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Research Publications (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215

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Subject: search.filters.subject.Optimization

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Now showing 1 - 8 of 8
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    On demand and supply management in domestic microgrids
    (Turkish Online Journal of Qualitative Inquiry (TOJQI), 2021-12-01) Chidzonga, Richard; Nleya, Bakhe; NLEYA
    Standalone or residential microgrids (MG) are becoming increasingly common. Their success is premised on optimal operational strategies like demand side management (DSM). It is not uncommon in optimization problems to deal with competing objectives in the context of multi-objective optimization. In a domestic MG, optimization objectives may encompass minimization of OPEX, maximization of consumers’ utility, and minimization of CO2 emissions etc. This article employs a technique which transforms a bi-objective energy optimization problem into a single objective problem, then solving the problem using the heuristic technique of binary particle swarm optimization (B PSO). The random phenomena associated with the statistical load profiles and multiple renewable energy sources (RESs) are modelled using established statistical approaches. Results obtained using simulation show that the pro-posed model can minimize the OPEX of isolated MG whilst simultaneously meeting the utility expectations of the consumer.
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    Optimization of university campus microgrid for cost reduction: a case study
    (Trans Tech Publications, Ltd., 2022) Akindeji, Kayode Timothy; Tiako, Remy; Davidson, Innocent
    This paper presents an optimization model to minimize the fuel cost and CO2 emision on university campuses using an hybrid power system (HPS). The HPS is made up of solar photovoltaic (PV), diesel generator (DG), wind turbine (WT) and battery energy storage system (BESS). Two university campuses are used as case study to investigate the efficiency of the proposed HPS. The objective function is formulated such that each campus load is met by the renewable energy source (RES) when available and the DG only swicthes on when the output of the RES is not eneough to meet the load. The resulting non linear optimization problem is solved using a function in MATLAB called “quadprog”. The results of the simulation are analyzed and compared with the base case in which the DG is used exclusively to meet the entire load. The results show the effectiveness of the optimized HPS in saving fuel when compared to the base case and reflect the effects of seasonal variations in fuel costs.
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    Energy optimization for a smart prosumer
    (PONTE International Scientific Researches Journal, 2020-04) Chidzonga, Richard F.; Nleya, Bakhe
    This paper outlines the optimization of cost of electrical energy consumption for a small microgrid typical of a residential area where each household has renewable generation capability and the daily load is portioned into essential none-interruptible and schedulable or interruptible loads. Dual tariffs exist, for buying and the other for in-feed into the utility grid. The optimization makes appliances scheduling decisions to suit prevailing power availability as well amount of power to sell or procure from the utility depending on availability and prevailing real time pricing. We assume availability of time-variant energy parameters, then formulate a global optimization problem whose solutions leads to quantification of the optimal amount of energy purchased and sold for each of the individual households. When the unrealistic assumption of availability of information is removed from the implementation of the global optimization, an online algorithm that only requires the current values of the time varying supply and demand processes shows by simulation that the distributed algorithm can realise credible scheduling of prosumer household electricity usage. This is imperative as the very requirement of involving the consumer for appliances scheduling defeats the optimization cause as humans are not suitable for such repetitive and mundane tasks.
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    Optimisation of a hybrid PV-diesel system for rural application : the case of Oluundje village, Namibia
    (University of Namibia, 2017) Hamatwi, E.; Nyirenda, C. N.; Davidson, Innocent Ewaen
    The absence of electricity in remote and rural areas is one of the major challenges faced by many poor and developing countries. Hybrid energy systems (HES) based on photovoltaics (PV) are considered to be an effective option to electrify remote and isolated areas, which are far from conventional grids. This is true for areas that receive high averages of solar radiation annually. This research investigation involves the modelling, simulation and optimization of a PV-Diesel hybrid system for Oluundje village in Namibia. A site survey was conducted in a form of questionnaires and interviews for the purpose of load forecasting and system modelling. HOMER software was used to design and model the proposed hybrid energy system. Costs of different components, hourly solar radiation, and rating parameters are inputs of the simulation program. Sensitivity analysis was carried out using Homer. The optimal PV-Diesel hybrid system and diesel-generator-only system were compared both technically and economically. Based on simulation results, it was found that electrifying a remote village using a PVdiesel hybrid system is more advantageous when compared to the diesel-generator-only system as it has lower operating costs and emissions. This system may be used as a preliminary design to guide in the planning and modelling of similar systems for other remote villages.
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    Data pre-processing for process optimization at a drinking water treatment plant in Ugu District Municipality, South Africa
    (Business Perspectives, 2015) Magombo, James; Dzwairo, Bloodless; Moyo, Sibusiso; Dewa, Mendon
    When testing and recording water quality data from treatment plants, errors arise. The errors are in the form of re-cordings left blank (missing values), obvious errors in writing or typing, or they can be as a result of values being very small to detect and are therefore censored. The censored values are known to be below the limit of detection (LOD). In statistical analysis, the blank cells can be filled with a certain value. Censored values are often corrected by substituting with a constant value throughout. This value will be a fraction of the limit of detection and most commonly used frac-tions are, half the limit of detection, the limit of detection divided by the square root of 2, or multiplying the limit of detection by 0.75. The direct substitution method for handling missing and values below the limit of detection results in a uniform distribution for values below the limit of detection, and a true distribution for those above. As a result, treat-ment of the values below the limit of detection is dependent upon their percentage in the sample size. An alternative method used will mimic the characteristic of the distribution pattern of the values above the limit of detection to esti-mate the values below it. This can be done with an extrapolation technique or maximum likelihood estimation. In this study, data from the Umzinto Water Treatment Plant was used to develop a data pre-processing program using Visual Basics for Applications (VBA) and Microsoft Excel 2013. The procedure involved 4 stages: data preparation, data pre-processing for blanks and non-detects, data pre-processing for the censored values and finally the identifica-tion of the outliers. The developed program was then used to pre-process raw water quality data, which resulted in satisfactory process time and data conversion. The methodology used can be borrowed for the pre-processing of data driven environmental models and hence it has a great influence on sustainability of water treatment plants.
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    A comparative analysis of evolutionary algorithms in the design of laminated composite structures
    (De Gruyter, 2015) Tabakov, Pavel Y.; Moyo, Sibusiso
    Abstract: The increased use of composite materials and structures in many engineering applications led to the need for a more accurate analysis and design optimi-zation. While methods of stress-strain analysis devel-oped faster, optimization techniques have been lagging behind. As a result, many designed structures do not ful-fill their full potential. The present study demonstrates the major achievements in recent years in an application of evolutionary algorithms to the design optimization of fiber-reinforced laminated composite structures. Such structures are of much interest due to high structural design sensitivity to fiber orientations as well as complex multidimensional discrete optimization problems. Using an anisotropic multilayered cylindrical pressure vessel and an exact elasticity solution as an example, we show how the optimum, or near–optimum, solution can be found in a more efficient way.
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    A technique for stiffness improvement by optimization of fiber steering in composite plates
    (Springer, 2010) Tabakov, Pavel Y.; Walker, Mark
    A methodology for stiffness improvement by optimal orientation of fibers placed using fiber steering techniques of composite plates has been developed and is described here. A genetic algorithm is employed to determine the optimal orientation of the tow fibers and, in addition, once the plate has been divided up into cells in order to apply the technique, the orientation gradient between adjacent cells is capped. The finite element method (FEM) is used to determine the fitness of each design candidate. The approach developed also differs from existing ones by having a more sophisticated chromosome string. By relying on the algorithm for the calculation of the fiber orientation in a specific cell, a relatively short and rapid convergence string is assembled. The numerical results obtained show a significant improvement in stiffness when the fiber orientation angle is allowed to vary spatially throughout the ply.
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    Lay-up optimization of multilayered anisotropic cylinders based on a 3-D elasticity solution
    (Elsevier, 2006) Tabakov, Pavel Y.; Summers, E. B.
    Exact elasticity solutions are obtained using the stress function approach, where the radial, circumferential and shear stresses are determined, taking into account the closed ends of the cylindrical shell. The system of the governing algebraic equations is derived to accurately analyse a multilayered pressure vessel with an arbitrary number of layers and any thickness. The approach used is straight-forward compared to other three-dimensional solutions found in the literature. The design of multilayered composite pressure vessels is accomplished using the genetic algorithm and subject to the Tsai–Wu failure criterion. The genetic algorithm is optimized to serve this particular problem