Angle though isn't ideal, unless the PV panel pops off the lid so you can position it better (and still be able to open the screen far enough back to read - though that's often not great in bright sun). I remember the OLPC could be run by hoisting a bucket of sand or water up on a rope and pulley on a tree branch and letting it drive a small generator as that came back down - and that was almost 20yr ago).