Leonardo da Vinci designed a solar furnace that used a large lens to concentrate sunlight for industrial heating.
In his studies of optics and applied engineering, Leonardo proposed arranging mirrors or lenses so that sunlight converged on a small target. Concentrating the rays increased the temperature at the focus, offering a possible method for heating materials or melting substances without ordinary fuel.
A solar furnace is not simply a telescope or a handheld magnifying glass. Its purpose is to collect and concentrate radiant energy for heat. Leonardo’s drawings explored the geometry and placement needed to direct sunlight effectively, although the proposed industrial installation was not demonstrated as a working Renaissance plant.
The idea reflects Leonardo’s interest in using natural forces as practical power sources. Modern solar furnaces use large fields of mirrors and can reach extremely high temperatures, but the underlying concentration principle is the same.