Fast charging supercapacitors

In cities from Belgrade to Shanghai, the diesel buses that have crisscrossed town for decades are being quietly replaced by an electric alternative. Many of these electric buses are powered not by batteries, but by supercapacitors.

Today’s supercapacitors hold a fraction of the energy that a lithium-ion battery can, limiting the range of a supercapacitor bus to tens rather than hundreds of kilometres. But supercapacitors can make up for this shortfall in two significant ways.

Supercapacitors’ first natural advantage is super-fast charging and discharge – a characteristic ideally matched to stop–start bus travel. At certain stops along the supercapacitor bus route, its roof-mounted recharging wire connects with an overhead charging bar as the bus comes to a halt. In the seconds that the bus is stationary while passengers alight and embark, the supercapacitor is fully recharged and ready for the next phase of the journey.