Thermodynamic Analysis of a Parabolic Trough Collector (PTC) operating with gas-phase nanofluids

Parabolic Trough Collectors (PTC) are the most developed and established technology among the concentrated solar power systems. However, the majority of the PTC power plants currently in operation uses synthetic oils or molten salts as heat transfer fluids (HTF), with a limited operating temperature range. To operate at higher temperatures, the use of pressurized gases as working fluid has been recently proposed in several studies. However, in this case a large pumping power is required. In this work, the use of gas-solid suspensions in a commercial PTC has been analyzed. A thermodynamic analysis has been performed to investigate the effect of three different gas-solid suspensions: Argon-Al2O3, Carbon Dioxide- Al2O3 and Air-Al2O3. The performance of these gas-phase nanofluids has been compared to the use of pure gases. Power output, pumping power, outlet fluid temperature and global efficiency of the parabolic trough system have been determined. The analysis shows a substantial decrease of the pumping power. Thanks to this advantage, the use of gas-phase nanofluids in parabolic trough collectors could represent an interesting possibility.