Leonardo da Vinci designed a solar furnace using a large array of mirrors to concentrate sunlight.
In his notebooks, Leonardo proposed arranging many small mirrors so that their reflected rays would focus on one target. Concentrating sunlight in this way could produce intense heat, potentially useful for melting metals or other high-temperature work. The concept belongs to his investigations of optics, engineering, and practical manufacturing.
Leonardo's proposal was not a modern photovoltaic device. It did not convert sunlight into electricity; it concentrated solar radiation into heat. Nor was it necessarily a single giant mirror. The important feature was the coordinated arrangement of many reflecting surfaces.
Solar furnaces later became practical with improved mirrors and tracking systems. Modern installations can reach extremely high temperatures, but Leonardo's sketch was an early conceptual contribution rather than a demonstrated industrial machine. His design also reflects the Renaissance fascination with using geometry and optics to control natural forces.