Photos: Let there be light off the grid

Zieff said when he founded Dissigno in 2005, he had to explain repeatedly to the business community that even the poorest people spend money on products, and they spend a huge percentage of their income at that. But now investors better understand the potential for profit in helping people, he said.

"There's an unbelievably impressive amount of attention being brought to the developing world," said Zieff. "They're living in the base of the economic pyramid and they're suffering. It's simply not an equitable use of resources of the capacity of our planet. It creates instability. If you can provide a business opportunity for 5 billion people in the world, you'll solve their problems."