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Guest Post: Can we store electricity to transform the grid?

The views expressed are those of the author and are not necessarily those of Scientific American.

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Over the next several weeks, we’ll be joined by Robert Fares, a graduate student at The University of Texas at Austin researching the benefits of grid energy storage as part of Pecan Street Inc.’s ongoing smart grid demonstration project. Robert will be contributing a series of guest posts discussing grid storage technologies, and how storage could benefit the electric grid.

It may come as a surprise that essentially no electric energy is stored between the point of generation and the point of delivery in today’s electric grid. Each kilowatt-hour you consume in your home is generated, transmitted, and delivered to your particular electrical outlet in real time. In other words, the present electric grid operates totally on demand. This seemingly inefficient operating paradigm stems from the high cost of electricity storage technologies; it is less expensive to oversize every component of the grid to serve peak energy demand than it is to store electric energy.

Adding energy storage to the electric grid would improve its reliability and permit the widespread utilization of intermittent renewable energy. However, the present cost of grid-scale storage technologies remains prohibitive. To overcome this barrier, the U.S. Department of Energy has set an ambitious long-term cost goal of $150/kWh for battery energy storage—about one third the estimated cost of existing commercial battery systems.

Despite the present prohibitive cost of storage, large-scale grid storage has been used in the United States since 1930, when the Connecticut Electric Light and Power Company built the first American pumped-hydroelectric storage facility. The Connecticut pumped-hydro plant used excess electricity to pump water from the Housatonic River into an enormous water reservoir 230 feet above. During peak electric demand hours, the stored water was fed downhill through a hydroelectric turbine to produce electricity.

Pumped-hydro technology stores excess electricity by pumping water uphill. Stored high-elevation water is used to produce electricity during peak-demand hours.

Today, pumped-hydro dominates the U.S. energy storage landscape: 95% of U.S. grid storage capacity was pumped-hydroelectric in 2011. Nevertheless, energy storage is still just a tiny part of the grid system, making up just 2% of U.S. electric generation capacity. So, what’s standing in the way of further pumped-hydro development? Pumped-hydro requires a large elevation difference between suitable water reservoir sites, like the site of the Connecticut storage plant. Furthermore, a huge volume of water is required to store energy. These difficulties don’t make further development of pumped-hydro impossible—just impractical and expensive.

Consider the illustrative example of West Texas. With its enormous swath of wind farms, West Texas could benefit from some energy storage capacity. However, pumped-hydro is a not a feasible option in drought-prone and geographically flat West Texas. Incidentally, the state of Texas has invested nearly $7 billion in new transmission lines to pump West Texas wind energy to eastern cities in real time.

While pumped-hydro is not the solution to the electricity storage problem, there are a number of emerging technologies that could one day break our electricity-on-demand paradigm. I’ll describe three of the most promising technologies: compressed-air energy storage, flywheel energy storage, and battery energy storage.

Compressed-air energy storage is similar to pumped-hydro in many ways. Both technologies borrow components from traditional methods of generating electricity, and both technologies store energy in the potential energy of a working fluid. While pumped-hydro stores energy in the gravitational potential energy of water, compressed-air technology stores energy in the pressure potential energy of air. To store electricity, an air compressor pushes high-pressure air inside an underground cavern, such as a vacant salt dome, or a depleted gas well. Electricity is extracted from the high-pressure air by burning it with natural gas and allowing the hot combustion gases to expand inside an ordinary gas turbine generator. Compressed-air storage is less water-intensive than pumped-hydro, and only requires a suitable underground cavern to operate effectively.  Because of its advantages over pumped-hydro, the U.S. Department of Energy estimates compressed-air provides cost savings of nearly 40% over the long-established pumped-hydro technology.

While compressed-air storage is less expensive and less water-intensive than pumped-hydro, it still requires an underground cavern to store electricity. Flywheel and battery energy storage, on the other hand, operate as a “box” for electricity. They could be installed almost anywhere on the electric grid.

Flywheel storage converts electric energy into the kinetic energy of a rotating mass. To store electricity, an electric motor spins up a massive flywheel. To discharge, the flywheel’s kinetic energy is used to spin an electric generator and output electric current. Flywheel storage devices require complex technology like magnetic bearings and a vacuum enclosure to operate most effectively. Grid-scale flywheel technology is still nascent, but has the potential to act as a buffer between intermittent renewable energy and the grid in the future.

Battery energy storage is unique in that it requires no moving parts, is relatively compact, and can be sized for diverse grid applications. Batteries utilize electrochemical reactions to convert electric energy into materials. A battery consists of two materials (a cathode and an anode) that “want” to react together due to their electrochemical potential difference. An electrolyte separates the materials inside the battery cell, so that reaction is blocked unless an external electric load connects the positive and negative sides of the battery.

One of most prominent battery technologies, lithium-ion, has grown commonplace from its widespread use in portable electronics. Lithium-ion is just one member of a diverse population of battery chemistries that could one day transform the grid’s operational nature. High-temperature, molten-sodium batteries have been commercialized in Japan by NGK Insulators for grid applications. A Texas company, Xtreme Power, is working to commercialize an advanced lead-acid battery for the grid. Other companies are working to develop proprietary chemistries, or unique liquid-metal designs to overcome the limits of existing technology. Still other companies are developing advanced “flow batteries,” which store energy in liquid chemical solutions.

The battery energy storage field is exciting, and batteries are the focus of the Department of Energy’s energy storage program. Over the coming weeks, I will write more about where storage is needed in the present grid, how storage can make the grid more resilient, and some of the barriers limiting adoption of grid energy storage. While there are a number of challenges that must be overcome before we can store electricity on a massive scale, storage has the capability to fundamentally transform the way we deliver electricity from the point of generation to the point of consumption. It will be exciting to witness how storage and other innovative energy technologies transform the aging grid over the coming years.

Photo credit:

  1. Pumped-hydro graphic courtesy of the U.S. Geologic Survey and can be found here.

Robert Fares is Ph.D. student in the Department of Mechanical Engineering at The University of Texas at Austin. As part of Pecan Street Inc.’s ongoing smart grid demonstration project, Robert’s research looks at how energy storage models can be used with large-scale data and optimization for economic operational management of battery energy storage. Robert hopes to develop novel operational methods and business models that help to integrate distributed energy generation and energy storage technologies with restructured electricity markets and retail electric tariffs. Through his research, he hopes to demonstrate the marketability and technical compatibility of these new technologies.

David Wogan About the Author: An engineer and policy researcher who writes about energy, technology, and policy - and everything in between. Based in Austin, Texas. Comments? Follow on Twitter @davidwogan.

The views expressed are those of the author and are not necessarily those of Scientific American.

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Comments 18 Comments

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  1. 1. outsidethebox 10:48 am 12/19/2012

    I couldn’t help but notice that the cost efficiency of batteries was left out of the discussion. But they are “exciting”. Which of course is much more important.

    Link to this
  2. 2. dwbd 12:24 pm 12/19/2012

    Much more practical to focus on batteries for Electric Vehicles. You want to subsidize Energy Storage when you can both create energy storage and replace terrorist funding, job killing, very expensive and soon to be depleted Oil with Electric Vehicles. By charging EV’s & PHEV’s at night you can even out grid demand, replacing the need for storage, as well as a greater reduction in emissions, the spectre of Oil imports & Oil wars, and city smog.

    So much smarter to invest & subsidize battery storage for EVs than for Grid energy. And essentially the EV is much cheaper, much more reliable, much simpler, superior performing and cleaner than the ICE vehicle except for battery cost. Spend money on that.

    Grid Storage? Still much cheaper to just build the NG peaker power plants instead of stupidly using NG to supply baseload power. It incredible how government morons are advocating wasting precious NG supplies replacing baseload Coal & Nuclear. A real bad idea.

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  3. 3. ejh12 6:48 pm 12/19/2012

    This is a good overview of various electricity storage methods, but there’s no mention of newer compressed air energy storage (CAES) technologies. Companies like SustainX, Lightsail, and General Compression are developing ways to use isothermal (near-constant temperature) methods to reduce energy losses from the compression-decompression process and improve efficiency. The ICAES process uses water to conserve most of the heat produced during compression and thus completely eliminates the need to incorporate fossil-fuel combustion during decompression — as is the case with the two grid-scale CAES plants in operation today. Another advantage is that the compressed air can be maintained in various types of conventional storage vessels, such as high-pressure containers or pipe, making it possible to site such systems almost anywhere (above or below ground) without the need for caverns.

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  4. 4. dwbd 8:24 pm 12/19/2012

    ejh12 you haven’t shown the most important info, namely cost & round-trip efficiency.

    What really infuriates me is, the public has been sold a bill-of-goods on Wind & Solar power, mainly Wind. Cheap, clean, so wonderful. Fact is it has twice the capital cost as the cleaner & greener Nuclear and the Carbon Abatement cost is 5-20X that of Nuclear. Or just going CCGT over Coal to reduce CO2 emissions is < 1/10th the carbon abatement cost of Wind.

    Now after all this Wind is installed, they are now telling us, Oh, now we need storage to make the Wind practical. Wind just doesn't work without storage. Go figure – what a surprise. But that is no problem, we'll just take the 2X, 5X, 20X more expensive (depending on criteria) Wind and we will double that cost again by adding Grid storage, and of course it will be John Q. Public that is forced to pay for that, NOT the Wind Power companies.

    What a RIP-OFF!

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  5. 5. MoEnergySci 3:20 am 12/20/2012

    There are cases where batteries already make economic sense – for example, in the author’s home state of Texas at the Presidio, TX installation

    Here, batteries seemed to have been more practical than putting in new transmission lines to the town. While the cost was still high, it was cheaper than putting in a new set of high voltage transmission lines. Plus, faster to complete the project.

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  6. 6. FactsDontMatter 2:38 am 12/21/2012

    Certainly he must have meant $150/MWh, not $150/kWh. The former figure is the same as 15 cents/kWh, which is in the range of a typical residential rate, fully loaded. $150/kWh is 1000 times more than that. However, cost per unit of energy is a problematic way to express the cost of storage, which after all, is a net energy consumer. Its value is to be found in its application in a system that includes energy sources, reducing the cost of the system relative to the no-storage alternative. Its cost is a component in that cost/benefit analysis.

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  7. 7. dwbd 10:04 am 12/21/2012

    Dude, if you could get batteries for $150/Mwh the price of Oil would collapse, the ICE vehicle would be doomed, the power grid would just about disappear, and a whole host of other revolutionary changes.

    $150/kwh storage is NOT PAYING $150/kwh for power. The only thing you pay for is the lost energy in storage/recovery plus the capital cost of the batteries. So simple minded example if you pay $150/kwh for batteries and use them for 1000 full cycles that means you are paying $150/1000 = 15 cents per kwh capital cost for storage, not including investment costs.

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  8. 8. robertfares 12:27 pm 12/21/2012

    @FactsDontMatter Yes, as dwbd says the price of storage capacity can’t be directly compared to the price of electricity. Storage doesn’t make electricity. It doesn’t make anything. Instead, it holds onto electricity for later use. Comparing storage to an electricity generator is like comparing a warehouse to a factory. They do different things and the cost of storage volume can’t be directly compared to the cost of production volume.

    Think of the cost of storage as the upfront cost of a warehouse per unit volume, and the cost of electricity as the cost of a commodity per unit volume. The warehouse will be much more expensive, but it is still valuable because it allows goods to be produced and delivered in a more efficient and less costly way. If storage fell to $150/kWh, it would likely become the least-cost solution for a number of grid operations. Furthermore, the grid would likely be able to achieve unprecedented availability and resiliency.

    It seems that a lot of commenters want to know more about the costs and benefits of different storage technologies. Because storage technologies and grid economics are subject to change, nothing authoritative can be said about the costs and benefits of storage at this early stage. That said, here are links to two excellent (and long) documents that discuss the costs and benefits of grid storage. The first one is a handbook on grid storage by the Electric Power Research Institute and the U.S. Department of Energy. It discusses a number of storage technologies. The second is a report from the U.S. Department of Energy discussing grid storage economics from a technology-neutral perspective.



    Thanks to all for reading. I hope that the links I’ve posted above are helpful.

    Link to this
  9. 9. dwbd 8:40 pm 12/21/2012

    Thanks for the links. Good info.

    Link to this
  10. 10. CleanDG 5:47 pm 12/22/2012

    Forget batteries and compressed air storage. The most cost effective way to store electricity is in the form of chilled water. The Texas electricity peak occurs in the summer as a result of air conditioning. Using night time wind power from West Texas in conventional chillers in Houston at night and storing that cold water in relatively low cost tanks will do far more peak shaving than batteries could ever dream of. The Texas Medical Center already uses an 8.8 million gal tank to offset summer daytime use of 32,000 tons of chillers, shaving about 16 MW from their summer peak demand.

    Link to this
  11. 11. dwbd 8:37 pm 12/22/2012

    CleanDG, that is an excellent point. You can level out grid demand with EV charging, ice storage for hot areas and heat storage for cold areas. In the north ceramic plates are used to store cheap nighttime electricity for use in daytime, called Electrical Thermal Storage, and it is quite economical to use, like ice storage much more so than batteries or CAES.

    So using cheap baseload Nuclear & Coal plus EV charging, Ice storage & ETS is much better than Electricity storage.

    The only problem is that the powerful Big Oil/NG lobby has bought enough Politicians to force through a massive expansion of Wind energy which destroys baseload power, converting it into a new and expensive form of peaking generation, a function traditionally reserved for NG power generation.

    The persons responsible for this Wind Energy Scam need to be brought to justice. A long, long prison term is entirely justified for those despicable cretins.

    Link to this
  12. 12. Quinn the Eskimo 10:11 pm 12/22/2012

    Elevated / dropped water system has been used in Ludington, Michigan for a couple of decades now.

    You guys just finding out about this?

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  13. 13. robertfares 2:46 pm 12/23/2012

    @CleanDG you bring up a really good point. Yes, thermal energy storage can greatly reduce the level of peak energy use on the demand side of the grid, and it is significantly less expensive than electricity storage.

    That being said, it’s important to remember that thermal storage and electricity storage are two different things entirely. Electricity storage technologies like batteries and compressed-air can connect directly to the grid because they work in the energy currency of electrons. Thermal storage works in the energy currency of heat, and heat energy can’t be readily converted to electricity without significant losses. Because of this fact, thermal storage is primarily utilized on the demand-side of the grid, where savings can be had by storing thermal energy to reduce peak A/C use. Because it works in the currency of electrons, electricity storage could work on the supply-side, demand-side, and in between to make the grid more efficient. I guess what I’m saying is that electricity storage and thermal storage can’t be directly compared.

    Thanks for the comment, and for bringing up the important topic of thermal storage. I hope I’ve helped to illuminate the difference between the two technologies.

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  14. 14. HubertB 8:54 pm 12/23/2012

    (When I lived in Austin, the Columbia River Dams were back pumped at night to provide power in the daytime as were dams all up and down the Balcones Escarpment. This nation has a lot more storage capability than it uses.)
    An important part of the current problem is infrastructure, politics, and business. During the Great New York City Blackout, politics prevented the use of one power line from bringing power into the city. Florida power had a dam in Maine which could have provided power to New York but did not have a contract to provide power and the grid did not exist. Otherwise, it would have been possible to throw a switch and end the blackout. Thus, the blackout was caused by a refusal by politicians to upgrade the infrastructure and get rid of bureaucratic red tape.
    The California Blackouts were caused by incompetence at Enron. They reserved a high tension line but did not use it. California politicians should have thrown them in jail then!
    Better storage will not solve the problem of a lousy transmission and political system unless the storage resides at or near the point of use.

    Link to this
  15. 15. Keefwivanef 9:40 pm 12/25/2012

    How many billions of dollars have been stolen from investors and taxpayers by fraudulent Green Widget companies.
    Flavour of the month is energy storage.

    Dozens of New Battery Widget companies…coming real soon send money. I’ll be naming and shaming them in my next post.

    Compressed Air energy storage….WHOO HOOO!

    The laws of physics determines that the process is dreadfully inefficient. Never mind that claim the Compressed Air Widget companies, we’ve got a new adiabatic, isothermal, whatever – process which will be ready real soon (send money now)

    I really can’t pick a better example of the genre than LightSail Energy

    Well known philanthropist (yeah right) Vinod Khosla CLAIMS that he has put in $37M and it’s all good so punters and gummints should get on board quick.
    Naturally Khosla will be first in line to get back his investment with interest and move on to the next big thing.

    Aside from the fact that SustainX
    and many other start-ups are making the same claims and are hoovering up taxpayers money, how credible is Chief Scientist Danielle Fong.
    Supposedly a “child prodigy” and PhD dropout.

    Well, I’ll let you make up your own mind on that one!

    It doesn’t bother me that Danny chooses to dress up in women’s clothing.
    It does bother me that he pretends to be a Chief Scientist who only wants to save our small blue planet.
    The hypocrisy is breathtaking.

    It DOES bother me that a lot of money is going to be stolen from taxpayers, pension fund contributors, and well intentioned green investors.

    Here’s Danny!
    September 2nd 2007: Realize I’d make a terrible employee.

    September 3rd 2007: Realize that I’ll starve if I don’t take matters into my own hands and start my own thing;.

    September 4th 2007: Realize that I might have a halfway decent chance at making a difference.

    Until May 2008: Struggle to launch any of dozens of startup ideas, while working side jobs and supporting cofounders/friends.

    June 2008: Start working feverishly on compressed air technology.

    June – September 2008: Couchsurfing.

    August 2008: LightSail Energy Founded

    July 2009: Funded!

    September 2010: First spray — it works!

    May 2011: Present our progress to Bill Gates

    December 2011: Named the Energy Standout in the Forbes 30 Under 30 for my work with LightSail

    January 2012: Elected as mentor at the Thiel Fellowship

    Until the present: Saving the world…


    Link to this
  16. 16. Keefwivanef 10:22 pm 12/25/2012

    Now where was I?

    Batteries….new Green Widget coming soon!

    Redflow takes cap in hand to charge up battery storage plan
    By Giles Parkinson on 16 August 2012
    Less than two years after what appeared to be one of the most exciting clean-tech stock exchange listings seen in Australia, the board of battery storage developer Redflow has had to return to the market with its cap in hand and a major mea-culpa.
    The Brisbane-based Redflow (RFX.AX) announced on Wednesday that it wanted to raise nearly $5 million from shareholders in an equity issue. The raising is priced at just 6c a share – a pale fraction of the $1 issue price when it floated in late 2010 and the $1.70 peak it reached in the heady days soon thereafter. The market value of the company has fallen from more than $100 million to less than $7 million.

    The board of Redflow is still confident that the zinc bromine flow batteries it is developing is among the most advanced in the world and can play a crucial role in Australian and overseas energy markets – providing storage to off-grid systems, balancing renewables such as solar and wind, strengthening the outer reaches of the grid and reducing peak demand.

    Would you like some more?

    How about Zinc Bromide Batteries ZBB

    Nice little earner for the directors.Total disaster for the shareholders.
    $6 a share at IPO, now 30 cents and heading for bankruptcy.
    ” There are at least three companies developing the technology: Premium Power and its Zinc Flow Technology, ZBB Energy Corporation with its Zinc Energy Storage System (ZESS), and RedFlow Technologies with its Zinc Bromine Module (ZBM). (There may be other companies. It’s a big world out there.)

    ZBB, with US headquarters in Menomonee Falls, Wisconsin, was recently approved by the Internal Revenue Service (IRS) to receive a $14,685,000 Advanced Energy Manufacturing tax credit under the American Reinvestment and Recovery Act, a.k.a. the stimulus package. The tax credit will enable ZBB to install $49.55 million worth of equipment in a facility ZBB has proposed to construct in Southeastern Wisconsin. When ZBB proceeds with this project, it will manufacture its ZESS and PECC energy storage products that store energy from renewable power sources.

    Premium Power, of North Reading, Massachusetts, and its utility partners National Grid and Sacramento Municipal Utility District (SMUD) along with Science Applications International Corporation (SAIC) will receive a $7.32 million grant under the Recovery Act to run a three-year project that incorporates the fleet control engineering, manufacturing and installation of seven 500-kilowatt/6-hour energy storage systems. The systems will be installed in Sacramento, California, Everett, Massachusetts, and Syracuse, New York beginning in the third quarter of 2010.

    RedFlow, of Brisbane, Australia has recently hired a representative to begin sales and marketing operations in the US and Canada.”

    WHOOOO HOOOO….give us some more MUNNY suckers!

    GREEN ENERGY! I’m so green I could just PUKE!

    Link to this
  17. 17. marshel456 8:31 am 05/22/2013

    Thanks for taking the time to discuss this, I feel strongly about it and adore finding out additional on this topic. If feasible, as you acquire expertise, would you thoughts updating your blog with much more details? It is extremely useful for me. We are also Provide Removals and Storage service namely removals containers

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  18. 18. stevenorwood1963 4:17 pm 12/27/2013

    Compressed air storage is definitely something that I feel we should take advantage of if we are looking to save money as a country whole. How many traditional commercial air compressor machineswould this take for say 1 vacant salt dome as the article suggests?

    Link to this

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