By Cat DiStasio
As the cost of solar energy falls, more and more buildings are being outfitted with photovoltaic systems -- and some even generate more electricity than they use. Structures like that are called "energy positive" and it's a pretty impressive feat. If your home or business can produce more power than it needs, it can actually turn a profit, since local utility companies can buy that excess electricity from you and feed it into the grid for others to use. We've rounded up some of the most incredible energy-positive buildings from around the world -- read on for a closer look.