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MIT engineers create an energy-storing supercapacitor from ancient materials

news.mit.edu

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Re: MIT engineers create an energy-storing supercapacitor from ancient materials

#81

Post by slow_typist »

jszymborski wrote: post #76
slow_typist wrote: post #74

For 2 m^3 of the material you will need around 1 metric ton of cement. You need around 2.8 GJ to produce 1 t of cement. Therefore you need 63 GJ or 17500 kWh to produce a capacitor of 45 m^3 that can hold 10 kWh. (Omitting the 3% carbon in the mixture obv.) I hope the thing is really resistant and cycles forever without degradation. BTW cement production contributes substantial amounts to global carbon emissions.

In fairness, I think the idea is that you would create this from concrete structures that would be built regardless and used in other ways. Adding extra capacity to the grid for "free" would good. Of course, this is a press release and they usually consist entirely of breathless exaggerations and wilful omissions of limitations.

Point taken, but we need to reduce cement usage anyway.

Re: MIT engineers create an energy-storing supercapacitor from ancient materials

#83

Post by pengaru »

slow_typist wrote: post #80
pengaru wrote: post #79

Earlier quoted context omitted.

Is your math accounting for the volume the added water occupies? The paper describes using excess water for deliberately creating voids the electrolyte can access. AIUI when mixing cement any excess water in the initial mix weakens the cured product by leaving voids behind. You end up with a less dense cured result. Usually when you mix cement it's a balancing act of using as little water as possible while maintainin…

Admitted, it could be less cement. But then the material could not be used for structural parts of a building.

It could still be well within the required compressive strength for things like foundations...

But it's unclear to me how you'd get enough electrical capacity in such mixed applications since concrete is mostly aggregate (rock, gravel, sand), not cement, by volume.

I think those areas of the MIT press release are just fantasy.

Re: MIT engineers create an energy-storing supercapacitor from ancient materials

#85

Post by bumby »

labster wrote: post #13

Typical university press release: this technology can revolutionize our energy grid by storing energy in a building’s foundation, because we powered an LED with some tiny cells we made.

Tbf, that's often how science progresses.

The first sustained artificial nuclear reaction [1] managed to produce...half a watt. I'm glad they weren't overly cynical about future possibilities.

[1] https://en.wikipedia.org/wiki/Chicago_Pile-1

Re: MIT engineers create an energy-storing supercapacitor from ancient materials

#86

Post by mitjam »

slow_typist wrote: post #74

For 2 m^3 of the material you will need around 1 metric ton of cement. You need around 2.8 GJ to produce 1 t of cement. Therefore you need 63 GJ or 17500 kWh to produce a capacitor of 45 m^3 that can hold 10 kWh. (Omitting the 3% carbon in the mixture obv.) I hope the thing is really resistant and cycles forever without degradation. BTW cement production contributes substantial amounts to global carbon emissions.

45 m3 wall volume is enough for a small single detached home even not counting the cellar or foundation. 10 kWh battery for a solar roof is also often large enough for single family. Having a battery that is not a huge hazard in case of a fire is also valuable. Sounds attractive to me.

Re: MIT engineers create an energy-storing supercapacitor from ancient materials

#87

Post by klyrs »

harvie wrote: post #51
rob74 wrote: post #44

Earlier quoted context omitted.

Yeah, let's go ahead and store huge electrical charges in the foundations of every new house built! What could possibly go wrong?

i guess the voltage would be rather low... but current capacity might be enough to melt your drill bit, if you decide to drill hole through both of the electrodes :-D

Current kills. If your foundation cracks, say, in an earthquake, the electrodes can become exposed. Flooding is also common in earthquakes. As another poster said, floor is lightning.

Re: MIT engineers create an energy-storing supercapacitor from ancient materials

#88

Post by klyrs »

porkbeer wrote: post #6

So i get the electrolyte, but how does this polarize?

> Two electrodes made of this material, separated by a thin space or an insulating layer, form a very powerful supercapacitor, the researchers found.

The image of a huge cube is a bit misleading. If you made a huge cube, you'd probably want a sandwich of thin layers separated by thin film, wired in alternating polarity. Not exactly something you could pour in a foundation.

Re: MIT engineers create an energy-storing supercapacitor from ancient materials

#90

Post by javcasas »

Twirrim wrote: post #71
robinzfc wrote: post #29

Earlier quoted context omitted.

To estimate the cost and practicality, assume you build a tower 120 meters tall and machinery able to lift 60 tons block of concrete to the top, then retrieve the stored energy by lowering it to the ground level. Think for a moment how much that would cost. Then calculate: mgh = 60000kg x 120m x 10m/s^2 (assume acceleration of gravity is 10m/s^2 for simplicity, no energy losses due to friction etc). The result is 72…

I love comments like the one above yours "just do this eyesore/expensive/impractical thing instead!" Good enough is good enough. There is no one size fits all, and we really need to start leveraging everything we can to tackle energy storage. Each thing used doesn't need to be perfect for energy density, it just has to be good enough. > assume you build a tower 120 meters tall. vs sticking a concrete block in the gro…

All right, now assume making a 120m deep hole is cheaper than building a 120m tower. BTW, how many 120m deep holes have you seen in your life? You seem to be expert at them.

I have seen a few 120m towers. They call them skyscrappers.

Anyway, all this for 20Kwh. I can get a Nissan Leaf with a 40/60Kwh battery for way less than a skyscrapper. Most likely for way less than what it costs to make a 120m deep hole.

Long story short: cranes and concrete don't make a practical battery, but they make for many articles and publications.

Before you say "but lithium is hard to find, and concrete isn't": you can also make lead batteries, and ni/cd batteries, and liquid air batteries too. I don't expect the Earth to run out of air in the next decades.

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