**Funding**

*Advances in Microfluidics and Nanofluids*

Thermal (PV/T) systems.

of solar thermal systems.

**5. Concluding remarks**

challenge.

thermal energy.

**Acknowledgements**

oils used in this study.

**Conflict of interest**

The authors declare no conflict of interest.

A theoretical model assessing the performance of a solar thermal system using

In such configurations, the electrical and thermal energy are simultaneously generated by a photovoltaic module and the working fluid, respectively [96]. Furthermore, nanofluids, exhibiting magnetic properties, offer the possibility to increase the thermal conductivity of a working fluid upon the application of a magnetic field [97, 98]. Nano ferrofluids, standing amongst, were found to improve

However, the major challenge with such types of nanofluids is the formulation of stable working fluid. This is so because nano ferrofluids have the propensity either to agglomerate in solution [100] or to suffer from chemical instability [101]. The combination of Fe3O4 with other MO-NP in composite materials usually allows to overcome those limitations. Therefore, exploration of the thermophysical features of composite MO nanofluids is an interesting direction aiming at the optimization

The present chapter has covered the topic of metal oxide nanoparticles (MO-NP) and nanocomposites (MO-NCP) and their application for carbon capture utilization and storage (CCUS). It was shown that MO-NP (or MO-NCP) can be synthesized using physical, chemical, and biological methods. Each approach is tuned to give a MO-NP (or MO-NCP) with specific features. Regardless the production route, it was highlighted the stability of the nanofluid was the main

In respect of CCUS application, the most prominent results were obtained from silica (SiO2) and alumina (Al2O3) oxides. SiO2-NP could alter the wettability in a manner to increase the production of heavy oil. Dispersed into polymeric base fluid, it was shown SiO2-NP could yield a gel-structure, which can plug the large voids of formation, leading to either an increment of oil production or prevent the leakage of sequestered gases. On the other, Al2O3-NP and its silicate composite could delay the deposition in heavy materials during the oil production using carbon dioxide (CO2) injection. On the other hand, it was shown that ferrous and ferric nanofluids could improve the heat transfer of the fluid, making them good candidate for solar

The authors would extend their acknowledgement to Mitsubishi Chemical and Japan Petroleum Exploration for supplying respectively the polymers and the crude

Al2O3-water based nanofluid as Direct Absorber Solar Collector (DASC) has shown an increase of 10% of the collector efficiency compared to water-based flat plate solar collectors operating in the same conditions [94]. However, the optical performance of MO-NF as DASC depends of the volume fraction of MO-NPs [95]. MO-NP can also be associated with photovoltaic devices within hybrid Photovoltaic

significantly the efficiency of the photothermal or PV/T systems [99].

**146**

The works presented in this chapter were supported JSPS KAKENHI (Grant Number JP20K21163 and JP19K15490).
