Supercapacitors are electrochemical devices that are well integrated with primary electricity generators in mobile systems powered by electric current. They are characterized by providing high electrical power for short periods (seconds), while the primary generators (batteries, fuel cells) are more suitable for supplying electric currents for long time and at constant load. Supercapacitors are advantageously coupled to systems of batteries and fuel cells, in electric vehicles, in transceivers, in video cameras, in UPSs for which variable demands for electric power occur during operation.

https://www.powerelectronicsnews.com/technology/supercapacitors-energy-harvesting-with-nanotechnologies