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Study: wind and solar can power most of the United States

Posted on 26 March 2018 by John Abraham

In order to combat climate change, we need to rapidly move from fossil fuel energy to clean, renewable energy. The two energy sources I am most interested in are wind and solar power; however, there are other sources that have great potential.

Some people doubt how much wind and solar can supply to a country’s electricity grid. This is a particularly challenging question to answer in part because both solar power and wind power fluctuate in both space and time. We all know solar panels work well during the day, when the sun shines – they don’t work so well at night. And wind turbines only send electrons when the wind is blowing. 

Fortunately, these two sources of energy fluctuate in ways that complement each other. For instance, solar power generation is highest in the summer and lowest in the winter. Wind power is greatest in the spring and fall. Wind turbines work at night when solar panels are dormant. So, can these complementing variations help balance out the power that the two technologies can provide? 

This question was addressed in a very recent paper published in the journal Energy and Environmental Science. The author list included Dr. Ken Caldeira, who is extremely well known for his years of work in environmental science and energy.

The authors analyzed 36 years of hourly weather data (1980–2015) in the US. They calculated the available wind and solar power over this time period and also included the electrical demand in the US and its variation throughout the year.

With this information, the researchers considered two scenarios. In scenario 1, they imagined wind and solar installations that would be sufficient to supply 100% of the US electrical needs. In the second scenario, the installations would be over-designed; capable of providing 150% of the total U.S. electrical need. But the authors recognize that just because a solar panel or a wind turbine can provide all our energy, it doesn’t mean that will happen in reality. It goes back to the prior discussion that sometimes the wind just doesn’t blow, and sometimes the sun isn’t shining.

With these two scenarios, the authors then considered different mixes of power, from all solar to all wind. They also included the effect of aggregation area, that is, what sized regions are used to generate power. Is your power coming from wind and solar in your neighborhood, your city, your state or your region?

The authors recognized that sometimes these systems generate too much power to be used. Under this situation, you could store the energy for later use. Imagine a solar panel generating excess energy during the day and able to store that power for night use. Power can be stored in several ways, for example in batteries or by pumping water into elevated tanks and then letting the water fall at night and turn a turbine. 

Click here to read the rest

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Comments 1 to 40:

  1. There is no question that solar and wind can provide our energy. The real question is how much energy, can we use it easily, and can how much does it cost. We can't afford the cost of slightly more expensive FF energy, there is not enough surplus to drive the economy so how can we afford more expensive, less surplus solar and wind?

    When ever an author puts "Imagine..." in an article it should be dismissed. If we had the storage tech we could cut FF use for electricity by more than half right now. What makes anyone think we will do it later if we can't do it now?

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  2. please, this is hopium bullshit. there is no way 7.6 billion rapacious human animals (increasing at 1,000,000 ever 4.5 days) can live our lifestyles of waste and massive consumption on "magic green", which by the way is 100% dependent on the underlying, fossil fuel powered industrial infrastructure.

    please familiarize yourself with the limits to growth. technological cornucopianism cannot mitigate finite planet realities.

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  3. In a world of self-driving cars, floating offshore windpower should really not be all that difficult.  Put each tower on GPS and let it stationkeep with onboard navigation and power from a combination of wind and wave (no wind and wave=  no need to stationkeep).  Each tower should be floating, perforated to allow wave action to go through and around it, and anchored 100ft below the surface to plastic sheeting (i.e. a 'water-brake').  At 100 ft and below, surface wave-action is negligible.  A water-brake of sufficient size and perhaps multiple levels can be designed to hold the tower quite still, even in the waves of the N Atlantic).  You can design the tower so that, absent the force of its own buoyancy, it tends to sink from wave action more than rise, so that it tends to align itself with the wave-troughs rather than the wave-crests.  Thus the water-brake is in no danger of being pulled to the surface and destroyed by waves.  After securing a stable platform via sunken water-brake, but still an untethered platform capable of being motored horizontally using locally available power and GPS, then its just a matter of making the tower tall enough to clear the tallest waves.  This kind of windpower favors very large blades the size of jumbo jets.  Since the system is unanchored, probably one of the most expensive parts of this system is the (sunken) power feed back to land.  The advantage of floating offshore wind power is it has little to no NIMBY effect and the wind is stronger.  I sent a design concept to GE a few years ago but they passed.

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  4. jef @1

    "There is no question that solar and wind can provide our energy. The real question is how much energy, can we use it easily, and can how much does it cost. We can't afford the cost of slightly more expensive FF energy, there is not enough surplus to drive the economy so how can we afford more expensive, less surplus solar and wind?"

    The article answered how much energy. Solar and wind can provide up to 80 - 90% depending on the two scenarios. I mean with respect I don't understand how you missed that, unless you were concerned about future demand or something? There's no reason to belive this would be a problem.

    It's hard for me to see why the energy would be hard to use. It's the same electricity as any electricity, and is transmitted the same way. Some lines upgrades would be required of course because of inter state transmission to deal with intermittency issues, although this depends on which option is preferred. The article demonstrated that intermittency issues can be dealt with effectively in varrious ways.

    I don't understand how you can claim we can't afford the cost of "slightly more expensive" energy. If its only slightly more expensive, then by definition it's affordable. Buy slightly fewer coffees or something. Poor people are the one group that might struggle, but they could be subsidised.

    Wind power and solar power is now very affordable low cost power in general terms. Its the same cost as coal in some places, and is expected to be cheaper in the future. Lazard cost analysis here. Prices had literally plumetted in recent years.

    "When ever an author puts "Imagine..." in an article it should be dismissed. If we had the storage tech we could cut FF use for electricity by more than half right now. What makes anyone think we will do it later if we can't do it now?

    Maybe the article worded it less than ideally,  but battery storage is improving fast and its not unreasonable to conclude costs will drop in the future very significantly. Likewise there can be good confidence wind and solar prices will continue to drop. Solar may be nearing the limits, but wind could drop considerably further yet.

    The article suggested one scenario of 80% renewables and 20% hydro nuclear etc. This is a very affordable option right now, and a total system would not be hugely more expensive than coal. Given price trajectories its very likely such a system could be cheaper than coal in the near future, and the nuclear component might not be essential and it may be viable to use battery storage or hydro storage. Such decisions do not need to be finalised until the renewable component of the grid starts to get over about 30%. Alternatively, theres the other option that uses a surplus of wind and solar  power, and less use of hydro and nuclear etc.

    Of course we would have to replace existing coal fired power for example, sometimes before it's at the end of its life. Costs of completely converting a totally fossil fuel grid including generation and transmission lines upgrades have been estimated at 1% of a countries total gdp (gross domestic product) per year, and quite probably less, a number that is clearly not "unaffordable". In return we get clean energy, a more sustainabe form of energy, and a system that is very likely ultimately cheaper tnan fossil fuels, so whats not to like?

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  5. shastatodd @2

    "please, this is hopium bullshit. there is no way 7.6 billion rapacious human animals (increasing at 1,000,000 ever 4.5 days) can live our lifestyles of waste and massive consumption on "magic green", which by the way is 100% dependent on the underlying, fossil fuel powered industrial infrastructure. please familiarize yourself with the limits to growth. technological cornucopianism cannot mitigate finite planet realities."

    Why not? Lets take some specific examples. Theres enough lithium in known current reserves for one billion electric cars. Lithium reserves data here.

    Lithium can be recycled endlessly, so thats enough for hundreds to thousands of years of use provided waste is minimised. This is before we get to new discoveries of lithium, more efficient use of lithium, aluminium based batteries, and the new carbon based batteries.
    The same principles tend to apply to other materials.

    Yes minerals are a finite resource, but they can be recycled where fossil fuels cant be recycled. Provided we use mineral resources wisely we can maximise technology. I do believe however that we are going to have to be more prudent in how we use resources, with some reduction is use, and prioritising of essentials and population growth must stop. But that is not incompatible with renewable energy at a decent level.

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  6. shastatodd@2,

    I agree that high levels of consumption and waste are a serious concern.

    My recommended solution is to demand/require the wealthiest and most powerful to lead the develpment of 'low consumption, no-negative-impact, zero-waste' ways of living that the entire population can develop to enjoy virtually eternally on this, or any other, amazing planet.

    The Winners are the ones who can afford to behave better. And they are the ones who should not be allowed to claim that 'they did not know better'.

    It boils down to correcting the incorrectly developed socio-economic-political systems to restrict the freedoms of people to 'believe what they want and do as they please', with more restrictions as people become wealthier and more influential. The wealthiest and most influential should only be allowed to properly increase the awareness and understanding of the entire population about how to develop sustainable ways of living.

    Allowing Winners to do as they please, the standard Libertarian argument, is undeniably a recipe for disaster. It has been proven to develop self-reinforcing systems that are certain to result in the development of more damaging irresponsible undeserving Winners, unless those type of winners get caught/penalized/restricted.

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  7. shastatodd@2,

    An understanding that is related to my previous comment is: If the 1% of the total current population (about 75 million people) that 'per-capita causes or personally benefits (profits) from the highest levels of consumption, waste and negative impacts' became Zero contributors to the problem there would be a far greater than 1% reduction of the problem.

    And the actions of those 75 million would provide education and leadership toward ways of living that the other 99% could sustainably develop to also enjoy.

    The only potential problem is that those 1% would no longer be able to appear to be, or put on a show of appearing to be, the Biggest Winners. However, any perceptions that are not the result of living/acting in ways that are truly sustainable and helpful to others will only be temporary delusions of grandeur and superiority.

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  8. the power from a windmill is not stable enough to be used solely on the grid, due to flucuations and needs some means of stabalsing the electric parameters and needs a  base load which needs to be provided by fossil or nuclrear or say some storage scheme. this report does not address ths matter

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  9. Alchemyst,

    All those considerations are included in the study.  Large areas average out the wind.  The article discusses storage.  Base load is not needed to stabilize the grid.

    Please provide a citation for your false claims or withdraw your argument.

    If you do not know what you are talking about you should remain silent.

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  10. Michael Sweet @9, new article you and others may be interested in:

    "Stunning drops in solar, wind costs mean economic case for coal, gas is ‘crumbling"

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  11. Sweet

    it is this simple 10 seconds to find a reference. Please stop being abusive

    Windmill produced electricity is not stable it needs a baseload or stabilisers.

    currently using a baseload is the only proven method of stabaising the current parameters.

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    Moderator Response:

    [GT] Link established. Please use the linking tool in the toolbox.

  12. Alchemyst, from what can be reached through the link you provided, your referenc does not treat of the use of baseload power. It explores ways to optimize the use of wind by doing short term, high accuracy projections of demand vs production capability. There was nothing I saw in it about baseload. The intermittency of the renewables considered in the article referenced in the OP is well known and has been well known for a long time. The intermittency is the very reason for the study. The entire point of the study is to determine the region size and relative capacity necessary to afford not only 100 % renewable but 100% from wind and solar. You seem to not have read the OP and followed the links. Your own reference is from 2013 and, if anything, makes the 2018 study by Kaldeira and others more relevant, as the methods described in your study could in fact reduce the region size and overcapacity necessary for the goal of 100% wind/solar.

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  13. This is from Alchemyst's link and contains the gist of the story:

    "In a paper published in the American Institute of Physics' Journal of Renewable and Sustainable Energy, researchers propose a new strategy to optimize power-generation efficiency and so better control wind farms."

    More detail: "The new strategy is based on continuous predictions of how fluctuating winds affect each turbine's maximum generation capacity. It also incorporates factors missing in other wind-farm control strategies, including differing power generation between turbines, actual fluctuations in power generation capacity, errors in prediction, communication disruptions preventing active control, and even turbines without the capacity for continuous active control."

    So, as Alchemyst shows us, there are ways to optimize generation that have not yet been implemented at large scales.

    It goes on to say :"To demonstrate the feasibility of the new strategy, the researchers compared their predictions to raw data from a single wind turbine. The team then further refined their calculations and simulated a control operation with data from a wind farm of 33 turbines.The results suggest that wind-farm managers can improve their power-generation efficiency with the new strategy." Rather encouraging I'd say. And it took only a few seconds to find that reference. There is a wealth of knowledge about renewables out there.

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  14. nigelj at 6:02 an 28 march.

    You are correct at the moment we can only use wind power to supplement other generating systems. the problems are in transmission and stability (not just power but synchronising every windmill in the grid and making sure that they don't operate ot 60.01 Hz instead of 60Hz which the author has not touched on). This brings us to storage which  strongly aids stabilty. This technolgy is not currently proven and in itself with its own set problems and costs. With  current resources and technology a conventional baseload is essential

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  15. Alchymst,

    Philippe Chantreau has noted that your reference does not support your false claims.  Please link a reference that supports your claims.  It is not my responsibility to search for support for your false claims.

    Your claims at 15 are also false.  You have provided no references to support your wild claims.  It is sloganeering to make unsupported claims.  The moderators wil start to delete your posts if you continue to refuse to support your wild claims.

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  16. My claims are sustansiated.

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    Moderator Response:

    [GT] Link corrected. Please use the linking tool in the toolbox

  17. Sweet for point 15

    To reliably meet 100% of total annual electricity demand, seasonal cycles and unpredictable weather events require several weeks’ worth of energy storage and/or the installation of much more capacity of solar and wind power than is routinely necessary.

    I think you are going to need a back up

    your report missed

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  18. Storage technology has been proven.

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  19. Alchemyst @15

    "You are correct at the moment we can only use wind power to supplement other generating systems. "

    I only said that in the sense that wind and solar can provide 80 - 90% of power with the remainder as biofuels, nuclear or hydro. (or gas as a last resort). This system provides a stable baseload according to the article, and is also economically viable right now.

    Storage options are however dropping fast in price and could replace the need for biofuels, nuclear etc. This would be preferable to me.

    Your science daily link didn't say anything about baseload power requirements.

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  20. Alchemyst @17

    Your claims don't appear to be sustained. These appear to be problems about wind power maintaining an even voltage and frequency.

    The abstract of the thesis in your link is about the problems of fixed speed generators in terms of stable voltages, and notes these are common in existing wind farms. However it notes that direct drive variable speed generators are feasible, although  more expensive. However it did not say prohibitively more expensive, and its not clear why they would be given the nature of generators.

    I couldn't see any obvious reference to frequencies or problems with this.

    I really don't see that the thesis found some fundamental unsolvable problem with anything.

    If you meant problems with functionality of storage technology, I'm not sure where you get that from. Have a look at the huge Tesla battery instillation working in southern australia.

    Clearly batteries are still expensive, but numerous options are under investigation in prototype that use relatively cheap materials including alluminium, carbon, sodium sulphur etc. And note my post above on how much lithium batteries have dropped in price in just a few years.

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  21. As Nigel has noted, the thesis linked by Alchemyst does not point to any fundamental problem. In fact, the introduction of the thesis states that it is of interest because of increased contribution from a specific type of wind generator into the grid and an even greater anticipated future contribution.

    Alchemyst, I suggest  that you read more carefully the materials you link. Also, you need to argue on topic. The topic of this thread is 100% wind/solar generation and the geographical are and overgeneration capacity to achieve that goal. The paper in the OP discusses that topic, that's what you need to argue about here on this thread. Your comment at 18 indicates that you did not carefully read the OP paper.

    The instability caused by increased contribution of intermittent sources in a grid prinarily fed by conventional sources is a different enough topic to warrant looking for a more appropriate thread.

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  22. Just some points to nore about Amethyst's links. The first is a paper dated 2013, so 5 years ago, and an eternity in the fast developing world of wind power, And it deals with managing power output from individual turbine and management of individual wind farms. No mention of frequency whatsoever.

    The second link, a PhD thesis, is from 2014, still some time ago. It discusses voltage stability and response to transient events, but does not discuss basic frequency management at all. As the thesis notes many older turbines were designed for fixed rotor speeds but that has largely been superseded now - new designs manage rotor speed, blade angle of attack etc to maximise energy extraction from the wind. This has been an  important part of the cost reductions in wind recently, turbines that are more efficient,

    On the subject of frequency, everything on a grid has to synch frequency very accurately. If each machine's frequency deviates by even fractions of a percent, the overall supply becomes totally chaotic in seconds. But this frequency isn't exactly constant. As loading on the grid varies there ia a natural small variation of frequency - most grids are designed to stay within +/- 0.5 hz of their nominal frequency. Under higher loads for example frequency typically dips a fraction of a hz. But importantly, everything on the grid stays sufficiently synched together, even as they all fluctuate. If the frequency deviates too far too fast generators are often required by the operating rules of the grid to disconnect to protect themselves and the grid.

    And wind power systems participate in this successfully. Look at places with high wind penetration. South Australia has around 50% wind, and at times wind is supplying around 1/2 the states power. And there are no problems with wind not synching with everything else. If there were, with that level of wind, the grid would collapse in seconds.

    There are some issues with higher levels of wind (and solar) reducing the supply of synthetic inertia to the grid that the fossil fuel (and hydro) generators need to stay in synch.

    Essentially Coal, Gas & Hydro plants need the grid to help them stay synched, providing inertia for the spinning machines to work against to help stabilise their speeds and thus output frequency. And some participants on the grid actually supply frequency control services, rapidly adding or removing demand on second timescales to vary the loads that the FF & Hydro generators work against to prevent them varying in speed to much as demand varies. This allows the control systems in the FF & Hydro plants enough time to change the flow rate of the steam for example to adjust the power output of the generator. Essentially the FF generators can't maintain grid frequency stability on their own, their response times are too slow. So instead of them stabilising the grid, they are actually stabilised by it, by other systems.

    Wind hasn't detracted from basic frequency management but at high penetrations levels it has reduced the level of synthetic inertia available on the grid. It hasn't directly destabilised the grid, but it has made it harder for the actual stabilisers to stabilise the FF plants. This issue is well recognised, and there are technologies to address this, adding extra components to increase synthetic inertia.

    Alchemysts's point about 'baseload' stabilising wind isn't true. Baseload (meaning things like coal) actually need to be stabilised by other systems.

    Modern wind turbines have completely decoupled the rotational speed of the turbine from the frequency of the power they put out onto the grid. Two methods used are:

    • Doubly Fed Induction Generators. Essentially using an AC-DC-AC converter to manipulator the energisation of the windings so the power output from the turbine has the right frequency, independent of the speed of the blades.
    • Direct AC-DC-AC conversion. Instead of messing with the windings, the complete AC power output from the turbine, at whatever voltage and frequency, is fed into a converter. First the conversion to DC removes any consideration of the rotor speed. Then the second DC-AC stage creates the desired voltage and frequency, 60 hz say. And the control system for these can then vary this output frequency to follow the variations in the frequency on the grid. Solar power from PV's, being DC, is fed onto the grid in a similar manner, with a DC-AC conversion that handles managing output voltage and frequency. Similar technologies are used in High Voltage DC Transmission lines to convert AC to DC, transmit DC, then convert from DC back to AC at the other end.

    If these approaches didn't work, then places like South Australia or Denmark with high penetrations of wind would have totally collapsed grids. They don't!

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  23. Glen at 1606 

    The Danes have 40% wind powr generation and rely on other nations goodwill for when the wind doe not blow.

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  24. Alchemyst

    And there are periods where they generate more power than they need and it is exported, some to Germany, some gets sent to Norway where it is stored in Pumped-hydro in the mountains.

    And it's not goodwill, it is an energy system spanning multiple countries.

    None of which is relavent to the point that highlevels of wind don't endanger frequency management just because it is wind.

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  25. Even the premier manufacurer of electricty storage devices states that a baseload is needed.

    But the higher the proportion of the energy mix represented by renewable energy sources such as solar and wind power, the greater the fluctuations in electricity generation – varying by the minute, hour, day and season, depending on energy source and region. To offset these fluctuations, the power network needs flexible electricity producers, such as decentralized energy storage systems and gas turbine power plants. These would accumulate electricity when generation exceeds demand, and would release it when renewable sources fail to supply enough.

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  26. Alchemyst,

    "Flexible energy producers" is not baseload.  Learn your terminology.  At 26 your quote describes the system proposed for a 100% renewable energy system that requires no baseload power.  Use quotation marks and indent to show that you are quoting your source.  The OP discusses how much storage is needed in the USA.  Your citations do not support your arguments

    You need to acknowledge that Glen Tamblyn has explained how frequency regulation works and that renewable energy does not have a problem with frequency regulation.

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  27. "Your claims at 15 are also false. You have provided no references to support your wild claims. It is sloganeering to make unsupported claims. The moderators wil start to delete your posts if you continue to refuse to support your wild claims."

    before I go on please state exacly which claims that a wrong in para 15. 

    It is extrememly difficult to understand what you are against, 

    Please elucidate, thank you

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  28. Sweet, I think I should remind you of your past reasoning with regards to the passage and that you offenviveness to anyone who disagrees with you

    It doesn’t take a stretch of the imagination to suppose that losing half the Arctic sea-ice cover in only 30 years might be wreaking havoc with the weather, but exactly how is not yet clear. As a research atmospheric scientist, I study how warming in the Arctic is affecting temperature regions around the world. Can we say changes to the Arctic driven by global warming have had a role in the freakish winter weather North America has experienced?

    michael sweet at 07:43 AM on 2 February, 2018
    Idle claims that the sea ice expert who wrote this article was incorrect are easily dismissed with actual data.
    To answer your question: "could someone please explain this disepancy [sic] or is it due to inflation and projection?"
    The discrepancy is due to the asker being uinformed of the actual data. The linked article was a summary article and did not detail all the sea ice data.

    michael sweet at 11:33 AM on 2 February, 2018
    You are cherry picking your start year as 1979. That is when satalite records start, but not when scientific records start. This graph from Cryosphere Today

    Michael just a reminder of your logic, now the author stated 30 years that is from 2017 is 1987, not 1979.
    I’m sorry but I have great difficulty in accepting your comments seriously (ps 1979 makes 38 years not 30)
    And yes the author has retracted her comments!

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  29. Glen Tamblyn 16 07

    "If these approaches didn't work, then places like South Australia or Denmark with high penetrations of wind would have totally collapsed grids. They don't!"

    But the South Australia grid has collapsed!   Sept 2016, due to a storm that forced most of the windfarms to shut down and black out the whole state!

    Is Elon there now on a rescue mission?

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  30. Glen at 20 13,

    It is goodwill should we have an europe wide energy crisis eg Russia stopping the natural gas flow, I have a feeling that certain countries will put their own needs above others. It is already happening with the UK breaking away.  similar things have been happening in Australia where I understand that other states are not as helpful as they could on the energy scene with Tasmania and south australia.

    "Hydro is sourcing 200 diesel generators which could supply up to 200 megawatts by April."

    Its sad really , if human nature should see that cooperation works, but when the chips are down self interest comes first.

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  31. Alchemyst,

    I am sorry for the confusion, apparently one of your offensive posts was deleted so the posts were renumbered.  I referred to your post now numbered 14.

    Your primary false claim was about renewable energy upsetting the grid frequency which Glen Tamblyn has shown was false.  You then make false claims about storage of energy and the necessity of baseload energy on the grid which you have not supported.  

    Alchymist has been posting for a long time here at SkS without providing citations to support his/her arguments.  Many posters have pointed out false claims that (s)he has made.

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  32. Alchemyst

    You have made a number of claims on this page  1) that wind, solar and storage wont work without base load power (nuclear, gas etc) 2)wind voltages are unreliable and 3)wind frequencies are unreliable and 4) wind, solar and mass storage is too expensive.

    These are just assertions without any details. The sources you quote dont support your assertions. People have refuted your assertions with technical detail and / or real world examples in comments above as pointed out by MS.

    Heres something more on costs of battery storage in this article: "Plunging costs make solar, wind and battery storage cheaper than coal" Please note theres no baseload power in this instillation either.

    In all fairness its not a massive instillation, (500 mw) but it shows how fast things are growing and how competitive costs are becoming.

    You say "But the South Australia grid has collapsed! Sept 2016, due to a storm that forced most of the windfarms to shut down and black out the whole state!"

    The primary cause was actually an exceptionally severe storm and multiple transmission line failures. It appears the wind farms shut down automatically when the transmission lines failed, (in other words it wasn't that the wind turbines couldnt handle the wind)). This shut down in turn was due to the software settings of the wind farm systems,  and appears to be an issue that can be changed. This wikipedia article has the details.

    And more here in this article :"Overly sensitive protection mechanisms in some South Australian wind farms are to blame for the catastrophic statewide blackout in September last year, the Australian Energy Market Operator (AEMO) says."

    "AEMO said changes made to turbine control settings shortly after the event has removed the risk of recurrence given the same number of disturbances."

    So yes the system had some problems not unexpected with new technology, but they were not intractable sorts of failings, and have been fixed.

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  33. Alchemyst

    Firstly, the situation in South Australia was an exeptional event. My earlier point about grid collapse was that a grid running under perfectly normal conditions would collapse in seconds without everything matching frequency exceptionally. Consider a grid where half the generators are running at 50 hz, and the other half are running at 50.5 hz. Assume all their waveforms start out synchronised. 1 second later half of them have put out 50 cycles, the other half have put out 50.5 cycles. The second half are now completely out of phase with the first half. They are generating in complete opposition to each other! The final volatage that the end user sees is zero volts. another second later they are in synch again, thena another second totally out of synch. Every 2 seconds the supply voltage to the end used fluctuates between 240 V AC and 0 V Ac. If the the difference was only 0.1 Hz, this would be a 10 second pattern. 0.01 Hz it would be a 1 miniute 40 seconds pattern. Do you see that happening, do the lights dim and return every few seconds?

    Now imagine what the supply would look like if each generator deviates by differing amounts from the target frequency. An absolute dogs breakfast of a power supply, visible in seconds. Thats what I mean by collapse.

    Now, to the SA black state event. Yes, as others have commented the software setting on the turbines meant that they shut down a bit prematurely. Not intrinsic to wind, but an overly aggressive setting on a software safety switch. But it wouldn't have helped any way on that day. Once those storms did the damage they did, a Black State event was almost inevitable.

    Adelaide, the capital city consumes most of the states power. Originally there were two coal poer stations well north of Adelaide at Port Augusta,  orthern and Playford B. They were located there to use coal from the nearby Leigh Creek coal mine. Power from both stations was fed into the large Davenport substation and from their 4 high voltage transmission lines carried the power to Adelaide. Combined with the Heywood Interconnector from Victoria coming up from the south, this is the backbone of the states grid. 

    Various wind farms have been built in SA, mainly in that Adelaide/Port Augusta corridor, taking advantage of those 4 power lines to connect to the grid. And the two coal stations have been closed and are currently being demolished.

    So what happened on that day? Storm roared through the region between Adelaide and Port Augusta, including some tornadoes. Over about 1.5 minutes they ripped up 3 of those 4 high voltage lines. Literally towers smashed, one tower sucked out of the ground, concrete footing and all. And the power lines lying on the ground, shorted out.

    When it frst started and faults started to occur on those lines, the controllers started to react and shut down the lines. Yes, some of the wind farms shut down needlessly early due to the software settings. But they would still have had to shut down soon any way since the transmission lines they were connected to had failed. With this loss of power from the north, the rest of the system to the south struggled to meet demand in Adelaide over the next few seconds and freqquency started to drop as turbines slowed under the excess load. So frequency was running out of control, and the grid rules meant that everything would have to disconnect fairly soon anyway.

    They Heywood interconnector rapidly ramped up the power being drawn from Victoria to try and meet the load. So the interconnector reached overlaod and was disconnected. SA now had hardly anthing still on-line. The remaining generators, mainly gas, couldn't cope and slowed radically, dropping frequency and eventually they disconnected. In fact the last couple of seconds of voltage and frequency gyrations was due to the erratic behaviour of the gas plants under overload.

    Now, what if the wind farms had kept operating, without their safety switches tripping out? Well most of them couldn't have, their transmission lines were lying on the ground so even without the software setting they would have been forced to disconnect seconds later anyway. Only the 1 or 2 farms connected to the remaining operational line, to the west, might have been able to keep running. But the frequency would still have been swinging wildly, possibly causing them to have to disconnect.

    Importantly, the remaining farms weren't large enough to carry enough load, so the Heywood interconnector would still have overloaded. Then those remaining frms, with the gas stations, would still have been inadequate to meet the load and the frequency slew would have forced all of them to disconnect anyway, so the sam result. And all of this happenbed too quickly for the system controllers to institute controlled load shedding, blackouts in some regions to stop the whole system going down.

    The collapse wasn't caused by wind, or even software settings. It was caused by tornadoes tearing power lines down.

    Now a hypothtical scenario. No wind and those two coal stations were operating instead. Most of their power would have been going to Adelaide, down those 4 power lines. Then the storms ripped up 3/4 of their transmission capacity. Operating at high output, with now only 1/4 of their transmission capacity, a race would have started over a few seconds. With high output but unable to get the power out, the generators in those power stations would have started running away, driving frequencies up rapidly, equally something where they are required to trip out and disconnect from the grid. No way in the world could an old coal power station throttle it's output back by 75% in a few seconds and still keep running. And the one remaining powerline would have overloaded and the safety systems on the powerline would shut it down as well, tripping circuit breakers at the substations. The race would have been which would trip out first in those few seconds but either way, the same thing would have occurred - power from the north died, Heywood collapses and the system goes down.

    On that day, given the layout of SA's power grid, given where it's generation assets were, both old and new, and where the storms did their damage, the Black State was almost inevitable. Nothing to do with it being wind per-se. How many networks can survive loosing 75% of their transmission capacity?

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  34. nigelj and Glen Tamblyn,

    Interesting discussion.  I read the abstract to the paper and I am surprised that it has generated such a reaction.

    But one thing that has started to "niggle" me is the potential vulnerability that we would create in the US with a grid system reliant on large transmission lines covering the country that are critical to supplying power to areas far away from the source of the wind or solar.  

    We worry about terrorists taking out a nuclear plant but large transmission lines would seem to be sitting ducks for terrorists let alone some country with which we had a conflict (that did not escalate to nuclear war).  When the source of power is more localized we do not have the same risk.

    Maybe this is only theoretical.   Has anyone considered this?

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  35. Yes, NorrisN, long transmission lines are a vulnerability, but so too are large centralised power stations, to terrorists or warfare.

    Ultimately you need a hybrid mix of everything taking a weighted assessment of all the risks to work out the optimum configuration. These risks are climate change (likely & severe risk), war(unlikely but severe risk), terrorism (more likely but lesser risk), equipment failure (likely but low risk with good design).

    If we could get by with local distributed power with storage that would be best, but we must get by with zero-carbon power. The options for this, depend on location. In the tropics, Solar with local storage can probably handle it all. But at higher latitudes solar varies so much more over the seasons amd wind has variability on scales of multiple days so we need to add some long range transmission, particukarly north/south to ease the load that storage alone might try to carry. Local storage is fine for daily variations but not multi-day or seasonal. Nuclear and big hydro may be limited in the sites they can be located at, both can be vulnerable to drought and all of them are sitting ducks to war or terrorism, no escaping that.

    We have lots of pieces of the puzzle, all the Lego blocks we need, but we still have to put them together into a sensible design.

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  36. Alchemyst

    Tasmnaia is mainly powered by hydro - over 2200 MW of it. Some gas (200 MW) and some wind (300 MW). Then it has a single cable link to the mainland, limited to 500 MW. In the few years before those events, Tasmania had been cooperative selling (remember these are commercial exchanges) to the mainland. Then there were several drought years - the achilles heel of hydro. But they would still probably have been OK with power back from the mainland. Then a fault developed in the cable and it was down for months so they had to take emergency measures.

    Too much cooperation? Or not enough? If there had been a second cable or even a third, linking Tasmania to the mainland and also to much more wind assets in NW Tasmania as well as off-shore wind hubs centred around islands in Bass Strait, they wouldn't have had a problem.

    This is the thing. You can try to do your power supply from local sources, but if something goes wrong, you have very little fall back. If you interconnect to your neighbours a little, you are vulnerale to failures of your few links. However if you have high interconnectivity, it is hard to knock out lots of links, and the syetm as a whole is stronger.

    So Russia cuts off gas? Hydro in Norway and Sweden go to full output, Nuclear in Sweden ramps up, etc. The more diverse your energy sources and connection the better your system. It's like being a little bit pregnant. Being a little bit interconnected is an oxymoron.

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  37. Alchemyst

    "Even the premier manufacurer of electricty storage devices states that a baseload is needed."

    Hmmm... The word baseload doesn't appear on the Siemens page you link to. They discuss storage which is a recognised part of the mix and also gas. Sure they are promoting the particular flavours of storage they are invested in but we will need all types of storage, again a diverse mix. And we need storage precisely because it is flexible, unlike 'baseload' meaning typically coal which is actually relatively inflexible,

    This is what our future energy system will look like. Diverse energy sources, with diverse generation patterns, combined with diverse energy storage options that will balance ALL the variability - supply side and demand side. Add in long distance interconnection to take advantage of differences in weather patterns geographically to reduce the variability on the supply side, with demand-side management to also reduce the variability on the demand side.

    The problem with fixating on 'baseload' as an idea, as if it is some Holy Grail, is that it misleads us into totally underestimating how hugely variable our demand is as well. And getting more so as things like hotter weather increases the use of air-conditioners, in summer. Our power demand is becoming less 'base', more 'peaky'.

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  38. NorrisM @34

    "But one thing that has started to "niggle" me is the potential vulnerability that we would create in the US with a grid system reliant on large transmission lines covering the country that are critical to supplying power to areas far away from the source of the wind or solar. We worry about terrorists taking out a nuclear plant but large transmission lines would seem to be sitting ducks for terrorists ..."

    Fair question, however I think the terrorist threat is over stated. Far more people have died each year on average in America from drowning since 911. Property damage from terrorism in America over the last couple of decades has been virtually insignificant in the greater scheme of things. Yes 911 was terrible, and in no way am I downplaying this, but it was one event when America was caught off guard. The psychological impact of terrorism appears to me greater than the real risk of problems, and understandably enough.

    This could of course all change, but it's hard to see why it would. If terrorists haven't been able to launch multiple attacks by now on people or property, and given ISIS is in retreat its hard to see things getting worse, provided the western world does not inflame islamic sentiment.

    And the towers and power lines can be replaced remarkably quickly within about a day. You will see this in articles related to the 2016 Australian event.

    Alternatively cables can be buried underground, however this is expensive at about five times the cost. But then it does insulate the system from stormy weather and tornadoes as well as other risks.

    And climate change is expected to make storms worse.

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  39. Recommended reading:

    How energy storage is starting to rewire the electricity industry by Eric Hittinger & Eric Williams, The Conversation US, Mar 22, 2018

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  40. Wind turbines operate under great turbulence, with consequences for grid stability( —While previous research has shown that wind turbulence causes the power output of wind turbines to be intermittent, a new study has found that wind turbulence may have an even greater impact on power output than previously thought. The researchers modeled the conversion of wind speed to power output using data from a rural wind farm. The results showed that the intermittent properties of wind persist on the scale of an entire wind farm, and that wind turbines do not only transfer w…

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