Selective energy absorber using Aluminium substrate - which is coated with replaceable aluminium foil and is used in solar collectors

摘要

An aluminium foil is exposed to alternating current while travelling continuously through a bath contg. 2-4% HCl, so electrochemical action forms an absorption layer on the foil. This treatment is pref. for 1/2 to 1 min. at ca. 50 deg. C., using 25-45 A/sq.dm; and the treated foil is pref. washed in a bath of 3-4% HNO3. An elastic, heat-resistant adhesive is pref. used to glue the treated foil onto a substrate sheet or plate made of Al or its alloys. The foil is pref. pure Al and e.g. 0.05mm thick. The adhesive is pref. a silicone resin. Used in solar collectors, but also in heat pumps. Absorber is low cost and the foil can easily be removed and replaced when worn.