Arthur T Knackerbracket has processed the following story:
Fuel cells powered with the metal could provide a new source of electric power that's far more energy-dense than lithium-ion batteries.
A new type of fuel cell that runs on sodium metal could one day help clean up sectors where it’s difficult to replace fossil fuels, like rail, regional aviation, and short-distance shipping. The device represents a departure from technologies like lithium-based batteries and is more similar conceptually to hydrogen fuel cell systems.
The sodium-air fuel cell was designed by a team led by Yet-Ming Chiang, a professor of materials science and engineering at MIT. It has a higher energy density than lithium-ion batteries and doesn’t require the super-cold temperatures or high pressures that hydrogen does, making it potentially more practical for transport. “I’m interested in sodium metal as an energy carrier of the future,” Chiang says.
The device’s design, published today in Joule, is related to the technology behind one of Chiang’s companies, Form Energy, which is building iron-air batteries for large energy storage installations like those that could help store wind and solar power on the grid. Form’s batteries rely on water, iron, and air.
One technical challenge for metal-air batteries has historically been reversibility. A battery’s chemical reactions must be easily reversed so that in one direction they generate electricity, discharging the battery, and in the other electricity goes into the cell and the reverse reactions happen, charging it up.
When a battery’s reactions produce a very stable product, it can be difficult to recharge the battery without losing capacity. To get around this problem, the team at Form had discussions about whether their batteries could be refuelable rather than rechargeable, Chiang says. The idea was that rather than reversing the reactions, they could simply run the system in one direction, add more starting material, and repeat.
[...] Chiang and his colleagues set out to build a fuel cell that runs on liquid sodium, which could have a much higher energy density than existing commercial technologies, so it would be small and light enough to be used for things like regional airplanes or short-distance shipping.
The research team built small test cells to try out the concept and ran them to show that they could use the sodium-metal-based system to generate electricity. Since sodium becomes liquid at about 98 °C (208 °F), the cells operated at moderate temperatures of between 110 °C and 130 °C (or 230 °F and 266°F), which could be practical for use on planes or ships, Chiang says.
From their work with these experimental devices, the researchers estimated that the energy density was about 1,200 watt-hours per kilogram (Wh/kg). That’s much higher than what commercial lithium-ion batteries can reach today (around 300 Wh/kg). Hydrogen fuel cells can achieve high energy density, but that requires the hydrogen to be stored at high pressures and often ultra-low temperatures.
[...] There are economic factors working in favor of sodium-based systems, though it would take some work to build up the necessary supply chains. Today, sodium metal isn’t produced at very high volumes. However, it can be made from sodium chloride (table salt), which is incredibly cheap. And it was produced more abundantly in the past, since it was used in the process of making leaded gasoline. So there’s a precedent for a larger supply chain, and it’s possible that scaling up production of sodium metal would make it cheap enough to use in fuel cell systems, Chiang says.
[...] "If people don't find it crazy, I'll be rather disappointed," Chiang says. "Because if an idea doesn't sound crazy at the beginning, it probably isn't as revolutionary as you think. Fortunately, most people think I'm crazy on this one."
Journal Reference: Sugano, Karen et al., Sodium-air fuel cell for high energy density and low-cost electric power, Joule, Volume 0, Issue 0, 101962
(Score: 5, Interesting) by Thexalon on Thursday June 05, @10:31AM (4 children)
I really hope this sodium metal doesn't ever interact with water. That could very easily lead to an unscheduled rapid disassembly.
I realize that's a problem with lithium too, but I'm just saying we need to be pretty damn careful with the stuff, because a rusty battery container or a drip in the factory ceiling could very easily lead to a day that was a lot more exciting than intended.
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(Score: 5, Interesting) by SemperOSS on Thursday June 05, @11:30AM (2 children)
You are absolutely right!
If we are afraid of lithium fires when exposed to water, we should be way more afraid sodium in the same situation as the sodium-water reaction is much more violent than the lithium-water reaction. And for both, it is not just the heat generated from the metal-water interaction but the possible explosive reaction of the hydrogen generated in the process.
I had a science teacher that wanted to demonstrate the sodium-water reaction by adding a "pinch" of sodium to a big Pyrex bowl of water. He had added some washing-up liquid to the water to prevent the sodium racing round the bowl from sticking to its side, only to see this counter-measure not working and the bowl splinter violently due to the heat-stress on the point where the sodium adhered.
Oops! 😬
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(Score: 1) by shrewdsheep on Thursday June 05, @01:41PM
LOL. I do remember this experiment from chemistry class, only it worked as intended in my case. Would have been more entertaining otherwise (for those sitting far enough in the back). Still it was impressive enough, I can vividly remember it > 30 yrs later.
(Score: 4, Funny) by Anonymous Coward on Thursday June 05, @03:31PM
Luckily we do not use such dangerous explosive materials in our transportation devices, nor put 2 ton vehicles capable of 100 mph in the hands of 16 year olds, let along on the streets next to pedestrians! Shockingly irresponsible to imagine the horrific idea of sodium!!!1! Who are these dangerous Nazis destroying America with their zany communist radical overthrow of Our Freedoms??
(Score: 2) by VLM on Thursday June 05, @04:54PM
I'll be hard to keep the water away. Worse in some desert climate areas than others.
The summary did not mention the operating temp; if its like 500C and they use some kind of controlled injection rate, perhaps it would be too hot to have high relative humidity and keep it "safe" or "safeish"
(Score: 2, Interesting) by pTamok on Thursday June 05, @11:21AM (7 children)
The Joule article says that the cell's economics could be comparable to 'green hydrogen', not including possible revenues for selling the chlorine by-product f sodium production
" As an open system, the Na-air fuel cell is projected to be cost-competitive with green hydrogen...and lower in cost than green ammonia"
I wonder how it compares with Vanadium Redox flow cells.
pv magazine: Chinese researchers develop high power density vanadium flow battery stack [pv-magazine.com]
There are lots of 'promising' technologies, often reported breathlessly as the 'next big thing' in battery technology, but commercial implementation seem relatively rare.
I travelled recently on the MF Tycho Brahe electric ferry [wikipedia.org] between Denmark and Sweden. Batteries are lithium ion The lack of smell of petrochemicals was nice. It even has enough power to spare to offer a recharging service for electric cars during the crossing.
(Score: 4, Informative) by HiThere on Thursday June 05, @01:13PM (6 children)
IIUC the vanadium flow batteries are a LOT heavier. Probably easier to recharge, but that's a different use case.
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(Score: 1) by pTamok on Thursday June 05, @02:28PM
I suspected as much when the article I linked to quotes volumetric power density rather than mass power density.
Much like hydrogen, which conversely has a wonderful energy per unit mass, not so much per unit volume at STP.
(Score: 1, Interesting) by Anonymous Coward on Thursday June 05, @03:44PM
I think the idea here is to reserve lithium for portable things, and heavier technologies for stationary power storage, especially considering economics due to availability and export restrictions.
Potassium is another potential alternative to lithium.
(Score: 3, Informative) by ElizabethGreene on Thursday June 05, @04:58PM (3 children)
I quietly suspect that Redox Flow batteries will be the long-term winner for grid-scale energy storage. There are significant advantages to having the energy storage mechanism separate and/or separatable from the energy conversion mechanism.
i.e. Doubling the storage capacity of an RFB means building another tank and plumbing, or adding another "fuel cell" generator doubles the output at half the capacity. It also "feels" like closing the valves and pumping out the electrolyte in an RFB makes it safer than a bunch of racks of LiPoFe4 cells, but that's primarily considering the "gigantic fire" failure mode. I don't have context to know how bad the "Accidentally spilled 10,000 gallons of Vanadium or zinc bromide solution is.
(Score: 0) by Anonymous Coward on Thursday June 05, @05:38PM (2 children)
I still prefer nickel-iron for stationary use, they're safe and durable, and it might even be worth harvesting the hydrogen that gasses off
(Score: 1) by pTamok on Friday June 06, @08:23AM (1 child)
I wouldn't class hydrogen off-gassing as 'safe'. Manageable, maybe.
On the other hand, I have a soft spot for NiFe cells [wikipedia.org] too. Very durable, as you say, but poor round-trip efficiency, and a high self-discharge rate.
(Score: 0) by Anonymous Coward on Friday June 06, @09:29PM
That shouldn't be a problem, since the power plant will always keep them topped off while it is generating
(Score: 3, Interesting) by bzipitidoo on Thursday June 05, @06:30PM
Let's see, terminology. It's a fuel cell if the energy carrying substance undergoes a chemical reaction that releases electricity, without destruction, but the system can't reverse the process. The difference between a fuel cell and a gas tank is that the former uses a chemical reaction to produce electricity, while the latter uses combustion to produce mechanical energy.
It's a primary cell if it produces energy like a battery, but cannot recharge or be easily reused. I was thinking of aluminum-air batteries, and wondering how this sodium based system differs. If this sodium based system really is a fuel cell, with energy density similar to aluminun-air, that does sound like a big improvement.
(Score: 0) by Anonymous Coward on Friday June 06, @01:32AM (3 children)
(Score: 1) by pTamok on Friday June 06, @08:35AM (2 children)
They do/did exist. I remember one produced for a laptop that slotted into the 'spare drive' bay. I can't remember if it was methanol or ethanol powered.
This is not it: https://dmfc-corp.com/product/model-3/ [dmfc-corp.com]
A bit of Internet searching reveals a prototype DMFC made by PolyFuel for a Lenovo ThinkPad T40. I thought it had actually been commercialised, but I probably remembered incorrectly.
(Score: 1) by pTamok on Friday June 06, @08:41AM (1 child)
This paper might explain why they are not easily available: not cost-competitive with Li-ion.
Journal of Power Sources (2007):A feasibility study on direct methanol fuel cells for laptop computers based on a cost comparison with lithium-ion batteries [sciencedirect.com]
The cost-competitiveness required a steep drop in the price of methanol as well.
(Score: 0) by Anonymous Coward on Monday June 09, @01:03AM
Those quadcopters could have a higher range and flight time with fuel cells.