So are there any solar powered red dot sights on the market?

I'm thinking that a solar cell on the top coupled with a back up battery for when there is no sun, would allow for a lot longer battery life. I don't really know anything about red dot sights like what kind of illumination they use or how much power it takes to run one. It seems like in the civilian market at least, it could be useful for plinking since most of that is done during daylight hours anyway.

Thoughts?