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Guest Post: The Value of Short-term Energy Storage for Renewable Energy

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


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This is a guest post 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 is contributing a series of guest posts discussing grid storage technologies, and how storage could benefit the electric grid. You can read the first post in his series here.

A lot of the time, grid energy storage is discussed in the context of renewable energy. Storage is cited as a necessary solution to the diurnal nature of solar and wind energy. “We need storage because the sun doesn’t shine at night.” “Wind energy is greatest at night, so we need storage to shift wind energy to the daytime.” While there is some truth to these statements, they don’t reflect the real need for energy storage on our present grid.

Even intermittent sources of renewable energy like wind and solar tend to adhere to a predictable output schedule. The availability of wind, for example, naturally conforms to a probabilistic Rayleigh distribution. Using statistical analysis and other prediction tools, Texas’ grid operator has been able to integrate more wind energy with the grid than ever before, setting an instantaneous wind record of 8,521 megawatts in November. Furthermore, the temporal nature of wind energy varies based on where a wind farm is located. Experience in Texas has shown that wind farms on the West Texas plains output most at night, while coastal wind farms output most on summer afternoons. At the same time, research has shown that west-facing rooftop solar panels can produce more energy in the late afternoon than south-facing solar panels. The varying characteristics of different renewable energy sources and configurations permit grid planners to build a mix of renewables that loosely lines up with our demand for electricity.

Different intermittent renewable energy sources can be combined to loosely line up with electric load, so long-term storage is not a necessity. However, fast-ramping technologies like energy storage are required to compensate for the short-term volatility of wind and solar power production.

So why do we need storage then? As I discussed in my last post, our present electric grid operates totally on demand. The amount of electric energy generated must match the demand for electricity at every moment in time. Because of this fact, intermittent forms of renewable energy can have a destabilizing effect on the grid. Presently, renewables make up just a small part of our generation mix, so other generators can usually compensate for the intermittent nature of renewable energy to balance electric supply and demand. However, there are times when the volatility of renewable energy outpaces present electric generators. Because conventional generators rely on slow thermal and mechanical processes, they sometimes cannot match the pace of renewable energy fluctuations. A number of such destabilizing events have occurred on Texas’ wind-heavy grid. For this reason, the Federal Energy Regulatory Commission (FERC) issued order 755, which prompts organized electricity markets to enable the integration of novel, fast-acting resources capable of tightly regulating the balance between electric supply and demand.

Smaller-scale storage technologies like flywheels and batteries fill the niche opened by FERC order 755. Because a flywheel storage device operates by continuously spinning the shaft of an electric generator, it can compensate for renewable shortfalls almost instantaneously. A flywheel system manufactured by Beacon Power has been deployed in California to demonstrate the fast-ramping capabilities of flywheel storage devices.

Like a flywheel, a battery can rapidly produce electricity to compensate for shortfalls in renewable energy. A battery operates through chemical reactions, so it can adjust its power output in milliseconds to seconds, compared with minutes to hours for electric generators.  Furthermore, a battery only needs a small amount of storage capacity to effectively back up renewables. For example, a purpose-built battery recently unveiled by Xtreme Power holds just enough energy to discharge for fifteen minutes. What does this mean? Smaller, less-expensive battery systems can fill a niche on our present electric grid.

By complementing renewable energy at this early stage of our transforming grid, storage establishes its role as a key grid technology going forward. For highly scalable technologies like redox flow batteries, the space opened by order 755 could pave the way to large-scale electricity storage in the future. This development could fundamentally decouple electric supply and demand in time, making the grid more robust and enabling the widespread use of renewable energy.

Photo credit: the figure in this post comes from the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy’s Solar Energy Technologies Program. It can be found in this document, which explains the ideas behind this post in more detail.


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? david.m.wogan@gmail.com Follow on Twitter @davidwogan.

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





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  1. 1. krohleder 12:37 pm 12/26/2012

    I like Donald Sadoway’s liquid metal battery concept. His new company Ambri may be just what the renewable energy industry needs. Very exciting stuff!

    Link to this
  2. 2. Soccerdad 4:20 pm 12/26/2012

    Trouble is that there are times that the sun doesn’t shine and wind doesn’t blow for significant periods of time. So, while short term storage may get you by, you still need all the generation capacity from more reliable sources standing by. The renewable sources do not allow for retirement of these more reliable sources, so your installed capital simply grows – it is not replaced. This economic disadvantage is quite significant, and usually not included in discussions around the economics of renewables.

    Link to this
  3. 3. rwerkh 6:46 pm 12/26/2012

    @soccerdad

    Yes for now the answer is to back with the currently existing reliable sources.

    The reason for that is that it’s easier and cheaper now to use what is available than to roll out the technologies that have just become available instantly at full capacity.

    Storage tech is hitting it’s strides now and is undergoing ramp-up of production and going from hand-built systems to full production. As a result the cost is going to drop in the same way the cost of PV systems has dropped.

    The short term part of the storage is the most significant factor. In my area the peak period is in the period just after most solar installations lose sunlight. A 2 hour storage capacity would significantly reduce the need for peak power generation resources.

    So your long term eceonomy argument is in fact outdated and short sighted.

    Link to this
  4. 4. sethdiyal 8:13 pm 12/26/2012

    Actually you may want to RWERK your last post.

    Cost is the key. The latest work on grid level storage at the DOE is aiming to get battery tech down to the cost of environmentally impossible pumped hydro at $150/kwh. That would add about 75 cents a kwh to the cost of an all green grid with the minimum one month of storage required for rare large scale climate events. Just a few years ago the PNW lost all wind power for 2 weeks in the middle of that years peak power demand.

    Short term these storage devices at a vast increase in wind cost could allow the replacement of expensive inefficient gas peaker backup plant run inefficiently with highly efficient CCGT plant finally allowing the wind devotee to be able to prove for the first time that their 40 cents a kwh alternative to fossil fuels at least saves some GHG’s over the all gas or nuke alternatives.

    Only massive Big Oil purchase of media and politicians, diverts valuable time and treasure on these worthless pursuits from the only possible green energy solution – nuclear power. If the money spent on grid level storage alone had been spent instead on building and mass producing the blueprinted ready to build IFR and MSR nuclear technologies these 1 cent a kwh power units would already be rolling out of the factory.

    If the money wasted on wind and solar in the last decade had been spent on nuke power the world would now be coal free saving a million lives annually from coal air pollution. The impeding warming precipice would have be moved back 50 years or more potentially saving billions of more lives.

    Link to this
  5. 5. dwbd 9:14 pm 12/26/2012

    I like how Solar & Wind advocates refuse to admit the high grid integration costs of their pet pixie power fantasies. And they NEVER count those costs when calculating either the Capital or Levelized Cost of Wind & Solar energy. And furthermore they NEVER show the actual Carbon Abatement cost of Wind & Solar, comparing it to other available tech, for which it is 10-100X higher.

    Even the cheapest, onshore Wind is about $10k/kw delivered energy, which is still more than Hydro or Nuclear, whereas the poor Availability and added Grid Integration costs of Wind make it a joke, an absurd waste of money. And 20 yr lifespan vs Nuclear at 60-100yrs. And Nuclear with many cogen applications which cut its cost in half.

    And you always hear these guys like rwerkh falsely projecting endless cost reductions in Solar & Wind tech. Like how’s that, they are already mass produced in mind-boggling proportions. Factory construction. Done. Assembly line production. Done. Robotics. Done. Massive R&D. Done. Scale economics. Done. Vast Subsidies. Done.

    But when it comes to Nuclear Energy they ALWAYS conclude costs will rise. FOAK First-of-a-kind GENIII plants built. NOT Done. GENIV. NOT Done. Factory construction. NOT Done. Assembly line production. NOT Done. Robotics. NOT Done. Massive R&D. NOT Done. Scale economics. NOT Done. Vast Subsidies. NOT Done.

    Be Honest. Show some integrity. Give Wind, Solar, Hydro & Nuclear the same Carbon Credit, $/ton CO2 avoided (although the calculation will in fact be WAY inflated for Wind & Solar, due to Grid Integration problems). Include ALL Grid Integration COSTS, transmission, overbuild, under-utilization, storage, backup, decommissioning, waste storage/processing for ALL forms of power generation up front. And then see who THE REAL WINNERS are.

    Link to this
  6. 6. Carlyle 12:16 am 12/27/2012

    What will eventually kill this madness will be countries like India & China developing & mass producing nuclear power plants. In the mean time, western economies will continue to decline. It is a shame to see so many bright young people like Robert Fares seduced by idealism & propaganda into pursuing a career in a dead end industry.

    Link to this
  7. 7. Carlyle 1:12 am 12/27/2012

    Tuesday February 07 2012
    http://www.independent.ie/opinion/columnists/kevin-myers/kevin-myers-energy-policy-based-on-renewables-will-win-hearts-but-wont-protect-their-owners-from-frostbite-and-death-due-to-exposure-3012098.html
    Russia’s main gas-company, Gazprom, was unable to meet demand last weekend as blizzards swept across Europe, and over three hundred people died. Did anyone even think of deploying our wind turbines to make good the energy shortfall from Russia?

    Link to this
  8. 8. dwbd 1:23 am 12/27/2012

    Carlyle, electricity storage does have some legitimate applications, like storing cheap nighttime baseload Nuclear and Coal for use to supply the daytime peak/shoulder demand. Pumped Hydro or Conventional Reservoir Hydro works best for that. It DOES NOT work well for Wind & Solar applications.

    Peter Lang does an analysis of Pumped Hydro storage for Wind Energy vs Coal or Nuclear in Australia. Wind is just not economical. You want a steady, cheap, all nightlong source of good solid baseload power to make Energy Storage cost effective. Wind is just a joke.

    bravenewclimate.com/2010/04/05/pumped-hydro-system-cost/

    Link to this
  9. 9. Carlyle 6:44 am 12/27/2012

    Pumped hydro does have some applications for energy storage but it is practically impossible to get approvals past the environmental legislation & protesters in Australia for new dams. Also you either need very large volume or very high catchment. As a nationwide solution for Australia I do not believe it is viable. Energy storage undoubtedly would be a wonderful thing. If used with conventional energy sources it would save more energy than all the alternative energy schemes combined could produce. I do not believe any of the proposed solutions will work.

    Link to this
  10. 10. Carlyle 6:46 am 12/27/2012

    N.B. I will read the link tomorrow. Always willing to learn.

    Link to this
  11. 11. jerryd 1:57 pm 12/27/2012

    This whole article and most of the posters here are a bad joke.

    The grid doesn’t need more storage as it’s far cheaper to just produce power when needed. We already have multiple battery types that are well under $100/kwhr from lead to molten salt, etc. Yet none are used, why?

    Maybe it’s because demand variability, far more variable that generation, has always been handled well at low cost.

    As for RE needing backup, that is another bad joke. Nukes for instance are the worst because they need a whole Gw of backup only used a few x’s/yr. Talk about waste!! If you say there are FF plants to do it, why don’t you credit RE the same way?

    Most RE is either on demand or happens when needed most like PV. Solar CSP, CHP, hydro, geothermal, biomass, etc are all on demand. So just where is all this variable RE? Facts are utilities pay more for both on demand and peak power from RE or other sources, Why? In fact these are far more valuable than steady power in $/kwhr, No?

    Only big distant wind farms are variable to any degree. But as they multiply and spread out they average out nicely. And even better wind, solar on homes average out even better.

    DWBD your numbers are a study in how to lie using strange associations and selective data to try to make your erronous points. It’s how much $/kwhr, not how much capacity that is used that counts. I have to notice you don’t ever increase coal, NG plants that are not used 24/7 of their capacity, Why?

    Again grid storage is a strawman argument that has little bearing on real life grid and how it works and has handled variability easily for 100 yrs without storage. Those who claim otherwise are not being honest.

    Link to this
  12. 12. dwbd 2:13 pm 12/27/2012

    Yes, Hydro and Pumped Hydro are very difficult to do now due to environmental constraints. There are areas in Canada that have best Hydro resources on the planet, but virtually all power & heat there is expensive Fuel Oil, sometimes even flown in. Natives are particularly adamant that rivers are not disrupted. It really would be a whole lot easier to get NPP’s accepted than Hydro or Pumped Hydro. And the costs of the newest Hydro developments in BC, Newfoundland & Quebec are well above those of Nuclear. Just doesn’t seem that Hydro is a very good option anymore except in Developing Nations with Dictatorships that sweep aside all environmental concerns and just rape, pillage & build.

    Link to this
  13. 13. sethdiyal 2:59 pm 12/27/2012

    Folks want to know – is Jerry is a self styled DIY’er working from his Mom’s basement or is he a prominent biofuels maker from the swamps of the Everglades doing quality control as he blogs on SCIAM?

    Perhaps this might enlighten us somewhat.

    jerryd as freedev ” I’m not that good researching on the internet ”

    I think we can all agree with that Jerry!!!!

    Google” the-lowest-cost-combinationof-wind”

    Link to this
  14. 14. Carlyle 6:39 pm 12/27/2012

    Thanks for the link. Very interesting.

    bravenewclimate.com/2010/04/05/pumped-hydro-system-cost/
    & the further contained link to: http://www.tva.gov/heritage/mountaintop/index.htm
    It is the kind of solution to energy storge on a large scale that I wish was viable. The fact that it is the best solution availabe yet still not practial except in rare circumstances, emphasises the futilty of persuing things like bateries or gyroscopes except for smoothing. Certainly not for grid scale storage exceeding minutes in duration.

    Link to this
  15. 15. jerryd 7:14 pm 12/27/2012

    You are a sad little man Sethdayal.

    Why not use some of your time to help people instead of spreading lies and misinformation? A real man would but you from your posts can hardly be called that.

    You post speak for you and show everyone what kind of person you are. Does it make you feel powrful?

    I do much for many. What do you actually do other than make up lies about people who help others?

    Link to this
  16. 16. jerryd 7:22 pm 12/27/2012

    DWBD, would you care to give in detail how you calculate your wind energy costs of $10k/kw?

    Here in the US most wind is going in for well under $2k/kw and next I’ll be producing them in home, building sizes that last 50 yrs for under $1.5k/kw retail. I should note mine peaks out over 4kw which as others are rated would be $.75k/kw.

    Link to this
  17. 17. sethdiyal 9:27 pm 12/27/2012

    Thanks for the reminder Jer.

    Otherwise folks here may not remember Jer’s DIY rooftop windmill that produces more power off his shack’s roof per sq ft blade area than Siemen’s most advanced 6 MW units can on a windy mountain top. Any luck on selling that patent Jer?

    Also let’s not forget the Jer’s line of ultra efficient run of river hydro units that can power Jacksonville from a slow movin’ crick.

    Jer has as well told us of his solar powered Harley, and his fabulous solar powered cabin cruiser. No sense wastin good tastin’ biofuels on fish – I’m with Jerry on that.I seem to recall Jer’ also has a solar powered truck if I’m not mistaken.

    The only problem with all these fab inventions is it takes a lot of biofuels to power Jerry’s amazing imagination since he tells us he hasn’t learned about the innernet yet. The many generations of Jerry’s family biofuel business is suffering since Jerry took over quality control, but we have been blessed with the product all the same here online at SCIAM.

    Link to this
  18. 18. Carlyle 9:40 pm 12/27/2012

    An excellent source of information on comparative energy costs plus a mostly informed & informative following discussion. http://nuclearfissionary.com/2010/04/02/comparing-energy-costs-of-nuclear-coal-gas-wind-and-solar/

    Link to this
  19. 19. dwbd 10:07 pm 12/27/2012

    jerry, as always uses cost per peak output Wind, when avg output is 15-30% of peak. So as I said, repeating “..onshore Wind is about $10k/kw delivered energy..”. That’s DELIVERED energy NOT rated PEAK output. Nuclear in the USA is running 92% CF, 92% of peak rating in delivered energy.

    Record Hill Wind Farm Roxbury, Maine, DOE Loan $102M, 50.6 MW, 96GW/yr, 11MWavg, 22% CF, Cost $130M total, $2.6k/kwpk, $11.8k/kwavg, i.e. > $10k/kw delivered

    Granite Reliable, Wind Farm, Wind Cost, Coos, New Hampshire, $169M loan guarantee, 99MWpk, 224GWh/yr, 26%CF, $275M, $2.78k/kwpk, $10.7k/kwavg, i.e. > $10k/kw delivered

    New Wales Wind Farm, Latest & Biggest onshore in UK, 1600MWpk, 20% CF, $3.1B plus $620M for transmission is $10.3k/kwavg or $12.4k/kwavg incl transmission.

    Caithness Shepherds Flat in east Oregon, 845 MW, 1797 GWh/yr, 205 MWavg, 24% CF, $1.3B loan, $1.9B total, $2.3k p kwpk, $9.6k/kwavg not incl transmission – a bargoon

    Kahuku Wind Farm in Hawaii, Wind Cost, $117M DOE loan, $3.9k/kwpk, 30 MW, 71 GWh p yr, 27% CF, $14.4k/kwavg

    Kibby Mountain, Maine, 132 MW, capital cost $320 million, Vestas claimed a 32% CF, in 2011 CF was 22.5%, $2.42k/kwpk, $10.8k/kwavg

    Hempstead, NY, 100 kw Wind Turbine, $615k DOE grant, 180MWh/yr or 20.5% CF, $6.15k/kwpk, $30k/kwavg

    University of Maine, 600 kw Wind Turbine, est. capital cost $1.5M, actual $2M, predicted CF=19%, actual 12%, $2M/.6k = $3.3k/kwpk, $27.5k/kwavg, a fair bit > $10k/kwavg

    Bolton Valley Ski Area in Vermont 100 kw Wind Turbine (to save power costs – aka Jerry), $800K (incl $250 cash grant), predicted CF 34%, actual 17%, $8k/kwpk, $47k/kwavg, just a tiny bit more than $10k delivered.

    And New York State’s Wind Turbines Vendor rated CF’s were 30-35% before installation. In actual fact avg CF 2006-11 was 24.9%

    And none of those high costs account for Grid Integration costs, extreme Tax subsidies, manufacturer subsidies, state RPS subsidies, total energy waste & economic loss.

    The last two are particularly noticeable in Ontario with a mere 1.9 GW of Wind installed of the 10 GW planned. Whenever the Wind is blowing typically 1) Hydro is spilled – Zero cost savings – Zero CO2 savings 2) Nuclear is dumped – Zero cost or CO2 savings & 3) the Wind is exported at an avg price of 1 cent per kwh. Ontarians pay 14 cents per kwh for the Wind plus a huge Federal Tax subsidy and other local & manufacturer subsidies. I regard losing 13 cents a kwh on Wind production A TOTAL LOSS and ZERO REAL Capacity. So effectively Ontario Wind costs OVER $infinite/delivered & used kwh. In other words Ontarians not only got ZIP for the $billions being funneled to Big Money Politically connected Wind Farm thieves, they are PAYING extra on top of that.

    theenergycollective.com/willem-post/61309/lowell-mountain-wind-turbine-facility-vermont

    theenergycollective.com/willem-post/53258/examples-wind-power-learn

    tinyurl.com/Kent-Hawkins-Wind-Costs

    Link to this
  20. 20. dwbd 10:36 pm 12/27/2012

    Here is an excellent article by John Droz on the Wind Energy SCAM with lots of great, informative comments:

    thehill.com/blogs/congress-blog/energy-a-environment/268477-getting-past-the-hype-behind-wind-energy

    wherestheproof comments:

    “…Wind ONLY makes sense as a tax sheltering scheme
    – not an energy producer. Per a March 2012 speech given by Senator Alexander:

    ” Wind developers often sell their tax credits to Wall Street banks or big corporations or other investors who have large incomes. They create what is called a ‘tax equity’ deal in order to lower or eliminate taxes. This is the scheme that our president, who is championing ‘economic fairness,’ would like to make permanent.”

    This tax avoidance scheme is why we have companies such as “Microsoft, Sprint” joining the growing list of major companies calling on the US Congress to extend wind Production Tax Credit …And why “nearly half of the world’s largest corporations plan to moderately or significantly increase investment in renewable energy over the next five years” as mentioned in this AWEA link…”

    “…”UK lawmakers will quiz executives of Starbucks (SBUX.O), Google (GOOG.O) and Amazon (AMZN.O) on Monday about how they have managed to pay only small amounts of tax in Britain while racking up billions of dollars worth of sales here…”

    Link to this

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