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Access status: Open Access ,
Finite element method based design approach for low volume roads using dynamic cone penetrometer results
(Central University of technology, 2025-11) Adedeji, Jacob Adedayo
Road networks are fundamental to national development, but their provision should prioritise structural efficiency and long-term sustainability rather than accessibility alone. Despite significant global advances in road construction, a large proportion of roads, particularly in developing and emerging economies, remain unsealed and prone to rapid deterioration. South Africa exemplifies this challenge: although it has the continent’s longest road network (764,978 km), almost three-quarters of its proclaimed roads are unpaved. Sustainable and cost-effective upgrading of such networks to sealed low-volume roads is therefore a pressing need, particularly under financial constraints. The aim of this study was to develop a Finite Element Method (FEM) model that utilises existing Dynamic Cone Penetrometer (DCP) correlations to improve the efficiency and cost-effectiveness of low-volume road (LVR) design, benchmarked against conventional empirical methods. Trial sections were established in two climatically distinct provinces—Northern Cape (dry) and KwaZulu-Natal (wet)—to enable material collection and in-situ testing representative of different geotechnical environments. The methodology integrated in-situ testing, laboratory characterisation, and computational modelling. DCP testing was undertaken across the trial sections to establish penetration resistance profiles, which were correlated with laboratory-derived parameters obtained from grain size distribution, Atterberg limits, California Bearing Ratio (CBR), and repeated load triaxial tests (RLTT). AfCP-LVR software was used to establish empirical DCP–CBR–modulus relationships, while comparative pavement designs were produced using CBR charts, AASHTO 1993, TRH 20, Odemark’s method, mePADS, and FEM simulations. FEM models (2D and 3D) were developed in Abaqus®/CAE to simulate pavement responses under traffic loading, incorporating both unsealed and sealed surface conditions. The findings indicate that while existing design guides such as TRH 20:2009 remain valuable references for unsealed road design, their limitations in accounting for surfacing seal effects underscore the need for integrated analytical approaches. In this study, the FEM model was developed to incorporate material parameters derived from DCP correlations, enabling a mechanistic evaluation of pavement performance under various loading and environmental conditions. This integration provided more consistent and realistic predictions of structural behaviour, particularly with respect to pavement deflections, stresses, and service life, than conventional empirical approaches. Model validation demonstrated strong agreement between mePADS, 2D FEM and 3D FEM Abaqus® simulations, confirming the robustness of the developed modelling framework. Furthermore, the inclusion of surface seals, both single and double treatments, significantly reduced critical tensile strains and extended pavement service life, emphasising the influence of binder stiffness and temperature on overall performance. This study concludes that the integration of DCP testing with FEM modelling offers a robust, field-applicable, and cost-effective approach for the design and upgrading of low-volume roads in South Africa. The research further delivers a simplified design model that incorporates new construction and rehabilitation options, supporting the use of surface seals as alternative wearing courses to achieve durable and economical LVR solutions.
Access status: Open Access ,
The prevalence of multidrug-resistant organisms in the burn units of three hospitals in the Free State and Northern Cape before, during and after the COVID-19 pandemic (1 March 2018–31 July 2024)
(Central University of technology, 2025-09) Beetge, Chene’
INTRODUCTION Antimicrobial resistance (AMR) is a global health threat; it has no limits and knows no borders and can be found on every continent across the globe. The impact is evident with the sixfold increase of AMR that has been seen in the world since 2017. It has been estimated by researchers that by the year 2050 there will be 10 million deaths across the world because of untreatable strains, due to the misuse and overuse of antimicrobials that led to the extensive development of AMR. This study was done to determine the impact that the COVID-19 pandemic had on the further development of AMR by comparing the bacterial resistance pattern before, during and after the pandemic. METHODOLOGY This was a retrospective study, and retrospective data were used to conduct this research. The data that were requested were pre-pandemic (1 March 2018 until 30 February 2020), during the pandemic (1 March 2020 until 30 June 2022), and post-pandemic (1 July 2022 until 31 July 2024). The burn units of the public hospitals of the Free State and Northern Cape were chosen as the study site for the research. The hospitals in the Free State include Pelonomi, National, Universitas, Bongani Regional Hospital, Boitumelo and Mofumahadi Manapo Mopeli Hospital. The hospital of the Northern Cape is Robert Mangaliso Sobukwe. In this study we wanted to determine the resistance profile of the bacteria in the burn units and compare the resistance before, during and after the pandemic. RESULTS AND DISCUSSIONS This study compared the resistance in the burn units of the Northern Cape and Free State before, during and post-COVID-19. It was noted that in most cases, resistance increased during the pandemic, and it did not decrease to the levels it had been before the pandemic. A total of 1 606 samples were collected for this study, of which 1 549 were from the Free State and 57 from the Northern Cape. Due to the small sample size of the North Cape, the results largely reflect those of the Free State. In both provinces Pseudomonas aeruginosa and Staphylococcus aures were the most frequently isolated organisms. In both provinces Acinetobacter baumannii showed a concerning and persistently high resistance (above 80%). The overall resistance increased in the Free State during COVID-19 (35.01% to 38.64%) and increased further post-COVID-19 (39.59%). The resistance rose sharply during COVID-19 in the Northern Cape (28.77% to 52.78%), but the levels decreased again post-COVID-19 (21.05%). The decrease could be attributed to the small sample size for this timeframe. At the organism level, the resistance of Staphylococcus aureus decreased in the Free State from 32.19% pre-COVID-19 to 21.9% post-COVID-19, while the resistance increased drastically to 50% in the Northern Cape during COVID-19. The resistance of Pseudomonas aeruginosa was quite high. It spiked during COVID-19 in the Free State (37.39% to 57.49%) and then decreased slightly (49.49%). The resistance was 34.72% pre-COVID-19 in the Northern Cape with no further comparable data. The resistance of Klebsiella pneumoniae rose markedly during COVID-19 (36.65% to 53.33%) in the Free State and decreased slightly post-COVID-19 (45.03%). Streptococcus pyogenes, while Proteus mirabilis showed a slight decrease in resistance in the Free State over the three timeframes. Escherichia coli showed a sharp decrease in resistance during the pandemic in the Free State (21.5% to 3.92%), and this then increased slightly post-COVID-19 (9.62%). The patterns of increased in resistance post-COVID-19 levels confirm the need for the reinstatement of antimicrobial stewardship programmes in South Africa along with infection-prevention measures in the burn units in South Africa. CONCLUSION Overall, this study has shown that during COVID-19, the AMR increased in the burn units of the Northern Cape and the Free State. Post-pandemic it is shown that the resistance levels remained higher than the levels pre-pandemic. The organisms that are the most concerning was Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae due to the persistence in elevated resistance levels. The resistance patterns vary across the different timeframes for the different antimicrobial classes, with the most worrisome trends seen among the last-resort antimicrobials. However, a common trend is seen, and this is that the resistance levels did not go back to pre-COVID-19 levels. This highlights the urgency of the matter to firstly strengthen and then re-establish the antimicrobial stewardship programmes in South Africa, and then also to prioritize the infection prevention measure in the burn units. If there is no intervention, the resistant infections that are currently in these burn units will continue to threaten and cause further harm to these burn unit patients that are already vulnerable and further strain the South African healthcare systems.
Access status: Open Access ,
Design of a ti-6al-4v heat exchanger using dimensional analysis for use in aeronautical turboshaft engines
(Central University of technology, 2025-03) Bester, Paul Michiel
While post-compression intercooling is a commonly utilised method to increase or optimise the performance of traditional turbocharged internal combustion engine layouts, there exists a potential in installing similar modifications in aeronautical turboshaft engines. The rise of additive manufacturing (AM) techniques now offers the potential for lighter and more compact heat exchangers to be designed and manufactured. To this end, a theoretical intercooler system was designed to cool the charge air supplied by the compressor stages of a turboshaft engine to increase the performance of the engine. With cooler air supplied by the compressor stage theoretically having the capacity to reduce the amount of work required by the compressor stages as well as benefiting the containment effects inside the combustor unit. A benchmark engine was selected and characterised by a simple Brayton gas cycle, which indicated that there was an overall temperature increase of 234.710 °C across the compression process due to the heat of compression. Using the Kays and London method for a full-sized multi-pass heat exchanger, a heat exchanger was successfully designed, which would fulfil all the requirements to evaluate the feasibility of the concept. A test piece was then extracted from the design and successfully manufactured at half scale using Ti-6Al-4V titanium alloy. The theoretical intercooler unit consisting of two full-size multi-flow heat exchangers was able to cool air supplied at a mass flow rate of 1.638 kg/s by an estimated 28.542 °C. Dynamic similarity constraints obtained via dimensional analysis techniques were then successfully applied to determine the experimental testing conditions required to verify the full-scale design. An experimental test bench was designed and fabricated to simulate the required testing conditions to attain dynamic similarity. A series of six tests, consisting of eight readings each, were performed over a time span of two weeks, where exact measurements were taken of the heat transfer across the test piece heat exchanger. The results recorded from the experimental testing phase of the project indicated that the process whereby a portion was extracted from a heat exchanger and verified using dynamic similarity was not only viable but yielded much better results than expected. The experimental results showed a substantial correspondence to the theoretically expected calculations. The outcome of this research aims to clarify the suitability of a heat exchanger manufactured using AM techniques for use in aeronautical turboshaft engines.
Access status: Open Access ,
Antifungal activity and toxicity assessment of traditional medicinal plants commonly used in the treatment of respiratory diseases in South Africa
(Central University of technology, 2025-09) Binyane-Motseki, Moleboheng Emily
Cryptococcus neoformans, Cryprococcus gattii, Aspergillus fumigatus and Candida albicans cause fungal respiratory coinfections in Human immunodeficiency virus (HIV) and Coronavirus disease 2019 (COVID-19) patients. Medicinal plants have been reported to have antifungal activities and other pharmacological properties against these fungal species. Defender is the indigenous herbal medicinal supplement prepared from medicinal plants, including Zingiber officinale, Salvia rosmarinus, Petroselium crispum, Allium sativum, Capsicum annuum, and Cannabis sativa, which have been used traditionally to treat various respiratory conditions and diseases. Felicia and Searsia species have been used traditionally to treat respiratory diseases and conditions. The aim of the study was to assess the antifungal activity and toxicity of traditional medicinal plants commonly used in the treatment of respiratory diseases in South Africa. This study also determined other pharmacological activities of these medicinal plants. Qualitative phytochemical analysis included tests for flavonoids, anthraquinones, tannins, steroids, and terpenoids. Quantitative phytochemical analysis included tests for total flavonoid and total phenolic contents and liquid chromatography coupled with mass spectrometry (LCMS). Total flavonoid and phenolic contents were tested using the Folin-Ciocalteu reagent and the aluminium chloride colorimetric method and were measured spectrophotometrically. The antioxidant activity was analysed using the diphenyl picrylhydrazyl (DPPH) radical scavenging method. The anti-inflammatory activities of the medical plant extract and Defender were determined by measuring their ability to inhibit nitric oxide production in RAW 264.7 macrophages activated by Lipopolysaccharide (LPS). Cytotoxicity of plant extracts and Defender was performed using the Hoechst 33342/Propidium iodide (PI) dual staining method and 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Antifungal activity of plant extracts and Defender was determined against Cryptococcus neoformans, Cryptococcus gattii, Candida albicans and Aspergillus fumigatus using the serial dilution assay. The potential inhibition of plant extracts on human P450 3A4 was determined using a Vivid® CYP450 Screening Kit. Plant extracts and Defender were tested against Cryptococcus gattii and Cryptococcus neoformans in the absence and presence (100-800 μg/ml) of exogenous ergosterol, and their Minimum Inhibitory Concentrations (MICs) were determined after 24 h of incubation at 35°C. Phytochemical analysis revealed the presence of flavonoids, tannins, anthraquinones, and steroids in the aqueous and methanol extracts of Searsia erosa and Felicia filifolia, and steroids and flavonoids in Defender. The highest phenolic contents were found in Searsia erosa methanol extract (426±0.1 mg GAE/g sample) and Defender (236±0.0 mg GAE/g sample), while Felicia filifolia aqueous extract had a phenolic amount of 127±0.0 mg GAE/g sample. The highest flavonoid amounts were observed in Searsia erosa methanol extract (257±3.3 mg QE/g extract) and Defender (86±1.4 mg QE/g extract), and Felicia filifolia methanol extract had a flavonoid content of 83±1.1 mg QE/g extract. LCMS analysis of Felicia filifolia methanol extract revealed the presence of Acerosin, Aphidicolin, Dictamnoside B, Lamiide, and Prostaglandin E2, 5,7,4'-Trihydroxy-3,6,8,3',5'-pentamethoxyflavone, Ranupenin 3-rutinoside, Rutin, Scandoside, and Loniphenyruviridoside D. LCMS analysis of Searsia erosa confirmed the presence of phytochemicals, including chlorogenic acid, caffeoyl quinic acid, 3,4-Dicaffeoyl quinic acid, flavonoid-7-O-glycoside, pentacarboxylic acids, quinic acids and derivatives, saccharolipids, and unspecified terpene glycosides. The antioxidant activities of Defender (74%), Searsia erosa methanol extract (74%), and Felicia filifolia aqueous extract (68%) were higher than those of the positive controls, trolox (64%) and ascorbic acid (53%), at a concentration of 250 μg/mL. The Felicia filifolia methanol extract at concentrations of 50 and 200 μg/ml, the Searsia erosa methanol extract at 7.5 μg/mL, the Searsia erosa aqueous extracts at 50 and 200 μg/mL, and Defender at 500 μg/mL demonstrated potential anti-inflammatory activities. Felicia filifolia methanol extract exhibited the most significant cytotoxicity at a minimum concentration (MIC) of 62.5 μg/mL on Vero cells. Searsia erosa aqueous extract (MIC=1 μg/mL), Defender (MIC=1, 10, 50 μg/mL), and Felicia filifolia methanol extract (MIC=1 μg/mL) were effective against C. neoformans, C. gattii, C. albicans, and A. fumigatus. Searsia erosa methanol extract (MIC=1 μg/mL) only inhibited the growth of C. albicans and A. fumigatus. MICs of all tested extracts and Defender increased in the presence of ergosterol, and the increase was concentration dependent. Results of the CYP3A4 activity assay revealed a concentration-dependent decrease in substrate production for tested extracts. Searsia erosa and Felicia filifolia methanol extracts are potential anti-inflammatory, antioxidant, and cytotoxic (anticancer) agents. They are also potential antifungal treatments against C. albicans, C. neoformans, C. gattii, and A. fumigatus. Defender is a potential antioxidant, anti-inflammatory agent, and antifungal treatment against C. albicans, A. fumigatus, C. neoformans, and C. gattii. Searsia erosa and Felicia filifolia are possible inhibitors of CYP3A4, and this finding has dose implications. Tested plant extracts and Defender are possible antifungal treatments for infections caused by C. neoformans and C. gattii, working by binding to ergosterol. Therefore, these medicinal plants and Defender can be used to treat fungal respiratory infections caused by C. albicans, C. neoformans, C. gattii, and A. fumigatus in COVID-19 and HIV patients.
Access status: Open Access ,
Knowledge, expectations and practices of somatologists in the Free State regarding the regulatory bodies of the somatology profession in South Africa
(Central University of technology, 2025) Claassen, Adri
The somatology profession in South Africa occupies a distinctive position at the intersection of health, wellness, and aesthetics. Despite significant growth and increasing societal demand, the profession continues to operate in the absence of a dedicated statutory regulatory framework. This study was conducted to investigate the professional regulatory context from the perspective of qualified somatologists, with a particular focus on the Free State province. Therefore, the study aimed to examine three core dimensions of professional engagement with regulation: awareness of existing regulatory entities, expectations concerning regulatory responsibilities, and behavioural alignment with ethical and professional standards. Data were obtained through a structured quantitative questionnaire supplemented by open ended responses, allowing for the integration of practitioner insights from individuals currently employed within the somatology sector. The findings revealed a pronounced sense of professional identity and ethical commitment among participants. However, substantial deficiencies were noted in regulatory knowledge, accompanied by inconsistencies in compliance-related practices. Participants expressed a critical need for structured regulation, legal safeguards, and ongoing professional development, all regarded as integral functions of a formally constituted regulatory entity. The observed misalignment between the expanding scope of somatology and the limitations of current governance structures highlights the need for regulatory reform. Accordingly, the outcomes of this study contribute to a deeper understanding of prevailing challenges in professional regulation and offer evidence-based recommendations intended to inform the development of future policy initiatives. Moreover, the results emphasise the imperative for regulatory frameworks to be clear, accessible, and adaptable, in order to promote professional advancement, ensure public safety, and reinforce the legitimacy of somatology as a recognised health-related discipline within the South African context.
Access status: Open Access ,
Energy efficiency improvements in a microbrewery in South Africa
(Central University of technology, 2025-11) Conduah, Joseph Eminsang
The brewing industry constitutes a significant portion of energy demand in the food and beverage sector, with microbreweries consuming approximately 0.65 kWh of electrical energy to produce 1 L of beer, which is almost 50% more than large-scale breweries. This equates to around 5.2% of total production costs, which highlights the critical need for energy efficiency improvements. Despite this substantial consumption, the implementation of optimised energy management strategies remains limited, particularly for thermal processes in craft beer production, which account for 8% of operational costs. More studies are needed to explore effective energy management schemes for breweries, with a particular focus on heating and cooling loads during critical production phases. This study shows that demand-side management, coupled with time-of-use (ToU) tariff optimisation, presents opportunities for significant cost savings in brewery operations. The research aimed to address key challenges in energy-intensive brewing processes, particularly in South Africa, where craft beer production has grown substantially in recent years. This work emphasises predictive modelling of brewery energy performance using machine learning, optimal control strategies, and comprehensive economic analysis to minimise energy costs while maintaining production quality. The study proposes an integrated approach that combines process optimisation, a hybrid thermal–electrical energy system incorporating solar thermal collectors, a heat pump, and TES, and an optimisation-based control methodology designed to leverage ToU tariff structures and reduce peak-period grid dependence. The investigation employed the Performance, Operation, Equipment, and Technology (POET) framework to systematically analyse energy usage patterns in brewery operations. A real-time monitoring system using a Power Quality Analyzer (PEL103) was installed in a Bloemfontein microbrewery to collect detailed load profile data. Subsequently, an artificial neural network (ANN) model was developed using shallow neural net fitting (nftool) to predict energy requirements across various production stages, including mashing, boiling, fermentation, and cold storage. The ANN model processed input variables such as process temperatures, flow rates, and equipment states, which achieved regression values between 0.90 and 0.98, with mean squared errors below 15%. The study also implemented optimisation strategies using model predictive control methods to evaluate hybrid energy system configurations that incorporated renewable sources and thermal energy storage (TES). Simulations demonstrated that shifting energy-intensive processes to off-peak periods could yield 33% cost savings, while the integration of photovoltaic systems with battery storage reduced grid dependence by 10% to 15%. The POET framework analysis projected potential energy savings ranging from 10% to 70%, depending on the level of implementation: conceptual improvements (50% to 60%), active controls (25% to 35%), technical upgrades (60% to 70%), and further engineering optimisations (10% to 20%). The results indicate that TES systems can achieve up to 69% energy savings compared to conventional grid-powered operations, with a breakeven point within 1.5 years for a system that costs approximately USD 50 000. The ANN model proved particularly effective in optimising batch scheduling to align with ToU tariff periods while maintaining product quality standards. Furthermore, the study found that comprehensive implementation of energy efficiency measures could reduce long-term energy costs by 35% over a 20-year period, assuming 5% annual inflation and 10% electricity price increases. The study demonstrates that the synergistic integration of ANN-based predictive modelling, an optimisation-based control strategy, and a hybrid thermal-electrical energy system significantly enhances energy efficiency in microbrewery operations. These integrated methods also improve operational costs by optimising thermal supply, reducing dependence on grid electricity, and increasing the effective use of renewable energy. The developed methodologies provide a replicable framework for energy management in food and beverage production, with particular relevance for small to medium enterprises in emerging markets. The findings underscore the importance of integrated energy solutions that combine technological improvements with operational optimisation to achieve both economic and environmental sustainability goals in industrial processes.
Access status: Open Access ,
Evaluation of different soil shear strength testing procedures taking inherent soil variability into account
(Central University of technology, 2025-10) De Villiers, Vivian Charles
For several decades, geotechnical engineers relied on the Working Load Design approach, where the uncertainty and variability of soil were addressed using subjective global factors of safety. The Limit States Design concept was first introduced in the late 1990s and later adopted in South Africa for geotechnical engineering. This approach involves selecting characteristic values based on experience, cautious estimation, standard tables, and/or statistical methods. However, relying solely on past experience and standard tables may not be sufficient to ensure safety against failure. The most logical approach to estimating the value of a soil parameter seems to be the use of statistical methods. Ensuring a high degree of reliability and confidence in the selected characteristic value requires extensive testing. Most testing standards only require a small number of tests, typically three, to obtain an average or “representative” value. Due to cost and time constraints, it is often unfeasible to conduct a large number of tests on a particular soil. This reduces our understanding and knowledge of the inherent soil variability at hand. To address these challenges three shear strength testing procedures, the vane shear, (undisturbed) fall-cone, and pocket penetrometer, were evaluated to enable more accurate testing and decision-making for measuring inherently variable soils. This leads to more reliable data analysis and establishing a less conservative characteristic value for design inputs. Testing was conducted on cohesive soils across multiple sites in the Mangaung Metro Municipality. The vane shear test proved to be inadequate due to a low shear strength capability. The fall-cone yielded very low penetration readings and underestimated the shear strength compared to the pocket penetrometer. Using Hansbo’s equation to convert penetration data to shear strength values scatters the data and introduces higher variability with an increase coefficient of variation. In contrast, the pocket penetrometer produced more consistent results with lower variation in testing data. None of the test methods appeared to be an ideal fit for a lognormal distribution. To improve shear strength measurements on undisturbed soil samples, the study recommends using a larger cone factor and a modified fall-cone apparatus
Access status: Open Access ,
Developing a communication architecture for improving production efficiency in smart manufacturing
(Central University of technology, 2025) Gericke, Gareth Andrew
Smart manufacturing units have become the latest manufacturing standard within Industry 4.0 for production floor requirements that enable functionality and data structures for the next-generation manufacturing scene. Accompanying these requirements, functionality and structures, there has been a vast sea of research to define requirements within smart manufacturing. These requirements can be satisfied with higher-order structures and lower-level implementations sharing strategies to naturally allow for the flow of requirements and data. The omission of consistency between higher-level and lower-level implementations often leads to lacklustre implementation of smart manufacturing setups, resulting in production inefficiencies and bottlenecks. These issues come as a direct contradiction of the solutions proposed for resolution in smart manufacturing. A literature review of Industry 4.0 and smart manufacturing reveals that there are similarities and complementing features for communication flows throughout all levels of a manufacturing setup. This study classifies these requirements between different levels using a communication architecture. This architecture type looks at the flow of information, organisation of data and a set of rules for responsibilities between levels. These additions allow for control and responsibility of data at each level, allowing for consistency and traceability throughout a manufacturing setup. This study outlines objectives to benchmark a current manufacturing setup in Simulink, identify its production efficiency and other metrics outlined for improvement. Additional objectives for creating a communication architecture, scoring the implementation of this new architecture, comparing the production metrics of the communication architecture against the benchmark and outlining the lifecycle of this architecture follow. Other authors approach the problem of consistency and production improvements with historically altered architecture from software and hardware domains; however, this study evaluates the use of a communication architecture to suggest the selection of this architecture in its applicable scenarios. The communication architecture implementation is tested on the benchmark Simulink model where the results discern meaningful cause-and-effect improvements with traits such as data organisation and responsibilities as opposed to coding timing improvements. The results are discussed to highlight how the communication architecture naturally allows for its requirements to leverage the possibility to include intelligence within smart manufacturing units.
Access status: Open Access ,
Assessment of ultraviolet radiation exposure amongst military outdoor workers: a case study of military outdoor workers at Lohatla, Northern Cape
(Central University of technology, 2025) Galawe, Sipho David
Background: Ultraviolet radiation (UVR) exposure poses significant health risks, particularly for individuals engaged in outdoor occupations. Military personnel, due to their extensive time spent in outdoor environments, are particularly vulnerable to the adverse effects of UVR, which can lead to skin damage, eye disorders, and increased risk of skin cancer. This study focuses on assessing UVR exposure among military outdoor workers stationed in Lohatla, Northern Cape, an area characterised by its intense solar radiation. By measuring ambient UVR levels and correlating them with self-reported health outcomes, the research aims to enhance the understanding of the exposure risks faced by military personnel. The findings are intended to inform the development of effective protective strategies and health guidelines tailored to this unique occupational group. Methodology: A cross-sectional study was conducted among military outdoor workers in Lohatla, Northern Cape, over three months from December 2024 to February 2025. The study involved the deployment of UV dosimeters to measure ambient UVR levels at designated outdoor work sites. Dosimeters were strategically placed in unobstructed areas to ensure accurate readings representative of daily UVR exposure. Data was collected on two separate occasions for each participant, specifically on the first and last days of each bi-weekly monitoring period. In addition to UVR measurement, participants completed structured questionnaires detailing demographic information, duration of outdoor work, sun protection practices, and any reported health issues related to UV exposure. The collected data were analysed to determine the correlation between measured UVR exposure and reported health outcomes, providing insights into the risks associated with outdoor military duties. Ethical approval was obtained from relevant authorities, and informed consent was secured from all participants before data collection. Results: The questionnaire survey was completed by 161 military outdoor workers, comprising males (n=94, 58.39%) and females (n=67, 41.62%). The age category with the most study population was 19 to 25 (n=51, 31.68%). The analysis revealed several significant relationships between sun protection behaviours and health outcomes. A strong positive correlation exists between wearing clothes that cover the arms and legs and avoiding sun exposure between 12 and 3 PM (r = 0.530, p < 0.001) and sunscreen use (r = 0.475, p < 0.001), indicating that individuals who adopt protective clothing are also more likely to engage in additional sun protection behaviours. A moderate positive correlation was found between working around reflective surfaces and blurred vision (r = 0.217, p = 0.006), highlighting potential eye health risks. A moderate positive correlation was found between working around reflective surfaces and blurred vision (r = 0.217, p = 0.006), highlighting potential eye health risks. Additionally, sunscreen use showed a weak but significant correlation with reduced eye pain (r = 0.216, p = 0.006). In terms of health outcomes, sunscreen use is significantly associated with fewer brown spots (r = 0.426, p < 0.001) and a lower incidence of sunburn (r = 0.319, p < 0.001). Conclusion: The study highlights the significant link between occupational health risks faced by military outdoor workers and their sociodemographic characteristics. The results indicate that outdoor military workers in Lohatla face a high risk of skin cancer and other UV-related illnesses, influenced by environmental factors and personal behaviours and no direct relationship between physical activity, sociodemographic characteristics, and UV radiation exposure. Military institutions can enhance their personnel's long-term health and safety by tac
Access status: Open Access ,
Optimizing energy management of a dual-source renewable energy system with thermal storage for hot water production
(Central University of technology, 2025-11) Gaonwe, Tsholofelo Priscilla
Healthcare facilities are one of the most energy-intensive buildings in the commercial sector due to the high energy consumption of space cooling and ventilation, as well as the high-water heating loads, continuous 24-hour operation for the majority of the facilities, and the high number of medical equipment. With South Africa relying almost exclusively on electricity for energy, a considerable increase in electricity prices has been noted in recent years which has placed a major strain on the country’s electricity supplier. Therefore, healthcare facilities tend to experience simultaneously high electricity demand, which exerts significant peak load pressure on the grid. This has, therefore, had a negative effect on both electricity suppliers and customers, resulting in financial and capacity challenges. Water heating is essential in high-capacity healthcare facilities for hygiene, medical operations, and space heating and is one of the high energy consuming processes in these buildings. Most water heating systems used are conventional, relying on fossil fuels or electricity as primary heat sources such as the electric storage tank water heating (ESTWH) systems. These systems are one of the highest contributors to the energy consumption during the high morning and evening peak periods, which may consume approximately 40-50% of the electricity bill, as well as the increase in the carbon dioxide (CO2) emissions. An effective energy conservation measure in the commercial sector is the implementation of demand-side management (DSM) strategies to reduce energy consumption and operating costs. One method explored involves using waste heat recovery (WHR) with thermal energy storage (TES) as a supplementary heat source to preheat water. As this practice is used for the purpose of load shifting under time-of-use (ToU) tariff price signals and optimal control, it guarantees to fulfil the above-mentioned purposes. Additionally, in high-capacity buildings, the high energy consumption may still be a challenge due to the continuous high demands of hot water supply. Incorporating energy-efficient and renewable energy systems such as solar thermal heating (STH) and heat pumps (HP) offers viable energy-saving solutions. These systems may be retrofitted as stand-alone supplementary thermal heat sources or be integrated as the solar-assisted heat pump (SAHP) system enabling energy efficient, stable, reliable and cost-effective heating system, working independently and simultaneously as heat sources. This study contributes to the field by developing an energy management and optimal control of the water heating processes, of WHR-TES tanks integrated with SAHP system, as a hybrid supplementary heat supply. The hybrid source-TES tanks are used to feed water to the 57 ESTWH systems in a high-capacity healthcare building. The system is developed through mathematical model using the analytical formulation approach, developing the system and formulating the optimal control problem for optimal control under the demand-side management (DSM) strategy. The baseline system and the proposed optimally controlled system was then simulated using MATLAB software to obtain the operation profiles of the system performance. Using the same formulation approach, the energy consumption and operational costs were determined for the economic analysis to evaluate energy and cost savings compared with the baseline system. In addition, the artificial neural networks (ANN) modelling was conducted for the performance validation of the proposed system, using some of the acquired data and the simulation results for variable selection, determining the input and output and training the model. The ANN model was developed and generated to train, validate and test the system under the summer and winter conditions using the Levenberg Marquardt (LM) backpropagation function. The ANN was modelled at the proportions of 70%, 15% and 15% of the training, validation and testing models, with each variable having 288 data points. Due to the tanks’ different parameters of the TWS tanks and the 57 ESTWH systems, with different sizes of 100L, 150L, 200L and 250L, the tanks were grouped by their parameters and different models were developed for summer and winter cases. The TWS tanks had 5 input variables and one output variable, which is the pre-heated water temperature inside the TWS tank and the ESTWH systems 4 input variables and one output variable, which is the hot water temperature inside the each ESTWH system. The data used for the ANN modelling was prepared, cleaned and processed using the MATLAB and Microsoft Excel worksheet. From the simulation results of the analytical models obtained, the optimally controlled system was able to shift the heating loads of the multifarious ESTWH systems to the off-peak periods of the ToU pricing structure. Additionally, the SAHP system, heating the preheated water in the TWS tanks and supplying the makeup hot water to the multifarious ESTWH systems has resulted in reducing, and even eliminating, the use of the electric resistive elements for most of the multifarious ESTWH systems. Consequently, the hot water temperatures inside the multifarious ESTWH systems were maintained within the range of 50 ℃ to 60 ℃, which is safe considering the health of the patients. The system was able to reduce the use of electrical power, during the operation, and shift the heating loads to the cheapest ToU pricing signals while maintaining the required heating loads, as well as the delivering the water at the safe temperature to the end users. For the economic analysis, the initial costs of the baseline case were lower as compared to the optimally controlled proposed case, which have however accumulated to be very high at the end of the project lifespan. This is due to the high cumulative costs incurred because of the continuous energy consumption throughout the day, even during the peak periods, where the energy costs are very high. Conversely, the optimally controlled proposed system accumulated lower costs at the end of the project lifespan due to the retrofitted renewable energy source water heating system, the optimal control and shifting the water heating loads to the ToU pricing signals. The analysis indicated the accumulated energy costs of 261.57 USD and 133.57 USD for the summer case and 625.34 USD and 145.09 USD for the winter case for the baseline system and optimally controlled proposed system, respectively, from the simulated results for a period of 24 hours. From the economic analysis calculations, in a typical day, the cumulative energy costs obtained for the baseline system and proposed optimally controlled system are 32.05 USD and 15.61 USD for the summer case and 83.96 USD and 18.55 USD for the winter case, respectively. For the energy and cost-saving analysis, the estimated potential annual energy savings were 15,001.93 kWh, equivalent to approximately 49.6% per annum. This amount of energy may equate to 15.93 metric tons of CO2 per year. At the beginning of the project, the costs of implementation of the baseline and the proposed systems are approximated to 40,464,82 USD and 93,335.37 USD, respectively. Over the estimated project duration of 20 years, based on the calculated results, the baseline system and the proposed optimally controlled system may achieve 943,559.91 USD and 341,860.80 USD of the cumulative energy costs, 74,817.81 USD and 94,755.08 USD of the cumulative replacement costs, 13,996.05 USD and 32,283.01 USD of the cumulative operation and maintenance costs and 8,092.96 USD and 18,667.07 USD of the salvage costs, respectively. Finally, at the end of the project span, comparing the proposed optimally controlled system with the baseline system, the total life-cycle costs may therefore be approximated to 1,064,745.62 USD and 543,567.18 USD, respectively. These estimates equate to the cost savings of 521,178.43 USD, which is about 48.95% of the costs of the baseline system saved. These results show significant economic and energy-saving potential, demonstrating a viable solution for reducing the energy consumption and operational costs in healthcare facilities. The ANN models indicated high prediction accuracy, with correlation coefficients (R-values) above 0.95 across training, validation, and test phases. TWS tank obtained higher R-values for the summer case of 0.99414, 0.99518, and 0.98063 and 0.99219 for training, validation and test, respectively. For the ESTWHS, the 100L and 150L size parameters obtaining higher R-values for the summer case and 200L and 250L size parameter models for the winter case. The 250L size parameter obtained the highest R-values of 0.99988, 0.99984 and 0.99988 for the summer case and 0.99986, 0.99984 and 99981 for the winter case, respectively, for training, validation, test results. For performance validation of the models, TWS tanks obtained the lowest MSE errors for the winter case, training for 16 epochs and indicating training phase MSE, cross-validation phase MSE and the testing phase MSE errors of 2.22e-05, 2.14e-05 and 1.97e-05, respectively, at 10th epoch. For the ESTWH systems, comparing the MSE errors between summer and winter cases for each season, 100L and 150L size parameters achieved lower MSE errors indicating more effective training for the winter case, whereas for the 200L and 250L size parameters it was for the summer case. When comparing between the size parameters, the 250L size parameters obtained the lowest errors for both cases, training for 21 epochs, obtaining 2.91e-08, 4.08e-08 and 3.08e-08 at 21st epoch for the summer case and training for 13 epochs, obtaining 3.26e-08, 4.54e-08 and 6.00e-08 at 13th epoch of training phase MSE, cross-validation phase MSE and the testing phase MSE results, respectively. For error distribution, TWS tanks indicate good concentration ranging between 70 – 80% around the zero for both summer and winter cases, indicating lowest maximum error range of ±0.015 for the winter case. For the ESTWH systems, the 200L and 250L size parameters show strong concentration of data points over 90% around the zero-error region, for both the summer and winter cases, with the lowest maximum error range obtained in the summer case for both size parameters, within ±0.05 and ±0.0007, respectively. For the 100L size parameter, good concentration ranges between 70 – 80% around the zero and the maximum error range obtained in the winter case within ±0.04. Whereas the 150L size parameter shows strong concentration over 90% of data plots around the zero-error region for the summer case and good concentration ranging between 70 – 80% around zero, where the lowest maximum error range is obtained in the winter case within ±0.04. These results confirm the robustness and adaptability of the developed ANN model across diverse operating conditions, making it a valuable tool for predicting the thermal performance of advanced hybrid water heating systems. Overall, this study contributes a practical, rapid, and reliable AI-based modelling approach for thermal heating systems, offering opportunities for improved energy efficiency, system responsiveness, and informed decision-making in building and industrial energy management contexts. For future research, the proposed water heating process of incorporating WHR-TES, SAHP system and energy management and optimal control may further be customized for various commercial buildings, from small clinics to large hospitals, hotels, etc., depending on their energy needs and available infrastructure. Additionally, other types of solar heating systems or heat pump setup may be explored in different climate conditions considering the geographical locations, for the system to work efficiently and assist in energy and costs savings. Furthermore, the integration of optimisation algorithms (e.g. GA, PSO) to the ANN model of the particular or similar system and also incorporating hybrid AI models (e.g. ANFIS or ANN-LSTM), may be explored.