OK then, so this is incredibly far from being near any real world application
I'd disagree with that, but we certainly need more info.
There are places on Earth where 300wh would be plenty and very far away from traditional power grids. Think like remote sensing weather stations or data collection stations. So a small solar panel could power these during the day and these supercapacitors would replace a wearable battery currently in use today.
We'd need more information how these perform under various temperature and moisture conditions.