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Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg. ; Abstract available in PDF.

This paper reports on the design and implementation of a wireless sensor communication system with a low power consumption that allows it to be integrated with the energy harvesting technology. The system design and implementation focus on reducing the power consumption at three levels: hardware, software and data transmission. The reduction in power consumption, at hardware level in particular, is mainly achieved through the introduction of an energy-aware interface (EAI) that ensures a smart inter-correlated management of the energy flow. The resulted system satisfies the requirements of a wireless sensor structure that possesses the energy autonomous capability.

With the advent of the new National Health Act, health care in South Africa is at a critical point as this will be the first time in history that a National Health Insurance is being implemented in this country. Globally National Health Insurance has been around for more than a hundred years, however some countries with long established national health schemes are currently grappling with funding issues surrounding their health systems. South Africa should take note of these issues as it embarks on this journey. The objective of this study was to perform a literature review on how South Africa’s National Health Insurance can be funded taking cognisance of the history of the country and experiences of other countries. It is imperative for each country to achieve optimal health care funding to ensure the success and long-term sustainability of National Health Insurance. The analysis of the problems experienced by other countries revealed that balancing the three main funding options namely, allocated from the national revenue fund, user charges and or donations or grants from international organisations, is critical as the funds needed in a system to achieve coverage at an affordable cost is dependent on the current state of health care in a country. Considering South Africa’s history and current inequality in society and health care it is clear that the majority of funding for the National Health Insurance should be supplied by the national revenue fund. The required funds can either be raised by increasing existing taxes or introducing a new tax specifically aimed at financing the National Health Insurance. The use of user charges is important however, although not purely for a revenue collection point, but from a cost control point of view as well. Some studies have revealed that the lack of user charges results in a misuse of the system. ; Financial Accounting ; M. Phil. (Accounting Science)

Doctor of Philosophy in Ecology. University of KwaZulu-Natal, Pietermaritzburg, 2017. ; The increase in dominance of woody species, observed in many grasslands and savannas worldwide, highlights the sensitivity of woody herbaceous biomass ratios to changed environmental conditions. While the major factors driving the tree–grass continuum have been identified as precipitation, nutrients, increased CO2 concentrations, fire and herbivory, the interaction of these driving forces determines the tree: grass ratio, and ultimately the occurrence/ absence of woody plant encroachment. Furthermore, with forecasted alterations to the global climate (such as an increase in the frequency and magnitude of climate extremes), and increased nutrient availability (either through extensive use of fertilizer or increased nitrogen deposition), more knowledge is required on the factors which promote woody plant performance. We conducted a series of greenhouse experiments to manipulate these factors, and a two-year field trial to disentangle the effects of varying climate and land use on woody plant encroachment. These studies are summarized below: (1) We investigated the effects of manipulated water availability and passive warming on the productivity of the commonly occurring grass species Eragrostis curvula, and the emergence and performance of seedlings of the woody encroacher, Acacia sieberiana. We simulated a typical savanna microhabitat by planting tree species within a grass matrix. Watering treatments altered to represent drought (minus 40% of the average), normal (same amount as the long-term average of the area), and excess (addition of 40% of the long term average) precipitation. Passive warming was achieved using open-top chambers. Tree seedling emergence was monitored in the first two weeks. Thereafter, weekly tree growth rate measurements were recorded. The final above-ground grass biomass, tree root: shoot ratio and specific leaf area were quantified. We found that water availability was the main limiting factor for ...

Systemic humanitarian, environmental, and socio-political problems are impeding current and future generations from meeting their very basic needs. The speed and scope of mainstream responses to the world’s most pressing problems are limited by agency failures and by the ‘rules of the game’. In this context, this research contributes to theory and practice by formulating and exploring the concept of Sustainability Hacking, a particularly advantageous change driver in situations where information is limited, resources are scarce, stakes are high, and decision-making is urgent. This research was conducted through 3 sequential stages. First, the researcher has systematically reviewed the literature on sociotechnical system change for sustainability. This review exposed and discussed 15 theoretical foundations that shape what changes are perceived as desirable and attainable, as well as how to navigate between all the coexisting pathways to drive positive change. By examining these foundations, it became possible to pinpoint opportunities for future contributions. Among them was the idea of investigating the meaning, characteristics and potential implications of Hacking as a change driver of sociotechnical systems. These were revealed in the 2nd research stage, after interviewing self-declared Hackers and cybersecurity experts to understand how they used the term and how they pursued their desired systemic changes. This stage provided the definition, as well as 9 dominant characteristics of System Hacking. The term refers to exploring unconventional solutions to a problem within sociotechnical systems. ‘Unconventional’ here means deviating from embedded institutions, i.e. the rules of the game in a society. Institutions represent sources of stability, coherence, and continuity of systems, while simultaneously shaping public expectations of what changes are viable and the heuristics of how they should be pursued. Differently from conventional approaches, system Hackers are not aiming at changing rules, neither are they passively complying with them. Instead, they work around the ‘rules of the game’ to accomplish ‘good-enough’ results promptly. The 3rd research stage consisted of investigating and working with Sustainability Hacks, i.e. System Hacks addressing pressing sustainability problems. This was performed through a combination of Action Research and Case Studies. Benefitting from a diverse database of 19 cases, the researcher conducted a cross-case analysis, which provided comprehensive observations on the 15 main similarities and 10 differences that constitute the key analytical variables of Sustainability Hacking. Furthermore, the analysis derived 5 Archetypes that can be used as frames of reference to provide guidance for practitioners evaluating possibilities of addressing pressing sustainability problems, as well as to support future academic contributions in this nascent field of research. Gates Cambridge

Large-scale energy storage systems typically withdraw electricity from the grid and transform it into another form for storage. When the grid is unable to meet demand, the process is reversed and the stored energy is transformed back into electricity. Instead of this traditional approach, the following thesis explores the concept of ‘generation-integrated energy storage’, in which a generator’s existing energy conversion pathway is used to store energy in an intermediate form. This has two benefits: (i) the hardware used for generation can be exploited to reduce storage costs and (ii) fewer energy transformations are required when compared to traditional ‘electricity-in-electricity-out’ forms of storage. This means a high effective (exergetic) round-trip efficiency can be achieved at low cost. Specifically, this thesis focuses on the integration of thermal energy storage with the feedwater heating system of steam plant. (In modern energy systems this is likely to be nuclear-powered.) In the proposed system, the plant’s electrical output is flexed whilst maintaining constant reactor power. During charge, the plant’s electrical power output is reduced below its normal full-capacity level, and during discharge, it exceeds this level. This approach provides the equivalent of an electricity storage system and facilitates the adoption of a load-following role for nuclear plant. By allowing the reactor to operate constantly at maximum power output, the system also avoids the economic constraints and practical problems of part-load operation, which currently favour the use of nuclear plant for baseload only. An important feature of the proposed system is that the wet steam turbine bleed flows automatically provide good thermal matching with the feedwater temperature profile. This means that heat can ultimately be transferred to and from sensible-heat thermal-storage media with high exergetic efficiency. Various options are discussed for the thermal stores, including pressurised water tanks, thermal oils, and packed beds. This thesis is focused on the engineering research and development of the feedheat- integrated energy storage system and how this technology would be valuable in a modern energy system. The following contributions have been made: (i) Thermodynamic analysis – Detailed thermodynamic analysis is presented for an elec- tricity storage system in which thermal stores are integrated with the feedwater heating system of steam plant. The findings indicate that a round-trip efficiency greater than 80% is likely and that the plant’s power output can be varied between 85–113%. The analysis is also extended for heat cogeneration applications, for which the effective COP is estimated to be approximately 8 for modern district heating and 4 for industrial process heat. (ii) Off-design steam plant operation – A detailed off-design steam plant model is created. It is shown that the plant performs sufficiently well when operated off-design, and is able to efficiently transfer work to heat and then heat back to work. (iii) Capital cost estimation – A comprehensive cost analysis of the proposed system is undertaken, with an emphasis on the marginal cost of oversizing existing compo- nents. Costs for a well-designed system are approximately 250–1000 $/kWe and 15–20 $/kWhe. (iv) Thermo-economic optimisation – Parametric studies and a genetic algorithm optimisa- tion method are used to determine the optimal trade-off between efficiency and cost, and inform best design practices. (v) Steam turbine operation – A streamline equilibrium throughflow method is used to numerically validate Stodola’s ellipse law, and to explore the unusual off-design conditions caused by the storage system. Throughout this thesis, these contributions are routinely placed in the context of the modern energy system. It is demonstrated that integrated systems which perform multiple roles – electricity generation, energy storage, and possibly heat cogeneration – will be highly valuable for the transition to a low-cost, secure, and decarbonised energy system.

PolyU Library Call No.: [THS] LG51 .H577P AP 2017 Qian ; xiv, 148 pages :color illustrations ; Due to the increasing energy requirements of the portable electronic devices, backup power sources and radio frequency identification (RFID) tags, there is a growing need of high performance energy storage devices, mainly including supercapacitors and lithium ion batteries. Particularly, a simple and large scale production of high performance electrode materials is highly sought. By now, many novel nanostructured materials, including carbon nanotubes, graphene, metal oxides, transition metal dichalcogenides (TMDs) and black phosphorus have been reported to be the promising candidates as electrodes for energy storage devices. Among them, graphene and manganese dioxide (MnO₂) have attracted much attention. On one hand, graphene performs unique electrical, thermal and mechanical properties, especially outstanding electrical conductivity (106 S·cm⁻¹) and large specific surface area (~2630 m2·g⁻¹), but suffers from a relatively low theoretical capacity (550 F·g⁻¹ for supercapacitors and 1116 mAh·g⁻¹ for Li ion batteries). On the other hand, MnO₂ exhibits a high theoretical capacity (1370 F·g⁻¹ for supercapacitors and 1232 mAh·g⁻¹ for Li ion batteries) but suffers from poor electrical conductivity (10⁻⁶-10⁻⁷ S·cm⁻¹). Hence, the MnO₂/graphene composites are expected as the promising candidates of the electrode materials with improved electrochemical performances for both rechargeable batteries and supercapacitors. In this work, the synthesis of MnO₂/graphene composites with different morphologies from zero- to three-dimensional were investigated. The electrochemical performances of as-prepared composites for lithium-ion batteries and supercapacitors were tested. MnO₂/graphene composite aerogel (MnGA) was prepared via a fast and simple wet chemical process. The as-prepared composite aerogel exhibits 3D rigid graphene networks embedded by MnO₂ nanoparticles. A maximum specific capacitance of 534 F·g⁻¹ at 1 mV·s⁻¹ is achieved by 1.33 wt% MnGA electrode due to the synergistic effect. The aerogel could be a promising candidate for large-scale production of energy storage devices. MnO₂/graphene composite ink (MnGI) was prepared via a facile synthetic path. The MnGI is formed by 2D hexagonal MnO₂ nanosheets and reduced graphene oxide (rGO) sheets. The ink could be printed on different substrates and suitable for mass production in industry. A maximum specific capacitance of 648 F·g⁻¹ at 5 mV·s-1 is achieved. All these merits allow the MnGI to be a promising candidate for high performance energy storage devices. ; A free standing, compact and robust paper comprised of reduced graphene oxide (rGO), multi-walled carbon nanotubes (MCNTs) and manganese dioxide nanowires (MnNWs) was prepared via a simple strategy. The combination of rGO, MCNTs and MnNWs exhibits high packing density but hierarchical porous structure, which facilitates the energy capacity, rate capability and long term stability. The rGO/MCNTs/MnNWs (GMM) paper electrode retains a specific capacitance of 48 mF·cm⁻² (28 F·cm⁻³) at a high current density of 20 mA·cm⁻² (11,765 mA·cm⁻³). A symmetric capacitor assembled by two GMM paper electrodes was investigated. The as-prepared device achieves a maximum specific energy and power densities of 7.96 mWh·cm⁻³ and 10,470 mW·cm⁻³ respectively, with a capacitance retention of 99% after 5,000 cycles at 1,176 mA·cm⁻³. All the results indicate that the free standing GMM paper electrode has a potential for the large scale production, low cost, environmental friendly and high performance capacitive energy storage devices. Furthermore, the synthesis strategy may be extendable to other composite materials for batteries, solar cells, fuel cells or other related fields. MnO₂/graphene quantum dots composite (MnGQDs) were synthesized via a low-temperature chemical reaction process. The MnO₂ quantum dots (MnQDs) were well mixed with graphene quantum dots (GQDs) to form a homogeneous quantum dots composite powder. To investigate the electrochemical performances, the as-obtained MnGQDs served as the anode materials for lithium ion batteries. An initial charge and discharge specific capacity of 662 and 1444 mAh·g⁻¹ are achieved respectively. Besides, a high coulombic efficiency of nearly 100% and good rate capability were measured. The discharge specific capacity remains at 246 mAh·g⁻¹ after 50 cycles. The results show that the MnGQDs anode could be an ideal candidate for lithium ion batteries with high efficiency and rate capability. ; Department of Applied Physics ; Ph.D., Department of Applied Physics, The Hong Kong Polytechnic University, 2017 ; Doctorate ; published_final

Energy consumption, depletion of natural resources and human induced natural disasters have all conspired to raise the profile of "sustainability", particularly environmental sustainability. The topic is now high on many nations and organizations lists of priorities and central for media attention. Despite the critical importance of such issues it is evident that management thinking often still adopts neoclassical economic views of accounting for and managing environmental sustainability. In this paper, we propose an alternative perspective to managing environmental sustainability based on a broadened model (BMSBM) which not only considers the biosphere in the broad sense but also people as fundamental elements that contribute to the conservation and improvement (or destruction) of the natural environment.

Thesis (MEng)--Stellenbosch University, 2023. ; ENGLISH ABSTRACT: This study aimed to develop a pilot system for low temperature solar thermal combined power and clean water co-generation. The system comprised a solar thermal steam generation system (6.5 kWth external compound parabolic concentrating collector array and kettle-type boiler) coupled to a condensing steam engine (reciprocating steam expander and condenser). The system uses solar thermal energy to produce steam at ~1 atm from raw feedwater. The steam is used to drive the steam expander (both through steam work and condensation) to produce mechanical work (which can be used directly for pumping or converted to electricity). The vapor exiting the engine is condensed and collected, providing distilled water for human use. The steam expander was designed by the University of Southampton and was manufactured at Stellenbosch University. The rest of the overall system (solar steam generator and condenser) was designed and constructed as part of this work with the intent to integrate the expander. Unfortunately, the expander did not operate, and this thesis thus reports on the design of the overall system and the measured performance of the solar steam generator and condenser (including measured distilled water production). The mechanical and electrical energy generation of the system was estimated using the measured steam generation and engine thermal efficiencies from literature. Results from three day-long on-sun tests are provided and prove that the steam generation system was able to meet its performance requirements (specifically providing steam at the required flow rate and condition to the condensing engine). The system produced distillate at an average specific energy consumption (SEC) of 2125 kWh/m3 and an estimated average mechanical energy output of 0.039 kWh/m2 of collector aperture area per day. The monthly and annual distillate production and energy generation were also estimated to illustrate the longer term expected performance with an ...

The repository software dream has been a team of dedicated, in-house developers who work within their institutions and the various OS communities, hand-crafting new functionality and sharing the code. The reality has always been more complicated and messy. For a variety of reasons, many institutions find themselves without expert repository developers, but still needing to have bespoke work carried out. And commercial service providers have stepped up with offers to bridge this gap. Increasingly, institutions are working with such service providers as their technical partners. For the institutions, it means that OS software remains a viable option even without an in-house technical team. But can commercial providers be invested in Open Source in the same way that in-house developers are? Do they contribute to the long-term stability, sustainability and accessibility of OS software and communities, or are they just taking the money? The panel will present a range of views from both commercial service providers, those who keep technical expertise in-house, and some who do a little of both. We expect the discussion to be lively, though-provoking and insightful, hopefully sparking further discussions in the community about how we might continue to sustain the OS community within repositories.