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hello and welcome to technically speaking where scientists and engineers come together to chat about common interests share knowledge and satisfy some curiosity i'm Laura and in this episode i'm joined by Antonia and Rwayda to talk about a new discovery that could make a battery out of cement apparently that sounds really futuristic to me antonia you brought this topic to the podcast team so what's your interest in it so i work in the energy industry and i also did a bit of a research project on
the environmental impacts of grid scale battery storage and when i saw this article i just thought that sounds interesting can't wait to uh discuss it with some other people basically everyone else i know that batteries are meant to be part of the future energy mix as we switch to more diverse energy sources so i guess that seems quite a relevant topic for climate change and various other things and when i heard about the article that you mentioned it sounded to me like they
were turning cement into a battery so that buildings could store electricity and rwayda you're a civil... you've got a civil engineering background so i guess you can help us decide whether this is feasible or not yeah i find it quite interesting with the whole common um theme now of sustainable energy and also environmental friendly buildings it's interesting to see if such technology could help us store electricity in our concrete so i guess we want to start with some of
the basics here so i know that cement is porous in that that poor water is alkaline and the alkalinity is the basis for some batteries we obviously have alkali batteries but antonia do you want to start us off with some of the basics and explain very briefly how batteries work sure so we always go back to what we learn in school of course you know you might remember a sort of beaker full of some sort of acid on one end you'd have one metal of a type another metal you could
hook them up to a current meter and it would have electricity somehow you know i genuinely don't remember doing that in school i've also made one out of aluminium cans as well you had an interesting school oh this was actually um engineers about borders that we did as a workshop to demonstrate basic principles but anyway so you've got two different metals and you've got them in some sort of liquid that does something yeah and if we lock in a bit closer beyond a microscope you know at the sort of
atomic ion molecular level what we're seeing is an exchange of charges there are certain combinations of metals which will have a what we call a potential difference in that they're sort of compatible that they would happily exchange these ions and in this exchange you may release some electrons which would generate your current this is going to get so confusing there's so many odes and ons and everything i think this might be why i don't remember it because there are so
many different confusing words when you put these together you know you you also have a solution of some sort electrolyte or some sort medium for these ions to kind of pass through and the potential difference is what attracts them from one metal to another and you get electricity it's kind of magic it's magic yeah it's electrochemistry i guess um and if anyone remembers a redox chemistry reduction and oxidation you know it's exchanging of electrons so that's the basic of a battery there are
now so many weird and wonderful ones like ceramic batteries so solid batteries rather than these liquid with metal in it talk about solid and liquid batteries and i'm guessing it's um it's the water in the pores of the concrete or the cement or the mortar or whatever you were using as your building material so although we think of concrete and cement as being solid things again when you get down to that microscopic level there is water in there and that's how the charge can flow
that's where the electrolyte is i think i am actually not sure i always thought of cement and concrete as a pretty inert material i wonder if it's actually some of the modifications that they made to the cement maybe it's the addition of the carbon fiber made it more like transparent for the energy because if you keep water in your cement that is not good because that would affect the strength strength of the bone in between the still and the cement as you said is an alkali material so
that would promote an alkali attack on the cement which would eat it up so i think they need a some sort of a different medium to get their aeons do their magic we talk about carbon fiber this this is the article that antonio had seen was based on a scientific study that was done in a lab in sweden i think at a university and i've read the paper and i think i just about understand it i didn't find a lot of it like a clear like a recipe for how to build the battery to be honest
but i've had covered so maybe it's just my brain isn't working properly but yeah they had they made their two different electrodes the anode and the cathode by using a carbon fiber mesh they coated in one of those metals that would turn it into either the anode or the cathode and then they had a third layer in between this electrolyte that separated the anode from the cathode and i think when they made that it was it was a mortar so it was basically water cement powder sand
and then to the water they added some hydroxide some i think it was potassium hydroxide and lithium hydroxide so they had this sort of multi-layer structure and they were doing it in a lab so it was quite small i got the impression from the paper that it was 10 centimeter by 10 centimeter squares and the whole battery was maybe a centimeter deep i think you got a lot out of that paper like you said it's not a recipe but i think um i think you might have cracked that i
hope so i might have misread something and everything i said might have been totally wrong but let's go with it let's use that as the basis that's the basis of the scientific thought you you think of something and then you also accept you could be wrong all right so if we take literally what they made in the lab i have two questions to this how useful is it is a battery and then can you actually build a house out of it let's start with the battery question is it useful as a battery okay
cool that's a big question in the abstract they said they got an average energy density of seven watt hours per meter squared so i had to kind of work out is that a lot and also what size are we talking so i built a house i built a a model of a house on paper to get sort of what sort of volume are we talking and so how much energy could you store in it i'd looked up some some sort of statistics on them the average size of a uk house to then work backwards and figure out
how much cement slash concrete do we have in our houses you know we have a sort of cement foundation well concrete foundation refer to the cement slash concrete episode to understand the difference between the two but you know in this article they kind of interchange between the two words confusingly so i'm going to do the same because i'm not sure which one they meant fair enough from your waiter and i will say not sure maybe it's this yeah but assuming it was a concrete
foundation and cement mortar for your brick walls average household it's about three bedrooms the floor area is seven by seven meters there's your sort of concrete foundation and i use a meter to make it easy so 49 meters cubed so times their 0.8 watt hours per liter we can get 39 kilowatt hours okay to put this into some sort of scalable thing your normal phone battery is maybe 15 watt hours so that's like a good 2 000 something charges of your mobile phone so in terms
of the volume of just your foundation it's not bad the walls not so much it was like 2400 watt hours just because you were assuming that it was brick built and the um the concrete base was only between the bricks yes cool my concern is if we use all the foundation how much weight this foundation can carry in terms of structure because foundation is a load-bearing element in the structure and it would need to be have a certain strength and if we introduce this technology into our foundation what
is the strength which brings on another question how much these foundation will cost carbon fiber materials expensive i think and would it be sufficiently carrying the the load that is supposed to be do we know what carbon fiber cement structural properties are there are some studies but not at the same kind of like integration of the material because they do use them on the the carbon fiber as strips that would add more strength to it but it's a fine kind of specimen that
they're working with now so i don't know how much that is applicable yeah it's a good point actually if they're talking about changing the mixed design of i think they're talking about mortar and i'm guessing if you were gonna make foundations for a building you'd put some aggregate in there which you know bigger rocks that give it more strength but then that reduces the amount of water and therefore the amount of charge capacity electrical capacity you'd have in your foundations but there was
something else that was mentioned in that paper if we sort of stick with the fundamentals that is it seemed to suggest that the battery would hold less charge with every charge cycle yeah again in the abstract they said the average energy density over six charge slash discharge cycles now plugging your phone in and out you know you could quickly use those cycles so there is some sort of degradation you expect over a certain number of discharge charge cycles and what that essentially means is
your material that you've been using as your anode in cathode is no longer that same material that produces that electrochemical reaction what would you do then if that was built into your house foundations would you dig it up to then change it and replace or do you just leave it in situ and it's just no longer a working battery wouldn't you have to completely demolish the house to do that though normally we will design concrete to be between 50 to 100 years as a design life
so if we need to demolish it that's a big problem oh that is a problem the other option is we use it in the non-non-structural number that does not carry law that is that are replaceable maybe we will have some sort of not a foundation of course but some sort of bits of the wall that we can store these uh magical concrete sails to do that which is made to be more accessible would you make non-structural sections of a building out of concrete yeah that's a difficult question it
depends on what you're doing sometimes you will need to use such a number for stability but it's not load bearing and if if it's not load bearing member you can take it out so in in terms of the beam that basically hold the building we have load bearing beam and not not load bearing beam so you can take the no load bearing beams out but you can't touch the load bearing beams so if you sometimes walk to a restaurant and you'll find a huge column in the middle
that's it right away is the lord bearing one you don't touch it no one is touching it because they refurbish the building loss of time redesigned it but they can't get rid of that big column so that's the same idea no but i guess we're talking about stuff in the future i suppose i mean this was something that was done in the lab and that's very different to doing something out in the wild i don't want to say in the real world because the lab is a real world it does
exist especially this one like you know they it wasn't a computer simulation they physically made these um these batteries so we can say real world here yeah yeah the other option we can use them as like um like in the bridge the beams or something and and as a precast because there's a precast concrete that you prepare it in a lab then go glue it and it's the the advantage of that you can unhinge that member even if that was a load bearing number so you enhance it
replace it with something else and you'll be fine so that's the other option that you wanna if they wanna use it in building things they can use them as precast one but they will be hell expensive to change so antonia you mentioned that you could probably charge a lot of mobile phones from the foundations of a house that sounds like a really weird thing to say in this theoretical house that we've built out of this wonder material yes that only exists on paper that's not in the real world
i wonder though i don't use my mobile phone a lot but there are lots of things i do use we now have a hybrid car so that is probably one of the biggest draws of electricity in our house i have no idea what the capacity of the battery is for that but could i charge something bigger or could i run my entire house from my foundations if i've charged them up somehow say i have solar panels as well oh so i charge him up on a day when it's sunny can i then use that on a day when
it's not sunny i mean i would almost just skip the foundation battery and just use your car as that battery but what if the car is in use when it's sunny fair point well then back to our hypothetical house from my understanding of electrical engineering is you have power and it's linked to current and voltage and what you need is a certain delivery to be able to charge your car so charging a phone the phone voltage is quite a lot lower and same with the amps but if we were trying to use a kettle
which requires a instantaneous high draw of power about two kilowatts that's going to be a big ask from a battery like this which would have high internal resistance i think you'd be better off not using that for your household oh it may be okay for low power applications so it's not going to solve all of my energy problems then i don't think so unfortunately but i am big on energy efficiency so if i have really energy efficient appliances well you were talking about load draw right
so you can run your lights off it your led lights yes maybe not incandescent fluorescent ones don't like those things [Laughter] they're not energy efficient enough i wonder what that means for the future of this technology that i mean obviously it's a concept that was developed in a lab and that always means there is more development work to do and it would be really cool to have my house powering all of my energy needs so i can maybe charge it up either from
the grid when demand is low so i can help balance the grid or i can just use solar panels can use both yeah it's a multi-pronged approach really i think also kind of like with solar panels when we first started with them the efficiency was quite low and same with this you know the energy density is not insignificant the application of it might be only for low power but as technology develops we could get a lot more out of it or does it even matter because if we have a high
volume of concrete and cement anyway and we could utilize it maybe that doesn't matter too much didn't you say the limitations on how much power we could draw from a concrete battery so it wouldn't be able to charge my um hybrid vehicle but it would power some of the lights in my house yeah i don't know basically i don't know what the future holds i wish i did this is definitely something that someone with more electrical knowledge will understand better i think maybe though like the
capacity of these batteries will be enhanced in the future you never know they might be better capacity they might generate or store and release their magical electricity in a better way and they'll be enough to charge your car in 10 years or so 10 years i like the optimism well you don't know sometimes technology just escalates that is true i still have more concern about their structural safety rather than their electricity generation um capacity there yeah i mean the thing
they were doing in the lab it was those like i'm saying they were 10 centimeters by 10 centimeter squares and they were a centimeter deep that sounds like a small thing to build a house out of and i can't imagine building up all those individual layers how long that would take so i imagine there'd be some way of um having like one side of the house as the anode and another is the cathode and not having all these little tiny tiles i have no idea what that would mean for
the capacity of the battery whether it would give it even more resistance i think it would i think it would give it a lot more resistance because you're basically asking for this potential difference to be spread over a large dimension i picture that you would have loads of little cells or there's some strange um some wonderful ways that batteries are built instead of just having cells next to each other they stack them and then they have a separator between them so you can have quite
a dense or battery or there's even ones where they have a sort of a spiraled structure how you get a spiraled cement battery is another question there's a very dexterized cement you have there to do that yeah practically how you pour cement in that fashion we do put them in squares or circles or cylinders yeah simple shapes not spiraling yet really we mentioned in the episode about skyscrapers the civil engineering is moving away hopefully moving away from using concrete and steels which aren't
necessarily all that sustainable because they have quite a high carbon footprint and we mentioned using wood instead so is it likely that we'll be using concrete in say 50 years yes i don't think concrete is going the way there's lots of solutions to try to reduce its impact using a local source aggregate let's say one of the things that would reduce the carbon footprint using admixture to reduce the amount of cement and there's lots of technologies we're using to reduce the carbon footprint so
when we demolish it lots of people are using the reclaimed aggregate so you demolish it and use the demolish concrete as aggregate for the new concrete so concrete and and steel are not going away okay so we could if this technology um this concept that came out of the lab continues to develop we could have houses that are actually batteries yes oh that's cool i also wonder how easy it is to tap into that electricity though because i now have a vision that my wall is made from concrete and i can
literally just attach hold a wireless charger to it i should say and it will just charge my device from that wireless charger magically you like the apple watch is where you just kind of use induction doesn't it you just kind of rest your watch on the charging plate and it charges you don't want your wall to electrocute you is it no i'm not too sure i could get electrocuted from an apple watch charger though that would mean i'd be dead and i don't think they carry enough
is it the current or the voltage i can never remember which it is which is the lethal part of that equation they will have to make it a safe port somehow the technology is in term of having the storage not the releasing right yeah i think if we were to try and harness it i don't think we would just have it just radiating out of the walls i think we would sort of you know maybe um some sort of concentrated way maybe cables that would be wild to just have energy just around ready to harvest in a
usable fashion because a lot of energy when we talk about waste energy it's just heat and it's just floating around and we can't use it it's just there because you know energy can neither be destroyed or created only transformed this is going into the the sci-fi world of transformers robots in disguise i am a bit disappointed that you're being very practical and saying we'll still have to use cables we can't just have power transmitted without wires although i know there is
research in that area as well maybe if we didn't make it into a battery straight away and got it to generate fields but then we'd have to have everything that would be able to use the mountain it would still convert it back into electricity though so maybe it's not very practical because of the conversion losses yeah with that field intervene with the other electrical field with like networks and internet and microwaves that's a lot of electromagnetic radiation flowing around it shouldn't
interfere though if it's on a very different frequency i don't know no i mean either i think we're straying so far from the things that we know about which is structural engineering and energy storage quite far away to be honest as we normally say in this show once we start to deviate so far off topic that we think that's probably a good point to leave it that's where we're gonna leave it so to answer the question can you build a house that stores electricity this question was inspired by a
discovery in a lab that they could use concrete to actually hold charge and use as a sort of a battery but it sounds like there's a lot more work to do to turn this concept from something in the lab to something that a civil engineer says that we could use and a lot of that seems to involve making it so that it's able to take a structural load and there's also a whole load of wild stuff to consider about whether you root cables or whether you can somehow make
electricity just magically appear where you need it when you need it so we're going to take a short break from the podcast in june and we'll be back in just a few weeks with more critical conversations like this one in the meantime you can find us on twitter instagram and reddit and if you're lucky we might even release a few pre-recorded goodies while we're on vacation but if you've enjoyed listening to this podcast over the past year or you've just discovered and love what we have to say
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