French physicist August-Jean Fresnel developed an optical lens in the 1820s, which reduced the amount of material needed and which was lighter and thinner than conventional lenses. He achieved this by breaking the lens into a set of consecutive sections.
The Fresnel solar power approach incorporates this principle. Incoming sunlight falls on a surface of several linear, horizontal mirrors – instead of one dish or parabolic trough. The mirrors are rotated at an angle and reflect the sunlight on a receiver unit. The receiver unit consists of a secondary mirror and an absorber tube. A part of the reflected sunlight falls on the absorber tube directly, another part is refocused on the absorber by the secondary mirror.
The absorber tube contains water which is converted in successive steps to superheated steam by the thermal energy of the concentrated sunlight. The steam is then available and can be used to drive a turbine for electricity generation or for other applications.