Study provides new insights into fluctuations of wind energy

Posted: January 3, 2017 by oldbrew in Energy, research, wind
Tags: , ,

At the end of the day this still looks like trying to make a silk purse out of a sow’s ear in terms of efficiency.

The amount of energy generated by renewables fluctuates depending on the natural variability of resources at any given time. The sun isn’t always shining, nor is the wind always blowing, so traditional power plants must be kept running, ready to fill the energy gap at a moment’s notice.

Because the grid has no storage, and unlike coal or nuclear, there is no control over the fluctuating production of renewable energy, the energy they produce has to be consumed straight away, or risk collapsing the electrical grid.

On particularly windy days, for example, surges in power generated by wind turbines have been known to overwhelm the electrical grid, causing power outages. To avoid this, operators of large power plants sometimes resort to paying consumers to use electricity on particularly sunny and windy days when there is too much excess power in the system, in order to balance the supply and demand of energy at the grid.

Dealing with the peaks and troughs of intermittent renewable energy will become increasingly challenging as governments try to phase out of more stable coal-powered energy sources in the coming decades. In order to mitigate or manage these fluctuations in renewable energy, we need to understand the nature of these fluctuations better.

Professor Mahesh Bandi, head of the Collective Interactions Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) has used turbulence theory combined with experimental wind plant data to explain the statistical nature of wind power fluctuations in a single-author paper published in Physical Review Letters.

Wind speed patterns can be depicted as a wind speed spectrum on a graph. In 1941, Russian physicist Andrei Kolmogorov worked out the spectrum of wind speed fluctuations. Subsequently, it was shown that the spectrum for wind power follows the exact same pattern. However, until now, it was simply assumed that these spectra were identical due to the relationship between power and speed, where power equals wind speed cubed. But this proved to be a red herring.

Professor Bandi has shown for the first time that the spectrum of wind power fluctuations follows the same pattern as wind speed fluctuations for a different reason.

[Talkshop note: for further technical details at this point – see link below]

“Understanding the nature of fluctuations in wind turbine power has immediate implications for economic and political decision making,” says Professor Bandi.

Due to the variability of renewables, coal-fired power plants providing back-up energy are kept running in case of sudden power outages, meaning that more energy is produced than needed. This means that ‘green’ energy is still contributing to carbon emissions, and there is an associated cost of maintaining reserve energy, that will only increase as the proportion of renewables increases in the years to come.

The discovery of a limit in geographical smoothing, articulated by Professor Bandi, will enable better estimates of the operative amount of reserves that needs to be maintained.

This discovery will also impact environmental policy. By considering the limit for averaging fluctuations of power, combined with the availability of different renewable resources such as sun, wind and waves in a particular area, policy-makers will be better equipped to work out optimal combinations of different energy sources for specific regions.

“Understanding the nature of fluctuations for wind turbines could also open up other avenues of research in other fluctuating systems,” says Professor Bandi.

Full report: Study provides new insights into fluctuations of wind energy, with implications for engineering and policy |

  1. rms says:

    When it is realised the environmental “cost” of keeping “non-green” power plants going to enable intermittent renewables to be viable, the pressed-for solution will probably be to use the so-called “smart-meters” to shut down demand until the lack of power from sun/wind is “corrected”. Far as I know, there is no commitment from the renewable energy industry/advocates to maintain current service levels.

  2. oldbrew says:

    What isn’t renewable is the wind turbine itself. Its life is likely to be half that of a fuel burning plant, maybe even less.

  3. ivan says:

    No matter how they dress it up ‘renewable’ energy will never be anything but a green dream. It is intermittent and no amount of load shifting and balancing is going to change that. It will never supply base load and will always be too expensive even with the vast subsidies it is given.

    If, instead of the billions that have been and are still being poured into ‘renewable’ energy, that money had been used to fund Thorium reactor research, or even build on the information gained from the Winfrith thorium reactor, we would have thorium reactors supplying reliable power now.

  4. Jaime Jessop says:

    Interesting study on wind turbulence and how it affects the power supplied to the grid by geographically dispersed turbine installations. Take home message: high frequency perturbations in power generated by short time-scale eddies tend to average out, but the effect of longer time-scale fluctuations (low frequency wind eddies) cannot be averaged out and hence the grid will be overloaded. In other words, when it gets generally very windy and the UK weather becomes dominated by a cyclonic pattern, all those lovely turbines dotting our landscape from the West Country to the Fens, to the Yorkshire Dales and Cumbrian Fells and up to the Scottish Highlands, are going to supply too much power to the grid and will have to be turned off and their operators paid handsomely from the public purse for the privilege of letting them stand idle. Which just goes to prove that, when it comes to insane energy policy in the UK, two Eds are better than one.

  5. tchannon says:

    I assume 1/f noise (flicker) but full access to the journal seems closed so I can’t check this out. Oddly all the advertising comprises hand waving.

    1/f averaged sufficiently looks like gaussian. The area over which this would have to be done is large and I think there will be a good parallel in hydrology for basins. Flood tend to correlate but not for collections of basins, the Rhine problem.

  6. oldbrew says:

    ivan says: ‘It will never supply base load’

    But with smart meters and other (expensive) tricks they plan to abolish base load 😎

    jaime – unless overall demand is quite low (e.g. overnight) there should only be ‘too much’ wind power if there’s a bottleneck in the transmission lines somewhere. In other cases it’s going to be the power stations that have to reduce their output.

    Dr Lee Moroney, of the Renewable Energy Foundation think tank, said: “What is often overlooked is that fossil fuel plants are required to generate the shortfall when wind farms are constrained off. This means consumers are paying Scottish wind farms not to generate and English gas plants at the same time to provide the necessary electricity.”

  7. oldmanK says:

    Quote from link: “Therefore, if all of the turbines in the same wind plant fall within the same short and long time-scale eddies, the energy they produce fluctuates as if the entire plant were one giant turbine.” And the opposite fluctuation happens when a football game ends on tv and everyone goes to bed.

    Quote ” By considering the limit for averaging fluctuations of power, combined with the availability of different renewable resources such as sun, wind and waves in a particular area, policy-makers will be better equipped to work out optimal combinations of different energy sources for specific regions.” It seems humanity is forever destined to keep rediscovering the wheel. Except that this time they are making the big mistake of relying on the “policy-makers” (who no longer confer with those who grew up with and made the power system).

    I have come across a good study worth reading –here:

  8. Jerry says:

    Perhaps a physical “battery” might be designed to accommodate wind variability. As an example wind power might be used to pump water to a higher elevation when wind is available and exploitable, and that elevated water reservoir could then be used at a steady rate to produce a constant level of power with conventional water turbines. That water power level would be well below the wind power peak — and that would be OK. Substantial infrastructure might well be required.


  9. oldbrew says:

    Jerry: these ideas always amount to trying to patch up the shortcomings of intermittent wind power by spending even more money.

    What they can’t do is overcome the fact of intermittency i.e. get from 30% to anywhere near 100% productivity. Which is why wind power can’t replace anything, only provide an irregular part-time alternative.

  10. tom0mason says:

    Backward thinking —

    “Because the grid has no storage, and unlike coal or nuclear, there is no control over the fluctuating production of renewable energy, the energy they produce has to be consumed straight away, or risk collapsing the electrical grid. “

    No, no, NO! The grid was designed to provide stable power on demand to the customer. To somehow get it to work backwards is doomed to failure.

  11. ivan says:

    Just to inject a bit of reality it has now been shown that the ‘smart’ metres that have been foisted on the population at vast cost and touted as the answer to grid stability in a world of ‘renewables’ can be hacked with ease.

    The script kiddies will have fun switching off sections of cities.

  12. Paul Vaughan says:

    It’s unfortunate that this has to come up in connection with power and policy, as the context poisons to death the possibility of fruitful discussion.

    Bandi’s a rare one with a spatial clue.

    We face a cultural problem: A lot of intelligent people — including a lot of otherwise very intelligent people — are fond of or inclined towards assumptions.

    This is the West’s Achilles Heel. Bon Courage decisively ending the reign of salespeople pushing confidence tricks. A quick outline of the collective buy in problem: it’s assuring Western decline.

    Geophysical data are multivariate. People are ready to admit that wind has direction. An assumption that precipitation’s geographic origins are random makes no sense.

    When bucket loads of rain come here in winter, that’s from the tropics. The atmospheric rivers always angle up from the equator and they never come the opposite way from the pole.

    Excluding direction from the analysis — as if precipitation data were univariate — may be an academic confidence trick. Naive consumers beware.

    Bandi is one person with a clue about multivariate limiting statistics, but the masses are far too ignorant to understand and lucid awareness is too rare in the human population for Bandi’s insights to transmit efficiently. There are people who will get the general idea, but then they’ll make other foolish assumptions that will fail in all but a few regions and times with special (“ideal”) properties. (I’m convinced that some geniuses are hardwired to – wink, wink, nudge, nudge – not even check.)

    The puzzle will change before we solve it (101)…

    First one needs to see what’s wrong with the assumptions — e.g.:
    • assuming uniformity where none exists
    • pretending something’s a time-only problem when there are obvious spatial dependencies
    • analyzing multivariate data as if they were univariate
    • fixating on the average ignoring other stats
    • etc.

    Second, other people need to be willing and able to understand.

    Third, the bullying system has to be razed.

    It’s not all going to happen.

    Choosing battles wisely comes up. We might as well just go hiking and kayaking because infighting is consuming the West like the used thing it has become.

    Survival 101: Fight or Flight

    Fighting with stupid people isn’t the answer.
    Fighting with smart people lost in fantasy also doesn’t work.

    Fly away.

    It’s real simple:
    Let’s just get away from false assumptions. Run like the wind towards stability.

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