What solar-energy device did Leonardo da Vinci investigate using concave mirrors?

Leonardo da Vinci investigated a solar furnace using concave mirrors.

His notes describe concentrating sunlight with curved reflective surfaces. By directing many rays toward one area, the mirrors could produce intense heat, potentially useful for heating or melting materials. The idea applied optics to a practical energy problem centuries before modern solar-furnace installations.

A concave mirror brings roughly parallel rays toward a focal region. The smaller and more accurately aligned that region is, the greater the potential temperature there. Leonardo’s interest reflects his wider experiments with light, vision, geometry, and mechanical technology.

This was not a photovoltaic device: it did not convert light directly into electricity. Nor was it a complete industrial power station. Leonardo’s proposal was a concentration-of-sunlight system, and the surviving drawings do not prove that a large working furnace was completed.