Nanomaterials and Nanoliquids: Applications in Energy and Environment

Due to several global energy and environmental issues like global warming, rising energy consumption, and severe ecological degradation, researchers have dedicated a lot of efforts to overcome these issues, such as seeking out clean energy sources (such as solar, wind, and nuclear energy), developing effective energy storage devices (such as batteries and supercapacitors), researching new technology for pollution purification, using environmentally friendly products rather than over-using natural resources and causing serious pollution, etc., it is urgent to continue studying the development of new high-performance nanomaterials. Batteries, supercapacitors, fuel cells, solar cells, photocatalysis/electrocatalysis, and other energy-related nanomaterials are used to store and convert energy. Nanomaterials have been successfully used for many applications. Thanks to their excellent optical, electrical, and magnetic properties, these last have gained a huge interest for many applications especially, environmental and energy applications. This chapter highlights the major types of nanomaterials and nanoliquids, their properties, and their fundamental applications. Also, some merits and demerits of the use of these last in energy and environment applications were given. This is followed by a critical discussion of the current challenges and some prospects.

As the global freshwater crisis worsens, this has resulted in the demand for new desalination approaches in order to provide clean water to the human population around the world. Furthermore, it has been known that high cost and energy intensive are some of the major disadvantages that are associated with the desalination methods. Moreover, reverse osmosis (RO) has been considered as one of the most popular desalination techniques, whereby this technique can be further enhanced by having a more effective membrane. Lately, due to its atomically thin two-dimensional (2D) material, permeability, selectively, tunable functionalities and along with other excellent features, graphene and its nanomaterials such as graphene oxide (GO) have shown its highest potential to serve as a key material for advanced membranes. In overall, after an introduction of membrane, graphene and its nanomaterials, this chapter presents a short overview of the current progress of the graphene-based separation membranes and its environmental applications. In our opinion, graphene and its nanomaterials are an ideal candidate for future membrane separation technology, as they offer a unique solution to the growing issue of water scarcity.

Water resource conservation and management require innovative ideas and improved materials in the today's era. Nanotechnology has the potential to assure the long-term availability of safe drinking water and the protection of water resources by employing cutting-edge materials and technologies for water purification, conservation and reuse. This chapter is primarily concerned with the nanotechnology-based water treatment techniques being developed and used for water augmentation, safe wastewater reuse, water disinfection and decontamination, through nanoadsorption for contaminant removal. This chapter also discusses noble metal nanoparticles, nanocomposites of organic supports and developing approaches to improve water filtration, such as biologically activated carbon.

The greenhouse gases have the ability to trap heat in the Earth's atmosphere which is vital for keeping the planet at a habitable temperature. Effective climate change mitigation measures include reducing greenhouse gas concentrations to levels prior to the Industrial Revolution and restricting additional emissions from development activities, burning fossil fuels, agriculture, etc. This necessitates switching to non-fossil, renewable energy sources as well as installing various new technology for emitted gas collection, providing affordable carbon-free energy alternatives. Worldwide regional-level valuations help improve inventories at a national scale and build effective mitigation plans at manageable scales. Nonetheless, more innovation and policy changes are essential to adequately balance out the long-term economic benefits of development needs. A comprehensive strategy must be devised to persuade the public that prioritizing actions to reduce GHG emissions is critical if sustainable energy is to replace fossil fuels and avert a serious environmental catastrophe. The present chapter emphasizes the factors that contribute to greenhouse gas (GHG) emissions, GHG trends over time, and various mitigation tactics. It will also talk about the role and application of nanotechnology in solving various environmental problems and delivering efficient and cost-effective energy. It's a win–win to develop climate change adaptation and mitigation strategies that work together.

Researchers worldwide are seeking alternative fuels due to the depletion of fossil fuel reserves and increasing pollution. In order to meet modern automobile emission standards, engineers are developing cleaner technologies and more efficient engines. To address both issues, current research focuses on using biofuel additives such as alcohols to compensate for fossil fuels in gasoline engines. Blending alcohol with exhaust gas recirculation (EGR) can improve the performance and emissions of spark-ignited (SI) engines. Methanol is a proven alcohol for blending in gasoline. Ethanol has recently become a more important fuel for automotive engines, as it reduces emissions and can be used in both SI and compression-ignited (CI) engines. Second-generation bioethanol, derived from bio-waste, can also be used as an alternative fuel for SI engines, leading to proper disposal of waste and a cleaner environment. Ethanol-gasoline blends can decrease CO and HC emissions, although NOx emissions may increase. This article delves into detailed information about various alcohol fuels namely methanol, ethanol and butanol fuels, their synthesis, their utilization in SI engines & their impact on engine performance parameters and on the potential benefits of using various nanoparticles in the fuel blends.

In this study, battery thermal management (BTM) of Li-ion batteries is considered using nanofluid and porous media in the cooling channel. Hybrid nanofluid of water including Al2O3-Cu nanoparticles is used as the cooling medium while the cooling channel is considered to be porous. A numerical model based on finite element method is developed and the nanoparticle volume fraction of hybrid nanoparticles is used up to 2%. The permeability of the channel is considered between Darcy number of 10^–5 and 10^–1. The maximum temperature drops when nanoparticle solid volume fraction and permeability of the medium are increased. When the lowest and highest values of permeability cases are compared, temperature drops of 1.25 K and 3 K are obtained for water and nanofluid with the highest loading of nanoparticles. At Da = 10^–1, the maximum temperature drop is 2.4 K while it is only 1 K at Da = 10^–5 when the cooling medium of water and nanofluid with the highest hybrid nanoparticle loading amount are compared. As Li-ion batteries is a promising way to energy storage issue, methods for thermal management designs such as those presented in this paper will be helpful for further performance optimization and system development.

Nanomaterials are of distinct origin and can be procured as naturally occurring materials, from combustion reactions or by specific engineered methods depending on their application. Owing to the compatibility in production methods, nanomaterials find a broad spectrum of applications including healthcare, space research, cosmetics, communication, electronics, defense, coatings, genetic engineering and environmental preservations. The present book chapter deals with the application of nanomaterials for phenolic waste treatment with a special focus on metal oxides and carbon-based materials. This includes novel and eco-friendly synthesis methods of nanomaterials and their performance in phenol treatment, mechanism of action, kinetic studies and machine learning methods.

Contamination of heavy metals in water is of great concern. Nanomaterials owing to their smaller size and higher surface area exhibit unique physicochemical characteristics that enable potential application in the removal of heavy metals. Nanoparticles and nanocomposites find a major application in heavy metals due to their tunable properties, facile synthesis and stability. This chapter gives an overview of the application of nanoparticles and nanocomposites in the removal of heavy metals from wastewater. Nanomaterials-assisted techniques in the removal of heavy metals include adsorption, membrane separation and photocatalysis. Nanostructured materials in the form of nanoadsorbents, nanomembranes and nanophotocatalyst provide higher reactivity and show specific affinity to targeted heavy metals. Several nanoparticles exhibit strong antimicrobial properties.

Desalination, which makes up 1% of the world's total water use, requires a lot of energy, and energy costs make up the majority of operational costs. However, at the moment, a sizeable amount of the energy is produced by conventional fossil-fuel-fired power plants, which offer a serious environmental danger due to the greenhouse gas emissions produced during the production of the energy as well as the discharge of concentrated brine. Because of their advantageous thermo-physical and optical properties, nanofluids have been extensively exploited recently to enhance the performance of several energy systems. Nanofluid technology has helped solar distillation in particular as an economical and dependable method of providing freshwater. The current developments and use of nanofluids in solar distillers have been the main focus of the review. A thorough conclusion has been reached, along with some suggestions for a futuristic strategy.

The main objective of the present investigation is the theoretical study of the impact of nanoparticle shapes on mixed convective flow on a stretching sheet. In this study, the incorporated nanoparticles and their shapes are SiO₂, TiO₂ and these are platelet and cylindrical shaped, respectively. The basic equations are solved using the shooting method. For some special cases, we denoted similarities between the current results and the accessible findings in the literature. The influence of the shapes of the nanoparticles on the flow of the fluid, heat transfer, and temperature is presented and discussed.

The objective of this study is to numerically investigate the heat and mass transfer characteristics of a nanofluid flow over a curved stretchable surface using the Darcy-Forchheimer model. Additionally, a comprehensive analysis of the entropy generation associated with the flow behavior will be conducted. It is widely recognized that entropy generation plays a vital role in reducing the energy demands of a system. The influence of Lorentz force due to the magnetic field and radiation caused by high temperatures near the surface are considered while modelling the problem. Along with the Hamilton-Crosser model for effective thermal conductivity, calculations also consider the thermophysical characteristics of water and alumina nanoparticles. The model's governing equations are transformed into a system of linked nonlinear ordinary differential equations using an appropriate similarity transformation before being numerically solved using Mathematica's finite difference approach. The results are graphically displayed as the outcome of velocity, temperature, and concentration profiles in order to assess the influence of various emergent characteristics. One significant result reveals that the amount of entropy generation grows with the curvature parameter, whereas the Bejan number exhibits the opposite tendency.

A Riga plate is a special electromagnetic magnetic sensor surface that can be exploited in numerous technologies including nuclear reactor heat transfer control. Although developed for conventional viscous fluids, the Riga plate system may be improved via the use of magnetic nanoliquids. Motivated by this, the current work examines the incompressible magnetohydrodynamic (MHD) Ti₆Al₄V-AA7075-H₂O hybrid nanofluid two-dimensional boundary layer flow and heat transfer from a variable thickness vertical Riga plate is studied theoretically and numerically. Viscous dissipation, heat source and thermal radiation effects are included. The governing partial differential boundary layer equations are formulated by employing the mass, momentum and energy conservation laws, and they are simplified into a nonlinear system of coupled ordinary differential equations with associated wall and free stream boundary conditions via appropriate scaling similarity transformations. The transformed nonlinear coupled boundary value problem is solved computationally with the bvp4c numerical function in MATLAB. The physical impacts of key emerging parameters on all key thermal and hydrodynamic characteristics, i.e. velocity, temperature, skin friction factor and reduced Nusselt number are computed, and the results are presented as graphs and tables. Validation is included for several special cases with earlier studies in the literature. The velocity of hybrid nanofluid \({{f}^{\prime}}\left(\eta \right)\) is enhanced with an increment in modified Hartmann magnetic number \(Q\). Hybrid nanofluid temperature is depleted with an increase in thermal Grashof number \(Gr\). An augmentation of fluid temperature is observed with a boost in thermal radiation. In addition, the rate of heat transfer \({Nu}_{x}\) of the unitary (mono) nanofluid is significantly lower than that obtained with the hybrid nanofluid. Hybrid nanofluids are demonstrated to achieve significant benefits in thermal management relevant to hybrid thermal reactors and advanced micro-coolers utilizing magnetohydrodynamics.

Engineers are finding more and more uses for sophisticated electrostatic nano-coatings. This new information prompted us to look into the theoretical and computational aspects of an unsteady EMHD incompressible two-dimensional heat-transfer tangent hyperbolic ternary hybrid nanofluid boundary layer coating flow outside of a two-dimensional porous wedge surface with the implication of Forchheimer-Darcy medium. The effects of electrical and magnetic fields, as well as the effects of surface/injection, suction, and zeta potential, are taken into account. The boundary conditions for convective heat transfer are analyzed. The watery base fluid (\({\mathrm{H}}_{2}\mathrm{O}\)) is combined with three metallic nanoparticles (Fe, Cu and Ag) to form the ternary compound nanofluid. Using suitable similarity variables, the controlling conservation partial differential equations for continuity and momentum and their related boundary conditions at the wedge surface and unconstrained stream are changed. MATLAB is used to computationally answer the arising ordinary differential nonlinear boundary value problem. Previous research is used to verify the results. With the aid of visual aids, the effects of the controlling factors on fluid movement and heat transmission properties are explored and debated. Both the positive and negative values of the electric field are considered in the discussion of the findings. For high values of the rheological parameter and Forchheimer number in both positive and negative electric fields, the velocity dispersion drops. The skin friction coefficient was enhanced for the increasing values of the zeta potential parameter and suction/injection parameter. The temperature distribution increases for the large value of the heat source/sink parameter and Brinkman number in both the positive and negative values of the electric field. The Nusselt number decays due to an increment in the permeability parameter.

In the current study, the author investigated the sensitivity of hybrid-nanofluid flow in expanding and contracting the channel with both MHD and thermal radiation effects. The mathematical model of the flow problem is developed. The lower plate is stationary and heated externally. The upper plate is porous which contracts/expands with respect to the time and allows a coolant fluid inside the channel. The governing momentum and temperature equations are transformed by the similarity transformation into the non-linear ordinary differential equations. The obtained ODEs are then solved analytically by the Homotopy Analysis Method (HAM) along with the defined boundary conditions. Copper and silver nanoparticles are mixed with the base fluid water. The numerical solution is obtained using the Mathematica package (BVPh 2.0). Then using Response Surface Methodology (RSM), the correlation between different parameters and the responses are shown through tables and graphs.