Has anyone considered using a dynamo and charging unit as an alternative to solar? No need to worry about sunshine - you just need to ride. :-)
I found these links on Peter White's website:
EWerk charger:
http://www.peterwhitecycles.com/ewerk.asp
Schmidt Dynamo Hub:
http://www.peterwhitecycles.com/schmidt.asp
I don't have experience with these products, but I'm giving them consideration as I spec my new LHT.
Something to consider, anyway!
Peace!
Brawny