ResearchSpace :: Browsing by Author "Grobler, Jan-Hendrik"

Browsing by Author "Grobler, Jan-Hendrik"

Now showing 1 - 17 of 17

A comparison of LiDAR and meteorological mast wind measurements in the Karoo
(2024-09) Grobler, Jan-Hendrik; Malatji, DB
Accurate wind resource assessments are key to developing efficient wind farms. Due to the steady rise in the dimensions of wind turbines in recent years, meteorological masts with heights of 100m and beyond are typically now required for wind resource estimation. There is a need to explore alternative methods in the interest of saving time and costs. In this study, an analysis is done to determine the feasibility of using new technologies based on remote sensing, such as LiDAR (Light Detection and Ranging), for measuring wind speed and wind direction. A measurement campaign was conducted over a 16-day period using ground based LiDAR and one of the meteorological masts erected near the town of Sutherland as part of the Wind Atlas of South Africa project. Sutherland is situated in the South African Karoo, an area known for relatively high altitude, generally non-complex terrain and low aerosol levels. A WindCube V2 LiDAR unit was deployed at the meteorological mast site. Measurements taken with the LiDAR and cup anemometers on the mast were compared at heights of 40m and 60m. A regression statistical analysis was performed on the datasets to calculate metrics such as the coefficient of determination. Data filtering, which includes wind speed range selection and application of LiDAR data availability thresholds, is done to ensure compatibility between the two datasets. In addition, an adjustment was required to account for time stamp differences between the data sets. The wind speed and winddirection results between the LiDAR and cup anemometers compared well. The coefficient of determination was 0.98 or higher for the two datasets evaluated.
A summary of green hydrogen as an upcoming energy storage technology
(2024-10) Karamanski, Stefan; Grobler, Jan-Hendrik; Hlalele, Thabo G
The increasing renewable energy production trend poses concerns about energy dispatchability. The intermittency of renewable energy requires compensating reliable and suitable energy storage technologies. An upcoming energy storage technology is green hydrogen. Green hydrogen has received both extremes of praise and criticism from the energy industry. This study aims to dispel misconceptions about green hydrogen. Green hydrogen and its applications are thoroughly yet concisely described, together with its suitability in power systems. The advantages and disadvantages of green hydrogen are discussed. It was found that green hydrogen has significant benefits of longterm energy storage and strong suitability in heavy industries. Despite green hydrogen decreasing in cost, it is still comparatively expensive and suffers from significant logistical constraints. Green hydrogen remains an important factor in the renewable energy transition and forms an integral component of the energy storage of the future. This study is useful for policy makers, system operators, renewable energy developers and financial institutions that would like an improved understanding of green hydrogen and its integration.
An aerodynamic CFD analysis of inlet swirl in a micro-gas turbine combustor
(2023-07) Meyers, Bronwyn C; Grobler, Jan-Hendrik; Snedden, GC
A combustor was designed for a 200N micro-gas turbine [1, 2] using the NREC preliminary combustor design method [1, 2, 3]. During the design process, there are various aspects where there are no definitive methodologies for specifying the design detail, such as the design of the hole-sets, and multiple options can be derived that can satisfy the required mass flow split and pressure drop for a particular hole-set.
Comparison of predicted design efficacy and environmental assessment for tuberculosis care facilities in South Africa
(2015-12) Nice, Jako A; Kumirai, Tichaona; Conradie, Dirk CU; Grobler, Jan-Hendrik
The impact of Tuberculosis (TB) is of epidemic proportions in South Africa (SA) being one of the developing countries. Furthermore, studies seem to indicate that health care facilities are contributing to the spread of Mtb (Eshun-Wilson et al. 2008). The contribution that the built environment has on airborne transmission, combined with erratic energy supply and the international sustainable agenda raised the need for research investigation for passive design building response for airborne contagion. Natural ventilation uses buoyancy or wind as the driving forces for air movement. In this paper Computational Fluid Dynamics (CFD) models were used to find out the optimum design for naturally ventilated Tuberculosis (TB) ward designs. Natural ventilation can reduce the concentration of airborne pathogens through removing and diluting airborne droplet nuclei. The effect of different parameters such as roof angle, window type and size, positioning of closures in the permanent ridge ventilators on natural ventilation performance were studied. The results indicated that the correct combination of the parameters mentioned can significantly improve the natural ventilation effectiveness. Tracer gas tests using carbon dioxide (CO2) were subsequently conducted for the real spaces with natural ventilation systems as designed using CFD to establish the actual ventilation rates achieved. The ventilation rates results indicate generally good to excellent ventilation rates especially in the coastal regions. These rates are in line with the recommended rates as per the World Health Organisation (WHO) and Centres for Disease Control (CDC). A Post Occupational Evaluation (POE) was undertaken through qualitative questionnaire and site assessment to evaluate the impact and potential success of the as built modelled design. It is evident though the various staff interviews and project team discussions that the new facilities have improved nursing standards and patient ward standards.
Developing demand driven ventilation criteria for airborne infection control in congregate spaces
(2020-07) Van Reenen, Tobias H; Grobler, Jan-Hendrik
This article presents the case that 12 air changes per hour (ACH) does not provide adequate control against the amplification of disease in different indoor congregate settings. It proposes an occupancy and risk-based algorithm for determining ventilation rates for spaces with a high airborne disease transmission risk. The method modifies the Wells-Riley airborne disease transmission model with the indoor space’s local disease amplification rate to estimate a ventilation limit in terms of space, disease, risk and population. This proposed ventilation capacity sizing strategy is subsequently economical, adaptable and application-specific in ways deficient in prescriptive ACH limits. While acknowledging that proximity effects increase individual exposure risk, the modelling conducted shows that far-field exposure is dominant in large congregate settings. It was found that the per-person ventilation demand tends to a definable lower limit as occupancy increases. This reveals how ACH is not a universally comprehensive metric.
Evaluating the efficacy of solar chimneys for heating and cooling: A case study
(Alive2Green, 2019-03) Grobler, Jan-Hendrik; Conradie, Dirk CU; Van Wyk, Llewellyn V
The Department of Science and Technology (DST) together with the Eastern Cape Department of Education (ECDOE) are co-funding the construction of a science centre in the village of Cofimvaba in the Eastern Cape. The purpose of the science centre is to promote the study of science, technology, engineering and mathematics (STEM) in the school district. The Council for Science and Industrial Research (CSIR) was appointed as DST’s Implementing Agent for the project. The express purpose of this appointment was to pilot, evaluate and demonstrate the application and efficacy of innovative building technologies (IBTs) on the project in accordance with a South African Government Cabinet Resolution of August 2013 regarding the application of IBTs in government projects. A key objective is to apply IBTs to enhance the economic, social, environmental and institutional sustainability of public buildings. For this project attention is focused on achieving net-zero energy and water consumption, and reducing waste water disposal and construction waste. A key strategy to achieve a net-zero building was to eliminate reliance on mechanical heating and cooling.
The importance of integrated system design for the effectiveness of portable air cleaners in airborne infection
(The Union, 2013-12) Van Reenen, Tobias H; Salie, F; Jensen, P; Nardell, E; Grobler, Jan-Hendrik
The results of the recent study into the effectiveness of portable air cleaners (PACs), as an infection control measure against TB, delivered unexpectedly low results. That finding initiated a further study to understand the contribution of system design to the effectiveness of PACs in airborne infection control. The objective of this further study was to quantitatively evaluate the contributions of combined ventilation and PAC systems and identify factors with the potential to reduce the functional effectiveness of such systems.
Modelling of fluid-solid interaction using two stand-alone codes
(2010-01) Grobler, Jan-Hendrik; de Villiers, R; Cooper, Antony K
A method is proposed for the modelling of fluid-solid interaction in applications where fluid forces dominate. Data are transferred between two stand-alone codes: a dedicated computational fluid dynamics (CFD) code capable of free surface modelling via the volume of fluid (VOF) approach and a physics engine code capable of predicting the movement of objects based on inputs of forces and moments. The method is weakly coupled, but has the advantage of accommodating a large number of independent objects which are allowed to touch or even overlap.
The numerical aerodynamic investigation of swirling inlet flow in a vaporizer tube micro-gas turbine combustor
(2022-09) Meyers, Bronwyn C; Grobler, Jan-Hendrik; Snedden, GC
A combustor was designed for a 200N micro-gas turbine for the model aircraft industry using the NREC design method. Multiple designs resulted which varied in terms of annular area split configuration, hole area splits and relative hole positions. In a previous study two likely preferable designs were selected using a devised scoring method. For this study, the effect of inlet (diffuser outlet) swirl on the internal aerodynamics of the two combustor designs previously chosen was investigated using a RANS CFD analysis. For each of the two designs a set of varying flow angles was applied at the inlet to the simulation domain. The effect on the establishment of the primary zone features is of specific interest; however, the effects and consequences of the swirl throughout the combustor were investigated. Some of the results such as mass flow splits and pressure drop are already quantitative in nature, however, the evaluation of the quality of the recirculation zone, mixing and outlet plane flow are of a more qualitative nature. A scoring system was previously devised in order to apply a quantitative value to the qualitative aspects of the flow, such as Recirculation zone (Rz), Outlet and Mixing, which are initially analysed subjectively. For each feature, the designs were subjectively evaluated relative to each other and given a rating/score. This scoring methodology for ranking different combustor designs proved to be an effective method for evaluating the effect of inlet swirl on the flow features and behaviour of the chosen combustor designs and thus provide an indication of the likely performance changes to be expected. The methodology was able to indicate which of the two top designs was the better option when considering inlet swirl, however the potential for improvement was revealed when considering scoring in a global context. This study suggests that for this engine, the inlet swirl could allow for the removal of NGV before the turbine since the flow is fairly well conditioned and “pre-turned” due to the swirling flow progressing to the outlet of the combustor. The removal of the traditional NGV allows for a reduction in NGV pressure losses which compensates for the increased combustor pressure loss experienced due to increased inlet swirl.
Optimising the energy mix for eco-industrial parks in developing countries: A least-cost analysis using PYPSA
(2024-11) Grobler, Jan-Hendrik; Karamanski, Stefan; Zandamela, Frank
As a result of persistent loadshedding since 2008, numerous industries have increased their efforts to adopt alternative energy technologies to lessen their reliance on the national grid. Industrial spaces are no exception, particularly with the emergence of eco-industrial parks - a group of manufacturing and service businesses situated on a shared property. Questions arise regarding how much an industrial park can decrease its reliance on the national grid and how much emissions can be reduced by utilizing an optimal combination of available energy technologies. These questions are addressed through a least-cost optimisation case study of a medium-sized eco-industrial park. A customised capacity expansion planning tool built on the opensource platform Python for Power System Analysis (PyPSA) is employed in the study. Renewable energy is sourced from rooftop solar PV and an offsite wind installation. Energy storage is provided by commercially available LiFePO4 containerised lithium-ion batteries. The model assumes a multiyear simulation horizon, with learning rate assumptions for the renewables based on the NREL Annual Technology Baseline report. Several scenarios are modelled, and the outcomes are compared to a "business as usual" case, where reliance is solely on the national grid and no embedded renewable energy is employed. The study shows that the employment of currently available renewable energy solutions offers industrial spaces a significant cost saving and a reduced carbon footprint while simultaneously reducing their dependence on the grid.
Performance of a solar chimney by varying design parameters
(Alive2Green, 2015-08) Kumirai, T; Grobler, Jan-Hendrik; Conradie, Dirk CU
Trombe walls and solar chimneys are not widely used or well known in South Africa. A previous Green Building Handbook article described the University of Fort Hare teaching complex in East London (Stratford, 2012) that inter alia used a trombe system for a naturally ventilated building. This article explores the use of these passive devices further. Solar chimneys are passive elements that use solar energy to induce a buoyancy force that drives airflow and naturally ventilate the building. Buoyancy refers to one of the mechanisms by which motion in fluids such as air is caused by natural means. Buoyancy forces are induced by density differences due to the variation of temperature of the fluid: warmer and thus lighter fluid rises and cooler and thus denser fluid sinks.
The effect of combustor hole-set arrangement when comparing two different hole-set design methods
(2024-07) Meyers, Bronwyn C; Grobler, Jan-Hendrik
This presentation focuses on the effect of combustor hole-set arrangement when comparing two different hole-set design methods.
The numerical comparison of various hole-set design methodologies for a micro gas turbine combustor
(2024-09) Meyers, Bronwyn C; Grobler, Jan-Hendrik
A combustor design programme was initiated to design a combustor for a 200N microgas turbine. The method is that of a phased approach in order to gain better insight into the effect of various aspects of the combustor geometry as well as the combustor boundary conditions. The preliminary combustor design was performed using the NREC design method resulting in multiple designs to consider. This first phase focused on the Annuli mass flow splits and ensuring an improved Primary zone by devising a configuration conducive to a Recirculation zone approaching that shown in the theory. In order to make design selections, and later evaluate the effects of boundary conditions and design methods, a scoring and ranking method was devised to effectively evaluate the cold flow CFD simulation results. The second phase involved the evaluation of the effect of inlet swirling flow on the designs selected in phase one. This study, constituting phase three, is focused on the design of the Secondary and Dilution zone hole-sets using multiple methods available in literature, namely Lefebvre, Lefebvre and Ballal, and Mattingly et al. The purpose of this design phase is to improve the Secondary and Dilution zone holes. The resultant hole-sets were evaluated for practicality and manufacturability and adjustments were made to the number and size of the holes while maintaining a constant Total hole-set area (Aht) and attempting to maintain a constant Jet Diameter - Momentum flux ratio (djJ0.5). In addition to the design improvements, the aim is to compare four additional design methods and identify the preferred hole-set design method as well as to evaluate whether the applied adjustments maintain the penetration depths as was indicated should be the case in the literature. It was found that although the Lefebvre method produced some improved designs, it also produced many designs that were not improvements, thus it can not be said that the particular method is a better one. In addition, there weren’t highly evident trends that emerged with the systematic changes, thus a change in the combustor design approach could be beneficial which involves design through the optimisation of a complete parameter space to determine a better design per application or engine.
The use of physics engines in quantifying breakwater damage
(2013-07-08) Gledhill, Irvy MA; Greben, JM; Cooper, Antony K; De Villiers, R; Grobler, Jan-Hendrik
The response of proposed breakwater packing strategies to incident waves is usually tested and evaluated in a model hall. There is currently also increasing interest in using numerical simulations to model both the packing of a breakwater, and its response to storms. In this paper, we test the use of physics engine software, which provides fast modelling of hundreds of units, as a means of gaining insight into damage quantification and breakwater disorder. Both dolosse and Antifer armour units are investigated. An order parameter P2 is proposed which is shown, using the numerical models, to be a useful measure of orientational order or disorder when the randomness of the packing is in question. A root-mean-square displacement parameter is proposed as a measure of the movement of armour units from their original positions under cyclic forces. Both parameters are easy to use in simulations and the use of these parameters in model halls and in the field is discussed.
Using battery energy storage systems and renewable energy to reduce municipality energy costs: A South African town case study
(2024-11) Karamanski, Stefan; Grobler, Jan-Hendrik; Erfort, G
With the ever-increasing energy challenges in South Africa, towns are interested in reducing their dependence on the system operator along with optimising their energy usage. A town in the Western Cape region of South Africa, Hermanus, aims to become the sustainable energy hub of South Africa by having a high renewable energy (RE) penetration. It is also in their interest to reduce energy costs as much as possible. In this case study, RE sources coupled with battery energy storage systems (BESS) are modelled to achieve this goal. Other considerations such as electric vehicle (EV) charging facilities are also important to consider in the town’s planning. A Homer Grid model is developed in this research. It includes the process of load profiling, utility tariff structuring, grid connection capacity, grid sales, load shedding, PV and wind generation, energy storage, EV charging and economic modelling. An LCOE of R1.37/kWh was achieved by including 6 MW of PV and 4.5 MW of wind in the model, together with a 39 MWh lithium-ion BESS. The model achieved its objective by reducing the annual consumption and demand charges by R175 million. The economic modelling yielded an internal rate of return (IRR), return on investment (ROI) and payback period of 25.3%, 39.5% and 5.1 years respectively. The model performs as expected, by minimising costs, maximising RE self-consumption, intelligently managing the BESS to mitigate unserved loads, and effectively allowing the town to operate more energy independently. This research is valuable for stakeholders such as town planners, renewable energy developers, BESS developers, grid operators, transmission line planners and EV institutions.
Viability of open-source wind resource assessment software
(2024-08) Karamanski, Stefan; Grobler, Jan-Hendrik
As the world shifts towards renewable energy sources, newer and larger projects come to fruition every year. Renewable energy projects require a complex analysis before proceeding with development. Part of this analysis procedure is resource assessment. This research aims to determine the viability of using open-source software for industry applications. This is performed through a comparison of the current industry standard software, WAsP, and Continuum. A site with a wide range of land cover conditions is chosen to see how the different software performs under varying conditions. Multiple different measured wind data inputs are used in the comparison, allowing for a comprehensive study. A focus is made on the software’s accuracy, while also comparing the analytics and outputs. The interface, workflow, input data, outputs, computational cost and additional requirements of each software package are discussed. It is found that Continuum is accurate within 8% when compared to WAsP’s annual energy production and capacity factor outputs. Due to the open-source nature of Continuum, it also lends itself to further customised developments that could be advantageous when performing resource assessments. WAsP is found to have preferential reporting outputs, however. This research highlights the opensource resource assessment process, from input to output.
Wind resource assessment: Open-source methods and analysis in South Africa
(2024-10) Karamanski, Stefan; Grobler, Jan-Hendrik; Erfort, G
The energy mix in South Africa has a rapidly increasing renewable energy penetration, but it is still being dominated by fossil fuels at approximately an 80% share. It is evident that development of renewable energy plants have prolonged durations, especially in the case of wind energy. One of the major preliminary requirements in this development is a wind resource assessment to evaluate the suitability of a potential site. This can be very expensive and difficult. The Wind Atlas of South Africa (WASA) supplies publicly available time-series wind data for South Africa. This research aims to describe a Python-based method of creating accurate desktop wind resource assessments in South Africa using the WASA data as an input. Subsequent energy modelling software requires a time-series of capacity factors from the resource assessment, which is useful in further integrated analyses, such as in energy master plans. The model’s performance is evaluated on capacity factor outputs from Continuum, an open-source wind resource assessment software package. It was found that the Python-based model performs reasonably well, producing a 32.69% capacity factor compared to Continuum’s 35.5% result, obtained from a site in Mpumalanga, South Africa. By creating this model based on publicly available data and open-source coding practices, the wind development process is simplified. The suitability of wind energy as a preferable energy resource as well as the suitability of a potential site is supported by this research. Stakeholders such as wind farm developers, municipalities, planners and energy operators can find value in this research.

Browsing by Author "Grobler, Jan-Hendrik"

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