MIT boffins build battery alternative out of cement, carbon black, water Researchers at MIT claim to have found a novel new way to store energy using nothing but cement, a bit of water, and powdered carbon black – a crystalline form of the element. The materials can be cleverly combined to create supercapacitors, which could in turn be used to build power-storing foundations of houses, roadways …
Nah, one slab. Bottom floor, common area for family. Next floor up, kids bedrooms, a couple baths. maybe office space and/or a large common landing. Next floor up, master suite.
Note that I'm assuming off-grid, so no electricity wasting by heating of water at point of use, and no electric heat and cooling. All that is covered by a GSHP. The single slab, as described, should be able to handle that overnight, even in northern climes (how much juice do you use when sleeping?). During the day, the PVs recharge the slab, and handle electricity needs for the house. When the sun is not available and the slab is discharged, an appropriately sized propane generator handles the house's needs, including recharging the slab.
Works for me, but I'm not using concrete/carbon for my electricity storage.
If you're not properly insulated, start there ...
Ah, concrete. I get it now.
The article had me confused with ...45 cubic meters of the carbon-black-doped cement
I thought to myself how can a building or road be built on a loose pile of powder. Then the penny dropped, this piece was written by someone from the US who give different meanings to common words, like " gas powered". That could either mean powered by gas or by gasoline which is what they call petrol.
I think it was George Bernard Shaw who described the UK and the US as "Two nations divided by a common language."
0.5 meters (just under 20 inches) does not get you below the frost line in much of the US. The only house I have owned on the East Coast required over twice that for a foundation (42 inches, to be exact). Granted, it was a perimeter foundation, not a slab ... They have a fetish for basements in that neck of the woods.
They have a fetish for basements in that neck of the woods.
Most of the houses around us (built about 5 years before or group of 5 were built) had the usual concrete raft foundation. Our soil is clay (specifically London clay, even though we're in Wiltshire) and we live on a slight slope.
After a couple of years the slabs started cracking as the clay moved under them..
Our group of 5 houses were built with deep traditional foundations rather than concrete slab (when we first went to see it the lounge hadn't been fully boarded-out and there was about a 6 foot void under the floor). any movement of the house (no cracks other than the usual drying and shrinkage cracks in the plaster).
I have a plan to (someday) convert it into a proper basement/wine cellar..
The "perimeter foundation", ie footing, is what is doing most of the work in your basic house foundation. The slab in the middle is over an appropriate base and moisture/air barrier and only supports the items on it. Internal load bearing walls, posts, etc, should have footings instead of being supported by the slab.
Footings have to go past the frost line or end in sold rock if not.
All of this, of course, is reliant on your builder not slipping the inspector an envelope instead doing the right thing.
In the UK, the ever changing Building Regulations, with their associated Building Inspectors, mean that my house (just above a spring line) has bugger all foundations in the very old part, 2 foot strip in the 1980's part and 6 foot strip in the 10 years old part (due to the clay subsoil being saturated).
As the huge Articulated lorries (up to 44 tonnes now) pass by on the narrow and rough village road that originally was only used by Oxen and cart, the three parts of the house move against each other, with the associated wall cracks at the interfaces.
As parts of my property are older than the USA, with the associated listings, underpinning it all so that it moves a one is not an option - it's also nearly impossible to get house insurance at a reasonable price if you are underpinned.
But what do they mean by cement? My understanding of cement is Portland cement - the calcined mix of clay and lime. Mortar - the stuff that holds the bricks together contains mostly of sand with some cement. Concrete, the stuff your foundation are made of, consists mostly of aggregate, sand and cement. The amount of cement is an order of magnitude less than the volume of the foundations.
Other than contact cement, rubber cement, dental cement, and all of the other "glue" class products that are referred to as cement, as opposed to mortar and concrete type cement.
But yeah, cement and concrete are used mostly interchangeably outside construction and engineering circles, because it's Portland Cement and aggregate or fill material.
Is it fair to call it lazy when the potential for confusion makes more work for us? British English is an ugly bastard, but it met it's match in the colonies when it comes to savage incompetence.
"We don’t just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary." as the saying goes right? We don't even use them properly when we do. Look at football and French toast.
"and all of the other "glue" class products that are referred to as cement,"
Good thing you used the quotes. "Glue" is made from animals and is an organic adhesive. The best generic term is "adhesive", but glue is used so frequently that people will understand what's meant. Just don't use it if you are in the adhesive industry as somebody may interpret that you want an animal based product. The use of the trade name "Loctite" to mean 'thread locker' is also a problem. Loctite, a division of Henkel, makes a wide array of adhesive products and I've made some good money remediating products when somebody went into stores and got out some cyanoacrylate adhesive rather than thread locking compound and made a mess of a whole run of products. The label read "Loctite" and they were told to use "Loctite" rather than thread locker (242 for the blue stuff).
The mental arithmetic works for my little house ('compact and bijou town house in a vibrant urban area') in the UK similarly. I've often thought that local storage at point of use would help smooth out grid demand and make wind/solar electricity more viable. And there is no pressing need for that local storage to be high power density especially. And you can sequester some carbon into the bargain.
I hope this idea becomes an actual product in the fullness of time.
... from bleeding off to ... err ... ground?
Presumably you can't use reinforcing steel. Where do I put my Ufer ground?
Can I bolt an auto lift down on it? (I won't ever own a garage without a lift again. HIGHLY recommended.)
What happens if the dawg lifts his leg on the corner of the foundation? Every day for a decade?
What does it cost to dig a 45 cubic meter (60 cubic yards, close enough) hole in the ground, and then fill it full of this mixture? (60 yards of concrete, delivered, is kinda spendy. I'm sure it'll cost a lot more with the carbon in it. To say nothing of the cost of testing, then disposing of 60 yards of material removed from the hole.)
What happens when it develops a huge crack, right down the middle? (With a block that big, you know it will.)
And last, but hardly least, How does the above price compare to equivalent energy storage in LiFePO batteries?
I won't mention size ... but the LiFePo batteries will easily fit in a space smaller than a tack trunk.
I'd imagine if you make the concrete in a series of square blocks to reduce the likelyhood of cracking over time. you can wire them in series or parallel, whichever works best with the chosen invertor design. I'm curious though, there's no mention of the safe sustained current level the concrete can supply. Can the stored energy be extracted quickly enough to run my oven, or even just my fridge.... Not that I'm likely to ever own a concrete battery, my house has a solid concrete floor, and I won't be getting the house knocked down to get battery storage equivalent to the £3000 10 kWh LiFe battery I already own... Makes sense for new builds, and we haven't finished concreting over the whole of the south of the UK yet, although we do seem to be trying quite hard ...
Building foundations as a series of concrete tanks with this as an infill would get around most construction issues, I can see it being used under commercial buildings with large floor areas to achieve quite impressive capacity levels.
Of course the cost will be interesting, green cement production requires a vast amount of electricity and to use this stuff will probably require a large multiple of the current concrete volumes involved in construction, all of which has to be transported in bulk.
Before I'd put this under any building I'd really want to know how long it will last as electrical storage.
and how many residential houses have lightening rods anyway?
We have - it's called "the TV aerial"..
(Well - it got hit once. Fortunately, the TV wasn't actually plugged into it because the TV signal is crap, even with a masthead amp. Something to do with the hill and big hotel between us and the nearest transmitters).
In fact, since we had it installed (in 1997) we've only used it once or twice - basically until we could get Sky installed.. (the free satellite stuff wasn't around then and,even now, doesn't carry some of the channels we use like NHK World [1])
I'm not a fan of Sky generally but they do have a decent channel line up. And, compared to what we got through the aerial, a decent picture.
[1] For the bi-monthly Sumo Basho coverage.
I've seen a ground-strike take out all the plugged in electronics in three properly wired houses[0] surrounding the strike point ... strangely enough, an identically wired fourth house was closest to the strike by about 20 feet, and yet remained untouched.
Lightning is funny stuff.
[0] Post-Korea tract housing in Santa Rosa, California.
The article doesn't explain how this makes a capacitor, and not just a conductor. A capacitor has two poles, and doesn't conduct between them, but this talks about "self-assembling nano-wires", which sounds a lot like a conductor.
Presumably, there's more to this than just mixing the concrete and pouring it, and it will require some sort of membranes or something to act as the dielectric, otherwise what you have is one big circuit.
As the article says, this is fine for underfloor heating if you want to pass a current through it, but this is light on the details of how it is made into an actual capacitor.
There's a reason that the electronic symbol for a capacitor is two parallel lines that don't touch...
As I understand it, each concrete block's carbon is one electrode, with huge surface area because it spreads through the concrete in tiny rivulets as it's formed. Then they place the two concrete blocks into some sort of container with electrolyte and an insulator.
The breakthrough here is the huge surface area, because capacitance is a function of electrode surface area.
The article mentions fractal-like structures, so I'm thinking graphene-analogue dendrites (graphene is a very good conductor due to in-plane electron delocalisation) rather than fullerenes, and it is these which provide a large surface area. It doesn't explain, however, how you'd produce and maintain two separate sets of them separated by dielectric, which is what would make them into a capacitor and not a conductor.
It's in the MIT link.
The material is then soaked in a standard electrolyte material, such as potassium chloride, a kind of salt, which provides the charged particles that accumulate on the carbon structures. Two electrodes made of this material, separated by a thin space or an insulating layer, form a very powerful supercapacitor, the researchers found.
It's not the amount (at least here in the UK) of energy a house uses in a day, it's the amount of electricity it uses. The quote ignores space heating, which is more than that by a factor of about 4.
It's bad enough when media types, bless their innumerate selves, get confused, but in a technical setting this simply shouldn't happen.
"... It's bad enough when media types, bless their innumerate selves, get confused, ..."
Yep. The article's description of a capacitor seems like it came from Pins and Needles magazine.
Any two conductors that aren't connected to each other form a capacitor. No need for any electrolyte. It's the bane of the integrated circuit manufacturer. Yes, surface area matters. You can store charge (and thus energy) on the surface of a glass rod that you hold in your hand. I did that at school, back in the 1960s. Of course the amount of energy that you can store on a hand-held glass rod won't power your TV for very long.
The 10kWh(e) that you could store in a hundred tonnes of concrete could by comparison be significantly more useful, but not so significantly that I'd be likely to shell out for it. After all, as has been pointed out already, there's a *lot* more thermal energy in that mass of more or less *anything*. For one degree C temperature rise of a hundred tonnes of water for example, you have ten times the energy that this capacitor stores and you'd also be able to make practical use of it - quite possibly without any extra effort, for example it would keep you warm in winter if you just put some of it in a hot water bottle.
As a useful yardstick, a gasoline gallon is very roughly 33 kWh.
Somebody wake me when you can put that in a capacitor that will fit in a shoebox. That's the sort of thing that you're going to have to do to get any, er, traction.
"As a useful yardstick, a gasoline gallon is very roughly 33 kWh."
That's latent energy, but in an internal combustion engine, the vast majority of that energy is thrown away as heat.
Delta T is a big deal if you want to recover useful amounts of power. One ton of water that's 1deg above ambient does represent a fair bit of energy, but good luck trying to harness it. Carnot and that lot.
Unfortunately, concrete absorbs water. Used as building foundations, it will never entirely dry out. Consequently, it will never be a really good insulator so there will be electrical leakage to some extent. Also the permittivity of concrete is not well defined as it will depend on the mix and the amount of residual water present, so the "value" of the capacitor will be uncertain and possibly variable. The idea of using carbon filaments is really neat, but a more reliable dielectric should be sought, as concrete might work OK in the lab but is fraught with potential problems in the field.
The language used (reported by the article) seems a little sloppy:
"Masic said that as the mixture cures, water is absorbed into the cement."
The process of curing concrete is hydration - the water is used up in a chemical reaction, with the water and cement particles forming initially a gel-like paste which then hardens around the aggregate particles. It's a long time since I actually looked at this sort of stuff, so I won't try to go into the actual chemistry. (but 'absorbed' is not the right word).
The amount of water that then penetrates hardened concrete depends on a whole range of factors, but you are right, in general, water (moisture) does get into concrete - that's one reason why there are requirements for minimum cover of concrete over reinforcing bars. However, it is possible to produce very low permeability concrete.
Which leads to another question - this seems to be describing mass concrete (no reinforcement). Fine for a basic concrete foundation (say a strip footing to a house). However, anything that might be subject to any form of tension loading will need reinforcement - so that's any form of beam, column or suspended slab; also the foundation for a wind turbine (which has to deal with the lateral loading that acts on the turbine).
So what happens if you have half a dozen lengths of 25mm diameter mild steel rebar running through the concrete?
From memory (may be wrong!) 1kWh of energy will heat a cubic meter of water very roughly 1 degree (centigrade, sorry Americans).
So if all you need is heat, you could replace 45 cubic meters of concrete (that is actually a lot of concrete) with 1 IBC (1000 litre water container) and heat it up by just 10 degrees above ambient. Add in a Stirling engine to get electricity out, and even with a fair amount of inefficiency you can store a good chunk of energy in a small, cheap space.
So.. um... I don't think this is terribly useful. In common with a lot of MIT (and a number of other high profile Universities) engineering Press Releases, the headline is *way* more exciting than the actual work being done. If you could extract energy out of their self-promotion you would probably get a better result.
You need quite a lot of available energy delta (enthalpy in thermodynamics terms, high temperature in "normal people" language) to run an efficient sterling cycle. You might be able to cheat a little bit by using a different working fluid from air (so probably more accurately a Rankine cycle) but you'll still need quite decent enthalpy in your storage medium to extract at anything approaching useable efficiency.
Such energy storage has been proposed, but it's far more efficient to make use of the phase transition of water (ice to liquid) at around 0 degrees than to heat it. Taking water at 0 degrees C from fully fluid to fully frozen solid at 0 degrees C extracts the same amount of energy as cooling the same volume from (iirc) 60 degrees C to 0 degrees. And the inverse for heating it. Using a heat pump setup that allows for very efficient heat storage and extraction. The difference though is that it's specifically for HEAT storage, which is very different from efficient electricity storage.
For sure - but missing the point. 45 cubic meters of concrete is an incredibly inefficient way to store a relatively small 10kWh, especially given the current demonstrator is a few grammes of the stuff, and there is no obvious way to integrate a complicated 45 cubic meter electrical component into a sensible structural element.
There are simpler, cheaper, and massively smaller ways to store energy than this - yet the reporting doesn't put it in context, and we get breathless repetition of the PR that this is somehow game changing.
That's an interesting idea. I read about a guy in Montana that was using solar water heating. He had these glass tubes through which water was pumped, with the backside of the tubes painted black as I recall. He claimed that even in the coldest part of winter, the water inside the tubes would reach boiling temperatures within 10 minutes of the Sun coming up. He was using this setup to heat a large heavily insulated tank, like 5000 gallons, or roughly 19,000 liters, which he used to heat his entire house. He said there was enough heat to keep his house warm for several days of no sun. It would be nice to use something like this to just run your entire house.
"I read about a guy in Montana that was using solar water heating. He had these glass tubes through which water was pumped, with the backside of the tubes painted black as I recall."
There are a lot of scams with stuff like that so it pays to be wary. I have some evacuated glass tubes that have a heat pipe down the center that are heated by the sun and move the heat to a header manifold that takes the heat via a glycol solution to where you'd use or store the heat. The problem is that I got them from a guy off of Craiglist and he didn't know how to properly remove the system from his roof and did a bunch of damage. I have to remake the heat pipes as he just cut them. For a test, I filled up one of the tubes with water and watched how fast it heated up. The tubes are ~1.5m tall and the inside cavity is ~30mm. The temperature rise was very impressive and the water was boiling in a short period of time. I hope I'll have the time and money to get the system put back together for the winter.
Except, concrete is a major source of greenhouse gas emissions. So, unless the intention is to build the supercapacitor into the existing plans for a foundation, (not using more concrete) it may actually be creating more carbon than it's saving. Someone needs to do some sums. I'm sure the MIT guys are more than capable!
https://www.bze.org.au/research/report/rethinking-cement
That report, like others, focuses only on concrete production. Concrete also reabsorbs carbon dioxide over the years.
Not got an authoritive reference but media reports 30 percent of “production emissions”, however, without detail I cannot say if that is of the Portland cement emissions or of the much higher total production emissions.
Fancy supercaps will take 2.7 volts. The trick with these capacitors is that there's no dielectric insulator. It's just bunching up ions in salt water. Too much voltage and it becomes a fizzy conductor.
Like solar cells, you have to chain them in series to bring the amperage down to a sensible range. Whole home DC to AC inverters run off 400V to 500V.
I wonder how this compares in energy density to a sand battery. As space heating costs in the UK are more than electric for the typical household, it might be better to use a sand battery heated by solar/off peak grid, if you're gonna have big lumps of concrete / sand and cement under your house.
"As space heating costs in the UK are more than electric for the typical household,"
For now. Replacement gas combi boilers are being banned from 2035 or something like that. Everyone is going to have to go all electric eventually and certainly any new house built from about 5 years before the ban on sales of gas boilers, at least. At some stage, even people "hanging on" with gas boilers will either reach a stage of it being non-repairable and having to replace with electric, of eventually switch to local tanked/bottled gas as the gas network is under utilised to be uneconomic and turned off.
"Replacement gas combi boilers are being banned from 2035 or something like that. Everyone is going to have to go all electric eventually "
And that will mean the electric company is going to need to build a whole bunch of new infrastructure to be able to give homes that were built with gas in mind a much bigger electrical service. I have a tankless water heater that runs on propane. Whey I looked at an electric model, I'd have to pay some heavy bribes to the power company to up my service and pay an electrician to put in a new panel (customer unit). I expect that if the law stands, some homes are going to be worth much less to compensate for the cost of upgrading from gas to electric.
Lucky me that my usage is significantly less.
For as large as the US is and the wide range of climates, to state an average for the whole of the country is meaningless. Al Gore, former Vice President and climate botherer, uses several times the "average" at his compound. The current US eco-terrorist, John Kerry, has an energy footprint only rivaled by members of the Saudi Royal Family (they have bigger jets). Somebody that lives in an Earthship will use very much less than I do.
But I hope it works out. I suspect that it won't be as easy as casting a giant block from layers of the stuff though, and car charging roads smacks of fantasy and fiction.
I expect there may be longevity issues, I'm not sure how they would handle dendritic formations to keep them from internally shorting the matrix, a bunch of other potential issues, but this is an interesting discovery if it can be replicated.
If it were to turn out that a useful size of battery could be created as a foundation, how long could it be expected to last? It's possible to get large Li batteries built into small cargo-like containers that can be installed and removed with common construction equipment (forklift, flatbed truck). If your foundation battery fails, it's inconvenient to have a house built on top of it. There's also going to be a question of materials leaking into the immediate area and outgassing. It's not just pure H2O that would come in contact with the slab. I don't expect that new forms of life would spontaneously appear, but other inorganic chemicals could form.
If this sort of thing pans out, it could make more sense as something other than a foundation for a building. Walls between properties maybe? Perhaps internal plumbing can be installed so the wall can be used as a heat sink/source. Using it to make pedestals for a solar farm would mean energy could be stored immediately adjacent to the panels for use at night. Again, the material might be a good heat sink to help cool the PV panels so they are more efficient.
"Make bricks out of the stuff. Add a surface solar cell and use wall ties to wire everything up. Whole house becomes one giant solar battery."
The labor to construct that would be far too expensive and any damage would be costly to repair. That's been a problem with solar roof tiles. A panel built in a factory can have 36 or more cells connected up cheaply where a roof tile contains one cell and hundreds of them are needing for a useful system. That's a lot of labor on-site and any damage is tedious to repair.
"Solar shingles are already being sold as a product."
That was Elon's big pitch when he lobbied the Tesla board to bailout Solar City so he and his family wouldn't lose a bunch of money. Tesla does have solar roof tiles now, but they just buy them from China rather than make was he was showing previously.
A good half dozen or more companies have been sacrificed on the alter of solar roof tiles. Even Dow Chemical had a go and sold the division off to another company that they wound up killing.
I don't have a problem with what regular panels look like on a roof. There's nobody I need to impress.
The team has only built a tiny one-volt test platform using its carbon black mix, but has plans to scale up to supercapacitors the same size as a 12-volt automobile battery – and eventually to the 45 cubic meter block.
The snippet quoted above is reached near the end of the report. If the information had been imparted much sooner, I would not have bothered continuing. Yes, an interesting idea. Yes, immense practical potential if scaleable. Yes, go and knock on the doors of potential investors. Meanwhile, please don't trouble me until R&D shows the product is capable of impinging on my daily life.
This is a very interesting idea, hope something comes of it, it could be a game changer for a lot of things.
As to the comment about some of us on this side of the pond being hostile to climate change initiatives you're right, and we have good reason to be. Literally trillions of dollars are being spent to "decarbonize" our economy with no real evidence that all this spending will actually make any difference in the climate. But what it WILL do is make energy less reliable and much more expensive.
However, when an idea comes along that not only makes environmental sense it also makes economic sense a lot of us are all for it. This sounds like one of those ideas and I look forward to hearing about further developments.
"trillions of dollars are being spent to "decarbonize" our economy with no real evidence that all this spending will actually make any difference in the climate."
Think of all of the consultants that don't have to live in the street with their spouse and 6 kids and can instead stay in their 3,000 sqm home within a nicely kept gated community.
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