The dull concrete buildings that dot the skylines of virtually every city in the world are the antithesis of sustainability. The concrete industry is a huge carbon emitter, being responsible for up to 9% of all man-made carbon that ends up in the atmosphere.

This environmental burden could be significantly offset if a recent innovation from Chalmers University in Sweden bears fruit. Civil engineers at the university found a way to integrate electrically conductive fibers into a cement-based mixture. With this innovation, they could turn concrete slabs into batteries. This could pave the way for buildings that not only serve as shelter but also power our needs as well.

Electrified concrete

Dr. Emma Zhang and Professor Luping Tang designed this rechargeable cement-based battery by adding a twist to your classic concrete recipe. They added short carbon fibers to enhance conductivity and toughness, along with a metal-coated carbon fiber mesh, using iron and nickel as the anode and cathode, respectively.

This is not the first time someone has tried to make concrete batteries, but this new design is a huge step up in terms of the energy density it provides. The new design’s performance is at least ten times better than previous demonstrations. In addition, it is also rechargeable.

“This particular idea that we have developed — which is also rechargeable — has never been explored before. Now we have proof of concept at lab scale,” Dr. Zhang said in a press release.

The concrete batteries were tested in the lab — and they work. The energy density isn’t very impressive though. Currently it’s just 7 watthours per square meter or 0.8 watthours per liter. For comparison, lithium-ion batteries that power smartphones and electric vehicles have an energy density between 250 Wh/L and 700 Wh/L.

Although the energy density is orders of magnitude lower than commercial alternatives, there is still value here. Concrete buildings are huge. So, you could theoretically store significant amounts of energy across the large volume of concrete in new buildings that might incorporate this design.

Looking beyond the foundation

The applications envisioned range from powering LEDs to providing 4G connections in remote locations, and even protecting concrete infrastructure from corrosion.

“It could also be coupled with solar cell panels, for example, to provide electricity and become the energy source for monitoring systems in highways or bridges, where sensors operated by a concrete battery could detect cracking or corrosion,” suggests Zhang.

However, this concept is not without its challenges. Extending the battery’s service life to match that of concrete structures, which can last up to a century, and developing effective recycling methods are crucial hurdles to overcome. Despite these challenges, the potential of embedding energy storage capabilities into the world’s most widely used building material could significantly impact our approach to energy crises. It could turn every concrete surface into a potential power source.

“We are convinced this concept makes for a great contribution to allowing future building materials to have additional functions such as renewable energy sources,” concludes Tang.

Elsewhere, MIT engineers have mixed cement, carbon black, and water to make supercapacitors (another kind of battery) to store energy in the foundation of buildings.

The findings appeared in the journal Buildings.