3 ms·
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 t
by slow_typist 3y ago
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.
- jszymborski 3y agoIn 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.
- slow_typist 3y agoPoint taken, but we need to reduce cement usage anyway.
- pengaru 3y agoIs 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 maintaining workability and still having sufficient water to kick off the process. Then once it sets up you go crazy with the water keeping it hydrated while it cures. This stuff is deliberately being mixed very wet...
- slow_typist 3y agoAdmitted, it could be less cement. But then the material could not be used for structural parts of a building.
- pengaru 3y agoIt 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.
- mitjam 3y ago45 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.