Dropped energy is an entity that can be found on the ground. It's the result of creeps dropping it, or a residu from creeps that died.
Dropped Energy degrades at 1 per 1000 Energy per tick.
If creeps die, they sometimes drop multiple Energy units. Each degrades at 1 energy per tick. A creep can only pickup 1 Energy drop per tick, even if the Energy drops are at the same Position.
To be able to pickup Energy, a creep needs to have a Carry part and can be at maximum at a distance of 1. That means that a creep doesn't need to move to exactly the position of the Energy drop.
There isnt one, doesn't work.