Solar energy collection is by an array of identical collector panels. Each panel is made from two pre-formed glass sheets, sealed together, with a selectively absorbing tube network positioned between them in vacuum. The lower glass sheet is formed and silvered on its upper vacuum side to concentrate solar radiation onto the absorber tube network. Truncated Winston concentration with low gap loss is used. The upper glass sheet serves as a window to admit solar radiation in to the collector. It is fluted to provide strength to withstand atmospheric pressure