Masters Degrees (Civil Engineering)

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Development of an automation model for leakage reduction and energy harnessing through optimised placement and setting of pressure reducing valves and pump as turbine placement in water distribution networks.
(2021) Pillay, Ethan.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishna Vellaisamy.
Water leakage is of paramount interest in South Africa. Due to the increasing population density access to drinking water will be scarcer, as much of the water produced is lost through leakages. South Africa’s non-revenue water (NRW) accounts for approximately 30% of the total water supply, with leakages accounting for more than 70% of NRW in a network. Water leakage losses are defined as water lost during transportation to the consumer from the water source. Reducing leakage losses in existing networks is a major task for engineers, as replacing pipes is costly. There is a direct relationship between the pressure in a water distribution network (WDN) and the network’s leakage losses. Network pressure is affected by many factors such as consumer demand, nodal elevation differences and network characteristics. The easiest and most cost-efficient method of pressure reduction in existing WDNs is through efficient pressure management. Developing methods to reduce the excess network pressure will reduce the leakage losses in the network. There is currently little research that incorporates optimising pressure-reducing valve (PRV) placement to regulate network pressure and reduce leakage losses. Furthermore, the use of pumps operating as turbines (PATs) to harness energy in WDNs has not been fully explored. Literature gaps encompass optimising and automating these processes and creating an algorithm applicable to complex WDNs. This dissertation presents a new optimisation model aimed at minimising network leakage losses within a WDN by determining the optimal placement and setting of additional PRVs. Energy generation from excess pressure is a secondary benefit and by-product of pressure reduction and can be harnessed by replacing PRVs with PATs. Replacing PRVs with PATs to harness renewable energy from the WDN is also incorporated into the new optimisation model. Automation of the model has been achieved using MATLAB and EPANET. The objectives of this study are to create a mathematical model to optimise the placement and setting of additional PRVs within a WDN, following all hydraulic, mathematical, and linear constraints. The model must determine which PATs can feasibly replace PRVs within a WDN to generate electricity and the PAT’s potential power output and potential gross margin. The mathematical model must be automated using MATLAB and EPANET. The newly created objective function is made up of two stages to account for the multiple objectives. The model has been applied to two real-world networks: the Cornubia Integrated Human Settlement Development Phase 2A- Zone 1 network and the Pat Marshal Housing Project. The proposed methodology’s ability to reduce network pressures, reduce associated leakage losses, and generate energy has been demonstrated. The network leakage losses minimisation accounts for the hydraulic characteristics and constraints of each WDN in the form of mass continuity equation constraints at the nodes, momentum balance constraints along the pipes, network constraints, and pressure reducing equipment constraints. Five successful additional PRVs have been optimally placed and set within the Cornubia WDN, achieving a 12.8011% leakage rate reduction. Two successful additional PRVs have been optimally placed and set within the Pat Marshal WDN, achieving a 27.907% leakage rate reduction. The model has determined that nine of the 36 PRVs in the Cornubia WDN can be feasibly replaced by PATs to harness 135.48 kW of energy, equivalent to a Mini-hydropower plant, with a 948.67 MWh per annum output. One PAT can feasibly replace a PRV in the Pat Marshal WDN to harness 24.55 kW of energy, equivalent to a Micro-hydropower plant, with a 131.6 MWh per annum output. The energy produced could be sold to realise gross margins of approximately R920 211.17 and R127 662.30 per annum for the Cornubia and Pat Marshal WDNs, respectively. The results obtained from the newly proposed method are positive, significantly reducing the leakage rate in both networks. The excess pressure from the networks can be efficiently harnessed to generate renewable energy to be utilised or sold.
Feasibility of run-of-river hydropower for rural and agricultural productivity in South Africa.
(2021) Makalima., Lazola Qhawe Mfundo.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishna Vellaisamy.
The Southern African Community Development (SADC) intends to increase its irrigated area to increase the agricultural productivity of the land. Run-of-river hydropower systems present an attractive solution of providing energy where it is not feasible for alternative energy sources and extend the grid infrastructure to improve the livelihood of rural communities and increase agricultural productivity. The site geographical location and topography of power plants have made it impossible to guarantee fixed costs from suppliers and manufacturers, leading researchers to develop formulae that predict the cost behavioural tendencies of the electro-mechanical components of the power plant as a function of hydropower parameter inputs and other costs. Hydropower systems are very site-specific as they are affected by their geographical location and the site's topography. The difficulties from suppliers and manufacturers in failing to guarantee fixed costs have resulted in designers using developed formulae to determine the scheme's costs. This investigation aimed to develop a model that would allow designers to determine whether run-of-river hydropower would be feasible or not for a specific location in South Africa. This was achieved through a pre-feasibility model based on a '3 Pillar Concept' of social, environmental, and economic test for sustainability, which according to research, has 49 sustainability indicators for run-of-river hydropower systems measured directly or indirectly. The Levelised Cost of Electricity (LCOE) from hydropower was used to determine the economic feasibility of hydropower systems. From previous research, LCOE evaluation for small hydropower projects in developing countries ranged between 0.02USD/kWh and 0.10USD/kWh, making small scale hydropower systems very cost competitive for electricity generation to the grid or schemes for off-grid rural electrification. Run-of-River hydropower systems are classified as small hydropower systems and generate from 1MW to 20MW. The projects demonstrated in this report were Micro and Mini hydropower systems which are significantly larger than Pico hydropower systems. The sites selected for the study are U2H014 located downstream of Albert Falls dam, U3H005 downstream of the Hazelmere dam, U2H052 downstream of Inanda dam, and V1H002 downstream of Woodstock dam. The potential power of the available energy was quantified using available streamflow data. Flow duration curves were developed from streamflow data and were used to develop power duration curves for the hydropower plants. LCOE for the investigated sites ranged between 0.02USD/kWh and 0.10USD/kWh. The power duration curves showed that the smallest power plant was U3H005 and generated 48kW. The groundwater pumping requirements for rural and agricultural productivity is found to be 31.1kW. Results obtained at sites U2H014 and V1H002 were 238kW and 314kW, respectively. The smallest power plant could generate enough power for rural and agricultural productivity with power savings that could be sold to the grid or power the community. The results obtained at the sites were positive and acceptable.
The optimisation of baffle arrangements for minimal sediment washout in standard stormwater sumps.
(2022) Paideya, Leshalen.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishnavellaisamy.
Sediment in stormwater drainage systems is a matter of great concern due to its ability to collect within stormwater pipes to form blockages. Furthermore, sediments transport harmful pollutants, depositing them in stormwater discharge areas and disturbing the ecology of those areas. Standard stormwater sumps are a reliable and cost-effective solution to trap and retain sediment within stormwater drainage systems for manual removal. However, under high flowrate and fine sediment conditions, the effectiveness of standard sumps drastically decreases. A solution to this issue is the installation of baffles that can be retrofitted into the standard sump as a method of reducing flow velocities to allow sediments to settle to the sump bed. An aspect of this solution, as equally important as sediment trapping, is the prevention of sediment washout. During a storm event, sediment previously trapped in a stormwater sump can be washed out before the routine cleaning period. Therefore, it is paramount to ensure that the baffle arrangement effectively prevents the resuspension and washout of sediment already present in a standard sump. This dissertation investigates the use of baffle arrangements to minimise sediment washout in standard sumps and determine a baffle arrangement that will provide the best sediment retention results while remaining a feasible and practical solution in a real-world context. Three baffle arrangements, consisting of a combination of solid and semi-porous baffle plates of varying dimensions placed in different orientations, were chosen for this investigation based on their previous success with sediment trapping. The primary methodology of this research compared the effectiveness of these baffle arrangements in minimising sediment washout by comparing them to a control setup with no baffles, using a simple mass-balance process. Additional experimentation involved using an Acoustic Doppler Velocimeter (ADV) to develop flow velocity fields to motivate the observations made in the mass-balance tests. All baffle arrangements performed better than the control setup, with the least effective of the three designs improving sediment retention efficiency by 22% and the most effective by 71.5% under the worst-case condition. These results were then dimensionally analysed to determine the results of such testing under real-world conditions. The results of this analysis were also promising, with the best baffle arrangement achieving retained effluent concentrations of up to 0.4 kg/m3 when calibrated for typical standard sump dimensions and peak flowrate.

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Browsing Masters Degrees (Civil Engineering) by Author "Adu, Joy Tuoyo."