Rechargeable Molten Salt Battery Freezes Energy In Place For Long-Term Storage (scientificamerican.com) 40
An anonymous reader quotes a report from Scientific American: During spring in the Pacific Northwest, meltwater from thawing snow rushes down rivers and the wind often blows hard. These forces spin the region's many power turbines and generate a bounty of electricity at a time of mild temperatures and relatively low energy demand. But much of this seasonal surplus electricity -- which could power air conditioners come summer -- is lost because batteries cannot store it long enough. Researchers at Pacific Northwest National Laboratory (PNNL), a Department of Energy national laboratory in Richland, Wash., are developing a battery that might solve this problem. In a recent paper published in Cell Reports Physical Science, they demonstrated how freezing and thawing a molten salt solution creates a rechargeable battery that can store energy cheaply and efficiently for weeks or months at a time.
Most conventional batteries store energy as chemical reactions waiting to happen. When the battery is connected to an external circuit, electrons travel from one side of the battery to the other through that circuit, generating electricity. To compensate for the change, charged particles called ions move through the fluid, paste or solid material that separates the two sides of the battery. But even when the battery is not in use, the ions gradually diffuse across this material, which is called the electrolyte. As that happens over weeks or months, the battery loses energy. Some rechargeable batteries can lose almost a third of their stored charge in a single month.
"In our battery, we really tried to stop this condition of self-discharge," says PNNL researcher Guosheng Li, who led the project. The electrolyte is made of a salt solution that is solid at ambient temperatures but becomes liquid when heated to 180 degrees Celsius -- about the temperature at which cookies are baked. When the electrolyte is solid, the ions are locked in place, preventing self-discharge. Only when the electrolyte liquifies can the ions flow through the battery, allowing it to charge or discharge. Creating a battery that can withstand repeated cycles of heating and cooling is no small feat. Temperature fluctuations cause the battery to expand and contract, and the researchers had to identify resilient materials that could tolerate these changes. [...] The result is a rechargeable battery made from relatively inexpensive materials that can store energy for extended periods. "Right now the experimental technology is aimed at utility-scale and industrial uses," notes the report. "The PNNL team plans to continue developing the technology, but ultimately it will be up to industry to develop a commercial product."
Most conventional batteries store energy as chemical reactions waiting to happen. When the battery is connected to an external circuit, electrons travel from one side of the battery to the other through that circuit, generating electricity. To compensate for the change, charged particles called ions move through the fluid, paste or solid material that separates the two sides of the battery. But even when the battery is not in use, the ions gradually diffuse across this material, which is called the electrolyte. As that happens over weeks or months, the battery loses energy. Some rechargeable batteries can lose almost a third of their stored charge in a single month.
"In our battery, we really tried to stop this condition of self-discharge," says PNNL researcher Guosheng Li, who led the project. The electrolyte is made of a salt solution that is solid at ambient temperatures but becomes liquid when heated to 180 degrees Celsius -- about the temperature at which cookies are baked. When the electrolyte is solid, the ions are locked in place, preventing self-discharge. Only when the electrolyte liquifies can the ions flow through the battery, allowing it to charge or discharge. Creating a battery that can withstand repeated cycles of heating and cooling is no small feat. Temperature fluctuations cause the battery to expand and contract, and the researchers had to identify resilient materials that could tolerate these changes. [...] The result is a rechargeable battery made from relatively inexpensive materials that can store energy for extended periods. "Right now the experimental technology is aimed at utility-scale and industrial uses," notes the report. "The PNNL team plans to continue developing the technology, but ultimately it will be up to industry to develop a commercial product."
I have an even better idea (Score:4, Informative)
You take all the oppositly charged ions, separate them into two giant tanks or electrolytic fluid, and then put them on the back of two trucks, one going to LA, the other to Maine. Then when you need to discharge the battery, you drive them back and connect them up with a pipe.
Flawless.
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That sounds like a satirical description of a flow battery. And my question when I read the summary was "How is this new approach better than a flow battery?" https://www.sciencedirect.com/... [sciencedirect.com]
The requirement of a flow battery is that the electrolytes be liquid and stable. They aren't very portable, but this doesn't sound portable either.
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Same general idea, but without the requirement for the electrolyte to be a well-behaved liquid. From your link it sounds like current flow batteries use expensive materials.
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You take all the oppositely charged ions, separate them into two giant tanks or electrolytic fluid, and then put them on the back of two trucks, one going to LA, the other to Maine. Then when you need to discharge the battery, you drive them back and connect them up with a pipe.
Add in some vehicle velocities and times and you've got one of those damned math word problems.
Re: I have an even better idea (Score:1)
These days, numerical velocities aren't what matters in a math word problem; it's a full accounting of all the indian tribes whose stolen land the trucks traverse in service of the white man's agenda.
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An excellent example of tribalism being the cancer of civilization.
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Oh you poor little dear, the researchers do some actual research and now you complain bitterly about reading it. Tell you what, go get a physics and chemistry PhD, go solve the problem, and then come back here to tell us how you did it. We'll wait.
Re: Oh come on guys (Score:3)
Re: (Score:2)
You know this is a tech site, right? If you don't like hearing about pre-market stuff there's no shortage of online catalogs to browse.
If you're just complaining about "journalism", well, we had that discussion ten years ago on here. Consensus was "bloggers will do it for free so professional journalists can suck it."
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Don't worry, they will be sure to not tell you or anyone when they actually implement the thing, just like happens with most useful technologies.
Technological progress is always happening, but being barely reported in many cases.
Freeze it in the excited state (Score:2)
I think I watched that movie in 1985.
https://youtu.be/0ds0wYpc1eM?t... [youtu.be]
I don't get it (Score:1)
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If I'm even understanding it correctly, I think it's more like you have to heat the battery up, to use it for charging or discharging.
Heat it, charge it, then cool it to store the charge long term. Cooling only "freezes" the discharge process.
Then when you want to use it, you heat it up again. Energy flows in this battery, at 180C.
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Nothing about a tank of hot salt makes me happy, except that it's cheap.
If you could maintain the temperature near enough to the melting temperature then it might be viable for long term storage. It seems to me like the goal has to be something like this with a much lower melting point somehow.
Re:I don't get it (Score:4, Funny)
Nothing about a tank of hot salt makes me happy, except that it's cheap.
How about if they add in some cold beer, soft pretzels and a little spicy mustard?
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To get Your goal use water: by freezing it you take the energy out and restore that (energy) later by melting it.
Have a look at https://en.wikipedia.org/wiki/... [wikipedia.org]
The energy storage is about 320 Mj per m3 and "i think" it can be easy stored for a few months by isolating that tank/reservoir/basement.
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Nothing about a tank of hot salt makes me happy, except that it's cheap.
Safety. There's likely a societal benefit in using salt vs. lithium. We might not have to warmonger so damn much for salt. Less death for minerals, should make most people happy. Somehow, people are oddly indifferent. Ah, Greed.
If you could maintain the temperature near enough to the melting temperature then it might be viable for long term storage.
Do you keep your frozen foods frozen, or do you maintain them at "near' melting temperature for some reason, even though you're not going to use it right away?
You use the tools and energy you have efficiently and when you need to. You don't throw all your wood in the furnace at
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Safety.
What makes you imagine this is going to be safer overall? Lithium batteries are getting very safe, especially the chemistries we expect to use in homes these days (e.g. LiFePo4). A big tank of salt has its own problems.
Do you keep your frozen foods frozen, or do you maintain them at "near' melting temperature for some reason
The freezer temperature IS near the melting temperature of water. It's very, very near. The temperature swing on a typical day on the coast is wider than the temperature difference between water in solid and liquid forms.
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Safety.
What makes you imagine this is going to be safer overall? Lithium batteries are getting very safe, especially the chemistries we expect to use in homes these days (e.g. LiFePo4). A big tank of salt has its own problems.
To sum it up in two words; Raw Materials.
One is so plentiful we could shit out desalinization plants like rabbits for the next decade and the impact would amount to pissing in the ocean.
The other, has already started conflict, and will lead us directly into WWIII. Stop thinking like the usual CEO about the next fiscal quarter and start thinking about the long-term bloodshed you're going to require to sustain business. Many countries are quite capable of holding a planet damn near hostage with a single but
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Isn't the battery only solid when it is empty and when self-discharge therefore is irrelevant?
Looks like it is also solid when it is charged.
Charging it means heating it, it becomes liquid and self discharges?
It means to access the charge you have to activate the battery by heating it. Electricity only flows in or out when the battery is in a liquid state.
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The thing is this battery can be frozen in a low-loss state without the need for continued refrigeration. That means exceptionally low losses in the frozen state. To use it, you need to heat it up and that will come with some losses. You could probably recover some heat when you let it cool down again and supposedly the energy needed to heat it up is a lot kess than what can be stored.
Of course, this is experimental and has maybe a 10% chance of becoming a useful product. But the idea is actually pretty nic
180 degrees (Score:4, Interesting)
What proportion of the energy stored in the battery (yes I know it'll come from an external source) is required to heat it up to operating temp. Because this needs to be deducted from its operating efficiency. If its similar to the discharge in a normal battery over the intervals this is expected to be used then you might as well use LiON.
Re:180 degrees (Score:5, Informative)
RTFA: At the moment about 10 to 15 percent.
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And they say they're working on it. Interesting research, but clearly this is going to be an issue for viability.
They're also not real clear on whether that 10-15% gets you up to operating temperature, or gets you there and keeps you there long enough to extract all the available energy. The latter may require significantly more, depending on whether the final product has better thermal insulation than the one in the photo.
The initial positioning seems to be as a utility-grade demand-leveling product, an
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RTFA: At the moment about 10 to 15 percent.
So not a lot. That is actually in a very competitive region compared to other storage approaches. Also, that heat could probably be reused to a degree.
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Not New (Score:4, Informative)
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The trick they seem to have added is cooling the junction so that current cannot leak while storing the charge. So go read the relevant patent and tell us how it has already done this. I'd read it but you are the one making the claim. Back it up or it didn't happen.
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Salt-based heat storage (Score:3)
I recently read another article [www.tue.nl] (in Dutch) about salt-based energy storage, although in this case it was heat rather than electricity.
The basic principle there is:
* you have a salt that has an exothermic reaction with water, so add water and you get heat. The heat gets recuperated by a heat exchanger.
* when you want to 'recharge' the salt, you boil it until all absorbed water is gone
As long as the salt is kept dry, it keeps its (chemical) energy and hence there's no storage loss over time either. The main challenges were finding a salt that could be reused many times without the crystals shattering or becoming one big blob, and a compact and efficient way to extract the heat when rehydrating.
All hail to salt-based energy storage!
Wish them luck! (Score:3)
Likely to remain in the lab (Score:3)
Reading through the paper it sounds like they did come up with some innovations but this was a set of very small-scale experiments. "A cell was charged at 3 mA to a cutoff voltage of 1.1 V" and their discharge rates were also about 3 mA. Not very exciting, though they do claim a cost of "$23.4/kWh with an 85% total energy efficiency" which would be excellent if it can be scaled up. Meanwhile this will go nowhere like a lot of other battery innovations unless someone risks a lot of money on next steps which would take years.
And they admit "it is difficult to predict the market landscape for seasonal energy storage", not sure if there is actual demand for this. I guess you could charge up a giant mass of these batteries in the summer with solar panels and then draw the power off in the winter, but then they are sitting idle most of the year which doesn't seem cost-efficient.
A lot of battery (Score:2)
Pumped storage hydro, etc (Score:2)
Can't pumped storage hydropower or some other form of energy storage where the difference in height plays a part also store the energy for an indefinate period of time?
And for those who think the water will evaporate if kept for months, just use something which is covered, so no evaporation happens.
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I think the basic problem is they don't and won't have enough reservoir capacity to regulate the annual runoff cycle. (Also there are ecological impacts to regulating the flow of a river based entirely on energy needs).
But that certainly raises the question of whether this battery is more dense (land-efficient) than, say, firing up the bulldozers to make more reservoirs.
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Well, there are other forms of energy storage dependant on heights. Like the company which is keeping heavy weights up a high location and dropping it down to generate energy.
Just look up gravity energy storage to see the companies involved.
Example articles :
https://spectrum.ieee.org/grav... [ieee.org]
https://www.wired.com/story/en... [wired.com]
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Stored hydropower has some serious issues, especially environmental. Your storage pond will get stagnant and hot, when used you're now dumping hot stagnant water into a river or lake's ecosystem. You're not going to be making the people downstream very happy. There are also not a lot of appropriate locations available.