MIT research: concrete supercapacitors - must read

Hey all!  Just read this awesome article about MIT figuring out you can make superconductors from concrete, water, and carbon black.  It sounds really doable and I think it'll be a game changer in energy storage.  It's just concrete with 10% carbon black.  For example, the foundation of your house could store an entire day's solar energy.  Definitely a must-read.

https://scitechdaily.com/new-breakthrough-in-energy-storage-mit-engineers-create-supercapacitor-out-of-ancient-materials/

Robert Murray-Smith on YouTube did a video on this yesterday. I believe he still does consulting for battery chemistry and design. He has loads of videos exploring different ways to create and store energy, and often repurposes things to make his projects accessible to more people. It sounds like the capacitance isn't so great compared to current methods and other issues that make it much more complex than being able to make a concrete slab into an energy storage device with simple changes. Here's the video:

Thank you!  That was very enlightening!

Reading the article reminded me of a few things. When I went to tech for electrical, my teacher taught us about a number of things outside of electricity to look out for to avoid serious problems. One of those things was ordering concrete. It is very easy to divide incorrectly or be off a decimal place. He showed us some examples to give us an idea of how much volume something should take up. Even if you do a rough estimation, you can get a rough sense of what would be the correct amount versus being massively off.

A few years ago I was fixing some outlets and my friend was talking about installing a sidewalk along the side of a building, and came up with around 98 cubic yards. I immediately thought back to what I was taught and saw red flags. I explained that the number he had would be around 20 trucks of concrete, which he initially thought was OK but I persisted. Apparently he used an online calculator and put in a decimal place that the calculator didn't register. 9.8 yards, or two trucks of concrete sounds like a perfectly reasonable amount for a long wide sidewalk. I didn't measure it myself so I have no idea how precise it was, but certainly much more reasonable. I can't imagine spending all that money and having a row of trucks that absolutely have to dump their contents before it hardens.

I have seen lots of news like this in recent years, specifically from MIT, but I don't blame them since exploring these things is what they do. Science communicators need clicks so they can get their ad revenue, and some of it has gotten bad. I'd also imagine many people simply have no gauge for how large 45 cubic meters can be. Going by average slab thickness and housing square footage in my state, that is well over 50% more concrete (nearly 3200 sq ft vs almost 2000 sq ft @ 6" thick). I don't know if anyone is interested in the math, but I figured I'd put it out there.

My battery bank is 30kWh, roughly. AZ is hot, you need cooling at night. So for only 135m^3 (a mere 683,000 lbs) of concrete...  Better buy the 80lb sacks. And ask a friend to help load.

But really, 18 standard trucks, at current Cemex pricing, gets me to about $30k (excluding labor, forming, additives, and labor will be substantial). I can replace my whole battery bank for the same amount, for considerably less labor. That would be a 5-15yr system which would weigh less than 1000lb. I'm also wondering about life of the C-doped concrete. Carbon aggregates water over time, water shorts circuits.

If I were to go Iron-Nickel (from Alibaba, now that Iron-Edison is gone), I would be out $13k for an equivalent energy storage system which will last my lifetime and beyond (60 cells, 400A*hr, 1.2V, kinda squishy math because that wouldn't string right, and you'd need 80 for a 2-parallel 40-series setup)   And it's got nice terminals to wire to. And weighs substantially less (ok, 37,000lbs ain't light... but better!)

So... we'll see. I wonder what would ground surge currents do to your system in a solar flare? Anyway, neat physics, possibly impractical.

Adding carbon to concrete is not a new technology. I researched this 15 years ago for a big project to use fly ash containing activated carbon in making conductive concrete. Fly ash from coal-fired power plants is commonly used as an additive in concrete. The activated carbon was injected into the flue gas to collect the mercury. This carbon in the fly ash really messed up the concrete due to it's reactive nature, but we made some batches that would solidify. Essentially, adding mercury control to the power plant made their ash unsalable and they lost money.

Even in 2008 I found that many other people were working on conductive concrete. Add activated carbon, carbon black, or similar carbon materials to concrete and it will conduct electricity. Due to the resistance in the ash and concrete, the electrical charge heats up the mixture. There is a sidewalk somewhere in Canada (don't remember now) that stays warm in winter to keep ice off as long as a charge is applied. The video above is a great explanation as to why the whole idea from MIT is technically workable, but not at any scale or economics that make sense. That's the way research is though. Very few ideas are actually winners once you look at the details. Our conductive concrete work didn't go anywhere because it takes a LOT of energy input to heat concrete. And you have to keep the concrete wet. Maybe someone will figure out a way to make this idea economical.