Electric concrete: storing energy in the ground

The Problem

One of the major hurdles with renewable energy forms is their intermittent use; solar only generates energy during the day, wind turbines only when it’s windy, etc.

This means we have to be able to get the energy but store it too. Massive solar panel farms or rows of wind turbines don’t do us much good if we lose most of the energy that they generate.

Larger energy storage solutions are a must. There are many ways to do this, including huge batteries, but the necessary high-quality batteries are expensive, flammable, and the raw materials are super rare. And, well, they’d be huge.

Instead of building new batteries to store the energy, why not turn some of our societal “deadspace” into energy storage?

The Solution

What’s the most common building material? I’ll give you a hint; it’s used for building foundations, walls, roads, sidewalks, parking lots…

Concrete.

Concrete takes up space. A lot of it. And in places like the U.S., it’s literally everywhere. Just parking lots alone take up ~5% of city space in the U.S. In some cities, it’s actually closer to 40%.

Making concrete hold electricity would provide us with massive storage spaces without building actually-massive batteries. In fact, researchers have been trying to do just that for a while now. But in typical researcher fashion, they’ve been using expensive materials.

This week’s authors decided to give electric concrete a try, but using inexpensive starting materials. They mixed run-of-the-mill concrete with something called carbon black.

Carbon black is abundant, inexpensive, and relatively easy to work with. Historically, it was used as a pigment to dye cloth black, but recently it’s been gained popularity for its electrical properties. Carbon black is a good conductor of electricity, and due to its powdered form, it’s easy to mix into other materials to make them conductive.

The authors of this week’s paper took advantage of this. They mixed concrete, water, and carbon black together to form a conductive cement. When mixed with water, carbon black powder tends to clump up and form long wire-like threads through the concrete.

Then, they stacked two dime-sized pieces of this conductive concrete on top of eachother and soaked them in a bit of electrolytes (potassium chloride or KCl) and sealed it all together. The charge stored in this device can be used as electrical energy.

The KCl carries the charges around through the porous concrete. The two slabs of carbon black-infused concrete act as conductive plates while retaining their structural stability.

You can imagine a future where the foundation of buildings, the roads you drive on, sprawling parking lots, and all the concrete you see around you is all capable of storing electricity. Being able to cheaply make concrete into an energy storage system would be a huge benefit and open up a ton of applications.

For example, the authors point out that energy-storing roads could charge electric vehicles that drive over them, much like a wireless charger works on a phone. Very futuristic, but a cool idea.

The authors are currently working to scale up their design. Maybe we’ll see it soon.

See you next week for more science,

Neil