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Rechargeable membrane-less hydrogen bromine flow battery shows high power density

16 August 2013

Braff
Schematic of reactant flow within the HBLFB. During discharge, liquid bromine is reduced to hydrobromic acid along the lower solid graphite electrode, and hydrogen is oxidized at the upper porous electrode. Credit: Braff et al. Click to enlarge.

MIT researchers have engineered a new rechargeable, membrane-less hydrogen bromine laminar flow battery with high power density. The membrane-less design enables power densities of 0.795 W cm−2 at room temperature and atmospheric pressure, with a round-trip voltage efficiency of 92% at 25% of peak power.

That is about three times as much power per square centimeter as other membrane-less system—a power density that is an order of magnitude higher than that of many lithium-ion batteries and other commercial and experimental energy-storage systems. A paper on the work is published in Nature Communications.

Low-cost energy storage remains a critical unmet need for a wide range of applications, including grid scale frequency regulation, load following, contingency reserves and peak shaving, as well as portable power systems. For applications that require the storage of large quantities of energy economically and efficiently, flow batteries have received renewed attention. A wide variety of solutions have been proposed, including zinc-bromine and vanadium redox cells. This includes recent efforts to incorporate novel concepts such as organic electrolytes for greater voltage stability and semisolid reactants for higher reactant energy density or chemistries to reduce reactant cost.

One such permutation is the hydrogen bromine flow battery. The rapid and reversible reaction kinetics of both the bromine reduction reaction and the hydrogen oxidation reaction minimize activation losses, while the low cost ($1.39 kg-1) and abundance (243,000 metric tons produced per year in the United States alone) of bromine distinguishes it from many other battery chemistries. However, theoretical investigations of such systems have revealed that the perfluorosulfonic acid membranes typically used suffer from low conductivity in the absence of sufficient hydration. In the presence of hydrobromic acid, this membrane behaviour is the dominant limitation on overall performance.

...In this work, we present a membrane-less hydrogen bromine laminar flow battery (HBLFB) with reversible reactions and a peak power density of 0.795 W cm-2 at room temperature and atmospheric pressure. The cell uses a membrane-less design similar to previous work, but with several critical differences that allow it to triple the highest previously reported power density for a membrane-less electrochemical cell and also enable recharging.

—Braff et al.

Laminar flow batteries—which rely on diffusion to separate reactants—eliminate the need for an ion-exchange membrane. In such a device, two liquids are pumped through a channel, undergoing electrochemical reactions between two electrodes to store or release energy. Under the right conditions, the solutions stream through in parallel, with very little mixing. The flow naturally separates the liquids, without requiring the costly membrane.

However, the authors note, although the laminar flow design has been explored for a variety of chemistries, none of those systems have achieved power densities as high as their membrane-based counterparts—largely because the chemistries already work well with existing, optimized membrane technologies.

Two new characteristics of the MIT team’s hydrogen bromine laminar flow battery (HBLFB) enable the high-power-density storage and discharge of energy at high efficiency:

  • The use of gaseous hydrogen fuel and aqueous bromine oxidant. This allows for high concentrations of both reactants at their respective electrodes, greatly expanding the mass-transfer capacity of the system.

  • Both reactions have fast, reversible kinetics, with no phase change at the liquid electrode, eliminating bubble formation as a design limitation.

Although the chemical reaction between hydrogen and bromine is promising for energy storage, earlier fuel-cell designs based on hydrogen and bromine have had mixed results, as hydrobromic acid tends to eat away at a battery’s membrane, effectively slowing the energy-storing reaction and reducing the battery’s lifetime. Without a membrane, however, that is not an issue.

This technology has as much promise as anything else being explored for storage, if not more. Contrary to previous opinions that membrane-less systems are purely academic, this system could potentially have a large practical impact.

—Cullen Buie, assistant professor of mechanical engineering at MIT, co-author

The prototype HBLFB has a small channel between two electrodes. Through the channel, the researchers pumped liquid bromine over a graphite cathode and hydrobromic acid under a porous anode. At the same time, the researchers flowed hydrogen gas across the anode. The resulting reactions between hydrogen and bromine produced energy in the form of free electrons that can be discharged or released.

The researchers were also able to reverse the chemical reaction within the channel to capture electrons and store energy—a first for any membrane-less design.

The team operated the flow battery at room temperature over a range of flow rates and reactant concentrations and found the maximum power density of 0.795 W cm−2.

In addition to conducting the experiments, the researchers developed a mathematical model to describe the chemical reactions in a hydrogen-bromine system. Their predictions from the model agreed with their experimental results—an outcome that co-author Martin Bazant, a professor of chemical engineering, sees as promising for the design of future iterations.

The researchers estimate that the membrane-less flow battery may be able to cost as little as $100/kWh—a goal that the US Department of Energy has estimated would be economically attractive to utility companies.

This work represents a major advance of the state-of-the-art in flow batteries. To the best of the authors’ knowledge, the data presented here represent the highest power density ever observed in a laminar flow electrochemical cell by a factor of three, as well as some of the first recharging data for a membrane-less laminar flow electrochemical cell.

Although previous work has identified the appropriate scaling laws, the result presented here represents the first exact analytical solution for limiting current density applied to a laminar flow electrochemical cell, and serves as a guide for future designs. The HBLFB rivals the performance of the best membrane-based systems available today without the need for costly ion-exchange membranes, high-pressure reactants or high-temperature operation. This system has the potential to have a key role in addressing the rapidly growing need for low-cost, large-scale energy storage and high- efficiency portable power systems.

—Braff et al.

Resources

  • William A. Braff, Martin Z. Bazant, and Cullen R. Buie. (2013). Membrane-less hydrogen bromine flow battery. Nature Communications. doi: 10.1038/ncomms3346

August 16, 2013 in Batteries, Power Generation, Smart Grid | Permalink | Comments (59) | TrackBack (0)

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Battery-only advocates might like to elucidate on whether this is a battery or a fuel cell, and whichever the choice is, why? ;-)

In reality of course the two technologies are intertwined.

It's a battery. Fuel cells consume the fuel and expel an exhaust. They are one time pass through systems. Batteries can be recharged. Although there are similarities between flow batteries and fuel cells. It also depends in this case whether the hydrogen is cast off after regeneration or stored for reuse.

I have an issue with the statement that this is a higher power battery, especially when they report power on the electrode area basis only. This technology is not a higher power density based on system volume than lithium ion.

Don't get me wrong, for a stationary system their power definition might be all that is pertinent but to make a comparison between Lithium ion for mobile applications and a flow battery is misleading. The flow batteries have reservoirs of charged or discharged liquid electron carrier material and multicell systems have the same stack/flow/plenums as would be typical of fuel cells, and so why they are even making comparison to lithium ion is beyond me.

A couple of better questions would be how much does it cost and how long will it last. The point is, how much does it cost to store an electron. For the stationary applications, that your only metric. You don't need energy density and you don't need power density except as those would minimize cost. Yes, I do see they quote the $100/kwh, which is very good, but they also say that is speculation. Quote "membrane-less flow battery may be able to cost as little as $100/kWh", translation when something "may" be able to acheive a specific cost target, it means they are not sure.

That all said, $100/kwh is about where utilities need the energy storage costs to be for broad economical implementation of storage for solar, wind , and peak shaving etc.

@Brotherkenny:
All fuel cells can run in reverse.
What the efficiency is is another matter, but your distinction is not a sufficient one.

They are looking for good costs on this for the simple reason that the materials are cheap, and there is no expensive membrane.

"MIT researchers have engineered a new rechargeable, membrane-less hydrogen bromine laminar flow battery with high power density."

The researchers REPEATEDLY called this a battery and never is the term 'fuel cell' mentioned - but what do they know..

Flow batteries could be suitable for autoaplocations. Electrolyte could be recharged outside vehile and exchanged with depleted one. In that case battery weight not matters so much since you can find wide application for freight transport.

@kelly:
They could call it either and be accurate.

They said:
'In addition to bromine’s low cost and abundance, the chemical reaction between hydrogen and bromine holds great potential for energy storage. But fuel-cell designs based on hydrogen and bromine have largely had mixed results: Hydrobromic acid tends to eat away at a battery’s membrane, effectively slowing the energy-storing reaction and reducing the battery’s lifetime.

To circumvent these issues, the team landed on a simple solution: Take out the membrane.'

http://web.mit.edu/newsoffice/2013/rechargeable-flow-battery-enables-cheaper-large-scale-energy-storage-0816.html

In practical terms where you are thinking of using this for grid storage, and recycling the hydrogen, then you are likely to call it a battery.
Where you are thinking of mainly supplying hydrogen, say in a vehicle, then you will probably call it a fuel cell.

The chemistry does not change although some of the engineering does.

Downside to this chemistry: hydrogen will have to be replenished over time due to loses :/

HBr and Br2 are quite toxic or dangerous (acid), and you still need H2 and need a return to regenerate the HBr & Br2. For a (stationary) battery it may work, but for a fuel cell I'd simply use only use H2 and dump my waste on the street.

"...a critical unmet need for a wide range of applications, including grid scale frequency regulation, load following, contingency reserves and peak shaving, as well as portable power systems."

Of course the power industry does it everyday. There is no unmet need.

Of course the power industry regulates frequency.
Increasing use of renewables makes that ever tougher to do as they swing about a lot.
One tool which they have not had are cheap and durable batteries.
Lead acid are cheap but not durable, other chemistries are durable but not tough.
This is clearly the unmet need they are referring to, as anyone of normal intelligence should easily see.

Demand patterns are very predictable, wind patterns are predictable. One a few occasions in the US generation from wind has not been dispatched because low demand and high wind output. If you could store power from a windy day in the spring to a hot summer day, then maybe storing power would make some sense.

Think about it. Electricity is a cheap commodity. Not using a relatively small amount excess power from wind is not a problem that requires an expensive solution when wind turbines can be just turned off.

Theoretically, if batteries were cheap enough they would allow power plants to run at optimum efficiency at a high enough output to meet average demand. I'd imagine that this would save some fuel...

Then again, the batteries would have to be pretty damn cheap AND efficient. That's a tall order.

How a so-called engineer can talk such absolute cobblers is a mystery, perhaps only possible by resolutely ignoring facts.

'At other industrial companies, executives at the highest levels are also thinking about freeing themselves from Germany's electricity grid to cushion the consequences of the country's transition to renewable energy.

Likewise, as more and more companies with sensitive control systems are securing production through batteries and generators, the companies that manufacture them are benefiting. "You can hardly find a company that isn't worrying about its power supply," said Joachim Pfeiffer, a parliamentarian and economic policy spokesman for the governing center-right Christian Democratic Union (CDU).

Behind this worry stands the transition to renewable energy laid out by Chancellor Angela Merkel last year in the wake of the Fukushima nuclear disaster. Though the transition has been sluggish so far, Merkel set the ambitious goals of boosting renewable energy to 35 percent of total power consumption by 2020 and 80 percent by 2050 while phasing out all of Germany's nuclear power reactors by 2022.

The problem is that wind and solar farms just don't deliver the same amount of continuous electricity compared with nuclear and gas-fired power plants. To match traditional energy sources, grid operators must be able to exactly predict how strong the wind will blow or the sun will shine.

But such an exact prediction is difficult. Even when grid operators are off by just a few percentage points, voltage in the grid slackens. That has no affect on normal household appliances, such as vacuum cleaners and coffee machines. But for high-performance computers, for example, outages lasting even just a millisecond can quickly trigger system failures.'

http://www.spiegel.de/international/germany/instability-in-power-grid-comes-at-high-cost-for-german-industry-a-850419.html

Re: Germany swearing off nuclear--what a self-destructive policy! Turn off safe, low-carbon, reliable, cheap, base load generators in favor of expensive, unreliable, intermittent renewables. Build new coal plants to make it all work. What a great idea.

How a so-called engineer can talk such absolute cobblers is a mystery, perhaps only possible by resolutely ignoring facts.

It's no mystery if you consider that he's probably one of many sock puppets run by some propagandist.  Then all the pieces fit, including the contradictory statements and name-calling.

I suspect that a cheap Br/HBr flow battery would favor nuclear power more than unreliables.  Suppose that your flow battery costs $150/kWh and is discharged 50% each weekday and recharged 40% each weeknight, coming up to full charge on the weekend with 30% discharges Sat/Sun.  Each kWh of capacity takes 3.1 kWh of charge per week, returning it at 90% efficiency.  At 5% interest and 20 year amortization, you pay 8.2¢/kWh output for amortization.

If O&M doesn't cost much, this appears to be quite competitive.  Overnight nuclear power generated at 3¢/kWh could be stored and sold at upwards of 20¢/kWh peak rates, also avoiding any costs related to emissions and eliminating cost uncertainty due to fuel prices.

@KP, "Of course the power industry does it everyday. There is no unmet need."

Cleanup Attempt At Japan's Fukushima Plant Could Release 14,000 Times As Much Radiation As Atomic Bomb

http://www.businessinsider.com/fukushima-radiation-hiroshima-atom-bomb-2013-8

KP, your every comment is a barometer of falsehoods.

kelly, if you are trying to compete with the pro troll for off-topic comments and non-sequiturs, please don't.

@Davemart
Which facts am I ignoring? Since I live and work in North America I do not spend much time worrying about Germany. I do know that the grid in North America is much more robust than the EU. Over the 60 years of our US design of a similar design to that in the EU, our design will have 35 million less cycles of the control system. I know because I dd the US calculation.

I am also the author of my companies technical guide on designing for grid frequency and variations to meet new FERC requirements. The grid is one huge inter tied system with all the machines synchronized at the same frequency. If there is a sudden disruption like a wild fire or tornado taking out a transmission line. Voltage and frequency would drop. The turbine control system on load following plants would respond immediately and stored thermal energy would match demand. More fossil fuel would then be burned restoring the boilers to normal pressure.
As described in the Spiegel article Davemart this can result in equipment failure. If that failure is the boiler feed pump motors, for example, at another power plant, that power plant might trip. The could lead to cascading grid failure. So new power plants are being designed to keep running through a disruption.

Again, the US is not having a problem managing renewable energy without storing the energy.

“Cleanup Attempt At Japan's Fukushima Plant Could Release 14,000 Times As Much Radiation As Atomic Bomb ”

Classic fear mongering. Bombs, chemical or nuclear, hurt people by the sudden release of near people.

“The operator of Japan's crippled Fukushima nuclear plant is preparing to remove 400 tons of highly irradiated spent fuel from a damaged reactor building, a dangerous operation that has never been attempted before on this scale.”

Spent fuel and spent fuel pools were not damaged at Fukushima. The blow out panels above the spent fuel pools were blown out by the hydrogen explosion. Moving fuel assemblies to dry cask storage is routine. A small crane is used to move fuel assemblies on at a time. This is done underwater and requires about 7 feet of water to protect the operator.

“INADVERTENT CRITICALITY
"There is a risk of an inadvertent criticality if the bundles are distorted and get too close to each other," Gundersen said.”

Storage racks are designed to preclude that. Of course Gundersen knows that. Fear mongers always fail to explain how they would cause the dangerous thing to occur. Having done integrated safety analysis and initial fuel load at a nuke plant, I am an expert on this subject. If you picked up a fuel assembly and dropped in at one end of the fuel where there is not a storage rack to maintain. Here are mechanical and electrical interlocks to prevent that. Then you would have to do it over and over hoping no one would notice.

This is somewhat akin to committing suicide by jumping off a building with a parachute and drifting over the ocean to be eaten by a shark. If could happen right.

@KP, FOR YEARS, the Japanese and many of the world's experts have now tried to keep Tokyo and the Pacific from becoming a Chernobyl and still appear to be failing.

The nuclear company-line "nothing to see here - move along" approach in "Of course the power industry does it everyday. There is no unmet need." is very dangerous.

Sorry EP, but even "Rechargeable membrane-less hydrogen bromine flow batteries" are charged by the power grid and every time there seems to be energy progress KP carps a unsettling energy ad.

FOR YEARS, the Japanese and many of the world's experts have now tried to keep Tokyo and the Pacific from becoming a Chernobyl and still appear to be failing.

Appear to be failing?  The only problem they haven't handled neatly is tritium, which cannot be chemically filtered from the water pumped out of the plant basements.  This tritium could be trivially discharged into the Pacific ocean without materially increasing radioactivity (tritium does not bio-accumulate).  If they wanted to be ultra-careful they could put this water in tankers, mix it with salt to make dense brine, package it in plastic bags and sink it in some deep ocean trench.  Tritium has a 12.3 year half-life, so isolating this water for a couple hundred years is sufficient to get rid of it almost completely.

even "Rechargeable membrane-less hydrogen bromine flow batteries" are charged by the power grid and every time there seems to be energy progress KP carps a unsettling energy ad.

Forget the troll, deal with the facts.

"Re: Germany swearing off nuclear--what a self-destructive policy! Turn off safe, low-carbon, reliable, cheap, base load generators in favor of expensive, unreliable, intermittent renewables. Build new coal plants to make it all work. What a great idea."

Nick, perhaps you remember that Chernobyl went sour next door to Germany. And that radiation from Chernobyl is a continuing problem for Germany. Perhaps not a major problem, but a constant reminder. But since that was a USSR reactor it was possible to write that off as a poorly built and poorly operated reactor.

Then the Japanese melted a few. Japanese reactors built with US designs. Well, if those could go and one is familiar with all the other 'oops' events that keep happening in reactors it's a bit more understandable that some people might decide they'd rather not live next door to one.

Renewables are neither expensive nor unreliable. Wind and solar are variable. They aren't dispatchable. Working with those limitations is simply an engineering exercise.

Germany is doing fine. They're incorporating renewables and starting to work on storage which they will need later on as the percentage of renewables grow.

As for coal, Germany's new coal burning plants are replacing (not adding to) the older plants that either have been or will soon be decommissioned.

These new plants were planned and construction was started prior to the decision to close nuclear plants.

By 2020, 18.5 gigawatts of coal power capacity will be decommissioned, whereas only 11.3 gigawatts will be newly installed.

Furthermore those plants will be more efficient, releasing less CO2 per unit electricity produced than are the ones they are replacing. And the new coal plants are partially load-following.

Chernobyl went sour next door to Germany.
With no verifiable harm to anyone in Germany.
radiation from Chernobyl is a continuing problem for Germany.

No, the FEAR of radiation is a continuing problem for Germany.  There is no proof that the Chernobyl fallout itself has caused any actual problem.

Then the Japanese melted a few. Japanese reactors built with US designs.

Again, with zero radiation fatalities and no injuries outside the plant.  3 workers with beta burns (because they were sent into the plants with neither rad monitors nor proper protective gear!) fully recovered.  The phenomenon which knocked out the plants' cooling systems (tsunami flooding) is impossible anywhere in Germany, and the plants themselves are of the earliest commercial design.  It's as if the word "nuclear" induces panic.

Renewables are neither expensive nor unreliable.

Tell that to the German people who cannot afford electricity any more, and the neighboring nations installing switches to keep Germany from dumping its surges of surplus on their national grids.

Working with those limitations is simply an engineering exercise.

The engineering "solution" the Germans have hit on involves burning more coal.  Really "green".

hose plants will be more efficient, releasing less CO2 per unit electricity produced than are the ones they are replacing.

Instead of the nuclear plants, which emit ZERO CO2 in their operation.  This is a giant step backwards, and everyone except the ideological anti-nuclear "greens" admits it.

"Forget the troll, deal with the facts."

The nuclear power industry has failed for over SIXTY OPERATIONAL years to solve its lethal accidents and radioactive waste storage disasters.

Most people have simply seen ENOUGH nuclear multi-hundred percent cost overruns and the total costs of the DECADES of JUST ONE Chernobyl wipe out any nuclear "cheap energy" claims.

Sorry, but "deal with the facts".

Meanwhile, renewable costs - including battery advances - fall by factors a decade.

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