Master of Science in Engineering (Electrical) University of the Witwatersrand July, 2016 / This dissertation uses historical electrical consumption/load and actual solar radiation data to design a solar array for the University of the Witwatersrand’s West Campus. The array must meet the campus’s minimum demand as selling excess generated power back to the utility is not possible at this stage. The financial and spatial impact of adjusting the size of the array, design losses and cloud cover are also investigated. In addition to this, the influence on the payback period of financial variables such as taxes, electricity and start-up costs are also explored. The solar array system design process starts by determining the amount of power that the array must produce or supplement. Thereafter, load estimates and electrical consumption figures that are provided by utility bills or measured with load monitoring equipment are analysed. Furthermore, system losses are factored in which ultimately increases the size of the array. Once all the input variables are analysed, the amount of available solar radiation in the area where the array will be installed is required to determine the amount of energy that the array can produce. Several free databases with this information are available but it is found that this data over predicts the availability of solar radiation. The University has been monitoring the electrical consumption of West Campus since 2012 and solar radiation data is also available for this site. Comparing the satellite derived and measured datasets found that the ground monitored data is 25 % more accurate and therefore better suited for designing a solar array. Individually adjusting the design and financial variables changes the payback period between 3 – 17 %. Combining all the variables can reduce the payback of option 1 from 9.6 years to 6.1 years. Clear legislation needs to be developed for the uptake of renewable energy resources and supported by better rebates for renewable users and harsher taxes for non-renewable users. Should legislation change and if additional capital is available, a larger array will benefit the University more and should be installed as the difference between payback periods is not significant. This is mainly due to decreased costs associated with a higher yield. The financial benefits of a larger array will also be more lucrative if better rebates are enforced. / MT2017

Cholera is a water-borne disease that continues to ravage resource poor communities around the world especially those in developing countries. The disease is caused by Vibrio cholerae microorganisms whose natural habitat is the aquatic ecosystem. It is believed that this microorganism prior to becoming the primary cause of cholera acquired virulence factors expressed by two separate genetic elements. These genetic elements are known as VPIФ and CTXФ were acquired in that order for known physiological reasons. However only V. cholerae in possession of the CTX genetic element are capable of causing cholera disease. At present only two serotypes are known to have the ability to cause cholera and these are V. cholerae serotypes O1 and O139. SODIS (Solar disinfection) is an extremely low cost refined technology that can be used for the disinfection of water especially in areas where there is a considerable amount of sunshine. Although this technology is a composite of various factors the underlying principle is the use of solar ultraviolet radiation (SUVR). The preliminary target of SUVR is the cytoplasmic membrane and this was confirmed by flow cytometric analysis. The consequences of leaky cytoplasmic membrane include cellular death to the microorganism as well as an increase in cholera toxin secretion. The main objective of this study was to investigate the effect of solar ultraviolet radiation on the growth of V. cholerae and on the secretion of cholera toxin and to provide supporting information for the use of SODIS in South Africa while observing the possible role that climate may play in the onset of cholera disease. The initial part of the study evaluated the culturability, biomass increase and cholera toxin secretion in both a nutrient poor and a nutrient rich media by two toxigenic and one non toxigenic strain of V. cholerae. A series of pH and temperature combinations were used to achieve this objective. The result revealed that the microorganisms survived in both media. An increase in biomass was observed for all the bacteria grown in the nutrient rich media whereas in the poor nutrient media the bacteria remained culturable but no increase in biomass was observed. Interestingly lower temperatures seemed to provide more optimal growth conditions while high temperature on most occasions favoured cholera toxin secretion, in both media.The second part of the study required the exposure of the microorganisms to SUVR. A SODIS approach was used with a few modifications. The V. cholerae strains were exposed to solar radiation during all the seasons of the year. Evaluation of the viability, the increase in biomass and the detection of cholera toxin secretion was determined after each exposure to solar radiation. The results seem to suggest that the effect of SUVR depended on the season of the year, the nature of the media, strain, solar conditions and in the duration of solar exposure, in no particular order. The secretion of cholera toxin was mainly dependent on the media used, the season of the year and on the serotype of the strain. This study represents the first report on the evaluation of SUVR for the disinfection of water under South African conditions (Pretoria area) during all seasons of the year with variations in solar radiation levels and temperature. Furthermore what actually happened to V. cholerae during solar exposure in terms of cell morphology, cell viability and secretion of cholera toxin is also reported and this can give an insight of the possible role that SUVR may play in the onset of cholera. The main recommendation emanating from this study is the sensitisation of communities worldwide about the capacity that, SUVR carries to lighten the burden of communicable water borne diseases especially, in resource limited areas through the implementation of SODIS. / Life and Consumer Sciences / M. Sc. (Life Science)

Cholera is a water-borne disease that continues to ravage resource poor communities around the world especially those in developing countries. The disease is caused by Vibrio cholerae microorganisms whose natural habitat is the aquatic ecosystem. It is believed that this microorganism prior to becoming the primary cause of cholera acquired virulence factors expressed by two separate genetic elements. These genetic elements are known as VPIФ and CTXФ were acquired in that order for known physiological reasons. However only V. cholerae in possession of the CTX genetic element are capable of causing cholera disease. At present only two serotypes are known to have the ability to cause cholera and these are V. cholerae serotypes O1 and O139. SODIS (Solar disinfection) is an extremely low cost refined technology that can be used for the disinfection of water especially in areas where there is a considerable amount of sunshine. Although this technology is a composite of various factors the underlying principle is the use of solar ultraviolet radiation (SUVR). The preliminary target of SUVR is the cytoplasmic membrane and this was confirmed by flow cytometric analysis. The consequences of leaky cytoplasmic membrane include cellular death to the microorganism as well as an increase in cholera toxin secretion. The main objective of this study was to investigate the effect of solar ultraviolet radiation on the growth of V. cholerae and on the secretion of cholera toxin and to provide supporting information for the use of SODIS in South Africa while observing the possible role that climate may play in the onset of cholera disease. The initial part of the study evaluated the culturability, biomass increase and cholera toxin secretion in both a nutrient poor and a nutrient rich media by two toxigenic and one non toxigenic strain of V. cholerae. A series of pH and temperature combinations were used to achieve this objective. The result revealed that the microorganisms survived in both media. An increase in biomass was observed for all the bacteria grown in the nutrient rich media whereas in the poor nutrient media the bacteria remained culturable but no increase in biomass was observed. Interestingly lower temperatures seemed to provide more optimal growth conditions while high temperature on most occasions favoured cholera toxin secretion, in both media.The second part of the study required the exposure of the microorganisms to SUVR. A SODIS approach was used with a few modifications. The V. cholerae strains were exposed to solar radiation during all the seasons of the year. Evaluation of the viability, the increase in biomass and the detection of cholera toxin secretion was determined after each exposure to solar radiation. The results seem to suggest that the effect of SUVR depended on the season of the year, the nature of the media, strain, solar conditions and in the duration of solar exposure, in no particular order. The secretion of cholera toxin was mainly dependent on the media used, the season of the year and on the serotype of the strain. This study represents the first report on the evaluation of SUVR for the disinfection of water under South African conditions (Pretoria area) during all seasons of the year with variations in solar radiation levels and temperature. Furthermore what actually happened to V. cholerae during solar exposure in terms of cell morphology, cell viability and secretion of cholera toxin is also reported and this can give an insight of the possible role that SUVR may play in the onset of cholera. The main recommendation emanating from this study is the sensitisation of communities worldwide about the capacity that, SUVR carries to lighten the burden of communicable water borne diseases especially, in resource limited areas through the implementation of SODIS. / Life and Consumer Sciences / M. Sc. (Life Science)

Vapour pressure (interchangeably referred to as atmospheric humidity) and solar radiation data are, for different reasons, difficult data to obtain in South Africa. Relative humidity measuring instruments (from which vapour pressure values can be obtained) require constant maintenance , while solar radiation can only be measured electronically. Data from both of these variables are, however, required as inputs to the Penman-Monteith equation, which has become the internationally accepted reference for the estimation of potential evaporation. It is necessary, therefore, to produce estimates of vapour pressure and solar radiation over South Africa from more common surrogates, e.g. rainfall and temperature data. Several methods of estimating vapour pressure and solar radiation from the literature are reviewed in this dissertation. Considerably greater attention is focused on models of vapour pressure than solar radiation , as less literature exists on this subject. In general, the methods involved in estimating vapour pressure tend to be relatively rudimentary. The FAO 56 documentation advises using saturated vapour pressure at minimum air temperature as an estimate of vapour pressure, yet the implicit assumptions of using this approach can fail in many circumstances, particularly in the more arid regions . It was found that monthly vapour pressure at any given location in South Africa could be estimated from geographical (invariate) data alone. It was also found that the most influential factor affecting daily vapour pressure at a given location within a given time frame (less than one month) was "air masses". Air masses proved too complicated to model from surrogate data of temperature and rainfall , however, and were thus omitted from the final model. Daily values of vapour pressure and vapour pressure deficit were estimated by holding vapour pressure for a given month constant, but varying temperature on a daily basis It was found that this method produced acceptable results for both elements throughout South Africa. The need for estimating solar radiation has existed for considerably longer than for vapour pressure. Professions other than agriculture, principally architecture and civil engineering, have long required solar radiation data/values. For this reason the art of estimating solar radiation values is better established and more models were available in the literature. Several suitable and recently developed solar radiation models, which use surrogate data (temperature and rainfall) , were identified from the literature survey. These models were then applied in situ and the results were compared with observed values. It was found that the majority of models produced similar output to one another. However, the Liu and Scott (2001) model, which is an enhancement of the Bristow and Campbell (1984) model, was found to be the best available model of those tested, particularly in the more humid locations of South Africa . Verification analyses revealed that the Liu and Scott (2001) model could be used to interpolate solar radiation where a sparse network of solar radiation measuring stations exists, e.g. in the arid locations of South Africa . The structure of the Liu and Scott (2001) model , however, prevented it from being employed in a subsequent exercise on mapping solar radiation over South Africa . For this purpose, the Hunt et al . (1998) model was employed. The estimation of two elements , vapour pressure and solar radiation , was improved upon, and the Penman-Monteith equation can thus now be more confidently applied throughout South Africa. Of these two elements, it is vapour pressure , which, because of a paucity of research to date on the subject, lends itself to expansive research in the future . / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Bibliography: leaves 166-174. / There is a lack of information suitable for planners and architects to determine the distribution and intensity of solar radiation in urban spaces. New, tall buildings often reduce the quality of their immediate environment by intercepting sunlight before it reaches street level. While planners and the local authority recognise the necessity to rehumanise the city centre and to protect spaces with human appeal, certain squares are under threat of being overshadowed by the redevelopment of old buildings on their perimeter. This study explores an alternative to existing methods for evaluating the distribution and intensity of solar radiation. Greenmarket Square in central Cape Town was selected as a study area where radiometer readings at fifty-four points were made at one minute intervals from sunrise to sunset in midwinter. Several examples of graphical methods of depicting the readings are critically discussed and results of the field work are analysed in depth using one of the methods. An attempt is made to relate observations of solar radiation levels to human use of the Square. In addition to providing specific information necessary for a full understanding of the new procedures suggested, broadly-based background material on the subject of sun and shade in urban spaces is provided.

MSc (Physics) / Department of Physics

PhD (Physics) / Department of Physics / The knowledge of solar radiation in this dispensation is crucial. The lack of grid lines in the remote rural areas of South Africa necessitates the use of solar energy as an alternative energy resource. Solar radiation data is one of the primary factors considered for the installation of renewable energy devices and they are very useful for solar technology designers and engineers. In some developing countries, estimation of solar radiation becomes a challenge due to the lack of weather data. This scenario is also applicable to South Africa (SA) wherein there are limited weather stations and hence there is a dire need of estimating the global solar radiation data for all climatic regions. Using a five year global solar radiation (𝐻) and bright sunshine (𝑆) data from the Agricultural Research Council (ARC) and South African Weather Service (SAWS) in SA, linear Angstrom – Prescott solar empirical model was used to determine regression coefficients. MATLAB interface was used whereby the linear regression plots were drawn. Annual empirical coefficients of 22 stations were determined and later the provincial values. The range of the regression coefficients, a and b were 0.216 – 0.301 and 0.381 – 0.512 respectively. The 2006 estimated global solar radiation per station in a province calculated from the modified models were compared with the observed and statistically tested. The root mean square errors were less than 0.600 MJm−2day−1 while the correlation relation ranged from 0.782 – 0.986 MJm−2day−1. The results showed the regression coefficients performed well in terms of prediction accuracy. / NRF