Collector tubes on which solar radiation is focussed - are enclosed in vacuum tube or chamber with reflectors

摘要

So that an installation can be operated with the maximum of efficiency, the degree of absorption of a collector tube for solar energy is raised as high as possible, and heat losses are reduced to the minimum by having the collector tubes vacuum-insulated over most of their length. The collector tubes which may be of metal or of boron-silicon glass, and may have a black surface layer, are enclosed in a tube of larger dia., transparent to infrared rays, which is evacuated. The outer tube may have over part of its inner periphery, e.g. over an arc enclosing 30-60 degrees an inwards directed mirror surface, whilst bellows joints are fitted to compensate for differences in temp. between outer tube and collector tube.