The researchers added short carbon fibres to a cement mixture, which also contained a metal-coated carbon fibre mesh: iron for the anode and nickel for the cathode.
There is now proof of concept on a laboratory scale. Although the energy density is still small (7 Watt hours/m2 on average), an enormous volume is available for use in high-rise buildings or infra.
By using concrete to store solar energy from PV panels, for example, it can be made somewhat more sustainable. However, some practical problems still need to be solved to ensure that the ‘concrete battery’ remains functional for as long as the building or artwork in which it is applied.