[Pearls Before Swine]

Looks HEAVY. That is a LOT of glass.

Perhaps it could be filled with liquid.

The real issue is that it isn't a concentrator...rather, it's a redirector, much like a corner reflector. That means that you are substituting the spheres for the tracking control to follow the sun. It's a fixed-geometry trade-off.

[Pikachu_Dad]

liquid is pretty heavy too.