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Ambri and Utility-Scale Storage: Another Emerging Story of Government Investment in Energy Innovation


Utility-scale energy storage start-up Ambri is emerging as a potential clean energy game changer, but is also a budding story of the role of government in supporting breakthrough technologies. Its potential impact cannot be overstated. Utility-scale energy storage is critical for making clean energy-produced electricity a viable option everywhere.

Intermittency is a key drawback of using solar and wind power (in addition to the higher costs of existing technologies) at grid-scale (i.e. to power a city or region). The amount of energy produced by the sun and wind varies greatly over time and “when intermittent electricity sources like solar make up more of the power supply mix,” Sydney Kaufman of Solar Novus Today observes, “utility operators have less control over how much power is produced. This is one of the largest hurdles to increasing renewable grid penetration and it causes utility managers to have to constantly be prepared for dips in renewable output.”

Utility operators have typically compensated for the ebb and flow of renewable power by running back-up natural gas power plants that can be quickly brought on line, but as Kaufman points out, this “means that at least some of the time, more energy is being produced than is needed, which leads to throwing away some of the renewable power generated. This leads to an increase in the cost of electricity.” In addition, relying on peaking-natural gas plants also limits potential greenhouse gas reductions from switching to clean energy.

Ambri, which recently changed its name from Liquid Metal Battery partly as a tribute to Cambridge, the city where it was founded, might have a solution. MIT’s Technology Review summarizes the company’s technology:

Liquid Metal Battery is so named because the powders its researchers pour into its battery cells are heated to the melting point, when they naturally segregate themselves into three layers, the positive and negative electrodes, and the electrolyte that separates them. These now-liquid materials are highly conductive, so the batteries can be discharged and charged quickly, accepting charge one millisecond and returning it the next, if necessary, to help stabilize fluctuations of supply and demand on the power grid.

Ambri’s battery would thus solve the solar and wind energy intermittency problem by giving utilities the flexibility of storing energy when demand for power from the grid is low and releasing it during times of peak demand. “We like to say that with this battery, you can draw electricity from the sun, even when the sun doesn’t shine,” as its co-inventor, MIT professor Donald Sadoway, put it. Existing grid batteries tend to be very expensive and weak, with little guarantee that renewable power will be available when the sun isn’t shining or the wind isn’t blowing. Ambri’s simple battery design, however, offers the promise of utility-scale energy storage that is both inexpensive and reliable.

The inspiration for the technology came from Sadoway’s earlier work on aluminum smelting, which occurs under similarly high temperatures as the Ambri battery. Thanks to early funding through the MIT Deshpande Center, which provides grants to breakthrough researchers, and the philanthropic Chesonis Family Foundation, Sandoway and a group of researchers were able to demonstrate the viability of the battery idea at the laboratory scale at MIT. Developing the technology further, however, only became possible with the awarding of a three-year (2010-2013), $6.95 million grant from ARPA-E in late 2009. “If successful,” the accompanying press release declared, “this battery technology could revolutionize the way electricity is used and produced on the grid, enabling round-the-clock power from America’s wind and solar power resources, increasing the stability of the grid, and making blackouts a thing of the past.” It has been one of the largest sums bestowed by the agency to date and the public vote of confidence from ARPA-E was followed by a string of private sector investments. (This turn of events is not unique to Ambri as an ARPA-E awardee; the agency pointed out last year that eleven of its projects secured more than $200 million in private capital investment after first receiving ARPA-E grants). For example, the French oil company Total committed to a $4 million, five-year joint venture with MIT to further develop the Ambri battery. Since then, Ambri has also received $15 million from venture capital firm Khosla Ventures and an untold sum from Bill Gates. Thanks to the investments from ARPA-E and others, the company has built a 16-inch prototype, but continues to tinker with it in order to increase its stability, determine an optimal shape, and decrease costs. Commercialization is estimated to be around two years away, with the company planning on building the battery in existing factories through contract manufacturing, thus greatly reducing capital costs.

Of course, Ambri isn’t just a story about smart government investment – it’s also a story about the need for government reforms that build incentives into regulations. As related by MIT’s Technology Review, the company’s viability depends on taking advantage of other government policies that reward innovation, such as “a ruling by the Federal Energy Regulatory Commission that technologies with fast response times can be paid more for their services.” (The battery could ultimately respond in milliseconds, in contrast to several minutes for existing power plants).

If successful, Ambri’s battery could greatly help renewables’ competitiveness vis a vis fossil fuels. But the development of the battery thus far is also a telling indication of the need for innovation in clean energy in general and how government can most effectively foster it. The need for better utility-scale energy storage technology tends to be overlooked by policymakers because the go-to policy of deployment subsidization for existing technologies simply doesn’t apply, as nothing like the Ambri battery even existed until recently because of key investments through ARPA-E and others. Any new national energy policy should reflect the realities of innovation stories like Ambri’s to get the investment and policies right.

Photo credit: Wikimedia Commons

Clifton Yin's picture

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Paul Ebert's picture
Paul Ebert on September 6, 2012

I find this very exciting.  Is a 4 MW battery large enough?  What is the output of a typical wind farm (if such exists)?  Also, I understand that electrical current keeps the metal and salt melted, but would there always be sufficient current flow to assure this and what would be required should they solidify?  I suppose the worst case would be needing a system to sense solidification and to burn some fuel (gas?) to avoid or remedy it.

Clifton Yin's picture
Clifton Yin on September 6, 2012

Hi Paul,

Thanks for reading. Good to hear that you find the technology exciting. The battery's technical details obviously escape me, but I did a little digging to find some answers to your questions. The 16-inch prototype batteries only contain about 1200 Wh, but that could change as they approach commercialization. For now, the batteries are small enough that the plan is to stack them into shipping containers for a combined 2MWh storage capacity:

As for keeping the battery interior melted: "The whole device is kept at a high temperature, around 700 degrees Celsius, so that the layers remain molten. In the small devices being tested in the lab, maintaining this temperature requires an outside heater, but Sadoway says that in the full-scale version, the electrical current being pumped into, or out of, the battery will be sufficient to maintain that temperature without any outside heat source." (

Hope this helps.

Nathan Wilson's picture
Nathan Wilson on September 10, 2012

The important thing to understand about this technology is that while it might carve out a niche for regulation service (i.e. moving power on or off of the grid for a few tens of minutes while the fossil fuel plants ramp up or down), it is very unlikely to be cheap enough to smooth out multi-day long variations in wind power.

The DOE's Sandia labs did this study comparing energy storage option:

For an eight hour system, pumped hydro was best at about $0.11/kWh over the cost of electricity; the lead-acid battery system costs four times more.  For long running systems (dominated by the energy storage cost), pumped hydro was 15x cheaper than batteries.

So advanced batteries need to improve cost by more than an order of magnitude compared to lead-acid, and that is just to convert cheap night-time power to peak daytime power.  The cost (of the batteries and the renewable power) would have to fall even more to make cost-competitive night-time power.

Paul Ebert's picture
Paul Ebert on September 11, 2012


This is a good point.  If you watch the youtube of Professor Sadoway describing the technology (, he makes a big point of it being very inexpensive as a primary design goal, but an order of magnitude?  Perhaps not.  We'll see, I guess.

I've wondered from time to time if pumped hydro is viable on a small scale - say, a neighborhood, a farm or even single family residence - in conjunction with a small turbine or solar panels.  I suppose it would depend on the implementation.

Nathan Wilson's picture
Nathan Wilson on September 11, 2012

Thanks for the youtube link.  Interesting talk.

He did mention high power.  In batteries, this usually means that each cell can be completely drained in the range of 0.2 to 1.0 hours.  So apparently speeding-up fossil fuel ramping is a target market.

The size of the 1kWh proto seems to be about the same as 1kWh worth of lead acid batteries (1.6 car batteries).  So this could beat flow batteries, which have very poor energy density. 

The big question is can they really beat the cost of lead acid.

George Stevens's picture
George Stevens on September 28, 2012

Awesome comment Nathan and thanks for the link.

Solar and wind are generally portrayed with such great promise by the media, and the advertised costs of their energy never account for the grid stabilization measures that will be necessary with large penetrations of intermittent, unpredictable generation.

The truth is that a large penetration of solar and/or wind would require a huge breakthrough in storage technology and/or demand side management in order to be cost effective. By huge I mean solutions that are orders of magnitude more cost-effective than current technologies. Is it possible? Yes, but shouldn't we consider other approaches such as next generation nuclear (thorium and TWR reactors) for producing clean energy that are more likely to have a reasonable cost?

The general public doesn't understand this issue which worries me because it drives public policy and investment. Yes we all want green energy but I think we have to stop and ask ourselves what the actual benefit will be of providing billions of dollars in subsidies for solar PV power that will offset less than 0.25% of fossil fuel generation.

Sorry if I'm preaching to the choir.

Paul Ebert's picture
Paul Ebert on September 28, 2012

Agreed, George.  We should absolutely be considering next gen nuclear, especially LFTRs, in my opinion.  I wouldn't be surprised if a ready to commercialize LFTR couldn't be developed for a billion dollars, perhaps much less.  The problem there is getting regulatory approval.  My understanding is that getting approval from the NRC would be a huge investment because the existing regulations wouldn't line up.  A catch-22 if there ever was one.

So, the good news is that there seems to be sufficient innovation to make significant headway.  The bad news is that everything always seems configured against it one way or the other.

George Stevens's picture
George Stevens on September 28, 2012

China, Korea, and India are the ideal environments for early deployment of next gen reactors. Terrapower is planning to build a traveling wave reactor in Korea. These governments will support such technology and remove unwarranted barriers.

Germany and Japan may be looking to ban nuclear all together, but I think with time and the right party in office the US will come around and offer support to new nuclear technologies once they have been fully developed through American entreprenuerial investment and deployed on foreign soil.

I'm sure wind and solar will maintain a market share where wind and sun are plentiful, and should for the sake of energy diversity, but I dont see either providing more than 10% of our energy due to grid issues and high costs. Global warming may turn out to be a very positive thing in as much as it is forcing us to be very proactive in finding alternatives to finite fossil fuel supplies. If there wasn't such motivation we wouldn't likely be so prepared for the time when fossil fuel resources become spent.

Lewis Perelman's picture
Lewis Perelman on October 2, 2012

Nathan, I thought the distinction made in that Sandia report between bulk storage, distributed generation, and power quality applications was significant and useful.

OTOH, when one considers the practical demands for "backup" power, those storage solutions ought to be compared with alternatives like generators. Especially at the more granular 'distributed' and 'power quality' scale of applications.

Paul Ebert's picture
Paul Ebert on October 3, 2012

Yes, and I think there's enough interest in the military that it represents another venue for American entreprenuerial efforts.  I just find it frustrating that we can't be directly in the lead with this technology, especially since we laid the groundwork for it a half-century ago.

I do think that wind and solar would be cost effective even given the cost of storage if the externalized costs of fossil fuel were also included.  But, then again, it's hard to externalize the cost of the Amazon becoming a desert and the midwest one giant dustbowl.

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