In a small workshop near Vicenza, Italy, artisans make traditional-looking roofing tiles with a hidden difference: Each module contains solar photovoltaic cells.

The family-owned company that makes the tiles, Dyaqua, started developing its “Invisible Solar” products more than a decade ago. Solar panels “were spreading much faster than before, and our first thought was about heritage cities like Vicenza,” says company spokesperson Elisa Quagliato. The city, a World Heritage Site, is covered in a sea of red terra-cotta roofs.