There have been lots of great innovations using solar in the past few years and solar backpacks are amongst the most popular.
They are available in quite a number of different styles as as well as sizes and their functions can also differ quite a lot. From simple backpacks that can charge only the smallest of items you can also get very good quality ones that can charge quite a number of items.
Perfect for hikers or for people who wish to charge phones and other portable appliances while they are on the move they really are a very good invention that is becoming more and more popular. What you will find is that the better models all have a battery pack with them. This means that any energy collected by the panels can be stored in the battery and this enable you to use it whenever you need to, be it day or night.
Cheaper models do not have this capability and although they do work well at charging during the daylight hours they will not allow you to charge anything at night. It does come down to price though. Think about what you would like to use it for and make a purchase accordingly. You may find that a small inexpensive solar backpack is more than adequate for your needs and then you do not need to pay the extra for a pack with storage capabilities.