The present invention relates to vacuum apparatuses which collect energy from the sun and enable a heat-exchange fluid to be heated, as desired. It is essentially characterised by resistance to thermal shocks, irrespective of the temperature which the apparatus reaches or the conditions in which it is used. To this end, the apparatus comprises, within a double cylindrical glass shell 1, 4, defining an annular space under a vacuum, an absorption/heat-exchange unit 8, 9 consisting of plates and metal tubes which are fitted together without welding, with no direct contact with the shell, from which it is separated at the same time by a volume of air 10 and specifically designed insulating end sleeves 11 and 12. Selective coverings 14, 15, 16, 17 are arranged outside the volume under vacuum and over the absorber. Among the most advantageous applications of the invention figures the production, in sunny weather, of steam and hot water for sanitary purposes or for domestic heating, at any time of year and in any part of the world. IMAGE
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