I don't know for power genreation, but it would make awesome weapon.

Sounds like the Memento Mori (from Mobile Suit Gundam 00): http://gundam.wikia.com/wiki/Memento_Mori

It actually makes for pretty good power plants, usually they're called some variant of 'solar power towers'. The plants use a bunch of adjustable mirrors that focus sunlight in order to heat water and make it into steam that powers a turbine. There are also ones that use molten salts as a heating element, but that technology is a lot newer.

I remember reading about such a device being planned to "send power" to remote US army outposts e.g. near front lines.

Idea in "Die Another Day", hard to secure it to not be used as weapon.