# Fewer Dimensions for Higher Thermal Performance: A Review on 2D Nanofluids
## 3 Application of 2D Nanofluids
### Concentrated Solar Power
It was stated that the prepared nanofluids enabled a superior thermal performance in CSP technology, mainly due to the improved TC and enlarged specific surface area of the BN nanosheets, which reduced the thermal resistance and facilitated the formation of additional semi-solid boundary layers and active nucleation sites. The authors reported that the TC and specific heat of the nanofluids were superior by 76.8% and 12.8%, respectively, compared with those of the solar salt itself. Simultaneously, the supercooling degree was reduced considerably from 12.2 \({}^{\circ}\)C to 4.7 \({}^{\circ}\)C. The obtained results were of relevance in the CSP field since the ameliorated TC and specific heat provide an enhanced heat transfer capability, an appreciable reduced cost, and dimensions of the necessary equipment. The decreased supercooling degree averts the phase separation and the blockage of the piping. Hence, the researchers concluded that this type of 2D molten salt nanofluid can be employed as improved heat transfer and thermal energy storage fluids in CSP plants. Table 9 summarizes some of the recently published works on the use of 2D nanofluids and their hybrids in the CSP field of actuation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Reference** & **Authors/Year** & **Nanomaterial/Concentration** & **Base Fluid** & **Main Findings** & **Remarks** \\ \hline  & & & & Long-term stability even after eight \\  & & & & months in the ethylene glycol and \\  & & & & propylene glycol-based nanofluids, \\
145 & Hordy et al., 2014 & MWCNTs 55 mg/L to 55 mg/L & & & The MVCNTs were highly absorbed \\  & & & & \\  & & & & allowing for nearly 100\% solar energy \\  & & & & absorption, even at low concentrations. \\ \hline  & & & & Increases of 12\% and 64\% in the TC at \\  & & & & 20\% C and 60\%, respectively, and at \\  & & & & 20\% higher than that of \\  & & & & & \\  & & & & 0.10\% wt. \\ \hline  & & & & Increase of 6.5\% in the TC. \\
146 & Hosseingorbany et al., 2020 & GO at 0.5\%, 1\%, and 2\% wt. & Ionic liquid & Increase of 27\% in the specific \\  & & & & heat capacity. \\ \hline  & & & & Increase of nearly 76.8\% in the TC. \\
144 & Yan et al., 2022 & h-RN at 0.5\%, 1.0\%, 1.5\%, and 2.0\% wt. & & & Increase of 29.8\% in the specific \\  & & & & heat capacity. \\ \hline  & & & & Maximum energy efficiency of nearly \\  & & & & 72.1\% at 1.5\% vol. & 0.401 \%/s \\  & & & & mass flow rate. \\
147 & Kumar and Tiwari, 2022 & h-RN at 0.25\%, 0.50\%, 0.75\%, & & & The maximum increase in the energy \\  & & & & efficiency of approximately 84\% with \\  & & & & obtained at 1.5\% vol. & 0.401 \%/s \\  & & & 2.0\% wt. & & Increased with increasing \\  & & & & The maximum energy efficiency of \\  & & & & 13.1\% was obtained at 12.5\% vol. and & \\  & & & & at 0.017 kg/s of mass flow. & \\ \hline  & & & & \\
148 & Zhu et al., 2022 & h-RN-titanium nitrate at 20, 40, 60, 80, and 100 p.p.m. & Water & Energy efficiency of 83\% at 80 p.p.m. & Maximum of 78\% in the photothermal conversion \\  & & & & & problematical conversion \\  & & & & efficiency at 80 p.p.m. \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Recent works on the use of 2D nanofluids and hybrids in the CSP field of technology. There is a lack of studies on metal chalcogenide 2D nanofluids using base fluids of eutectic mixtures of biphenyl and diphenyl oxide, which are typical in CSP plants. More experimental works employing WS\({}_{2}\) and MoS\({}_{2}\) in the form of nanowires and nanosheets should be conducted, since these nanostructures are already known to possess higher stability over time. Further numeric simulations at the molecular level can offer useful insights into the structure and performance of the metal chalcogenide 2D nanofluids on their reactivity with the molecules of the base fluids most used in solar thermal energy collectors. Additionally, the feasibility of 2D nanofluid application in enhancing the overall thermal efficiency of several possible CSP configurations should be further addressed.