The Casimir Effect.

It holds great promise.
The source of the energy involved in the effect
has barely been tapped.
The subatomic quantum foam that appears
to be energy source behind the effect may hold
astonishingly high energy levels; even in a tiny volume.

Simple research involving Casimir plates have already
taken place, but no energy has been siphoned off
from the effects to generate enough power to light up
so much as a 60 Watt lightbulb...up to this point in time.

But....All the Casimir plate experiments that I know of
have not resorted to using dissimilar plates at this time.
i.e. one plate metal [or any high density material]; another plate
plastic or ceramic [low density material].
Or...one plate opaque; another plate transparent or translucent.

And certainly no cluster or battery of Casimir plates have yet
been experimented with...but that may all change, and may
create a breakthrough that could transform society.