Last year , i was trekking in the mountains and was surprised by the lack of electricity. Although there was an abundance of sunlight during the day, all lighting there during the evenings/night was with oil lamps which not only smoky but provided very little light. Vowing to return next year better prepared, i made a solar backpack. It can be also used to power widgets such as the arduino, raspberry pi, etc. Here are the features:
Can charge upto 6 mobile phones at one time!
140 lumen high power led lighting
27wh high capacity battery
Modular Design for expansion
To find out how to make it and for or more info, visit my website http://mysolaradventures.com/2012/06/how-to-diy-solar-backpack-with-solar.html