Turning Buildings Into Batteries

in STEMGeeks6 months ago

Cement is already quite the useful material. But it would be even more amazing if apart from just using it to build things it would provide us with something more. And new cement rechargeable batteries could allow us to turn buildings into giant batteries.


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Image by Engin Akyurt from Pixabay

Batteries are still the Achilles’ Heel of our technological civilization. But, there are many research teams working on this and creating various incredible types of batteries. One of the promising concepts is structural batteries that can be incorporated directly into the construction. Usually, these are used in planes, cars, or small electronic devices. But, what if we dreamed bigger.

A team from the Chalmers University of Technology in Sweden developed a battery that is based on cement and can also be used as cement – as construction material. This technology of a cement battery is the answer to all the problems cement current has. And I’m not even talking about how it is ugly and especially cities are full of it but its large impact on the environment that its traditional production has.

Creating the cement battery starts with regular old cement and a few other ingredients. Then you add a sprinkle of short carbon fibers that give the cement conductivity and flexural strength. Then you add two nets from carbon fibers. The first is covered with iron and works as the anode while the other is covered with nickel and plays the role of the cathode. This creates a functional rechargeable battery.

The new design of the cement battery is the result of many experiments in which the researchers tried to enhance previous types of similar batteries which sadly weren’t exactly successful. But the results of the initial experiments are quite promising for this design. It can store up to 7 Wh of energy per meter squared of material – about ten times as much as previous cement batteries. It is still low compared to other types of batteries but you can’t build large buildings from those.

The Swedish cement batteries come with various interesting possible applications. Buildings with these batteries combined with well-placed solar panels can provide energy for light, mobile networks cells in remote areas, or just run sensors in large cement constructions such as highways or bridges allowing us to monitor their structural integrity. Or, the most obvious – just use them to store energy created by renewable sources for later use.

What needs to be mentioned is the fact that the development is still in its very early phases. There are still technical issues that need to be solved such as the longevity of cement batteries. Buildings from cement are built to last for decades at least and the batteries in them need to be able to sustain their function for a long time or need to be easily renewed. But the researchers are optimistic.

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7 Wh/m^2, if we consider a typical medium-sized residential apartment with floor and walls (and possibly ceiling ), then perhaps it could store around 2 kWh totally (at least, that's the order of magnitude we're talking about). That's possibly a bit more than a typical Li-Ion battery on an electric bike, but not very much more. Well, difficult to say without knowing the energy density per volume (Wh/m^3). Perhaps it's needed to stack several layers of such batteries to make a solid outer wall or a solid horizontal floor/ceiling-layer, then maybe the number may be multiplied with two, three or four.

I think one good use case would be to build a residential apartment building, cover it with solar panels, put a windmill on the roof and have sufficient storage capacity in the building to at least get through a typical*) dark night with no wind. Unfortunately, those batteries does not seem to have sufficient capacity for that, so to get through the night one would probably end up installing Li-Ion batteries in the basement - then it would probably be easier and cheaper to install some few more batteries in the basement instead of providing walls and ceilings with power distribution infrastructure (one could possibly also stack more cement batteries together - but there are limits to that, one probably wouldn't want to have several meters with cement between each floor in the building, or have outer walls that are several meters thick).

For other purposes (i.e. powering LED-lights on a bridge throughout the night, sensors to check the integrity of said bridge, etc) it may possibly be great.

Costs are of course another question - if the extra price for building concrete blocks with built-in battery functionality as compared to ordinary concrete blocks is too high as compared to Li-Ion batteries, then it's not profitable. Actually, for changes to happen (on a bigger scale), the cost of "cement batteries" actually needs to be far less than Li-Ion batteries - we're talking about a conservative well-established industry, doing changes involves taking risks, and it's needed with good incentives for that to happen.

*) I've grown up with two months of constant daylight in the summer time and two months with no sun in the winter time, so that's what an "atypical" night and day may look like