Physics

Despite the enormous advantages associated with biogas technology, the level of awareness and perceptions still remain very dismay. The level of adoption is relatively low compared to the potential of the technology. This chapter therefore aimed at unravelling the awareness and perceptions of the technology at household level in Limpopo Province of South Africa. In this study, 200 households were sampled; 72 households with biogas digesters and 128 without digesters. Primary data collection was elicited with the use of open- and closed-ended questionnaires. A non-parametric test of Spearman rank correlation coefficient and chi-square were employed to show the association between the variables. Empirically, the results revealed that income earned, cost of digester, lack of awareness programmes, water and feedstock availability, technical availability and assistance, and private sector participation are among the factors limiting the dissemination, awareness and perception of the tech...

The encasing of wind turbines in a duct to enhance performance is not new. A ducted wind turbine produces more power than an unducted wind turbine of the same parameters. A number of approaches in studying the effects of diffusers and other wind concentrating devices have been done and have resulted in a number of prototypes produced but without any commercialization. The aim of this paper is to investigate the failure of commercialization of ducted turbines. A technical and economic analysis of a ducted turbine is also presented. The work shows that traditional economic methods used to evaluate ducted wind turbines are erroneous; they do not account for external effects of power generation and individual and community benefits derived from this technology. Failure to penetrate the market is due to negative publicity as a result of the erroneous evaluation undertaken and lack of appropriate engineering techniques to protect ducted wind energy systems in extreme wind conditions.

This paper reports the results of the temperature profile of the unheated and unstirred continuous fermenting bio-slurry in a fixed-dome Deenbandhu 2000 model. The digester is a brick-built system of bulk size 6 m 3 . The digester was monitored for eight months, measuring internal bio-slurry temperature. A K-type nickel chromium-nickel temperature sensor with a sensitivity of approximately 41 µV  and response time of 0.8s in liquids was positioned at the centre of the digester to measure the slurry temperature. The sensor was connected to the data logger and programmed to record temperature readings every second for the entire study period. The study results reported give a clear indication about the reaction of bio-slurry temperature in the digester at a local level, particularly for the eight months’ period, which covered all seasons. The calculated values of the daily average temperature reveal that the digester was operating within the range of psychrophilic 10.32  and mesophili...

Despite the enormous advantages associated with biogas technology, the level of awareness and perceptions still remain very dismay. The level of adoption is relatively low compared to the potential of the technology. This chapter therefore aimed at unravelling the awareness and perceptions of the technology at household level in Limpopo Province of South Africa. In this study, 200 households were sampled; 72 households with biogas digesters and 128 without digesters. Primary data collection was elicited with the use of open-and closed-ended questionnaires. A non-parametric test of Spearman rank correlation coefficient and chi-square were employed to show the association between the variables. Empirically, the results revealed that income earned, cost of digester, lack of awareness programmes, water and feedstock availability, technical availability and assistance, and private sector participation are among the factors limiting the dissemination, awareness and perception of the technology in the province. The study recommends interventions through more elaborate awareness and promotion programmes in disseminating the technology as well as provision of technical assistance, loans, credits and subsidies to households willing to adopt the technology.

Storing hydrogen in metals has received much attention due to the advantages of this approach for safely storing. It is a promising method of storing hydrogen and eliminates the challenges associated with storing hydrogen gas at high pressure, which includes material durability, tank safety, and overall weight. Much work has been done for the past decade to bring this approach closer to wide-scale application. However, much experimental research is needed to improve the volumetric and gravimetric capacity, hydrogen adsorption/desorption kinetics, material life cycle, and reaction thermodynamics of potential materials for hydrogen storage. Other important properties to consider are transient performance, the regeneration process of spent storage materials, effective adsorption temperature associated with activation energy, induced pore sizes in materials, increasing pore volume and surface area, and materials densification. In recent years, this solid-state storage has progressed at conditions close to normal atmospheric pressure and temperature, with metal hydrides (MHs) emerging as a promising option. Their high storage density per unit volume, volume storage capabilities, and their ability to reverse the process while maintaining stability have qualified the MHs for low-pressure storage and fulfilling the hydrogen storing requirements. However, understanding the principles of kinetics and thermodynamics is crucial for understanding the reactions of MHs as they absorb and release hydrogen. This review evaluates the current hydrogen storage methods, the different types of MHs, their thermodynamics and kinetics, as well as their applications and challenges. For the advancement of further research in this field of study, suggestions for future work and studies are also provided.

Given the limited observed and reliable data for solar irradiance in rural parts in South Africa, a correlation equation of the Angström-Prescott linear type has been used to estimate the regression coefficients in the Vhembe District, Limpopo Province, South Africa. Five stations were selected for the study, with the greatest distance between stations less than 180 km. Monthly regression coefficients were derived for each station based on an observation dataset of sunshine duration hours and global horizontal irradiance. The correlation coefficients appear to be above 0.9. The representative Angström-Prescott model for the Vhembe Region was found by collating the data for each station and then averaging the respective correlation coefficients. This paper presents the generated regression coefficients for each station and for the Vhembe Region.

Given the limited observed and reliable data for solar irradiance in rural parts in South Africa, a correlation equation of the Angström-Prescott linear type has been used to estimate the regression coefficients in the Vhembe District, Limpopo Province, South Africa. Five stations were selected for the study, with the greatest distance between stations less than 180 km. Monthly regression coefficients were derived for each station based on an observation dataset of sunshine duration hours and global horizontal irradiance. The correlation coefficients appear to be above 0.9. The representative Angström-Prescott model for the Vhembe Region was found by collating the data for each station and then averaging the respective correlation coefficients. This paper presents the generated regression coefficients for each station and for the Vhembe Region.

The theoretical and computational studies of dye sensitized solar cells (DSSCs) can contribute to a deeper understanding of these types of solar cells. The DSSCs are the novel design of solar cells which could be used as power producing windows or skylights. They represent a particular promising approach to a direct conversion of sunlight into electrical energy at low cost and with high efficiency. The light adsorption occurs in dye molecules adsorbed on a highly porous structure of TiO2 film. Despite the progress in the efficiency and stability of these solar cells, there is still a room of research on some of their operational aspects that are still not understood. One process, for which there is limited information, is the time taken to upload the dye on the TiO2 nanoporous film. The processes followed experimentally for dye uptake is by dipping the TiO2 semiconductor electrode into the dye solution for periods of several hours to several days. However, such long dipping times are not economical for industrial production of DSSCs. The factors controlling this process are not yet fully investigated. We propose a simple model based on the Langmuir isotherms to study and understand the diffusion and adsorption of the dye molecules in TiO2 films. Our computational modelling results show that the adsorption of dye into the TiO2 nanotubes film is controlled by the diffusion coefficient, the adsorptiondesorption ratio and the initial dye concentration. Our results show that the initial dye concentration plays an important role on the surface coverage. It is also noted that for a higher concentration shorter immersion time is needed for the sufficient surface coverage. Furthermore, it is observed that for the large values of the adsorption-desorption ratio there is a delay in the diffusion of dye molecules on the surface.

The South African Weather Service (SAWS) manages an in-situ solar irradiance radiometric network of 13 stations and a very dense sunshine recording network; located in all six macro-climate zones of South Africa. A sparsely distributed radiometric network and over a landscape with dynamic climate and weather shifts is inadequate for solar energy studies and applications. Therefore, there is a need to develop mathematical models to estimate solar irradiation for a multitude of diverse climates. In this study, the annual regression coefficients, a and b, of the Ångström-Prescott (AP) model that can be used to estimate global horizontal irradiance from observed sunshine hours were calibrated and validated with observed station data. The AP regression coefficients were calibrated and validated for each of the six macro-climate zones of South Africa using the observation data that spans 2013 to 2019. The predictive effectiveness of the calibrated AP model coefficients was evaluated by co...

The measurement of solar radiation is difficult to carry out due to the cost and techniques involved especially in developing countries like South Africa. A variety of solar models with different weather parameters as inputs have been used to estimate the global solar radiation around the world. Since air temperature records are readily available around the world, models based on air temperature for estimating solar radiation have been widely accepted. Estimation of global solar radiation (H) from the daily range of air temperature (ΔT) offers an important alternative in the absence of the measured H or sunshine duration.  In our present work, the estimation of the monthly average daily global solar radiation for Pretoria has been determined, based on two models:  Hargreaves -Samani and Clemence. The performance of the two models is validated by comparing the measured and the estimated global solar radiation for the three different stations under study. The statistical comparison be...

An attempt has been made to employ three different theoretical models for the determination of global solar radiation for the climate conditions of the Vhembe district of Limpopo Province in South Africa. The models are: 1) the Angstrom linear-based model, 2) the Hargreaves and Samani (temperature-based) model, and 3) the Garcia model. These models require the following meteorological data inputs: temperature, sunshine hours, and global solar irradiance on the horizontal surface. The regression coefficients from our previous study were also employed in the calculations. A 4-year (2007-2010) global solar irradiance and temperature data set from the Agricultural Research Council and the actual sunshine data set from the South African Weather Services were used. The monthly average global solar irradiance for the four selected areas of study were computed and compared with the in situ data. The results obtained show that the Angstrom linear and temperature-based models are suitable methods for predicting the global solar irradiance in this study area. The difference between the observed and the predicted data is less than 6.5 MJ/(m 2 day). Their root mean square error varies between 0.0112 and 0.0368. Graphical representations of the irradiances versus the days of the year showed high values during summer for all the models used.

Due to its variability, solar power generation poses challenges to grid energy management. In order to ensure an economic operation of a national grid, including its stability, it is important to have accurate forecasts of solar power. The current paper discusses probabilistic forecasting of twenty-four hours ahead of global horizontal irradiance (GHI) using data from the Tellerie radiometric station in South Africa for the period August 2009 to April 2010. Variables are selected using a least absolute shrinkage and selection operator (Lasso) via hierarchical interactions and the parameters of the developed models are estimated using the Barrodale and Roberts’s algorithm. Two forecast combination methods are used in this study. The first is a convex forecast combination algorithm where the average loss suffered by the models is based on the pinball loss function. A second forecast combination method, which is quantile regression averaging (QRA), is also used. The best set of forecas...

An attempt has been made to employ three different theoretical models for the determination of global solar radiation for the climate conditions of the Vhembe district of Limpopo Province in South Africa. The models are: 1) the Angstrom linear-based model, 2) the Hargreaves and Samani (temperature-based) model, and 3) the Garcia model. These models require the following meteorological data inputs: temperature, sunshine hours, and global solar irradiance on the horizontal surface. The regression coefficients from our previous study were also employed in the calculations. A 4-year (2007-2010) global solar irradiance and temperature data set from the Agricultural Research Council and the actual sunshine data set from the South African Weather Services were used. The monthly average global solar irradiance for the four selected areas of study were computed and compared with the in situ data. The results obtained show that the Angstrom linear and temperature-based models are suitable methods for predicting the global solar irradiance in this study area. The difference between the observed and the predicted data is less than 6.5 MJ/(m 2 day). Their root mean square error varies between 0.0112 and 0.0368. Graphical representations of the irradiances versus the days of the year showed high values during summer for all the models used.

The use of interactive computer simulations in improving the teaching and learning of physical science is considered. The importance of interactive computer simulations is the ease of being recycled and hence its sustainability. It can be reworked, retried and used by the learners. The simulations are simple computer programmes that are able to move or represent difficult concepts, ideas or representations. The research in this case was to compare Interactive Computer Simulations with the traditional talk and chalk. The background to this research is the difficult faced by learners in doing experiments in school using traditional equipment. An alternative is looked at in this research – the use of interactive computer simulations. Use of these simulations could be easier for the educators and learners. The experimental design is quasi-experimental, using intact non equivalent group design. The research design is a switching replications design whereby the treatment and control group...

The use of interactive computer simulations in improving the teaching and learning of physical science is considered. The importance of interactive computer simulations is the ease of being recycled and hence its sustainability. It can be reworked, retried and used by the learners. The simulations are simple computer programmes that are able to move or represent difficult concepts, ideas or representations. The research in this case was to compare Interactive Computer Simulations with the traditional talk and chalk. The background to this research is the difficult faced by learners in doing experiments in school using traditional equipment. An alternative is looked at in this research-the use of interactive computer simulations. Use of these simulations could be easier for the educators and learners. The experimental design is quasi-experimental, using intact non equivalent group design. The research design is a switching replications design whereby the treatment and control groups are used at certain times of the research. The study consisted of 104 learners from four schools in a rural setting in a predominantly rural province in South Africa. The learners were from four different schools which were selected purposively in such a way that the school average final grade 12 results were above 50% for a period of four years. The research design of switching replications design was used since it suited the different educator factors we had, with a teacher in each school confident with use of computers while others had to be strongly supported before using the computer simulations. These differences could be reduced through seeing them in both the control and treatment conditions hence the switching replications design. This also meant the intact classes would be the treatment group at one time and a treatment one in the other. Different groups would be seen how they reacted as a treatment group and also as a control group. In the case of the switching replications design with special reference to the treatment group in the first cycle, we would be able to determine if the treatment effect carries on to the second cycle when the roles are reversed and the group is a control group. There are two hypotheses that are looked at in this paper, the first one is, Interactive computer simulations will lead to higher performance on an achievement test than the traditional talk and chalk The second one was Interactive computer simulations will lead to a higher speed of answering questions in a unit on geometrical optics than the traditional chalk and talk method. The theoretical framework used for this research is based on the Sweller's Cognitive Load theory and Mayer's Multimedia Theory of Learning. The over-arching theoretical framework is the information processing wherein in order for information to go to the long term memory it must have been in the germane load. Sweller's Cognitive Load theory posits that the cognitive load is based on intrinsic, extraneous and germane loads (Mayer & Chandler, 2001 (Paas, Renkl, & Sweller, 2003)). The intrinsic load is based on the content or curriculum package, in our case, the geometrical optics, the way we teach and what we use to teach will determine the extraneous load and finally the free and what is left over is the germane load, the memory resources left for learning the actual stuff. On the other hand Mayer's

The aim of the study was to compare the effects of the use of interactive computer simulations for cognitive load change of grade 11 learners in the acquisition of knowledge and a science process skill in geometrical optics. Both the use of computer simulations and traditional teaching was teacher centred. The study was done in a rural area in South Africa, in the Limpopo Province in the district of Vhembe. The theoretical framework was based on the information processing model. Within the non-equivalent quasi experimental design a switching replications design study was used whereby 105 learners in four schools took part. This study found that in terms of the acquisition of knowledge, female learners gained more by the use of simulations than their male counterparts. No significant effect was found in the acquisition of the skill when computer simulations were used. Initial reduction of cognitive load was found when simulations were used and with time this increased. Experienced educators reduced the cognitive load through use of their knowledge and expertise and their role needs to be highlighted. Further studies are suggested to study the effect of a learner centred approach on decreasing the cognitive load and its effect on the acquisition of knowledge and skills.