We have arenamate solar lights on our 20x40 school and I like them. I've had them installed for nearly 7 years and they are still working well. The battery isn't as good as it used to be, but I have a feeling I need to clean the solar panels and that would sort it.
I spent around 1k on 6 of them so they aren't a cheap option, but significantly better value than running electricity out there. I've mounted them on scaffold poles and the fixings they come with fit perfectly on the scaffold. You use a remote control to turn them on and it lights up a 20 x 40 up nicely.