What Leonardo da Vinci device used mirrors to concentrate sunlight for heating?

Leonardo da Vinci proposed a solar furnace using mirrors to concentrate sunlight.

Leonardo’s solar-furnace concept used many small mirrors arranged to reflect sunlight toward a common point or area. Concentrating light in this way can produce much higher temperatures than ordinary sunlight spread over a broad surface. Leonardo considered such a device for industrial purposes, including heating and melting materials.

The design fits his broader investigations of optics, mirrors, heat, and mechanical engineering. It was not a modern solar-power station: it did not use photovoltaic cells to generate electricity, and the available mirror technology made large-scale construction difficult. The idea instead relied on concentrated solar heat.

Leonardo’s proposal also belongs to a much longer history of solar furnaces. Earlier thinkers had recognized that curved or arranged mirrors could focus sunlight, and later engineers built practical concentrating systems. Leonardo is therefore best credited with studying and designing a Renaissance version, not with inventing the underlying physical effect. The key principle is concentration of radiant energy, not combustion or steam generation.