In the next issue of Inc., we featured the Voltaic Generator, a solar-powered bag strong enough to charge a laptop. It's the latest product released by Voltaic Systems, which also makes less-powerful bags designed to charge cell phones and other gadgets. I caught up with Shayne McQuade, CEO of Voltaic Systems, at the Greener Gadgets Conference yesterday, and he gave me a demonstration of how the bags work.

They are compatible with most devices, though there are a few exceptions, most notably any laptops made by Toshiba or Sony Vaio. Five hours in the sun puts enough juice in the Generator's battery to fully charge most laptops, McQuade says. And the power will stay in the battery for months.

Some reviews have called the bag cumbersome. But you can always take the battery with you and leave the bag at home. Check out the video below for more; you can buy the bags here.