Abstract: A solar heating system for heating domestic water or a heat transfer heating fluid has at least one external heating element which receives solar energy. The heating element is in the form of a panel which is formed by a first plate and a second plate which is connected to the first plate, the first and second plates being symmetrically profiled so as to form, outside contact zones between the first plate and the second plate, a flow channel for the passage of the domestic water or the heat transfer heating fluid which is to be heated and which flows in the panel. The first plate and second plate are deep-drawn from steel and connected to each other by laser welding over the entire surface of the contact zones. At least one of the first plate or the second plate has been subjected to surface texturing by laser processing.

Abstract: A radiant heat transfer system for heating or cooling a room, has at least one heat exchange element in the form of a panel formed by a first plate and a second plate, the first and second plates being symmetrically profiled to form a flow channel arranged in a serpentine manner between the first and second plates for passage of a heat transfer fluid, wherein the first and second plates are pressed steel plates and are connected to each other by welding over the entire surface of the contact areas between the first and second plates, wherein the connection between the plates is made by laser welding, and wherein a surface texture obtained by laser treatment is present on the surface in contact with the heat transfer liquid of at least one of the first and second plates to increase the heat transfer.