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USC team develops novel organic redox flow battery for large-scale energy storage

Schematic of ORBAT. Click to enlarge.

Scientists at USC have developed a novel water-based Organic Redox Flow Battery (ORBAT) for lower cost, long lasting large-scale energy storage. An open access paper on their work is published in the Journal of the Electrochemical Society.

ORBAT employs two different water-soluble organic redox couples on the positive and negative side of a flow battery. Redox couples such as quinones are particularly attractive for this application, the researchers said. (Quinones are oxidized derivatives of aromatic compounds.) No precious metal catalyst is needed because of the fast proton-coupled electron transfer processes. Furthermore, in acid media, the quinones exhibit good chemical stability. These properties render quinone-based redox couples very attractive for high-efficiency metal-free rechargeable batteries, they found.

Since grid-scale electrical energy storage requires hundreds of gigawatt-hours to be stored, the batteries for this application must be inexpensive, robust, safe and sustainable. None of today’s mature battery technologies meet all of these requirements. The vanadium redox flow battery is one such battery technology that has reached an advanced level of development for grid-scale applications. However, the limited resources of vanadium, the high expense associated with the cell materials, and the toxicity hazard of using large quantities of soluble vanadium, have been the major challenges to the widespread adoption of the vanadium redox flow battery.

Aiming to overcome these disadvantages, we have demonstrated for the first time an aqueous redox flow battery that uses water-soluble organic redox couples at both electrodes that are metal-free. Such a battery has the potential to meet the demanding cost, durability, eco-friendliness, and sustainability requirements for grid-scale electrical energy storage. We have termed this battery an Organic Redox Flow Battery (ORBAT).

—Yang et al.

In ORBAT, two different aqueous solutions of water-soluble organic redox substances such as quinones are circulated past electrodes. The positive and negative electrodes are separated by a proton-conducting polymer electrolyte membrane. In the paper, the researchers a solution of 1,2-benzoquinone-3,5-disulfonic acid (BQDS) for the positive electrode; the negative electrode uses a solution of anthraquinone-2-sulfonic acid (AQS). By choosing the appropriate organic redox couples for the positive and negative electrodes, they projected that a cell voltage as high as 1.0 V is possible. The quinones have a charge capacity in the range of 200–490 Ah/kg, and cost about $5–10/kg or $10–20/kWh, leaving ample scope for achieving the US Department of Energy’s target of $100/kWh for the entire battery system.

The batteries last for about 5,000 recharge cycles, giving them an estimated 15-year lifespan. Lithium-ion batteries degrade after around 1,000 cycles, and cost 10 times more to manufacture.

—Professor Sri Narayan, corresponding author

Narayan collaborated with Surya Prakash, Prakash, professor of chemistry and director of the USC Loker Hydrocarbon Research Institute, as well as USC’s Bo Yang, Lena Hoober-Burkhardt, and Fang Wang.

The tanks of electroactive materials can be made as large as needed—increasing total amount of energy the system can store—or the central cell can be tweaked to release that energy faster or slower, altering the amount of power (energy released over time) that the system can generate.

While previous battery designs have used metals or toxic chemicals, Narayan and Prakash wanted to find an organic compound that could be dissolved in water. Such a system would create a minimal impact on the environment, and would likely be cheap, they figured. Currently, the quinones needed for the batteries are manufactured from naturally occurring hydrocarbons. In the future, the potential exists to derive them from carbon dioxide, Narayan said.

The team is currently testing testing and analyzing the behavior of other redox couples in the quinone family, assess the impact of solubility on full cell performance, and optimize the structure of the membrane-electrode assemblies. Solubility is still a challenge for this type of redox flow battery, they noted.

Choosing a substituent such as sulfonic acid to modify both positive and negative electrode materials appears to be the most promising approach at this time to meet the challenge of solubility in water. However, understanding the effect of substituent group type and placement on the standard reduction potential and kinetic reversibility are also important areas for further study.

—Yang et al.

The team has filed several patents in regards to design of the battery, and next plans to build a larger scale version.

This research was funded by the ARPA-E Open-FOA program (DE-AR0000337), the University of Southern California, and the Loker Hydrocarbon Research Institute.


  • Bo Yang, Lena Hoober-Burkhardt, Fang Wanga, G. K. Surya Prakash and S. R. Narayanan (2014) “An Inexpensive Aqueous Flow Battery for Large-Scale Electrical Energy Storage Based on Water-Soluble Organic Redox Couples” J. Electrochem. Soc. volume 161, issue 9, A1371-A1380 doi: 10.1149/2.1001409jes



5000 cycles, 1V and <$100/kWh. If real, then build them and sell them. What are you waiting for?


There's a lot of work between a demonstration in glassware in the lab and a turnkey industrial product.

I note that the estimated lifespan of 5000 cycles is translated to "15 years", or about 0.9 cycles per day.  This assumes that there is something to charge the battery every day.  Neither multi-day or multi-week lulls in generation nor seasonal surpluses and deficits appear to be considered.

Henry Gibson

There are many tons of uranium U238 in storage that will never be used for power but can be used for a redox battery as well as vanadium. The new organic compounds seem to be useful but how big of a unit has been built and tested. There is a large vanadium one in USA Utah and a newer one in USA Oxnard California. The very high power electronics now available make batteries very interesting for power reliability in factories and other buildings. The Edison power distribution system of direct current could be used again in local areas or buildings to save on AC losses in conduits. The battery power does not have to be converted to AC for lighting or motors: CFLs can run directly from batteries and so can efficient balasts for other lamps and efficient motor drives can be use modified easily to also run directly from the batteries as can computer power supplies. Inverters are available for other uses and can be modified UPS sysytems. ..HG..


Using the 700,000 tons of depleted uranium in fast breeder reactors could make enough electricity to charge a billion EVs every day for the next 1000 years.


If their costs and lifecycle are correct, this is great. If each kwh of storage costs $20 and lasts for 5000 cycles, that is $20/5000 = $0.004/kwh. This would make it viable to store wind generated electricity for use later. Probably not viable for solar yet in many locations. If solar is $0.12/kwh, it is competitive with daytime rates, but I have overnight rates of under $0.03/kwh, so probably not feasible to store solar generated electricity for overnight use, at least not yet.


You forgot the cost of amortization.  If interest rates are 7%, interest on your $20 is $1.40/year.

This really adds up if you use it for balancing week-scale or longer cycles in RE availability.  If your average cycle depth is 75% and you get 50 cycles a year, that adds $1.40/(50*0.75)=3.7¢/kWh; if you use it to balance seasonal cycles, you only get 1 or 2 cycles a year.  You also have the fixed per-kW cost of the gear to get energy in and out of the liquid.

Bob Wallace

" If solar is $0.12/kwh"

Solar PPAs (Power Purchase Agreements) are being signed in the US SW for $0.05/kWh and a bit less.

Add back in the federal subsidy and the price is around 6.5 cents. Adjust the price for the lower sunshine of the NE and the price would be around 8.5 cents.

We're well under 12 cents in the US.

We're getting close to the point at which is will make sense to store daytime solar for late afternoon and early evening high demand hours.

Stored solar isn't likely to ever be competitive with late night onshore wind (which is apparently now signing 2.5 cents/kWh PPAs).



There is zero need for RE storage in the USA. In 10 years when it might be nice to have some, intra-day is all you'll *ever* need.

Doing an analysis for multi-day or week-long is a ludicrous strawman for any real world power market with a rational (i.e. market based) mechanism. Its just FUD.

On days where both wind and sun don't show up you still have your already built nuclear and hydro, and you can just burn natural gas to make up the rest and then plant some trees.

Your strawmen only make sense in a universe with an infinite carbon dioxide cost, which is just an exercise in autofellatio.


<sigh>  Only someone like Bob Wallace could claim a subsidy as part of the accounting of what something costs.  All a subsidy does is shift part of the price away from the bill to other things/payers, just like the subsidy of free waste-dumping enjoyed by fossil fuels.


How about the huge multi billion $$$$$ subsidies given to the Nuclear and Oil industries?

Add to that the cost of the last Irak war (17,000 billion USD) and rising as indirect subsidies.

With due regards to the above, why wouldn't clean energy producers get $10,000 to $20,000 billion USD in subsidies?


It seems to me the cost of production has little meaning. These only make sense for "excess" producton of solar and wind, meaning the energy produced has no value unless stored. Now, for you engineers that assume the entire system is going to be optimized that is not a problem. But in the real world, there will eventually be more electricity produced than needed at certain times of the day, in some locations. Someone previously posted that Hawaii already has this problem.

I don't think we are going to build a nuclear reactor that will not go into operation for at least 10 years, on the assumption we can start it up on demand as backup capacity. Flow batteries may not be the only answer, but everything is on the table.

How about the huge multi billion $$$$$ subsidies given to the Nuclear and Oil industries?

Fallacy of division.  Just because all sources of energy taken together are given subsidies, does not mean that nuclear energy is subsidized.  Nearly the entire on-budget "subsidy" in the USA is military spending (or cleanup of military sites), and the so-called subsidy of Price-Anderson turns out to be pocket change at most.

Add to that the cost of the last Irak war (17,000 billion USD) and rising as indirect subsidies.

What part of this was supposed to be promoting nuclear?

why wouldn't clean energy producers get $10,000 to $20,000 billion USD in subsidies?

Because you need "reliable" and "dispatchable" to truly displace fossil fuels, and none of the scalable sources deemed "clean" by the greens are either.

That said, I'm looking forward to quinone-based flow batteries.  They would eliminate the argument against nuclear power, that it can't track varying demand curves.  It would take a lot less storage to follow the demand curve with nuclear than with wind.

Bob Wallace

E-P, try reading what I wrote.

Solar PPAs (Power Purchase Agreements) are being signed in the US SW for $0.05/kWh and a bit less.

Add back in the federal subsidy and the price is around 6.5 cents. Adjust the price for the lower sunshine of the NE and the price would be around 8.5 cents.

I started with the selling price of solar, 5 cents.

I then added back in the federal subsidy, ~1.5 cents to get 6.5 cents.

The non-subsidized cost of electricity from solar in the US SW is about 6.5 cents, far less than the 12 cent number used earlier.

You would be correct if I had claimed that the cost of solar was 5 cents and did not account for the subsidy.

Bob Wallace

And how about a little update on the cost of onshore wind in the US?

In 2011 and 2012 wind PPAs averaged 4 cents per kWh. Adding back in the PTC that's about 5.5 cents.

We have preliminary (non-confirmed) data that the average PPA for wind in 2013 was 2.1 cents. If confirmed that would mean that the full price of wind (without subsidy) has dropped to to under 4 cents.



You have shown why a battery like this would be useful. Audi is using excess wind power to make SNG. Efficiency obsessed people might say this is the wrong thing to do, but with the prices for natural gas in Europe, this may be practical. Europe does not have a 100 million EVs to use all that electricity at night, if they did not use it then it goes to waste, so much for efficiency.

Bob Wallace

Solar is currently between 6.5 and 8.5 cents per kWh (SW vs. NE). Wind is somewhere in the <4 to 5.5 cent range. The cost of both is expected to drop. Ten years from now it's very likely that both wind and solar will be producing electricity for well under 5 c/kWh.

The best estimate we have for new nuclear is from the recent LCOE numbers produced by Citigroup for the Vogtle reactors. They report that the price of power from those reactors will be 11 cents. If there are no further cost/schedule overruns.

They also report that it is very unlikely more reactors can be built and deliver 11 cent electricity. Vogtle has taken advantage of unusually low interest rates. Rates which will almost certainly not be available to future builds. We should expect any further nuclear electricity to cost 12+ c/kWh

Storage for nuclear would actually be more expensive than storage for wind and solar using identical technology.

Since onshore wind produces more at night and solar produces during midday storage systems would cycle twice a day. Nuclear would produce excess power only during off-peak hours resulting in a single storage cycle. The more frequently storage is cycled the larger the revenue stream.


If wind is so cheap, why do those regions with a higher fraction of wind generation typically have higher utility rates (see CA and Denmark, et alia)?

As for the cost of wars: humankind has killed one another over everything from the meaning of holy words to the control of spice trading routes. The idea that fragile, unreliable wind power will have us handing flowers to one another is sadly misplaced hope. Don't worry: we'll find plenty of other reasons.


Bob, I made one comment on cleantechnica a while ago.  It was removed within minutes, and I found myself unable to post.  Was that your doing?

Solar is currently between 6.5 and 8.5 cents per kWh (SW vs. NE). Wind is somewhere in the <4 to 5.5 cent range.

Solar is on "time of day" rates.  How much does it cost at night in January in Ohio, when the polar vortex is being a sloppy drunk and dipping the mercury below zero Fahrenheit?  (The answer is infinity; it's not generating anything, so no amount of investment will yield any power.)  Battery storage for overnight duration adds upwards of 10¢/kWh, with longer durations proportionately more costly.  I see 1.98 kWh (6 V 330 Ah, 20 hr rate) floor-scrubber batteries going for $250.  If we assume 1 cycle per day to 50% depth for 5 years, the battery costs $50/year (zero interest) or 13.8¢/kWh.  Adding this to your figure, on-demand solar power costs at least 20-22¢/kWh even before interest and O&M are added.  If you need to weather lulls of several days, multiply the bill for storage accordingly.

The bottom line is that Vogtle is cheaper.

Grid-tied solar PV looks cheap because its owners are (a) heavily subsidized in its purchase costs, and (b) not paying their fair share for the grid services they consume.  Net-metering users are being PAID by the utility for the utility to provide those services (the per-kWh rate includes them; only a small fraction is fuel).  This cannot end well, and it won't.


Thanks, E-P; I warn you in advance that after replicating your numbers in a few exercises I plan to lightly plagiarize your rhetorical approach.

Once again cheap wind: in my area we are able to purchase "renewable" energy from "cheap" windmills that thrive along I39. Last time I looked the heavily-subsidized Quixote targets could provide power for only about 20-25% more than Byron's good old WeCo PWRs.


Energy direct subsidies are huge:

1. Number one worldwide is 500B/yr for oil.
2. Number two worldwdide is $88B/year for renewables.

Direct USA's energy subdsidies are $25B/year

1. about 50% or $12.5B/year is for electricity production of which, 40% is for wind, 20% is for nuclear, 13% for clean coal, 10% for solar, 8% for NG, 4% for Hydro, 2% for geothermal, 1% for biomass etc.

Commercial nuclear got over $74B in R&D subsidies at the rate of $3B/yr to $7B/yr.

USA,s indirect energy subsidies are many times more. Oil indirect subsidies, including oil wars, are as high as $240B/year. It makes all other energy subsidies look small. It is much more than the Fed gas/diesel taxes. That may be why those revenues are not used/available to maintain the Fed Highways.


Since I work by day and blog later than you folks, I will add my 2 cents negawatts worth to the renewable debate.

This is all about opportunity costs. Is there a better way to spend renewable subsidies on meeting the objectives of renewable power? There has been for decades, and it is called conservation.

NREL estimates that building energy management cuts gross energy consumption in that sector by 57% Bus line capacitors, which merchant power providers are making a hefty profit on, cut gross electrical consumption by 25%. Proper use and fitting of HVAC, including overall airflow management, cut energy demand of this equipment by 30% -- which already consumes typically 40% of household electricity in the summer.

Compared to this, PV is an expensive toy (yes, I'm a ratepayer), whose subsidies are channeled to benefit the well to do: Namely, above-average-income homeowners who have the timeframe and financial security to realize their investment, and the credit to make an apparent "profit" after subsidies and assumed purchases by utilities.

In my locality, we hear the myth that PV "avoids" expensive capital investment in conventional power. That makes sense if your state is in a deep economic funk like mine. But "expensive" conventional power investments are being made out-of-state, which we import on a quite functional grid. Since our utility has nothing better to do than send men scurrying up telephone poles to install 3 foot wide PV panels, which are blocked off by tree shade, we are told that land is at a premium, and this makes sense. In parking lots, PV is installed above enough steel columns and joists to build a new office building -- Where's the sense in that?

My state can't even pay it's public pension obligations. The governor decided he would balance the 2013 budget by simply delaying pension benefits four days into the next year. Can you guess where I'm at?

All of you who will fall over your swords for a green economy, do so at your own leisure in your own bailiwick, not mine. That's my definition of a free country, and a federal republic at that.

I warn you in advance that after replicating your numbers in a few exercises I plan to lightly plagiarize your rhetorical approach.

Oh, dear, not THAT!  It might CONVINCE PEOPLE!!  (Please, cut and paste if you want to.)

Commercial nuclear got over $74B in R&D subsidies

I question that figure, given that ALL civilian efforts are only budgeted for $650 million in FY 2014, and $275 million of that is for military-related stuff at INL including naval reactor fuels.  But even if it's true, it's trivial.  At about 16000 TWh over the last 20 years, $74 billion comes to just 0.46¢/kWh, not even 1/4 of the wind PTC.

Bus line capacitors, which merchant power providers are making a hefty profit on, cut gross electrical consumption by 25%.

I'm calling BS on that one.  A search for "bus line capacitors" shows one unambiguous hit, and that's a comment from you on 6/17.


The total cost of nuclear energy is much higher than supporters admit.

Canada's AECL has spent $17B in R&D to support the dying Candu Reactor program. Ontario and two other provinces have spent as much for a total of about $35B in R&D subsidies.

The latest production cost at the largest nuclear facility in Ontario Canada is over $0.127/kWh. Ontario Hydro One is loosing money every year.


1. Our (Hydro-Wind) Quebec Hydro sells electricity at an average of $0.064/kWh for domestic use and $0.032/kWh for large industrial users. Net profits are about $3.5B/year of which about $2.0B/year are given to the Provincial government as dividend. That is done without subsidies from the Fed or Prov governments.

2. Next door Ontario's predominant (61%) Nuke +(Coal-NG-Wind) sells energy at an average of $0.12/kWh for domestic use and about $0.06/kWh average for large industrials users. It receives close to $450M/yr in subsidies and runs a large yearly deficit instead of giving a $2B/yr dividend to the provincial government.
The nuclear waste stockpile as not been disposed and could cost $BB to the next generations. Most of the Candu facilities are due for major overhaul. A $100B to $200B in subsidies will be required to keep nuke production going for another 40 years or so. That could raise total production cost to something between $0.16/kWh (like the recent UK nuke facilities) to as much as $0.20/kWh.

However, the Canadian Champion is Oil & Gas with $14B/yr in subsidies. Since a very high percentage is exported South at 80% of the international price, it is nothing to be proud of.


In the U.S. the nuclear power industry is suppose to be self insured for meltdowns. The fund has about $500 million in it and a meltdown is estimated to cost $500 billion, guess who picks up the rest of the cost?

Call it a subsidy, backstop, bailout or whatever you want, but the private sector wants YOU to take all the risk while THEY take all the profits. They say that is perfectly reasonable, those are the same people that tell you the private sector is our salvation and they need no handouts.



You obviously didn't Google very hard, as this link turned up immediately;


(read section "4.0: Conclusions")

You also missed an underlying point. If privately held merchant providers are willing to bet on the technology, to the tune of a 30% profit on savings, and they are, then your results may vary, but their results are factored in.

Why are you bloggers so eager to do the loop-de-loop on Atkinson engines, and tirades against big oil, and have so little smarts from the standpoint of consumers, businessmen, or even the electorate?


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