Home batteries are becoming increasingly popular ways to store solar energy to power houses at night, but what if one could make the whole house a battery? Rechargeable cement batteries prove the idea is possible, even if it has a long way to go to be affordable.

Dr Emma Zhang of Chalmers University of Technology, Sweden, mixed 0.9 percent carbon fibers into cement and poured it over a metal-coated carbon fiber mesh to make concrete blocks. In the journal Buildings, Zhang and colleagues report that with iron anodes and nickel cathodes these blocks become rechargeable batteries.

At 0.8 Watthours per liter, Zhang’s battery is hundreds of times less energy-dense than a lithium-ion battery, and completely useless for transportation purposes. However, it stores about ten times more energy than previous rechargeable concrete batteries. These, Zhang said in a statement; “Showed very low performance,” forcing her and colleagues to seek new ideas on how to produce the electrodes.