Getting a light weight and portable solar panel could save you from having to use electricity along the trek.
Another way to be self sufficient on a trek like this is to invest in a solar panel.  There are a lot of brands out there these days that make great products.  Getting a light weight and portable solar panel could save you from having to use electricity along the trek.  Remember however, if there is no sun, you may not be able to get any charge! Therefore, it is always good to have back-up batteries, pack or money to charge.