Rays of sun bounce off gleaming mirrors on the tiny Lake Colignola in Italy, where engineers have built a cost-effective prototype for floating, rotating solar panels.

"You are standing on a photovoltaic floating plant which tracks the sun, it's the first platform of its kind in the world!" said Marco Rosa-Clot, a professor at Florence University, proudly showing off his new project.

Rosa-Clot and his team say they are revolutionising solar power and that their floatin...