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Storage is Essential for Wind and Solar

May 30, 2014


Electricity must be generated as it’s being used, so that demand and supply are always kept in balance.

This is a critical factor with respect to unreliable, wind and solar. When the wind stops blowing or the sun stops shining, supply is cut off from these sources and another source must immediately be brought on line. Typically, the back-up source is a natural gas turbine that has been spinning, i.e., running, using natural gas, but not connected to the grid, which can be quickly brought on line. Using coal-fired power plants for back-up requires them to operate as load following units, cycling them up and down, which creates major thermal stresses on components, and increasing maintenance costs.

Standby power adds to the cost of wind and solar, but usually isn’t included when calculating their cost.

Storage is essential for widespread use of wind and solar, if large quantities of back-up power generation are to be eliminated.

It’s why the California Public Utilities Commission required utilities to add storage to their systems.

Unfortunately, storage of electricity isn’t cheap or easily accomplished.
It’s highly doubtful that storage of large amounts of electricity can be done cheaply.

Historically the most effective method for storing electricity has been pumped storage, which is actually an indirect method since it stores water that can be released from a reservoir to generate electricity.

Pumped storage, in so far as I can determine, was first used in the United States by Connecticut Light and Power in 1927 to pump water, using electricity generated by the hydro-power plant, back to the lake which was the source of water for their hydro-power. This application saved money by using a reservoir whose initial purpose was the storage of water.

Unless a reservoir is already in place, pumped storage requires building a dam, and there are only a limited number of locations for new reservoirs. Dams are expensive, and are usually objected to by radical environmentalists1.

But other methods of storage have been proposed, such as those listed here:

  • Batteries, such as Lithium ion, sodium sulfur, lead-acid and flow batteries
  • Hydrogen, produced from electricity when it isn’t needed on the grid, which can be used to power a gas turbine to generate electricity
  • Compressed Air (CAES), where air is compressed using electricity when it isn’t needed by the grid
  • Ice, where electricity is used to run a refrigerator to produce ice, which, when it melts, can return the energy to run a generator
  • Other heat storage, such as salt beds, to store heat for use later, to run a turbine to generate electricity

As can be seen, most are indirect methods where the stored energy is in hydrogen or ice, etc., which can then be used to generate electricity.

Converting energy from one form to another, and then back again, always results in losses.

All of the above methods use a great deal of space per kWh of storage, and are very expensive.

One supplier of storage claims to have a cost of $1,000 / KW, but this uses some fancy logic. AES Energy Storage President, Chris Shelton, said that a storage facility performs two functions: First it absorbs energy and then it discharges energy. Voila, costs are cut in half because it can both absorb and discharge electricity, so a $2,000 / KW system becomes a $1,000 / KW system with the stroke of a pen. Of course, the storage facility still costs $2,000 /KW.

Battery life is usually overlooked when calculating the cost of battery storage, where the investment must be repeated every several years when the batteries die2.

Huntorf, Germany, CAES plant. Photo from DOE.

Huntorf, Germany, CAES plant. Photo from DOE


Two CAES systems have been built, one in Germany, in 1978, the second in McIntosh, Alabama, in 1991. Both are large scale systems: Huntorf is rated 321 MW, McIntosh is rated 110 MW. Both were very expensive.

Underground caverns suitable for CAES are also not readily available.

The McIntosh CAES plant uses the compressed air in a natural gas turbine, so it is a hybrid system.

There are additional variations of CAES, and of other storage systems, but none, those listed here and others, singly or in combination, can economically provide the amount of storage needed to allow significant use of wind and solar on the grid.

It’s important to recognize that the cost of storage must be added to the cost of wind and solar. Storage makes electricity from wind and solar more expensive. Neither storage nor back-up generation are include in Levelized Cost of Electricity (LCOE) calculations, which is another reason why LCOEs can be misleading.

Equally important, storage is not essential for the grid to operate successfully without wind and solar. BUT, large scale storage is essential for wind and solar if the grid is to operate reliably without back-up power generation.

Currently, all storage methods are expensive, and none cost less than natural gas turbines for back-up power.



  1. The term radical environmentalist is used to distinguish between environmentalists, which includes most Americans who routinely support protecting the land and water, from those advocating extreme action. Many radical environmentalists are associated with extremist causes, such as stopping global warming; or stopping the use of nuclear power; or maintaining biological diversity.
  2. This may not be entirely the case with flow batteries, as the electrolyte can be replaced.
  3. Storage system size is usually published as Megawatts(MW), but this doesn’t accurately reflect the amount of electricity available for the grid. It would be more accurate to publish the rating in kWh, to reflect how much electricity is available. But, even this doesn’t indicate how long the electricity will be available. Is it consumed quickly, such as with Flywheel systems? Or spread out over hours, such as with the McIntosh, CAES hybrid system?


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9 Comments leave one →
    • May 30, 2014 3:16 pm

      Thanks for your comment and the link to an excellent article.
      The only problem with the referenced article is a claim that wind generates electricity at around 8 cents / kWh. I realize that the EIA has made this claim, but they use a 35% capacity factor and make some very generous assumptions, such as using a 30 year life when wind turbines are expected to last 20, possibly, fewer years.
      Most studies I have seen show wind costing around 11 cents / kWh.
      Other than that, the referenced article is very good and well worth reading.

  1. May 31, 2014 5:29 pm

    Right. My page links to a lot of articles, though too many unfortunately contain cost data that misleads, rather than meaningfully informs.

    “Cost,” including the term “avoided cost” as used net metering statutes (such as in my state), has become so politicized (and distortable) that I especially value your efforts to present accurate cost data (don’t know of any other well-written website that does this).

    I do always come back to you, however, on my belief that some credit must be given for pollution-sparing results. For example, I may agree to pay a higher electricity rate (to compensate my utility having to pay $.11/KWH for wind, versus $.05/KWH for coal) if in fact I get cleaner air to breath in the process. So I remind myself, when I read that brown power sources cost less, that a pollution premium should fairly be factored into its cost.

    In a sense, you and I have already made that choice by “agreeing” to pay more for our automobiles (the increased cost due to clean-air tech mandated by government) — something I don’t see you objecting to here, and I’m betting you would not advocate to go back to “the good old days” of dirtier vehicles. If we could buy a car for $400 less at the expense of its pollution control stuff being stripped from it we’d at least have to think about that car’s true cost to our environment.

    In that regard, I’m betting that tens if not hundreds of millions of Chinese would agree to pay more for clean electricity as they choke on their own outrageously dirty air (in a sense they already are paying more — via hyper-subsidies for solar power in China).

    Anyway, this is what politics/policy-making is all about: We get the true cost of choices, then we make them.

    So again, I appreciate your efforts to call BS on greenie cost claims.

    In fact, I wish you’d go further and pursue cost data that can be distilled down to “net-power-bill choices,” so Joe Six Pack can grasp the essence of the debate — so that he can be asked this question: Is clean energy worth the higher cost, as reflected in higher taxes and power rates to pay for all its subsidies?

    If so, how much? Would he pay, say, $25 more per month on his power bill in exchange for 25% less air pollution in his region of the country?

    My local utility, by the way, uses its billing insert to constantly warn us about higher power rates due to Obama’s “war on coal.” In that my EMC is heavily invested in coal power, and thus presumptively biased, I don’t know what to believe. An independent source on actual cost would serve me greatly here.

    But see, that sure isn’t going to come from my local newspaper, which sports an environmental reporter who’s laughably greenie-biased.

    So, I consult a variety of sources and collect them on my website, and hope the truth emerges in between.

    Keep the faith, brother!

    • May 31, 2014 5:40 pm

      Once again, great comments, and thanks for the kudos.
      I’m not as concerned about the cost of controlling genuine air pollution and the political judgments relating to them, as I am about the claim that CO2 is a pollutant.
      It’s the global warming issue that is distorting energy issues, and that will, I believe, cause great harm to the United States.

  2. June 1, 2014 10:44 pm

    I agree with you, Donn, that the CO2 and global warming issues have been politicized, and I think you win the day on your assertions that present policies will cause great economic harm to the U.S.

    But think for a moment about incremental safety/pollution cost regs imposed on our vehicles. I remember when cars had no seat belts. Twice I’ve been hit by drunk drivers in terrible accidents. Twice my seat belts saved my ass. Nanny government required them, and mass economies of scale (via that government compulsion) probably accorded those life-saving belts to me for, say, no more than $28 per car (versus a lot more had they never been required and I thus had to order them as custom add-ons).

    Ditto for the very real and measurable air pollution savings that accompanied government mandated shift from leaded gas, and increased pollution controls on our cars.

    Now ponder the smokestack emissions of your typical coal plant. It’s not comprised solely of CO2, but in fact plenty of other nasties that indisputably ain’t good for us.

    And if you said James, pay $20 more on your power bill for a 20% reduction in the amount of crap Georgia Power dumps over your farm, I’d go for it. Just like I’m eternally grateful for that $28 extra dollars I paid for those life-saving seat belts, and cleaner air for me and my son and, ultimately, his kids.

    See where I’m going? The car industry and US economy were not wrecked by Nanny’s safety and pollution compulsions, and the added cost of our cars is something you and I have long accepted (I would NOT want to go back to my seat belt-less, high-pollution 1962 Dodge Dart, and I don’t think you’d unwind all that, either).

    I’m thinking the same here, if prudent incrementalism is applied to brown power plants like coal.

    After all, industry adapts. Slowly raise the price on coal, and people start looking around for cheaper alternatives. You thus get responses like this:

    and this:

    Sure, they may not pan out. But necessity is the mother of invention.

    I guess we disagree on our respective bets on the future. You seem pessimistic, perhaps rightly so, about adaptive change and thus you want to stick with the status quo on coal and other brown power sources.

    I’m more optimistic, I guess, especially in light of the almost daily eruptions of new ideas, processes, inventions and techniques. Only by direct pressure did Detroit supply the seat belts that twice saved my life. And only by direct pressure (from jawboning greenies, if not government) will Big Power get off its coal-burning (and crapping on our environment) pot.

    At the same time, I’m the first to rail against (typically C-student) politicians and bureaucrats dictating clean-tech changeover by sheer government fiat. Our recent history is littered with Solyndra-class boondoggles fueling an obscene National Debt.

    But I also know that with no pressure at all, we’d still be driving 1962 Dodge Dart level cars.

    It’s a very tough question, and I’m glad you’re here talking about it.

    • June 2, 2014 9:07 am

      I can’t disagree with your comments re industries negative response to real issues in the past, such as seat belts.

      First, CO2 is not a real pollutant, and I stand by my concern that government is driving the country into a slow growth, possibly negative growth, economy, including hardships on people who will lack good paying jobs, because of its fixation on CO2. There is also the question of personal freedom as government encroaches on people’s lives. Try and build a fish pond on your property, if you live in the country, and see whether the EPA sues you under the clean water act.

      With respect to regulating real pollutants, it’s very possible that the law of diminishing returns has set in. It’s impossible to eliminate all pollutants, such as bringing NOx down to zero, and, as I’m sure you are aware, the cost of trying to do so is not worth the gain. Government doesn’t recognize this limitation, and, for political purposes, continues to beat the drum for lower emissions.

      Industries negative response to the seat belt issue, is no reason to assume that industry always reacts badly.

      Today, in fact, I think industry has bent over backwards to not appear to be negative. A good example of this is how the coal industry has tried to promote IGCC Clean Coal, a process for gasifying and burning the gasses while capturing CO2. They should have, in my view, built a strong case for Ultra-supercritical coal-fired power plants that are nearly as clean as natural gas fired power plants. They can meet all EPA regulations, except for CO2.

      I recognize you have a particular concern with coal, but it is an inexpensive source of energy that is the only source available in many parts of the world. Ultra-supercritical coal-fired power plants can provide low cost electricity with very few emissions, other than CO2.

      Here, in the United States, we need, for several reasons, base load power plants other than natural gas, and with the slow demise of nuclear, coal is the only alternative.

      As mentioned above, they are almost as clean as natural gas fired power plants.

  3. Lois Lane - MAWT permalink
    June 2, 2014 7:43 am

    Reblogged this on Mothers Against Wind Turbines Inc. and commented:
    Good explanation as to why storing energy for renewables is next to impossible….

  4. June 10, 2014 6:57 pm

    Hey Donn,

    Thanks for taking the time to further respond. I think we’re in agreement — it’s always a degree and extent argument about how far government should reach in regulating positive (or killing outright) industrial and product developments. I’d love to see convincing evidence that, as you say, coal can be made to burn as clean as gas. Maybe I’m just not sufficiently informed on that score.

    Here’s a (sure, liberal bent) cool read on government standard-setting and the various political blow-backs, then emergent truths, over the years:

    • June 11, 2014 8:13 am

      Just to be clear, ultra-supercritical coal-fired power plants can achieve emission levels almost, not equal to, as low as natural gas.
      The only power plant that comes close to this definition in the U.S. is AEP’s, John W. Turk coal-fired power plant.
      Thermal efficiencies of ultra-supercritical plants can reach 45%, versus the 33% of traditional coal-fired power plants. This results in a corresponding reduction in all emissions. With appropriate scrubbers etc. pollutants are nearly eliminated. CO2 will still be above the 1,100 pounds per MWh requirement of the EPA’s, so they can’t be built in the U.S. They are being built in China and Europe.
      There will still be the slag problem, so ultra-supercritical plants are not as good as natural gas combined cycle, but, as, mentioned earlier, coal will be needed for base load, something wind and solar can’t provide.
      As to the link you provided, industry doesn’t always respond correctly, but some of the items mentioned, such as problems with the 54 mpg regulation, may still be valid. Time will tell whether the 54 mpg won’t have to be reduced, unless EVs take off … which doesn’t seem likely without the government forcing people to buy EVs.

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