Synthesis, characterisation and thermo-physical properties of highly stable graphene oxide-based aqueous nanofluids for low-temperature direct absorption solar collectors and solar still desalination.

Humanities’ insatiable demand for energy and fresh water has never been satisfied and continues to increase with an ever-increasing global population. Because both demands currently rely heavily on fossil fuels, the resulting detrimental consequences of rising greenhouse gas emissions, global warming and environmental degradation present major challenges for every nation. Importantly, the efficient conversion of energy to perform useful work is a factor that directly contributes to the financial development and economic sustainability of a country. Furthermore, the current global water demand is already much higher than the Earth’s natural water cycle can sustain, and this shortfall is presently being made up by the use of high energy consuming desalination processes. Thus, there is currently extensive research into developing eco-friendly and viable renewable energy sources to meet the demands for energy and fresh water. Solar energy offers an alternative energy source with the potential to alleviate the problems associated with fossil fuel-based energy generation and desalination. The performance of conventional solar thermal collectors is limited by poor optical properties and low thermal properties. Traditional solar stills are not widely used today, due to their poor thermal properties and low productivity levels. The thesis focuses on developing new and novel nanofluids based on novel graphene based materials with enhanced optical and thermal properties to improve the performance of direct absorption solar collectors (DASCs) and solar desalination stills. The thesis is arranged in two parts. The first part extensively reviews current solar collector systems for converting solar energy to thermal energy and also reviews current progress towards developing high thermal efficiency solar desalination systems. The second part presents actual case studies that evaluate the performance of newly developed novel graphene oxide and reduced graphene oxide based nanofluids for use in DASCs and solar stills

Nanofluid types, their synthesis, properties and incorporation in direct solar thermal collectors: A review

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

Scanning electron microscopy study of di-calcium phosphate dehydrate coatings on magnesium substrates for potential use in orthopaedic implants

Magnesium has attracted considerable medical interest due to its mechanical properties being similar to bone. In addition, magnesium is also biocompatible and biodegradable, which makes it an ideal candidate for biodegradable orthopaedic implants. However, magnesium’s high corrosion rate in body fluids makes it an unsuitable material for the manufacture of implants. The present study investigates a straightforward chemical immersion technique that deposits di-calcium phosphate dehydrate (DCPD) coatings onto magnesium substrates to increase their corrosion resistance to body simulated fluids like phosphate buffer saline solution and Ringer’s solution. Scanning electron microscopy revealed the coating structures and morphologies were characterised by flower-like surface feature that were resistant to both body simulated fluids. Thus, indicating the coatings could significantly reduce magnesium corrosion rates in the body environment

Improved Scalable Green Synthesis of Noble Metallic Polygonal Micro/Nano particles from Waste Macadamia Nut Shells

RA2 Research Attachment

Solar thermal energy stills for desalination: A review of designs, operational parameters and material advances

The demand for high-quality freshwater is increasing due to global population growth, intensifying agricultural practices and expanding industrial development. Additionally, many global regions have low levels of rainfall which makes them arid and incapable of supporting large human populations or agriculture. Currently, large quantities of fossil fuels are used to generate the power needed to drive energy intensive desalination processes that deliver high-quality freshwater to many of these regions. However, the use of fossil fuels has led to high greenhouse gas emissions, environmental degradation and global warming. Solar-thermal desalination is a low-cost, sustainable and eco-friendly strategy for producing high-quality freshwater without using energy derived from fossil fuels. However, in spite of recent developments to advance solar-thermal desalination, the most effective strategies for achieving higher performance levels still remains elusive. To tackle this problem, the present article reviews several solar-thermal still configurations, including materials, system design parameters, influencing factors and operational parameters. Moreover, recent material advances in plasmonic nanoparticle-based volumetric systems, nanomaterial enhanced phase change materials and interfacial solar evaporators are discussed. These new material advances can have the potential to significantly improve the conversion of light-to-heat, enhance vapor generation and promote greater water production rates

The addition of graphene oxide to enhance the Photo-Thermal performance of a premier organic heat transfer oil

The present study investigated the improvement in photothermal response and temperature enhancement of a commercially available organic thermal oil when small quantities of graphene oxide (0.1 to 0.3% w/v) were added. Characterisation studies revealed the ultrasonic processing procedure did not change the chemical composition of the organic oil, which was found to be thermally stable up to 175 °C before complete decomposition at 315 °C. When the GO-based fluids were exposed to a solar irradiance of 985 Wm-2, the temperature enhancements achieved over the exposure period of 20 minutes typically ranged from 42.4 to 43.2%. The temperature enhancements achieved indicate the GO-based fluids have the potential to be used in direct-absorption solar collectors for improved performance

Energy, exergy, exergoeconomic and enviroeconomic (4-E) assessment of solar water heater with/without phase change material for building and other applications: A comprehensive review

Solar water heating is the most common method of using solar energy because of its technical viability and economic attractiveness. However, intermittent nature of solar energy and lack of energy storage limits use of Solar Water Heaters (SWHs). Phase change materials (PCMs) utilize the heat energy from the solar energy effectively. Integrating PCMs to SWHs overcome the limitation of limited use in the day time only and make it more efficient and user friendly. The main objective of this review paper is to review a broad variety of work on the energy, exergy, exergoeconomic and enviroeconomic (4E) approach of with and without PCMs integrated SHWs for building and other applications in recent years and to address the technical challenges associated with SWH systems. This review paper discusses the recent advances, practical techniques, appropriate specifications of solar water heating systems with and without phase change materials based on 4E (energy, exergy, exergoeconomic and enviroeconomic) analytical approach. It has been observed that solar water heater combined with PCMs are more efficient in terms of energy and exergy efficiency and energy payback period