| Abstract: | We consider a number of alternative designs for reflectors which are used in conjunction with cylindrical tubular solar collectors. The annual relative optical performance of the collectors is assessed, data being presented for a variety of tube absorptances and reflector reflectances. Both North-South (NS) and East-West (EW) orientations of tubes are considered. This performance data may be combined by the reader with his own local tube and reflector unit costs to make cost-effectiveness judgements between rival collector designs. The method is illustrated using some current Sydney prices, on which basis we make the following assessments: A reflector is always cost-effective, the best option being a stainless steel reflector of Winston-Hinterberger type with a geometric concentration ratio (C) of about 1.2, mounted either NS or EW. At higher C values EW is favoured over NS. Back-silvered glass mirrors are not competitive. A plane diffuse reflector with C 1.2 is also cost-effective for NS orientation. Since no allowance is made for thermal losses in the present work these conclusions should be regarded as tentative only. |
