We moved in two winters ago and had a fairly dark barn. I wanted to go solar and found "Shed Solar Lights" at Home Hardware for 24.99Cdn
I put the little solar panels ( 7" x 7" ) outside on the south facing wall of the barn. We've been using them ever since and they work great. If we accidentally leave them on during the day they have still been on 10 hours later! They are not very bright but you can safely move around and find (large) things. They have never failed to charge, even on a dark Canadian winter day.