abstract
- Copyright © 2019 American Chemical Society.Parabolic trough solar thermal power plants use a fluid to transfer thermal energy from captured solar radiation to a Rankine cycle to drive a turbine that, coupled to an electrical generator, produces electricity. Continuous improvement on their performance will lead these technologies to truly compete with either conventional or other forms of renewable energy systems. Nanofluids have been proposed as a way to improve heat transfer rates in thermal solar plants. Hence, nanofluid thermal solar plants coupled to dynamic optimal operating policies should render improved heat transfer characteristics as well as power production. The main objective of this work is to obtain optimal start-up policies of such plants using diverse nanofluids (Al2O3-water and TiO2-water) compared against pure water as base fluid, focused on power delivery and the time required for the system to reach target conditions. For the analysis, the deterministic dynamic mathematical model of a previously proposed solar thermal power facility was extended to deploy nanofluids for improved capture of solar radiation. Both nonlinear programming and mixed-integer nonlinear programming optimization formulations, consisting on energy and mass balances, were deployed for the comparison of various start-up scenarios when alternating between nanofluids and pure water as the working fluid on the solar collector. Results indicate that the TiO2-water nanofluid is the most suitable heat transfer fluid among the ones studied for improved heat transfer recovery, and that dynamic optimal control operating policies aid the system in reaching better operational conditions rather than when following simple heuristic-based start-up policies.