Simplified heat transfer model for parabolic trough solar collectors using supercritical CO2

Abstract

The main Concentrated Solar Power (CSP) plants type installed worldwide corresponds to parabolic trough (PT) technology transforming solar energy into thermal energy on the receiver tubes. The use of alternative Heat Transfer Fluids (HTF) in order to increase the solar-to-electric efficiency by means of either higher HTF temperatures or the use of supercritical cycles have opened a new line of research. In this framework, super-critical carbon dioxide (sCO2) seems to be a good candidate to replace current HTFs in PTs. This work implements a one-dimensional heat transfer model for a PT solar collector considering different HTFs such as synthetic oil, sub-critical carbon dioxide, and sCO2. The numerical results of the outlet fluid temperature are compared to experimental data and numerical results published in the literature, obtaining maximum temperature deviations of 0.9%, 2.9% and 2.7% respectively. Finally, a sensitivity analysis was conducted to evaluate the influence of the solar irradiation, mass flow rate and HTF inlet temperature on the thermal performance of a PT working with sCO2 showing that the solar irradiation produces the greatest variations.