But for now, a square meter of the building material holds roughly the energy of two AA batteries
Because it already surrounds us in the built environment, researchers have been exploring the idea of using concrete to store electricity-essentially turning buildings into giant batteries.
The idea has been gaining ground as we have come to increasingly rely on renewable energy from the wind and sun: rechargeable batteries are necessary when the breeze dies down or darkness falls, but ironically, they are often made of toxic substances that are far from environmentally friendly.
Experimental concrete batteries have only managed to hold a fraction of what a traditional battery does.
One team now reports in Buildings that it has developed a rechargeable prototype that could represent a more than 900 percent increase in stored charge, compared with earlier attempts.
Still, "You can make a battery out of a potato," notes Aimee Byrne, a lecturer in structural engineering at Technological University Dublin, who was not involved in the new study.
In a future where sustainability is key, she likes the idea of buildings that avoid waste by providing shelter and powering electronics.
"This is adding extra functions to the current building material, which is quite promising in my view," says study co-author Emma Zhang, who worked on the new battery design at Chalmers University of Technology in Sweden and is now a senior development scientist at the technology company Delta of Sweden.
She and her colleagues mimicked the design of simple but long-lasting Edison batteries, in which an electrolyte solution carries ions between positively charged nickel plates and negatively charged iron ones, creating an electrical potential that produces voltage.
"You can abuse this battery as much as you want without jeopardizing the performance," she says.
"We're getting hours as opposed to days of charge." But she adds that "Cement-based batteries are completely in their infancy, compared to other battery designs." The earliest batteries, including Thomas Edison's, were simple and bulky.