Novel, low-cost, CFRP pressure vessel design for hydrogen fuel cell applications

In 2015, the Ascension III water rocket shattered the previous long-standing world record of 633 m after reaching an altitude of 835 m. This feat was primarily attributed to the design of the Carbon Fibre Reinforced Plastic (CFRP) pressure vessel portion of the rocket. The pressure vessel was composed on a long, thin-walled commercial CFRP cylindrical tube that had two Poly Vinyl Chloride (PVC) end caps bonded onto either end with an adhesive. The inside wall of the CFRP tube was coated with a thin rubber liner to prevent leakage through the tube wall of the pressurised air-water mixture that provided the necessary thrust for the rocket. The outcome was that the CFRP pressure vessel design was thus, novel, low-cost and lightweight with the potential to be used in other gas storage applications for example in Hydrogen Fuel Cell (HFC) applications. This report details the research aimed at identifying the feasibility and suitability of the proposed CFRP pressure vessel concept for high pressure hydrogen gas storage for use in Hydrogen Fuel Cell Powered Vehicles (HFCPVs). The primary component of the pressure vessel to be designed was the CFRP tube which was to be commercially filament wound using carbon fibre and epoxy resin. With an angle ply laminate structure for the CFRP tube, an optimal fibre winding angle of 50° was initially chosen to maximise the burst pressure. The stress analysis and strain behaviour of the CFRP tube were modelled using the Classical Lamination Theory. Specimens were made using the same CFRP material as the tube and were tensile tested to give an initial set of approximate properties to be used in the design calculations. The distinct geometrical features of the end cap were designed, and Aluminium 6082-T6 was selected as a suitable material for its construction as it was easy to machine while it also possessed desirable mechanical properties. SpaBond 340 LV epoxy adhesive was used to bond the end caps onto the ends of the CFRP tube. A number of specimen CFRP pressure vessels were constructed with the inclusion of the rubber liner. Hydrostatic burst tests were performed on specimen vessels with different wall thicknesses (2 mm and 4 mm) to determine the pressure at which each type of vessel would fail. However, only the 2 mm vessels experienced failure of the CFRP tube section as the predominant failure mode while most 4 mm vessels failed by shearing of the interface between the adhesive layer and end cap. According to the ASME Boiler and Pressure Code Section X, the maximum design pressures at which the CFRP pressure vessels could operate at were at most, 2.25 times smaller than the respective failure pressures. The maximum design pressures were thus determined to be 147 bar and 182 bar for the 2 mm and 4 mm CFRP pressure vessels respectively. The specimen pressure vessels were also fitted with strain gauges on the external cylindrical surface of the CFRP tubes to measure the longitudinal and hoop strain during the burst tests. The strain measurements allowed the deformation behaviour of the CFRP tubes to be modelled which would prove useful for designing further CFRP tubes. For all specimen CFRP pressure vessels, it was observed that the deformation response of the CFRP tubes were linear up until a certain pressure. Beyond that point, a decrease in stiffness was observed which suggested that some form of irreparable damage had commenced. Other specimen CFRP pressure vessels were constructed and underwent hydraulic proof testing at 1.25 times the design pressure for 30 minutes and at the design pressure for a further 24 hours. The objective was to assess if the pressure vessels were durable and reliable of which all tested specimen vessels passed successfully. The hydraulic proof test results seemingly suggested that the rubber liner could adequately prevent leakage of water from the vessels at their design pressures. The long-term gas leak test was performed at the design pressure using air (i.e. a compressible fluid) on the proof tested pressure vessels to detect and localize any leaks for a duration of up to 72 hours. However, the leak rates were determined to be at least an order of magnitude larger than the recommended leak rate for hydrogen gas storage vessels. The leak test results strongly suggested that the rubber liner was insufficient to prevent air molecules from escaping the vessel, was not durable for repeated use and thus, not suitable for long-term gas storage. Therefore, it was concluded that the novel CFRP pressure vessel design concept was not yet suitable for hydrogen gas storage, but with improvements, could still prove possible for use in HFCPVs. Further work into these improvements could include improving the end cap design and testing other rubber liners

Digital Access to Research: Prospects of the Technology Bank Project of the United Nations

In 2016, the United Nations General Assembly officially established the Technology Bank Project aimed at supporting and strengthening Science, Technology and Innovations (STI) in selected Least Developed Countries (LDCs). The focus area of the project was to promote digital access to research and technology in LDCs. Working in partnership with research4life, a partnership of 5 UN agencies (WHO, FAO, WIPO, ILO, UNEP), highly rated science publishers, Cornell and Yale Universities, that have been providing free access to global academic research through the five research4life programmes, as well as in collaboration with the Uganda Focal Persons, the Technology Bank aims to achieve its objective. The DAR (Digital Access to Resources) activities of the Technology Bank started in September 2018, in Uganda. The activities were then officially launched in a workshop at Uganda Christian University (UCU) on the 7th of November 2018. Subsequent activities and workshops were held in which the project reached out to many researchers and institutions. This paper, therefore, presents a summary of DAR activities and their spread within the country until December 2018

The tax implications of a private equity buy-out : a case study of the Brait-Shoprite buy-out

This treatise examines the history of private equity as a context in which to understand its role in the economy and specifically, the background for the high profile leveraged buy-outs that have been entered into in the past year. The treatise then focuses specifically on the Brait-Shoprite buy-out, examining its structure and the tax implications. The treatise then reviews the reaction of the South African Revenue Authority (“SARS”) to the buy-out and evaluates whether it was the best approach that could have been taken under the circumstances. As a result of the research, the following conclusions have been reached: Private equity transactions Private equity transactions have a role to play in the business world despite the apprehensions of tax authorities. The perception that these transactions are tax driven as part of an avoidance scheme is not justified. Structure of the Shoprite buy-out transaction: The Shoprite buy-out transaction was structured to obtain deduction for interest. The transaction was also structured to utilise the relief provisions of Part II of Chapter II (Special Provisions Relating to Companies) of the Income Tax Act no.58 of 1962, as amended (“the Act”). The relief was for capital gains tax (“CGT”) on disposal of the Shoprite assets. Finally, the transaction was designed to allow the existing shareholders to exit their investments free of Secondary Tax on Companies (“STC”). The reaction of SARS to the Shoprite buy-out transaction Whereas SARS may have been justified in questioning the structure and its impact on fiscal revenue, the response in the form of withdrawing STC relief from amalgamation transactions in section 44 was not in the best interest of a stable tax system and the majority of tax payers who are not misusing or abusing loopholes in the income tax legislation. It may have been possible for SARS to attack the structure based on the General Anti-Avoidance Rule (GAAR) in part IIA of the Chapter III of the Act

Evaluating the implementation of guidance and counselling in a Zimbabwean secondary school

The purpose of this research study was to evaluate the Implementation of Guidance and Counselling in a Zimbabwean Secondary School that was seen to be running an exemplary programme. The study was a search for best practice meant to provide benchmarks that could benefit other institutions in similar set-ups to establish effective Guidance and Counselling (G&C) programmes. The rational for the study emanated from reservations expressed by some teachers and heads about the feasibility of G&C programmes in their schools citing numerous practical hurdles. Policy circular number 23 of 2005 expected all Zimbabwe secondary schools to institutionalise G&C programmes. Some questions that guided the study follow below. How did the school articulate the policy into G&C programme? How can insight into the implementation of G&C inform programme development? The research study was conducted at Trockley Secondary School in Harare where five participants were interviewed individually. Research findings showed that Trockley was running a functional G&C programme refuting the scepticism cited above. However, it is important to set standards that schools can aspire to elevate their programmes to; for now programmes can be qualified as functional or non-functional, but not exceptional, a yard-stick that could help to improve G&C programmes significantly in the whole country.Dissertation (MEd)--University of Pretoria, 2011.Educational Psychologyunrestricte

Numerical investigation of a packed bed thermal energy storage system for solar cooking using encapsulated phase change material

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.A numerical model for a packed bed thermal energy storage (TES) system using phase change material (PCM) is presented. The storage system is to be utilized for a solar cooking application. Sunflower Oil is the heat transfer fluid (HTF) during charging cycles. The packed bed TES consists of spherical capsules filled with erythritol, as the phase change material. The model uses dual-phase mathematical heat transfer equations while the phase change phenomena inside the PCM capsules is analyzed by using the effective heat capacity method. Results from the model are validated with experimental results from literature. Numerical and experimental results are reasonably comparable. The effects of inlet temperature and the flow rate of the HTF on the temperature profiles of the packed bed are presented.dc201

Performance comparison of two solar cooking storage pots combined with wonderbag slow cookers for off-sunshine cooking

Two similar storage cooking pots are experimentally evaluated and compared during solar cooking and storage off-sunshine cooking periods. One storage pot has sunflower oil as the sensible heat storage material, while the other has erythritol as the phase change material (PCM). To test their thermal performance during off-sunshine periods, the two pots are placed in insulated wonderbag slow cookers. Water and sunflower oil are used as the cooking fluids in the experimental tests. The sunflower oil cooking pot shows better performance during the solar cooking periods since it shows shorter cooking times (1.8–5.6 h) compared to the erythritol PCM pot (3.8–6.6 h). The sunflower oil pot also attains higher maximum storage temperatures (124–145 °C) compared to the erythritol PCM pot (118–140 °C). Storage efficiencies for the sunflower oil pot (3.0–7.1%) are also greater than those of the PCM pot (2.5–3.7%). During the storage cooking periods, the erythritol based phase change material cooking pot shows better performance as evidenced by the lower temperature drops (0.1–9.7 °C) from the maximum cooking temperatures compared to 8.3 to 34 °C for the sunflower oil pot. The heat utilisation efficiencies for the erythritol pot (4.8–14.3%) are also greater compared to the sunflower oil pot (3.7–6%)

Characterisation of edible sunflower as a heat storage medium for solar cooking

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Charging and discharging experiments to evaluate Sunflower Oil as a heat storage medium for domestic solar cooking applications are presented. An experimental setup to evaluate the thermal performance of Sunflower Oil during charging and discharging cycles is presented. Energy and exergy based experimental thermal performance parameters are evaluated. Energy, exergy, thermal gradient and exergy factor values are evaluated with experimental tests. High temperature charging is found to be the most viable option. This option results in higher energies, higher exergies, higher thermal gradients and higher exergy factors. For the discharging cycles, a high flow-rate results in a fast heat transfer rate. This fast rate of heat transfer destroys thermal stratification earlier but heats up water faster. The lower discharging flow-rate ensures that the discharging cycle can be carried out for a longer period. This is beneficial in utilizing the stored energy and exergy for a longer period, such that it can be used for cooking foods that take a longer time to cook. An optimal discharging flow-rate is also suggested. The optimal flow-rate comprises between fast heat transfer and using the stored energy more effectively. Exergy factor profiles during charging and discharging cycles show characteristic dips which correspond to the time when the thermal gradients begin to decrease. Sunflower Oil is found to be a viable and readily available TES medium which can be used in domestic solar cooking applications.dc201

Experimental comparison of a DC PV cooker and a parabolic dish solar cooker under variable solar radiation conditions

Solar cookers are not all-weather cooking devices and operate poorly during cloudy and low sunshine conditions. Their performance is evaluated usually during high solar radiation conditions. The objective of this study is to compare two solar cookers under variable non-ideal weather conditions. The comparison is carried out under variable solar radiation conditions to compare the all-weather performance of these two cookers. This is a major novelty compared to previous work reported where solar cookers are tested under high and ideal solar radiation conditions. Experiments to compare a PV DC battery-powered solar cooker and a parabolic dish solar cooker are presented in this paper. A total of six water heating tests are carried out to comprehensively compare these two types of solar cookers under different solar radiation conditions. Also, four food cooking tests are carried out with different types of food. The PV solar cooker shows almost constant input electrical power in the range of 160–180 W during the experimental tests whereas the input thermal power for the parabolic dish is highly variable depending on the solar radiation conditions (200–1200 W). The output water heating powers obtained using the PV cooker (66–100 W) are comparable to those obtained with parabolic dish solar cookers (78–142 W), regardless of the significantly lower input heating power. Water is boiled in all the heating tests with the PV cooker, whereas water is boiled for tests with low solar radiation variability for the parabolic dish solar cooker. Higher water heating efficiencies within a small range (0.38–0.57) are obtained for the PV cooker compared to the parabolic dish solar cooker (0.11–0.42). The water heating efficiency of the parabolic dish solar cooker is highly affected by ambient solar radiation and windspeed conditions. Food was well cooked with the PV cooker in all four food cooking tests, whereas food in only two tests with low solar radiation variability was well cooked for the parabolic dish solar cooker. The PV cooker proves to be an all-weather cooker from the experimental results obtained. Future work will extend the use of the PV system for other domestic applications such as lighting and refrigeration together with solar cooking for a multipurpose DC decentralized system for communities without grid connectivity

Selection of a suitable ligand for the supercritical extraction of gold from a low-grade refractory tailing

Reprocessing tailings for gold recovery is generating new low-grade refractory secondary tailings. Unlocking gold trapped within these secondary tailings potentially holds additional economic value. In this study, the use of supercritical carbon dioxide (scCO2) at 100 bar and 40 °C for gold extraction from such a secondary gold tailings sample (0.27 g Au/t) was investigated. The research identified and screened the following ligands as suitable extractants for gold in scCO2: 3-(trifluoromethyl)-phenyl-thiourea (TPT), 1,1,1-trifluoro-2,4-pentanedione (TFA), betaine bis(trifluoromethylsulfonyl)imide ([Hbet][TF2N]), 4-methyl-4H-1,2,4-triazole-3-thiol (MHTT) and hexafluoroacetylacetone (HFA). Results from screening experiments showed that extraction of gold for all ligands in the presence of a tri-n-butyl phosphate-nitric acid adduct (TBP-HNO3) as oxidant exceeded 50% after 18 h, with the highest extraction offered by [Hbet][TF2N] (82% after 24 h). A comparative study, where no scCO2 was present, showed that the presence of scCO2 offered a distinct advantage in extraction