Browsing by Subject "sensitivity analysis"
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- ItemOpen AccessDevelopment and application of a multi-criteria decision-support framework for planning rural energy supply interventions in low-income households in South Africa(2022) Dzenga, Bruce; Stewart, Theodor J; Hughes, AlisonProblems in the public policy decision-making environments are typically complex and continuously evolve. In a resource-constrained environment, several alternatives, criteria, and conflicting objectives must be considered. As a result, solutions to these types of problems cannot be modelled solely using single-criteria techniques. It has been observed that most techniques used to shape energy policy and planning either produce sub-optimal solutions or use strong assumptions about the preferences of decision-maker(s). This difficulty creates a compelling need to develop novel techniques that can handle several alternatives, multiple criteria and conflicting objectives to support public sector decision-making processes. First, the study presents a novel scenario-based multi-objective optimisation framework based on the augmented Chebychev goal programming (GP) technique linked to a value function for analysing a decision environment underlying energy choice among low-income households in isolated rural areas and informal urban settlements in South Africa. The framework developed includes a multi-objective optimisation technique that produced an approximation of a Pareto front linked to an a priori aggregation function and a value function to select the best alternatives. Second, the study used this model to demonstrate the benefits of applying the framework to a previously unknown subject in public policy: a dynamic multi-technology decision problem under uncertainty involving multiple stakeholders and conflicting objectives. The results obtained suggest that while it is cost-optimal to pursue electrification in conjunction with other short-term augmentation solutions to meet South Africa's universal electrification target, sustainable energy access rates among low-income households can be achieved by increasing the share of clean energy generation technologies in the energy mix. This study, therefore, challenges the South African government's position on pro-poor energy policies and an emphasis on grid-based electrification to increase energy access. Instead, the study calls for a portfolio-based intervention. The study advances interventions based on micro-grid electrification made up of solar photovoltaics (PV), solar with storage, combined cycle gas turbine (CCGT) and wind technologies combined with either bioethanol fuel or liquid petroleum gas (LPG). The study has demonstrated that the framework developed can benefit public sector decision-makers in providing a balanced regime of technical, financial, social, environmental, public health, political and economic aspects in the decision-making process for planning energy supply interventions for low-income households. The framework can be adapted to a wide range of energy access combinatorial problems and in countries grappling with similar energy access challenges.
- ItemOpen AccessEvaluating occupancy and the range dynamics of invasive bird species in South Africa(2022) Swingler, James; Distiller, Gregory; Clark, AllanThere is great interest in the distribution of invasive species that threaten indigenous wildlife. All effective conservation management decisions need to be based on sound inference and predictions so that these species can be controlled and the risk posed to the local ecosystem minimized. Thus, there is significant benefit in the study of invasive species as a means of aiding those charged with protecting indigenous wildlife. The occupancy and population range dynamics of the Myna and Mallard species are individually investigated in the South African region by fitting static and dynamic occupancy models to a set of citizen science data for a 10-year study period between 2010-2019. The occupancy and detectability of the respective species is analysed using static occupancy models for the 2010 study season. The covariates included in the best fitting static models are used to estimate the initial occupancy and detection parameters for the dynamic models which now include estimates for colonization and local extinction. A sensitivity analysis pertaining to the dynamic models is implemented by altering the data structures in terms of the number of analysed sites and length of the detection histories. The results find the Myna's proximity to urban environments to play a significant role on its occupancy in 2010, and yearly changes in climatic and anthropogenic factors influence its 10-year range dynamics. The models fitted to the Mallard are inconclusive possibly due to the violation of the closure assumption potentially caused by migratory behaviour. The results are limited by the presence of a potentially migratory species when using a poorly designed study and highlights the difficulties of conducting an occupancy analysis on a highly mobile avian species as opposed to their sedentary counterpart. The workings of this dissertation support previous claims that an increase in the quantity of sites, and thus the degree of overlapping sites over the different seasons, will improve the precision of the model estimates. However, caution must be exercised when increasing the length of the seasonal detection histories and should generally be set to no more than 10 repeated visits to a site.