In the present article, carbon dioxide is proposed as a heat transfer fluid for flat-plate solar thermal collector. Energetic, exergetic and economic analyses of flat plate collector using supercritical CO2 have been done and compared with conventional fluid (water) as well as advanced fluid (nanofluids). Effects of zonal ambient temperature and incident solar radiation on collector efficiency, irreversibility, second law efficiency and collector size reduction are presented. Due to lower critical temperature, the use of CO2 is restricted for lower inlet temperature application only. Results show that the improvement of heat transfer rate is more predominant than increase in irreversibility by using CO2. For the studied ranges, the maximum performance improvement of flat plate solar collector by using CO2 as heat transfer fluid was evaluated as 18%. Study shows that the reduction in collector size or cost by using CO2 is comparable with nanofluids, although CO2 is a better alternative with respect to fluid and operating costs. Keywords: Flat Plate solar collector, supercritical carbon dioxide, nanofluids, collector Efficiency, Area Reduction
