Quite pointless calculations, as no one sits full day outside holding phone in the way that it is facing always directly the sun. However, idea might seem to be interesting, but as I have used in the past Nokia 1610 with original solar battery (BBT-1L: http://www.nokiaport.de/content/de/a...pic/bbt-1l.png), I already know that we should not have very high expectations for such solution to actually significantly increase battery life of the Jolla...

Sorry to be bit pessimistic.