# Analysis of Nanofluids Behavior in Concentrated Solar Power Collectors with Organic Rankine Cycle
###### Abstract  
In this paper, the performance of nanofluids in a Parabolic Trough Concentrating Solar Collector (CSP)-based power generation plant, an Organic Rankine Cycle (ORC), and a Thermal Energy Storage (TES) system is studied. This study is intended to investigate the enhancement effect and characteristics of nanofluids Al\({}_{2}\)O\({}_{3}\), CuO, Fe\({}_{3}\)O\({}_{4}\) and SiO\({}_{2}\) in integrated concentrating solar power (CSP) with ORC, and TES under different solar radiations, angles of incidence, and different nanofluid concentrations. The refrigerant mixture used in the ORC loop to enhance the ORC efficiency is an environmentally sound quaternary mixture composed of R134a, R245 fa, R125, R236 fa. The results showed that the power absorbed, and power collected by the CSP collector and thermal energy stored in the storage tank are enhanced with the increase of the solar radiation. It was also found that the CSP hybrid system efficiency has been enhanced mainly by the increase of the solar radiation and higher nanofluid concentrations over the thermal oil as base fluid. Also, the study concludes that the nanofluid CuO outperforms the other nanofluids--Al\({}_{2}\)O\({}_{3}\), Fe\({}_{3}\)O\({}_{4}\) and SiO\({}_{2}\)--and has the highest CSP solar collector performance compared to the other nanofluids and thermal oil base fluid under study at similar conditions. Finally, it was found that the model's prediction compares fairly with data reported in the literature; however, some discrepancies exist between the model's prediction and the experimental data. C 201  
Rankine Turbine generator (ORC) using refrigerant, where electricity is generated [1; 7]. Thermal energy storage is an integral part of a CSP plant in order to overcome the intermittency of solar radiations for continuous production of power during the night and on cloudy days [8; 9]. Nanofluid is a mixture of an HTF and nanoparticles and can be used to enhance the thermo-physical properties of HTF. Recently, it was proposed in references [10; 11; 12; 13; 14; 15; 16; 17; 18] to nanofluids as a heat transfer fluid in solar power collectors, and to investigate their optical properties, which are essential to the phenomenon of direct energy absorption. The results reported in these references showed that the maximum allowable temperature at which the absorption coefficient does not change significantly is as high as 500 \({}^{\circ}\)C. This makes metal-oxide nanoparticles suitable for use at very high temperatures in heat transfer fluids in CSP plants. Heat transfer fluids with nanoparticles provide significant benefits in CSP solar power plants because of the enhancement of heat transfer, thermodynamic and thermophysical properties in absorbing heat induced by solar radiation. Enhanced heat transfer by the use nanofluids yields improvement to the receiver performance and absorption efficiency that may reduce the number of CSP collectors required to produce power using the basis fluid as thermal oil [28; 29; 30; 31; 32; 33; 34; 35]. It has been shown theoretically and experimentally that, in low-temperature solar collectors at around 100 \({}^{\circ}\)C, efficiency can be improved by using nanofluids [10; 11]. A paper was presented by [PERSON] and [PERSON] [12] on the design procedure and a simulation model of a novel concentrating PVT collector. The model considered a parabolic trough concentrator and a linear triangular receiver. This model was based on zero-dimensional energy balances. The simulation model calculated the temperatures of the main components of the system and the main energy flows. The results showed that the performance of the system is excellent even when the fluid temperature is very high (\(>\)100 \({}^{\circ}\)C). [PERSON] and [PERSON] [13] presented a paper review on nanofluid as a heat transfer absorber fluid to enhance heat transfer in solar devices. This review summarized the research done in recent years on the nanofluids' applications in solar thermal engineering systems.