Abstract: A solar collector for the generation of high temperatures including a tubke housing defining a cavity, a glass plate for sealingly closing the cavity, a selective absorber and a trasparent thermal insulation structure located on the inside of the glass plate. An air gap separates the selective absorber from the glass plate. The solar collector is operated at a vacuum of less than 10000 pascal by means of a vacuum pump. The transparent thermal insulating member reduces the air convection and acts similarly to a mulitple pane for the reflected, diffuse thermal radiation. High efficiencies are thus achievable even at large temperature difference between the absorber and the area outside the solar collector. The thermal insulation effect of the air gap and at the same time of the microporous thermal insulation located in the bottom of the housing is varied by regulation of the degree of vacuum.