Solar power is the most egalitarian of all energy sources, yet residents in many parts of the world still lack access to electricity. Three University of Michigan engineering students have created an affordable solution to this problem -- to the delight of camping geeks everywhere -- with the Emerald, a portable solar panel that does double duty as both a cellphone charger and personal light source. We've seen the personal solar panel idea before, but the price of entry made it an untenable solution for developing nations. Solar-powered light bulbs have been around for a while too, but the Emerald's light lasts for eight hours on a charge (as opposed to the bulbs' two to six hours), and it's able to fully charge a phone in the same time it takes an outlet to do the job. They aim to sell the device for the low, low, price of under twenty bucks for customers in the developing world, which is 90 percent cheaper than other solutions and 100 percent more awesome.

source: University of Michigan