Modelling wind turbines and pumped-storage hydro for renewables-only 24/7 electrical power

Discussion in 'Architecture & Engineering' started by Scottish Scientist, Apr 9, 2015.

  1. Scottish Scientist Registered Member

    This Scottish scientist produced a spreadsheet model of an electricity generating system composed primarily of wind turbines backed up with pumped-storage hydro-electricity schemes. Such modelling can predict how much wind power and pumped-storage energy capacity should be installed for satisfactory renewables-only generation.

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    The spreadsheet line graph above plots power & energy variables for the time-line modelled –
    • curves for power exported, demanded, from wind, for pumping, from the hydro-turbine &
    • a curve for the energy stored by water pumped into the upper reservoir.
    The time-line graphs data for the grid in Scotland, normalised in proportion to wind power and demand data for June 2014, as downloaded from the Gridwatch Database of the U.K. National Grid Status Website.

    Modelling assumptions for this graph –
    • the peak demand in Scotland in 2014 was 6GW
    • an installed maximum wind turbine power in Scotland of 33GW = 5.5 x peak demand
    • an installed pumped-storage hydro energy capacity in Scotland of 160GWh = 1.11 peak-demand-days
    • the pumps have a maximum power consumption of 6GW = peak demand
    • the hydro-turbines have a maximum power output of 6GW = peak demand
    • the pumps and the hydro-turbines both have an efficiency of 88%
    • no other power stations are generating power.
    I conclude that such models will help to take the guesswork and uncertainty out of renewable-energy electricity system design!

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    A real electricity system which had adopted wind power and pumped-storage hydro for future electricity generation would inherit existing power stations which could continue to serve on stand-by as a further back-up, reserve or emergency power supply.
    Last edited: Apr 9, 2015
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  3. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Welcome to sciforums. Great first post.
    Yes, where pumped hydro storage is feasible, that is a promising way to go and even economical when the full cost of burning fossil fuels is considered. Unfortunately it rarely is. Power / energy generation suffers from the problem of the commons. I. e. the power producer dumps for free the CO2 into the most important commons mankind has - the air.

    So I wonder if you could extend your model to compare KWH production costs. I.e. how much does almost 6 fold more wind generation capacity than peak demand add to the cost? (33 vs 6) And the same question for 1.11 demand days of storage? I assume the capital cost is really 1.11/.88 times greater.

    How much "load leveling" do you think steeper charges at peak demand times could do to make system more competitive? Is electric hot water heating significant in Scotland? Heating water only during the night can shave peak demand if it is.

    Also to get better capital utilization of the wind machines why not keep them fully utilized? I.e. don't leave most of their capacity un-used, make Hydrogen or something of value with little added capital cost.
    Last edited by a moderator: Apr 9, 2015
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  5. Scottish Scientist Registered Member

    Thank you for your interest Billy T.

    With wind and solar, intermittency of supply is an issue. Using an energy store is one promising approach to solving the intermittency issue. To date, pumped-storage has been the energy store technology of choice but it's not feasible everywhere, such as where there's no water or no height differences to exploit.

    The UK and EU governments have sought to account for carbon dioxide costs by imposing fossil fuel burning taxes on power generators. In the UK, these taxes and incentives have favoured the installation of wind turbines but not the building of the urgently needed new pumped-storage hydro, so the case for pumped-storage hydro back-up to provide 24/7 renewables-only generation has to be made to government.

    I have used estimates of the relative capital costs of wind turbines in proportion to pumped-storage hydro, not cost per KWh, to arrive at my recommendation of maximum wind power = 5.5 x peak demand and maximum energy stored = 1.11 x peak-demand days.

    Different maxima of wind turbines and pumped-storage hydro could provide a solution which still supplies the demand.

    If there are more wind turbines, less pumped-storage is required. If there are less wind turbines, more pumped-storage is required.

    If wind turbines become cheaper relative to pumped-storage hydro then the lowest cost solution is to have more wind turbines and less pumped-storage.

    If wind turbines become dearer relative to pumped-storage hydro then the lowest cost solution is to have less wind turbines and more pumped-storage.

    The spreadsheet model was very useful in being able to scope out the performance of different maxima of wind turbines and pumped-storage hydro.

    The absolute cost of each KWh produced by a wind turbine - pumped-storage hydro system was not a consideration for this model, though for another post on my blog I did estimate for Scotland the capital costs of the wind turbines and pumped-storage hydro which I was recommending. The modelling informed my recommendation and that changed my cost estimate. My first cost estimate was around £60 billion but the modelling enabled me to find a cheaper solution, saving £10 billion in the estimate. Even so, such a system still appears to be unaffordable at present prices.

    Well 5.5 x peak demand + 1.11 peak-demand-days is very much cheaper than a solution with only 1 x peak-demand because 1 x peak-demand would require very much more than 1.11 peak-demand days of storage.

    "the pumps and the hydro-turbines both have an efficiency of 88%" means that it takes 1.11/.88 or 1.26 peak-demand days of energy input to the pumps to fill up the reservoirs with 1.11 peak-demand days of potential energy. It also means that only 0.88 x 1.11 or 0.98 peak-demand days of electrical energy can be supplied by the hydro turbines.

    It's really only the taxes and incentives imposed by government which make wind turbines competitive versus fossil fuel burning power stations. Even more is that true backing up wind turbines with more expensive pumped-storage hydro. I do think off-peak cheaper rates at times of high wind make sense though.

    The off-peak times with wind turbines are at times of high wind, not at night. Therefore smart meters using mobile / cell phone / text-messaging technology to be aware of off-peak times are required.

    Already thought of. One option to extend my model would be to include back-up from hydrogen-burning power stations.
    Last edited: Apr 11, 2015
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  7. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    OK & Thanks.
    I understand you got to 5.5 times peak demand wind capacity as cost optimum in part due to "tax and incentive" factors. Glad they exist, but really the more economically rational and direct way is to charge for CO2 release. The Rhine river was once terribly polluted and mostly without fish, despite much of the chemical etc. discharges being illegal - hard to enforce with brief nocturnal dumping. Then Germany adopted new policy: "Dump almost any thing you want into the Rhine, and here is the cost per ton schedule of doing so." After that, you could again catch and safely eat fish caught in the Rhine. That is what needs to be done to clean the air and make economically rational systems develop. I. e. polluting the commons is OK but you will be charged the cost society pays for your doing it. Note that "full social cost" includes costs in the distant future, discounted to present values. Admittedly there is some error in doing this cost analysis - but lets try as it is better than not even charging for social cost as is now done.

    When all competing systems bear their full cost, then wind may still emerge as economically competitive, but I don't like Lobbyist controlling law makers deciding what systems are best. That is how "big oil" got "depletion allowance" and other tax breaks. Let accurate, full cost included, analysis determine our energy (and other systems like transport, etc.) systems.

    Yes, with "smart grids" lower off-peak rates can be dynamically set, not defined by time of day. When wind is strong or sun shining, in modern more environmentally sound system, that can be the low rate times.* Electric heated hot water is a very cheap form of "energy storage" in system with excess solar or wind energy available. About 4 decades ago, BG&E, my power company offered and I agreed that they could switch off my electric hot water heater when ever they wanted to - I got slightly lower KWH rate 24/7. They did it with cheap device that worked via my phone line.** That helped them load level and avoid (or delay) capital cost for capacity expansion. - A good deal for all, even if back then none of their power came from wind or solar.

    * Some with roof-top solar cells who "run the meter backwards" on sunny days will not like the low credit they get then. They are getting a huge cost break, imposed on others, of using the power company as their system's "battery."
    ** I assume they did that, but I never noticed it.
    Last edited by a moderator: Apr 11, 2015
  8. Scottish Scientist Registered Member

    Actually, I think you misunderstand something here.

    I got to 5.5 times the peak demand wind for the cost optimum installed maximum wind capacity only and alone by comparing the capital costs of installing wind power in proportion to the costs of installing pumped-storage hydro and independently of "tax and incentive factors" which apply rather to how much the power companies must pay power generator operators for their electricity generated.

    If the power companies were told to double what they pay for electricity from turbines, but the capital costs of turbines in proportion to pumped-storage hydro stayed the same, I'd still recommended 5.5.

    If the power companies were told to stop paying any incentives, it would still be 5.5.

    If the absolute cost of wind turbines and pumped-storage hydro overnight both quadrupled, it would still be 5.5.

    If there were no power companies and no customers but electricity was generated by, say, a university for academic reasons alone, it would still be 5.5.

    If fossil fuel burning was made totally illegal, it would still be 5.5.

    If all lobbyists were banned from all political lobbies, yup, you've guessed it, it would still be 5.5.
    Last edited: Apr 11, 2015
  9. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Thanks for clarification. You seem to optimized the trade off between wind and pumped storage, not the system optimum, which is more complex but more important.
  10. Scottish Scientist Registered Member

    Sure but only for the relative costs I estimated which were £1.6 billion / GW for wind turbines and £0.64 billion / GW-day for pumped-storage.

    If those figures were different in proportion to each other, so would the optimal balance between wind power and pumped-storage hydro be different from 5.5 x peak demand for wind and 1.11 peak-demand-days for storage.
  11. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    Even if those capital cost were permanent and correct you can not conclude that 5.5 is the system optimum, because their value in the system, not just their cost is critical and depends upon the full system design.

    For example pump-storage has little utility / value except to supply KWHs, but wind power can do that too AND SEVERAL OTHER THINGS, such as compress pipeline gas, make hydrogen, lower storm insurance costs, etc. probably. I.e. wind power can generate other values for a system than just KWHs.
  12. Scottish Scientist Registered Member

    I've extended my modelling to a include back-up generators and modelled some example working system configurations using scaled real world wind turbine generation data and demand data, from the UK grid during low wind conditions in September 2014.

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    Graph 8. Peak Demand (52,500 MW), Store – 0.6 days x peak demand (756 GWh), Wind – 2.7 x peak demand (141,700 MW), Back-up – 0.4 x peak demand ( 21,000 MW)

    I've summarised the results in a table.

    Table of wind, pumped-storage & back-up factors
    The factors in the table are peak demand power multipliers. Each row triplet describes a possible system configuration for 24/7/52 reliable 100% renewable energy generation.

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    Using these results, I have written a web-page script on-line calculator -

    Wind, storage and back-up system designer (my Scottish Scientist Wordpress blog post for documentation and discussion)

    Wind, storage and back-up system designer (the actual calculator web-page which has to be hosted separately because it uses javascript which Wordpress, the blog host, don't allow).

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    Peak demand, wind and back-up power / energy usage and storage capacity calculator

    For the specification and design of renewable energy electricity generation systems which successfully smooth intermittent wind generation to serve customer demand, 24 hours a day, 7 days a week and 52 weeks a year.

    Adopting the recommendation derived from scientific computer modelling that the energy storage capacity be about 5 hours [see note] times the wind power capacity, the tables offer rows of previously successful modelled system configurations - row A, a configuration with no back-up power and rows B to G offering alternative ratios of wind power to back-up power. Columns consist of adjustable power and energy values in proportion to fixed multiplier factors.

    The wind power generation Capacity Factor (C.F.) percentage can be adjusted too.

    Note: I should caution against unrealistic "green energy" expectations following news reports of commercial engineering companies peddling - "largest ever" batteries which can store only 10 or less minutes times the wind or solar power capacity. Such relatively small energy stores are grossly insufficient to design a power-on-demand system where energy is sourced in the main from wind and solar power generators.
    At best, expensive energy storage from batteries can cobble together wind and solar generators as bit-part generators in a grid system where most of the power must still come from conventional dispatchable generators, usually fired by fossil fuels. Therefore "largest ever batteries" or other battery sales in this context are a commercial marketing deception and a fraud driven by the profit motive which trick and lock-in grid managers into continuing fossil fuel dependence. Such batteries offer no "100% renewable energy solution" at reasonable cost. The established technologies to expect to be deployed for wind and solar energy storage are pumped-storage hydro and power to gas. So Elon Musk is every bit the enemy of renewable energy as Donald Trump is. At least Donald Trump is honest about supporting coal.
    Last edited: Oct 24, 2017
  13. Kittamaru Ashes to ashes, dust to dust. Adieu, Sciforums. Valued Senior Member

    I am... confused. Maybe I'm just listening to the wrong sources but... I've not heard anyone of note (such as Elon Musk) say that Solar or Wind alone could completely supplant power generation needs as the technology stands right now. Musk has claimed to make large improvements in power storage (and by all appearances, it seems he has delivered on those promises), but his goal has been to reduce dependence on coal/natural gas/oil generation, not eliminate it entirely.

    Renewable energy will almost certainly always have the issue of peak load support and inclement/unfavorable weather handling. Certainly, pumped-storage hydro can help alleviate some of the peak-demand issues, but nothing we have to date could supplant a solar farm being out of commission due to a several day hurricane, for example. This is, in my opinion, where nuclear plants could shine, able to stay at a relatively low output, working as a large capacitor bank in essence, leveling the power grid and able to spool up relatively quickly if the available solar/wind output diminishes.

    Geothermal could also be an option, though I believe it needs further examination to ensure we are not somehow adversely affecting the stability of the ground in putting up these plants en-masse.

    Additionally, and this is purely hypothetical, but what would the effect on-grid be if, for example, everyone that was in an area capable of supporting it, had a solar hot-water system or geothermal hot-water system installed, with an on-demand gas or electric heater as a backup (or even use a solar or geothermal pre-heater system, since it is cheaper to take 90 degree water to bathing temperature than it is to heat a full tank of 50 or 60 degree groundwater)
  14. Scottish Scientist Registered Member

    As an example of Musk-fanboy hyperbole, I'd quote this.

    Elon Musk's big battery brings reality crashing into a post-truth world

    "All the talk of building ... a Snowy Hydro 2.0, no longer sounds vaguely “truthy”. It sounds ridiculous. It sounds silly. It sounds like old men yelling at clouds."

    The snake oil salesman's goal is to make profits selling something to suckers that is not fit for purpose.

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    Here in the British Isles, winter is more of a solar-power killer than hurricanes. So far from the equator we would never rely only on only solar, but on mostly wind with a side-order of solar, which generates well half of the year while wind generates particularly well in the winter.

    Whereas I think portable nuclear emergency power supplies could be useful for hurricane and other disaster relief, as well as aircraft carriers, submarines, ice-breakers, tugs, remote location development and space, particularly outer-planet space probes where solar is not so useful.

    Iceland is good for geothermal. It's not so hot when you have drill down miles at great cost.

    Seasonal thermal energy storage has been demonstrated successfully in Canada but roll out has been slow, at least here in Britain.

    I focus mostly on the topics I have posted about in my Scottish Scientist blog.

    * Wind, storage and back-up system designer
    * Double Tidal Lagoon Baseload Scheme
    * Off-Shore Electricity from Wind, Solar and Hydrogen Power
    * World’s biggest-ever pumped-storage hydro-scheme, for Scotland?
    * Modelling of wind and pumped-storage power
    * Scotland Electricity Generation – my plan for 2020
    * South America – GREAT for Renewable Energy
  15. Baldeee Valued Senior Member

    I'm confused, somewhat: are you saying that Musk's battery is not fit for purpose, and that he's a snake oil salesman?
    On what basis do you base your opinion?
    Or have I misread your comments?
  16. Scottish Scientist Registered Member

    Yes I am saying that Musk's battery is not fit for the purpose as reported by Musk's fanboys. Musk is sly enough to have his lawyers draw up the contract to escape liability for delivering as promised by said fanboys. It is easy enough for Musk to egg his gullible customers and impressionable fanboys on to ever more ridiculous claims for his batteries while keeping himself out of legal hot water with the actual contracts he signs.
    "By extension, a snake oil salesman is someone who knowingly sells fraudulent goods or who is a fraud, quack, or charlatan."​

    Musk is peddling batteries dishonestly as some kind of "green energy solution" yes.
    I base my opinion on my knowledge as an applied energy scientist as to what energy storage capacity will be required to effectively manage the 1.6GW of wind power generation which South Australia already has.

    5 hours times 1.6GW = 8GWh energy storage required.

    Musk's battery only has about 0.1GWh and is therefore too small by a factor of 80 to serve the current needs of South Australia.

    This quote from the BBC story already linked to -

    Large capacity
    "The Tesla-built battery, paired with a Neoen wind farm, will operate around the clock and be capable of providing additional power during emergencies, the government said.
    "It will completely transform the way in which renewable energy is stored, and also stabilise the South Australian network as well as putting downward pressure on prices," Mr Weatherill said."

    Musk by appearing at press conferences with the South Australian Premier Jay Weatherill is clearly allowing and is content for his battery to be represented as a complete solution for South Australia's needs now, when it is not even a solution for the single wind farm it is to be built alongside.

    I also have enough life experience, if not as a qualified social scientist, to understand how these not-fit-for-purpose batteries are being peddled to and by non-scientists, like Tim Hollo, the executive director of the Green Institute, the Musk fanboy who wrote that Guardian article I quoted above.

    If you read my comments as a well-founded scientific criticism of Musk's inappropriate battery sales for grid energy storage purposes then you read me right.

    In terms of mood music, you might try listening to the lyrics of "Shania Twain - That don't impress me much".

    "So he's a rocket scientist, so he's got an electric car - that (battery) won't keep the people of South Australia cool in the summer sun."
  17. Kittamaru Ashes to ashes, dust to dust. Adieu, Sciforums. Valued Senior Member


    I'm not seeing the hyperbole here... Musk has (as far as I'm aware) committed to building it within 100 days, or it's free. That's... a bold claim, sure... and so long as he sticks to the agreement, I don't see the issue.

    What is your contention with the planned battery bank? That it won't be able to supply power as/when needed?

    Aye, but the British Isles are fairly different from Auzland in terms of climate, are they not?

    A portable nuclear supply would be interesting... though I'm not sure how you make a nuclear plant "portable" without a small floating city coming along for the ride (ala an Aircraft Carrier or Nuclear Submarine). The need for containment in a worst-case scenario is pressing, and that results in size.

    Where do you get the "miles down" number? Sure, for a mass power generation plant, you would want deeper to access more heat, but you can have them as little as a few dozen feet down, depending on purpose. For example, a geothermal water pre-heating system (to cut hot water costs), or even a home heating system, would only have to be a hundred or so feet down to be effective in most temperate climates:

    20 feet isn't that expensive all said and done.

    It just feels like you are maligning Musk et al for... well, I'm not really sure the reason. Granted, from everything I've read, the man is a bit of an ass to work for, and he expects 120% effort from everyone involved... but I think given what is at stake and how much he's sort of put himself "out on the edge"... well, I'd want the best from everyone working for me as well. I might not agree with his methods, but I can understand them.
  18. Kittamaru Ashes to ashes, dust to dust. Adieu, Sciforums. Valued Senior Member

    OK, now I have to ask the obvious... do you have any evidence that he is "having his lawyers draw up the contract to escape liability" et al? This sounds like simple hate mongering dialed to eleven...

    Also, how do you figure the batteries are not a "green energy solution" - with Solar and Wind, you don't have a constant supply, so when you generate excess, you want to store it. A capacitor or battery is the obvious solution, with something like pumped-hydro being a possibility in certain locations (though you'd be hard pressed to set up a pumped-hydro solution in, say, Florida)

    Uhm... what? So, your contention is that, because the farm cannot store the total output of the wind farm, it is useless? You... are aware it was proposed as a load balancing measure, right?
    The ability to take the needs of 4,000 homes off the backs of the current generation capability in times of lower-power generation and high-demand is nothing to thumb your nose at.

    As stated, it is meant to help with peak demands, not supplant the current generation in place. Nothing you have provided as been a "snake oil" type statement... nowhere is Musk (or anyone I saw) claiming this to be a "magic cure-all".

    Yet many experts in the field disagree with you... and you want us to take your word over decades of combined professional experience?

    Right... sorry Scott, but all you've done so far is come across as someone with a seriously throbbing rage-boner for Musk. In your own words - that don't impress me much.
  19. billvon Valued Senior Member

    It's very popular. Lots of people are jumping on the hate-Musk bandwagon. He's successful and has done things no one else has been able to do (like reuse booster stages.) That's threatening to many people; they feel that if they pull him down, they will make themselves feel better about their own accomplishments (or lack thereof.)
  20. Kittamaru Ashes to ashes, dust to dust. Adieu, Sciforums. Valued Senior Member

    Aye. Which is sad, because it seemed like this one might have had some ability to actually discuss the field intelligently... but if he's just looking to feed his incomprehensible anger, then there is no intelligent discussion to be had.
    Ethernos D Grace likes this.
  21. Scottish Scientist Registered Member

    The most relevant quote from your source
    is this

    "is part of an AEMO trial into demonstrating that wind power can supply a baseload level of energy, known as frequency control and ancillary services or FCAS, to compete with traditional baseload sources like coal and gas."

    It seems to have escaped you but that is precisely what my modelling does demonstrate, that wind power can indeed supply a baseload level of energy to compete with traditional baseload sources like coal and gas.

    That's what this whole topic is all about!

    The difference is that AEMO are doing a poorly planned, unscientific trial, no doubt by some engineers without much of an idea of how much energy storage is required - tacking on a silly little battery, sucking it and seeing what happens. So I guess maybe AEMO phoned up Telsa and asked how much their batteries were and they decided to buy the biggest one they could afford. It will be something like that. And no I don't have secret tape recordings to prove it. I know that AEMO don't know what they are doing because I know how to do it and they are not doing it right. Their trial will not succeed because the energy storage capacity of their battery is too small.

    The difference is that I am a world-leading expert scientist who is leading research in this particular field of applied renewable energy science. I know that it will take something like 5 hours times the wind power capacity to achieve that stated aim of baseload power from wind.

    I know it because I have modelled exactly how to do it successfully using computers, graphed my results and published it all, here in sciforums and elsewhere, for other scientists to read (real "scientists" mind you, not any Tom, Dick or Harry who happens to show up in an internet forum who may skim read my post, but ignore it completely until they read the juicy bit where I criticise a person (Musk) whom they usually trust as untrustworthy in this context).

    We won't get to 100% renewable energy by knowing Elon Musk.
    We get to 100% renewable energy by knowing how to do it.

    It's not who you know, it is what you know.
    Last edited: Oct 24, 2017
  22. billvon Valued Senior Member

    Exactly right. Musk merely provides the tools to do it.
  23. Scottish Scientist Registered Member

    No Musk doesn't provide "the tools to do it". He has provided a tool which is much too small for the job.

    To repeat again, what is required is an energy store of capacity of 5 hours times the wind power capacity.

    So South Australia with wind power capacity of 1600 MW requires an

    Energy store of capacity = 5 hours times 1600 MW = 8000MWh.

    Musk's battery is advertised as "129MWh" but on closer examination offers more like 100MWh of energy storage which is a factor of

    8000MWh/100MWh = 80 times too small.

    South Australia cannot afford to buy 80 batteries the size of the one they just bought from Musk. That would bankrupt South Australia and make Musk an even richer multi-billionaire than he already is.

    To get 8000MWh and more of energy storage at low cost, South Australia and everyone else on the planet cannot afford to buy expensive batteries but we must use the tried and tested method of storing electricity for the grid which is pumped-storage hydro.

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    There’s very impressive and confidence-inspiring leadership to be heard coming out of Australia now on the potential for pumped-storage hydro to complete a 100% renewable energy grid system to serve at the heart of a transition to a renewable energy economy.

    For example, here's web-page from the Australian Broadcasting Corporation Online –

    Pumped hydro storage ‘could make Australia run on renewable energy alone within 20 years’

    – includes a couple of great videos, a good review video from February this year

    Pumped Hydro: Australia’s energy future?

    Pumped hydro could be part of the solution to Australia’s energy instability problems. David Lipson explores the technology that’s been around for decades but is attracting new interest from the federal government.

    – and a new video of a TV News interview with world-leading expert in the field Professor Andrew Blakers

    Australia could use pumped hydro for ‘100-percent renewable energy grid’ says ANU analysis

    Professor Andrew Blakers from the Australian National University says Australia has the capacity to store up to 1,000 times more renewable energy than it could ever conceivably need.

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