Browsing by Author "Cowan, Bill"

Now showing 1 - 11 of 11
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    Battery performance characterisation for stand-alone photovoltaic systems
    (1991) Purcell, C J de V; Eberhard, Anton; Cowan, Bill
    One of the main factors limiting optimisation of PV system designs over the life of the system has been the lack of battery test data appropriate to PV applications. The main objective of this study was to determine accurate empirical data for locally available lead-acid batteries which could be used in photovoltaic systems and to present this data in a format directly applicable to PV system designers. The study included (i) a review of battery performance regimes typical of PV systems; (ii) a literature review of lead-acid battery performance and reactions important to PV applications, battery electrical models, battery life models, a review of specialist PV battery designs and the interaction of battery and voltage regulator in PV systems;. (iii) a review of testing and research literature, and the design of a suite of experimental procedures suitable for characterising batteries under PV operating regimes; (iv) the design and construction of a specialised battery test-unit to automatically perform tests and capture data; (v) selection, testing and characterisation of five generic types of batteries which could be used in local PV applications. The five types of lead-acid battery were: 1) conventional calcium alloy positive and negative grids, flat plate, flooded electrolyte, vented casing; 2) low antimony alloy positive grid, conventional calcium negative grid, flat plate, flooded electrolyte, vented casing; 3) low antimony alloy positive grid, heat treated calcium negative grid, flat plate, immobilised absorbed electrolyte, sealed casing with 0 2 cycle gas recombination; 4) antimony alloy positive and negative grids, flat plate, flooded electrolyte, vented casing; 5) antimony alloy positive and negative grids, tubular plate, flooded electrolyte, vented casing. Selenium grid alloy cells and gelled electrolyte batteries were not represented amongst the batteries tested, owing to problems of availability or cost.
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    The development of an energy education package for secondary schools
    (1994) Oxenham, Peter Eric Clinton; Cowan, Bill
    The central objective of this project was to develop a package of energy education workshops for secondary schools. The package contains nine energy workshops. Each workshop comprises a teacher's guide and a student worksheet. The package production process included choosing an education methodology, reviewing energy themes for selection as workshop topics and evaluating the energy workshop package. This dissertation provides insight into the processes of producing this package. My participation in the Community Education Resource's Masters programme introduced he goal of producing university resources in formats which are accessible to a broader audience. Energy themes for the workshops were drawn from a review of existing resources, particularly those f the Energy for Development Research Centre, and were selected for their relevance to energy as an agent of development, energy production and environmental concerns, energy policy formulation and vocational interest.
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    The electricity poverty tariff in South Africa : possibilities and practicalities
    (2000) Mavhungu, Justice; Cowan, Bill
    The general objective of this thesis is to investigate what price system will result in a sustainable electrification programme, a viable EDI, fit into the regulation system and address issues of equity and poverty. Specific attention is paid to the proposals around poverty tariffs for low-income domestic users. This research examines the form, level and financial implications of poverty tariffs in South Africa. The following are the specific objective of the thesis: * To evaluate the current system of prices in South Africa * To investigate what poverty tariff structures are possible and * To investigate the financial implications of poverty tariff options and their sustainability.
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    Energy policies for sustainable development in South Africa: options for the future
    (Energy Research Centre, University of Cape Town., 2006) Davidson, Ogunlade; Kenny, Andrew; Prasad, Gisela; Nkomo, Jabavu; Sparks, Debbie; Howells, Mark; Alfstad, Thomas; Winkler, Harald
    The purpose of this publication is to present a profile of energy in South Africa, assess trends and analyse some options for the future. It is divided into two parts – Part I presents a profile of energy and sustainable development in South Africa, while Part II uses modelling tools and indicators to assess future policy options for the country.
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    Evaluation of two prototype three phase photovoltaic water pumping systems
    (1994) Scholle, Axel; Cowan, Bill; Greene, John
    Two prototype three phase AC photovoltaic pump systems (Solvo, ML T) and a DC PV pump (Miltek) were tested on a farm borehole in Namibia (latitude 21°6', longitude 17°6'). The PV array consisted of twelve modules (636Wpeak) mounted on a single-axis passive tracker. The depth of the water was 75m and a progressive cavity pump with a self-compensating stator was used in all the tests. Customised data acquisition was designed to measure performance characteristics through a range of operating conditions (mainly steady state); a secondary data acquisition system was used to capture samples of high frequency signals. The data allowed detailed analysis of system, subsystem and component performance, as well as performance evaluation over Standard Solar Days. The focus of the investigation was evaluation of the AC prototypes, in terms of performance, other technical factors, reliability and economic criteria. The analog-based DC system served as a basis for comparison. Both AC systems employed microprocessor control and PWM variable-frequency variable-voltage inversion. Efficiencies, optimality, stability, start-up behaviour, non-productive operating modes and protection were examined. A number of recommendations were proposed for improvements in the basic control algorithms, monitoring and managing non-productive modes, improved protection, layout and user diagnostic features.
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    Farmworker families : towards equitable and adequate energy provision
    (1994) Hofmeyr, Ilne-Mari; Cowan, Bill; Eberhard, Anton
    Farmworker families that live and work on commercial farms are amongst the poorest people in South Africa. Poverty is experienced in several dimensions, including low cash income, poor access to services, isolation, intermittent and insecure employment, dependence on employers, and limited social, economic and political power to improve their conditions. This study investigates the worker households' access to and use of energy, in order to identify their domestic energy needs. An evaluation of energy supply, including all fuels used by workers, is undertaken. Guidelines for strategies to improve farmworker households' access to energy services are proposed. The research relied on the analysis of empirical information from both primary and secondary sources and placed this in an integrated energy planning framework. Primary data included a national postal survey of farmers (3000 questionnaires were sent, 575 returned) and interviews with worker families in the West Cape.
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    Global review of CSP technologies
    (2011) Sikhosana, Qedile; Cowan, Bill; Bennett, Kevin
    This global review of concentrating solar power (CSP) technologies is based mainly on an assessment of available international literature, up to 31 October 2011. It includes a review of major CSP projects currently operating or under development at this time; the respective CSP technologies employed; and an assessment of the present and future economics of CSP relative to other conventional and renewable energy electricity-generating technologies. Global outlook scenarios for CSP are discussed, as well as specific conditions and proposals for CSP developments in South Africa. The economic analysis has been limited by several challenges. Since the CSP industry is new, there are few well-documented projects on which to base the analysis. Most of the projects referenced here are from the USA and Spain. As the CSP market rapidly expands, competition in the industry tends to restrict the disclosure of detailed financial/economic information for projects under development. In general, it has been difficult to compare the publicly available economic data, on a reliable basis, since the financial costing parameters used may vary from case to case. In addition, most of the economic forecasts, which have been reviewed, are based on forward modeling rather than practical proven costs. There are uncertainties and quite wide variations in such predictions. This dissertation concludes, however, that there is great optimism for the growing employment of CSP technology in the near future and that CSP electricity-generating costs, in areas with high solar energy resources, are expected to become competitive with levelised electricity generating costs from other conventional and renewable energy technologies. The cost reduction potentials for CSP lie mainly in expected technical research and development advances, and production economies of scale, achieved by high volume deployment, supported by mid-term investment incentives from governments and other agencies. Another cost reduction potential, especially in the South African context, lies in the localization of skills and local fabrication of some plant structures and components.
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    The impact of electricity shortages on large- and medium-scale manufacturing industries in Ethiopia
    (2005) Woldesenbet, Almaz Bekele; Cowan, Bill
    This study examines the impact of electricity shortages on the Large- and Medium-Scale Manufacturing Industry (LMSMI) in Ethiopia, using data obtained from a case study of 16 LMSMI firms that was undertaken in Addis Ababa from January 2004 to February 2004. In addition, the study examines the causes of these electricity shortages. Ethiopia's electricity supply relies very heavily on hydroelectric power, with geothermal, natural gas, solar, coal and diesel together providing only 1% of the total electricity supply. Significant power shortages occurred in the years 1995/96, 1997/98 and 1999/2000, with a particularly severe power shortage happening in 2002/03. The causes of these included a general increase in electriCity demand, without a corresponding increase in installed hydropower capacity, and a sustained period of drought. The case study findings showed that power outages were particularly costly in the LMSMI sector, through production and raw materials losses, damage to equipment, and the additional investment and operating costs of self-generation among those firms that purchased and used their own diesel generators as a backup source of electriCity. The case study results indicated that power outages caused firms without backup generators to lose approximately 15% to 30% of their potential production in 2002/03. Even in the other years when the power shortages were less severe, losses could reach up to 10%. By extrapolating the sampled firms' production losses to the total number of LMSMI firms in the country, it can be estimated that the country may have lost 10% to 15% of total yearly gross value of production that could have contributed from this sector and 1 % to 3% of total yearly government revenue. In the past, because of the low level of development in the Ethiopian LMSMI sector, the costs of power outages on this sector had not been as big, despite their high frequency. It is envisaged that, when the country's economy grows and the government's new policy (the Agricultural Development-Led Industrialization strategic plan) increases the economy's dependence on LMSMI production, then power outages would certainly have a much greater impact on the LMSMI sector as well as on the total economy of the country. In order to avoid this, therefore, some of the constraints which contributed to power shortages in the past (such as poor planning and governance, bad decision-making, and a lack of integrated planning), should be addressed. In addition, unplanned power outages, which, according to the firms interviewed, had an even greater impact than scheduled power outages, should be minimized. Hopefully, in the future, these measures will improve the performance and reliability of the electriCity supply in the country.
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    An investigation into the performance and problems of first-year engineering students at the University of Cape Town
    (1992) Jawitz, Jeff; Martin, JB; Cowan, Bill
    The first- and second-year results of the 1989 engineering student intake were analysed and revealed that matriculants from Black Education Departments performed significantly worse in the first year than those from White Education Departments. Matric point scores were found to be good predictors for White Education Department matriculants, but less so for Black Education Department matriculants, with matric Physical Science a better predictor than matric Maths, for both first- and second- year courses. Using interviews and a survey of students, a set of academic and non-academic problems experienced by first-year engineering students were identified with black students found to have experienced a particular set of problems to a greater degree than white students. The data produced a portrait of the interaction between first-year engineering students and the academic and social systems of the university. The dominant feature that emerged was one of distance between the individual students and elements of the university environment, including staff, fellow students and the academic material. Factors from the student's personal and educational background that appeared to accentuate this experience of distance were identified. Recommendations to the Engineering Faculty were compiled on the basis of this analysis together with student suggestions for improving the first-year engineering programme.
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