Abstract: By means of a plurality of reflectors, solar rays are focused on at least one operative region in which there is disposed a solar-radiation absorbent body which is thereby heated and which transmits the absorbed heat to a liquid or vaporous heat carrier. By fabricating the reflectors of a material permeable to the short-wave portion of the solar radiation and reflective of the long-wave portion of the solar radiation, the ground area shaded by the reflectors can be utilized for other purposes, especially for growing plants.