Browsing by Author "Bekker, Bernard"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Classified atmospheric states as operating scenarios in probabilistic power flow analysis for networks with high levels of wind power
    (Elsevier, 2021) Dalton, Amaris; Bekker, Bernard; Koivisto, Matti Juhani
    ENGLISH ABSTRACT: Large-scale atmospheric circulation patterns are the primary drivers of wind power variability on power networks at timescales of hours to days. This paper proposes a methodology that allows power system operators and planners working on networks with high levels of wind generation, to conduct probabilistic power flow (PPF) analyses by defining network ‘operating scenarios’ – i.e. the probability density functions of generators, and correlations between generators representative of a future system state – based on concurrent classified atmospheric states. The most significant contribution made by this paper is in illustrating how PPF operating scenarios derived from clustering historic generation data as a function of a set of classified atmospheric states reduces simulation uncertainty within a PPF analysis. It is anticipated that the proposed methodology may provide network planners with more appropriate operating scenarios for PPF analyses when compared to an unclustered base state, and may assist network operators in converting wind power point-forecasts into probabilistic forecasts whereby the spatial correlations between generators are incorporated. This methodology is illustrated through a case study considering 11 geographically disperse wind generators on the South African transmission network.
  • Thumbnail Image
    Item
    Methods to extract maximum electrical energy from PV panels on the earth's surface
    (Stellenbosch : Stellenbosch University, 2004-12) Bekker, Bernard; Beukes, H. J.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: This thesis investigates methods to extract the maximum amount of electrical energy from a py panel. The thesis is divided into four parts, focussing on different aspects relating to this topic. The first part will investigate the role that py energy is likely to play in South Africa's future energy scenario, by looking at topics like the greenhouse effect and the economics of energy production. Secondly the thesis will look at how to position py panels optimally for maximum energy generation through the year. A software model of a py panel is developed which can calculate available py energy and energy generation costs for a given location, based on parameters like the positioning of the py panel and historic weather data. Thirdly the optimal design of a maximum power point tracker is investigated. The optimal design, based on a k-sweep voltage ratio maximum power point tracking algorithm, is implemented using a DSP controlled boost converter circuit. Finally, the best methods to store energy generated using py panels are explored. Energy storage technologies are compared for rural, off-grid applications in South Africa, and the design and implementation of a pulse-charging lead-acid battery charging strategy is explained.
  • Thumbnail Image
    Item
    Valuation of pumped storage in capacity expansion planning: a South African case study
    (MDPI, 2021) Van Dongen, Caroline; Bekker, Bernard; Dalton, Amaris
    ENGLISH ABSTRACT: According to South Africa’s national energy policy, network penetration of variable renewable energy (VRE) generation will significantly increase by 2030. Increased associated network uncertainty creates the need for an additional flexible generation. As the planned VRE is mostly nonsynchronous PV and wind generators, additional ancillary services will also be required. Pumped Storage (PS), which is a well-established flexible generation technology with fast ramping capability and the ability to contribute various ancillary services, could help integrate increased VRE penetration on the South African network. However, in the latest revision of South Africa’s energy policy, PS was left out in favor of gas turbines and batteries as favored flexible generation options. This paper explores the two-part hypothesis that PS was disadvantaged in the formulation of a national energy mix due to: (a) ancillary services provided by PS not being explicitly monetized in energy modeling software; (b) the uncertainties associated with project costing assumptions. The value of PS in terms of providing ancillary services is firstly explored using the international literature. Secondly, the impact of input-cost uncertainties is demonstrated by comparing pumped storage, gas turbines, and batteries using levelized cost of energy (LCOE) curves and the Tools for Energy Model Optimization and Analysis (Temoa), North Carolina State University, USA, optimization software. Based on LCOE calculations using revised cost assumptions, it is found that PS may indeed be preferential to gas turbines or batteries, particularly at large load factors. The authors hope that this research contributes to the scientific understanding of the role that PS can play in supporting the integration of generation from renewable sources for effective grid operations.