the storage ponds and extra grid capacity, this means that you have to install 7 times the present generating capacity in order to meet present demand from renewables instead of fossil and nuclear generators. 

Saying that
Quote
Also I don't see an urgent need to build additional renewable reserves since it would be acceptable at least initially to use other types of capacity - such as biomass fuel burning or even fossil-fuel burning power stations as a reserve.
is frankly ignoring the weight of the elephant. As I understand it, current biomass generators in the UK are net negative - the energy required to transport and process the fuel is more than they produce - and any "reserve" station has to recoup its costs from unplanned and intermittent running, which makes even gas an uneconomic investment. And it's intellectually dishonest! You can't start off with a plan for 100% renewables and then say "plus a bit of coal in case it goes wrong".

My preference would be to reinstate low-pressure gasholders and use wind power to generate hydrogen which we distribute through the existing gas grid. And before the usual smartasses tell us about the difficulties and dangers of hydrogen, let me remind them that until 1963, the gas grid contained 50% hydrogen: the dangerous stuff was 10% carbon monoxide.
 

Offline Scottish Scientist

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Re: How can renewable energy farms provide 24-hour power?
« Reply #22 on: 09/04/2015 01:33:29 »
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My model has been tested on real gridwatch data for 2014 and the more cost effective solution is not "14 days' of storage capacity" but only a bit more than 1 day of storage and more wind power.

and that, I think, is the fatal flaw in all proposals for wind power.
No testing my model on a whole year of real world demand and wind power data demonstrates there's no fatal flaw.

During a winter anticyclone, the whole of the UK (and most of Europe) can be covered by a high pressure zone with average winds of 5 kt or less, for at least a week at a time. "More wind power" won't deliver any power when there's no wind! You need to consider a supply that, in effect, can go to zero for several days at a time, and when it recovers, you need to supply all the present demand plus enough power to recharge your storage system before the next shutdown. Thus your installed primary generating capacity needs to be about 6 times average demand, plus 1 x peak demand for the pumped storage units. Ignoring the cost of building the storage ponds and extra grid capacity, this means that you have to install 7 times the present generating capacity in order to meet present demand from renewables instead of fossil and nuclear generators.
Well I tested my model on all the data from 2014, including the winter months.

Actually, as this graph of the January modelling shows, there was no such shortage of wind in January 2014.


Click for full size image - https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_january_b1.jpg [nofollow]

The biggest lull in the wind in 2014 was pointed to on this "Idiocy of Renewables" webpage.

"92 Continuous Days of LoLo Wind - That's EverSoLo Electricity from Wind Turbines!"
http://idiocyofrenewables.blogspot.co.uk/2014/10/92-continuous-days-of-lolo-wind-thats.html [nofollow]

To cope with this difficult time, I had to fine tune my solution, but it does work as this graph for June 2014 shows.


Click for full size image - https://scottishscientist.files.wordpress.com/2015/04/windpumpedstorage_june.jpg [nofollow]

But instead of pointing to real data which illustrates a wind condition, you simply wave your hands in a data-free way. That's not scientific Alan.

I admit I have not tested my model on data from all years. Maybe there is data set from Gridwatch which will break my model and force me to increase the wind GW or pumped-storage GWh, but you certainly have not pointed to such a specific data set, have you?

You have not done the scientific thing which the author of the "Idiocy of Renewables" did when he quoted hard data to make his point.

You know Alan, I love a challenge. I really do. If you can point to the data of a very low wind spell in the UK from Gridwatch, I'd be delighted to test out my model on it.


Saying that
Quote
Also I don't see an urgent need to build additional renewable reserves since it would be acceptable at least initially to use other types of capacity - such as biomass fuel burning or even fossil-fuel burning power stations as a reserve.
is frankly ignoring the weight of the elephant. As I understand it, current biomass generators in the UK are net negative - the energy required to transport and process the fuel is more than they produce
Really? Got some evidence for that? Mankind has long used wood as fuel so maybe they knew something you don't?

- and any "reserve" station has to recoup its costs from unplanned and intermittent running, which makes even gas an uneconomic investment.
Well the grid can hire power plants to stay on stand-by and pay a premium for emergency power and make reserve stations profitable.

And it's intellectually dishonest! You can't start off with a plan for 100% renewables and then say "plus a bit of coal in case it goes wrong".
If I had to resort to fossil fuel, gas would be the choice because a) it is a faster start up and b) renewable-generated hydrogen from power-to-gas can be added to the fuel mix.

My plan for Scotland recommends converting the last coal power station in Scotland at Longannet to burn biomass fuel.

I do offer a 100%-renewable 24-hours a day, 7-days a week electricity generation plan but it is much tougher to guarantee 52 weeks a year.

If that's as intellectually dishonest as the "teetotal" man who has one glass of sherry at Christmas, well I can live with that.

My preference would be to reinstate low-pressure gasholders and use wind power to generate hydrogen which we distribute through the existing gas grid. And before the usual smartasses tell us about the difficulties and dangers of hydrogen, let me remind them that until 1963, the gas grid contained 50% hydrogen: the dangerous stuff was 10% carbon monoxide.
Yes, my plan generates surplus wind power at times of up 60% of maximum wind power. This can be used to produce hydrogen in power-to-gas for injection into the gas grid.

However, it is not as efficient to re-generate electricity from power-to-gas hydrogen as it is from pumped-storage hydro, so we need the pumped-storage as I have described for more efficient energy storage.
« Last Edit: 09/04/2015 01:42:54 by Scottish Scientist »
 

Offline alancalverd

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Re: How can renewable energy farms provide 24-hour power?
« Reply #23 on: 09/04/2015 08:23:25 »
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You know Alan, I love a challenge. I really do. If you can point to the data of a very low wind spell in the UK from Gridwatch, I'd be delighted to test out my model on it.

As you say, we have 12 GW installed windpower in the UK.

According to Gridwatch, 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.

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

I am reminded of the statistician who, on learning that the average depth of the Thames is 3 feet, drowned whilst walking from Chelsea to Battersea.
« Last Edit: 09/04/2015 08:26:04 by alancalverd »
 

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Re: How can renewable energy farms provide 24-hour power?
« Reply #24 on: 09/04/2015 11:59:12 »
Quote
You know Alan, I love a challenge. I really do. If you can point to the data of a very low wind spell in the UK from Gridwatch, I'd be delighted to test out my model on it.

As you say, we have 12 GW installed windpower in the UK.
Yes.

According to Gridwatch,
Be aware that Gridwatch data for wind power is not what is served from the full 12 GW installed in the UK, but for only just over 50%. So Gridwatch's maximum wind power data reading in 2014 was only 6835 MW on 2014-12-09 19:50:02.

To check this, visit the Gridwatch website http://www.gridwatch.templar.co.uk/ [nofollow]
and hover your mouse above the wind power dial and a context pop-up text bubble appears which says ..
Quote
Wind: This is the total contributed by metered wind farms. Wind power contributes another about 50% from embedded (or unmetered) wind turbines that shows only as a drop in demand.

Which also means the demand data is slightly lower than it really is too but that can be discounted for present purposes.

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 [nofollow]

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.

I am reminded of the statistician who, on learning that the average depth of the Thames is 3 feet, drowned whilst walking from Chelsea to Battersea.
He should have gone to spec-savers.  :)
« Last Edit: 09/04/2015 12:19:35 by Scottish Scientist »
 

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Re: How can renewable energy farms provide 24-hour power?
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