Nanofluid Types, Their Synthesis, Properties and Incorporation in Direct Solar Thermal Collectors: A Review

Abstract

The global demand for energy is increasing and the detrimental consequences of rising greenhouse gas emissions, global warming and environmental degradation present major challenges. Solar energy offers a clean and viable renewable energy source with the potential to alleviate the detrimental consequences normally associated with fossil fuel-based energy generation. However, there are two inherent problems associated with conventional solar thermal energy conversion systems. The first involves low thermal conductivity values of heat transfer fluids, and the second involves the poor optical properties of many absorbers and their coating. Hence, there is an imperative need to improve both thermal and optical properties of current solar conversion systems. Direct solar thermal absorption collectors incorporating a nanofluid offers the opportunity to achieve significant improvements in both optical and thermal performance. Since nanofluids offer much greater heat absorbing and heat transfer properties compared to traditional working fluids. The review summarizes current research in this innovative field. It discusses direct solar absorber collectors and methods for improving their performance. This is followed by a discussion of the various types of nanofluids available and the synthesis techniques used to manufacture them. In closing, a brief discussion of nanofluid property modelling is also presented.

A Review on Nanofluids: Fabrication, Stability, and Thermophysical Properties

“…Another onestep approach also exists [112,113], with all being favourable in minimizing the agglomeration of nanoparticles in the basefluid. However, the downside of using the one-step approach is the presence of contaminations that are difficult to dispose of [106]. Figure 7 shows a sample of the one-step approach used to prepare nanofluids by vapour deposition.…”

“…In order to commercialise such type of advanced fluids, some factors are required to be improved and better understood by researchers. Examples of these factors are listed below [13,26,82,99,106,213]:…”

“…This is because nanofluids are not simply formed from a solid-liquid mixture but requires special conditions to be present in the suspension such as homogeneity, physical and chemical stability, durability, and dispersibility. There are mainly two techniques used to fabricate nanofluids, namely, the bottom-up approach known as the one-step method and the top-down approach identified as the two-step method [106].…”

Carbon-based Nanofluid Applications in Solar Thermal Energy

“…In the literature, there are some reviews on nanofluid based solar collectors. Chamsa-ard et al [15] reviewed the nanofluid types, synthesis, properties and applications in direct solar thermal collectors. They concluded that the stability and , 0 (201 Web of Conferences https://doi.org/10.1051/e3sconf/2019111010 9) 201 E3S 111 10 CLIMA 9 56 56 thermal conductivity are important performance parameters for solar collectors.…”

Physical Properties and Light Energy Harvesting Efficiency of Silica Nanoparticles

“…The results of density of samples were given initial reaction effects of sunlight exposed [32] of SiNPs and f-SiNPs with biocompatible molecules on a constant temperature 25 °C. The density (ρ) properties of nanoparticles were determined by used of the densitometer.…”