Do you have an eReader such as a Kobo or a Kindle that you read often under the sunlight, perhaps at the beach on your smoke breaks?
If so, you might be interested in turning some of that UV rays into charging your eReader as one user did with his Kobo eReader, attaching a 80mA output solar cells to the back of the unit.
Although most eReaders do have good battery life but this could be a good application to refer if you have similar projects.
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