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Vanadium Flow Batteries Could Become a Cost Effective Solution for Balancing Texas’ Power Grid

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


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David here. This is a post by Robert Fares, frequent guest of Plugged In. It’s also cross-posted at the Cockrell School of Engineering’s webpage. Robert and I engaged in a Twitter interview about his research on Friday, which you can read here.

The existing power grid has served us well for over a century. It persists as one of humankind’s most impressive feats of engineering. Nevertheless, the grid has a number of key limitations that have become increasingly clear in recent years. One limitation is a lack of energy storage. Understanding exactly how new energy storage technologies might improve the electricity system is a complex operational research problem. My research, under Dr. Michael E. Webber in the Department of Mechanical Engineering, seeks to reveal the best ways to leverage new energy storage technologies on the grid. One appealing application for grid energy storage is the real-time balancing of power supply with demand. Our work recently published in the journal Applied Energy shows that an emerging battery technology called a vanadium redox flow battery could become a cost-effective solution for balancing Texas’ grid.

Today, electric generators have to quickly ramp up and down to match electricity supply with demand at every moment in time because there is almost no storage buffer between electricity production and consumption. Even a temporary imbalance in power supply and demand could lead to a system-wide blackout. When power plants rapidly change their power output to keep the grid in balance, they deviate from their most efficient operating point, increasing fuel use and emissions.

Modern battery technologies could unlock a better way to match electricity supply and demand in real time. Because batteries can alternately charge and discharge without releasing emissions or suffering major efficiency losses, using them for grid balancing could save energy, improve air quality and reduce greenhouse gas emissions. At the same time, using more batteries to balance the grid could free up power plants, allowing them to operate at peak efficiency. Because batteries use fast electrochemical reactions to store energy, they can keep electric supply and demand in tighter balance than a power plant, and reduce the number of power plants we need to balance the grid and keep the lights on. For these reasons, there are already a number of pilot projects evaluating the potential advantages of using fast-responding technologies like batteries on the grid, including in Texas.

We sought to determine when batteries used for grid balancing will become cost competitive with power plants. To answer this question, we performed a model-based economic analysis of a battery participating in Texas’ wholesale electricity market, which is administered by the Electric Reliability Council of Texas (ERCOT).

A vanadium redox flow battery uses two different liquid vanadium solutions (an “anolyte” and a “catholyte”) to store large quantities of electricity. Source: Dunn et al, 2011.

We modeled a megawatt-scale vanadium redox flow battery (VRFB), in other words, a flow battery large enough to power nearly 1000 typical residential homes. Unlike a traditional battery, a flow battery stores electricity in large tanks of chemical solution—making flow batteries modular and highly scalable. The flexible design reduces the cost of the battery system, and the all-liquid active materials give the battery a long operating lifetime. VRFBs last for ten or more years and can be charged and discharged over 10,000 times before they wear out. These features make VRFBs one of the most promising emerging grid energy storage technologies.

We used our VRFB model with publicly available electricity market price data to show the potential value of a battery performing “frequency regulation service,” the technical term for balancing grid supply and demand. We implemented a decision-making program with the model to optimize when the battery offers frequency regulation service to the electricity market. The program shows when it’s most valuable to use the battery, and calculates the maximum revenue that could be obtained from providing frequency regulation for Texas’ grid with a VRFB.

Based on historic electricity prices published by ERCOT, our model shows that a VRFB with a ten-year life could be a cost-competitive solution for grid balancing if its cost were to fall below $1,500 per kilowatt of rated battery power. The cost of a battery is typically expressed in dollars per kilowatt of rated power because the amount of materials required to build a battery scales directly with the amount of power the battery can deliver. Because VRFBs are still an emerging technology, their precise cost is uncertain right now. The most authoritative studies estimate the cost of a VRFB system designed for frequency regulation is about $1460-1613 per kilowatt of rated power. Thus, our results suggest that large-scale flow batteries are nearly a cost-competitive technology for balancing electricity supply and demand

Despite our findings, there are still a number of technical and non-technical challenges to wider use of grid energy storage. Conventional electricity markets and policies weren’t designed around devices that can both produce and absorb electric energy. Furthermore, many energy storage technologies are relatively untested and still in the demonstration stage. Nevertheless, if the cost of grid energy storage falls significantly, it will almost certainly take on a larger role on the power grid.

Scientists and engineers around the world are exploring how to build large-scale batteries at costs suitable for grid applications. Along with the engineering challenges associated with building batteries, it is also important to understand the best way to utilize batteries on the grid in the future. Being a graduate student in the Cockrell School of Engineering gives me the opportunity to work with professors and other energy experts to find the answers to these difficult and prescient research questions.

In the future, I will continue my research exploring operational management of grid energy storage. As new storage technologies become more cost competitive, it will become increasingly important to understand the best ways to leverage energy storage to reduce the cost of electricity, increase the grid’s reliability and integrate renewable energy.


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. bigbopper 9:04 am 10/21/2013

    Very enjoyable and understandable article! I wish you the best of luck in your research project. It clearly addresses an important problem and has great promise.

    Link to this
  2. 2. rkipling 12:01 pm 10/21/2013

    Thanks for turning your comments back on.

    There may be a lot of work yet to be done with this, but based on this article, it may be feasible. Finally a non-fanciful (unicorns and rainbows) potential solution. The participation of actual engineers helps. Having an engineer blogger doesn’t hurt either. (Just so you can get your head through the doorway, please know I don’t agree with all your ideas. Then again, I’m not always right.)

    Do you have any sense whether this technology could scale up sufficiently to work with solar and wind?

    Link to this
  3. 3. Bob Wallace 2:00 pm 10/21/2013

    “(O)ur model shows that a VRFB with a ten-year life could be a cost-competitive solution for grid balancing if its cost were to fall below $1,500 per kilowatt of rated battery power.”

    David, how about running your model with $160/kWh batteries rather than $1,500/kWh batteries? And batteries with 3x the expected lifespan.

    EOS Energy Storage is in the process of testing their zinc-air batteries on Consolidated Edison’s (NYC) grid.

    EOS is claiming 75 percent round-trip efficiency, along with a 10,000-cycle, or 30-year, lifetime.

    Can they deliver what they suggest they can? At least six grids seem to be adequately convinced to partner up with them for live grid testing.

    http://www.greentechmedia.com/articles/read/eos-puts-its-zinc-air-grid-batteries-to-test-with-coned

    Then you might want to look at Aquion Energy’s sodium-ion battery. They’ve just signed an agreement with Siemens to see how they function with Siemens’ inverter.

    Aquion batteries are very interesting. Target price 95% efficiency. An earlier prototype was third party (US Navy lab) tested at >90% round trip efficiency and >5,000 cycles.

    http://gigaom.com/2013/10/01/a-new-power-grid-battery-emerges-with-a-deal-from-siemens/

    We might be living in a very different world a year from now if even only one of these batteries proves out. When we are able to store for <$200/kWh with at least a 10,000 cycle life we're within $0.02/kWh for wind and solar storage. (Add in the BoS costs.)

    Link to this
  4. 4. davidwogan 2:04 pm 10/21/2013

    @Bob Just to clarify: this is a guest post by Robert Fares about his model and results.

    Link to this
  5. 5. jerryd 2:49 pm 10/21/2013

    Except the fact utilities have shown they won’t buy them. There are many batteries under $80kwhr which makes this work.

    Yet utilities have not bought, Why?

    Many cost only $1/kwhr/yr from low cost and long life. Retail lead golf cart batteries well shopped only costs $10/kwhr/yr. Yet no utilities bought them!!

    And this was before NGCC GT’s now spreading around utilities that can throttle down to 50% power and still be eff making storage moot.

    And in the future so much on demand power from homes, buildings, businesses, EV’s make grid batteries moot too.

    Next demand shedding/smart grid. There are so many tools to balance the grid, but grid batteries are on the bottom of the list.

    BTW power is just peak. To find out if it’s worth it we’ll need energy/kwhr instead to find out how long it can put out peak, cycles, etc.

    Link to this
  6. 6. sethdayal 3:41 pm 10/21/2013

    ” stimate the cost of a VRFB system designed for frequency regulation is about $1460-1613 per kilowatt of rated power”

    What is this per kilowatt – is this dome kind of shorthand for kilowatt hour. Makes no sense. 1 KW for 10 seconds is a lot different than 1 KW for 4 hours.

    Maybe frequency reg application is great but for long term storage not so much.

    Cost of storage like pumped hydro is $100/KWh and we can only hope that we can get batteries capable of that cost per lifetime kwh – most efficient use.

    Given that at that rate, it would cost over a buck a KWh to back up wind or solar for a month long low wind or cloudy climate event it appears wind/solar is always going to have be backed with gas. All these batteries are ever going to save is gas – no ghg’s saved.

    Link to this
  7. 7. rkipling 4:23 pm 10/21/2013

    My guess is they mean the maximum design instantaneous output.

    Link to this
  8. 8. Bob Wallace 5:42 pm 10/21/2013

    David – I realized this later. But this site has no edit function. Or apparently gives no ability to follow a conversation.

    Jerry – would you link to golf cart batteries for that price. And show us the math using the normal cycle life for lead-acid batteries?

    Link to this
  9. 9. rkipling 6:51 am 10/22/2013

    davidwogan,

    Could you point me to references on how the grid is balanced currently?

    Link to this
  10. 10. jerryd 2:57 pm 10/22/2013

    How do I put my receipt up here?

    You either have to bargain or wait for a sale. Auto stores are very competitive now and those in the US all have access to a full range of lead batteries.

    I had 2 of them but liked the Johnson Control made ones best.

    And getting 50 mile range on 4 12vdc versions of them in my EV Streamliner prototype. More once the body is on. So an EV pack for $360 plus cores, sweet!!

    The same can be used in home size storage. I use a lot of these in my home, transport and business.

    I get them all the time at that price. Yes they only last 6-8 yrs. But they only need reforming as all the materials are recycled back into new batteries. But even then they give 1kwhr/day/yr for $10.

    At say 300kwhrs/yr that comes to $.03/kwhr retail. Or about $.015/mile in my EV’s.

    OEM/utility scale/type would do 1,000kwhrs/yr for 20 yrs so far less.

    But the lead batteries as you likely know are much different and last longer and cost much less sub/utility style ones. Likely $40/kwhr and 20 yr life. Actually with reforming onsite, unlimited life.

    But like I said, there is NO utility demand for them, making storage moot in utility sizes.

    But so many are others much better than that, yet still no utilities have bought them, Why?

    The VanOx battery has been around 20? yrs. Yet how many sold, not how many given, to utilities? Everyone I know of were paid by grants, etc or given free for testing.

    And the new 60% eff CC GT’s that are now able to throttle down to 50% eff put the nail in that coffin. No?

    A product isn’t much good if there is no market.

    Though California just made a law requiring utilities to get quite a bit of battery capacity, should be interesting. And the only way utilities will get them, forcing them to. Good idea for another article.

    Link to this
  11. 11. bucketofsquid 6:09 pm 10/22/2013

    Lithium sulfur batteries should also be cost effective when they reach market.

    I work for a small utility with around 150,000 residential and business customers. We have a mix of coal, natural gas, wind, oil (black start peaking units) and landfill gas generation sources.

    We have evaluated adding storage to our service area grid. Coal and natural gas don’t really need storage because they are generally base load suppliers. The oil is for emergency peak use anyway and very expensive so adding storage for power generated via oil is far too expensive. The landfill gas is mixed with the natural gas to add to our base load so that doesn’t need storage.

    That leads to our ever increasing wind generation. The wind turbines generate the second highest cost electricity coming in only after oil. By adding storage we would up the cost per kWh significantly. Sure it improves reliability but wind turbines are very expensive to maintain and already far higher in cost as it is. They also run off and on year round. This means that we would have to have substantial storage to balance the load changes from wind because we would need to store several hours worth of the wind off peak generation from windy days to use on the calm days during peak.

    You can say that the batteries are cheap all you want but they also contain hazardous waste which costs to dispose of. By adding storage we end up with a lot of expenses that simply ramping up or down generation from coal or natural gas covers without extra cost.

    Link to this
  12. 12. rkipling 7:33 pm 10/22/2013

    bucketofsquid,

    That’s interesting that you have firsthand information.

    What wind power penetration does your company have?

    A guy on another topic says there is a NREL study that says wind and solar can easily make up 33% of electrical generation. Is that realistic?

    Link to this
  13. 13. Dr. Strangelove 11:41 pm 10/22/2013

    @davidwogan

    “Using pumped hydro to store electricity costs less than $100 per kilowatt-hour and is highly efficient, Chu told his energy advisory board during a recent meeting. By contrast, he said, using sodium ion flow batteries — another option for storing large amounts of power — would cost $400 per kWh and have less than 1 percent of pumped hydro’s capacity.”

    http://www.nytimes.com/gwire/2010/10/15/15greenwire-doe-promotes-pumped-hydro-as-option-for-renewa-51805.html?partner=rss&emc=rss

    The wheel was invented long ago. No need to reinvent a more expensive one.

    Link to this
  14. 14. jerryd 4:29 pm 10/24/2013

    BoS,

    Doesn’t your load vary? How much and how do you handle it?

    Link to this

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