During his free time on the job as a Google employee, Carl Elkin began tinkering with the company's 3-D mapping program, wondering if it could identify rooftops that receive enough sunlight to make installing solar panels worthwhile.

When the U.S.-based engineer showed a handful of colleagues the results of his labor months later, they had a eureka moment.

"The light bulb kind of went off," said colleague Joel Conkling. "It felt like intuitively it had some real potential."