Abstract: The method and apparatus of the invention are intended to collect, in the intermediary space comprised between the transparent cover and the absorbing receiver surfaces of a solar insolator, the substantially parallel light beams from the sun by thermally insulated and orientable optical means for tracking said beams, to make said beams converge at a so-called `focal point`, to recover through an opening having a diameter as small as possible the bundle of beams from such focal point and to make the bundle of beams penetrate the thermally insulated fixed housing, to use the latter as a thermal focus containing exchange surfaces, to create a vacuum in the housing for letting air or another gas in, to receive the solar radiation which has not been previously collected on absorbing receiver surfaces while circulating air or another gas in said intermediary space and to have at disposal all of the incident energy transferred both to said thermal focus and to the air or gas circulating the whole of said insolator.