Edson L. Meyer

Microbial anaerobic digestion (bio-digesters) as an approach to the decontamination of animal wastes in pollution control and the generation of renewable energy.

With an ever increasing population rate; a vast array of biomass wastes rich in organic and inorganic nutrients as well as pathogenic microorganisms will result from the diversified human, industrial and agricultural activities. Anaerobic digestion is applauded as one of the best ways to properly handle and manage these wastes. Animal wastes have been recognized as suitable substrates for anaerobic digestion process, a natural biological process in which complex organic materials are broken down into simpler molecules in the absence of oxygen by the concerted activities of four sets of metabolically linked microorganisms. This process occurs in an airtight chamber (biodigester) via four stages represented by hydrolytic, acidogenic, acetogenic and methanogenic microorganisms. The microbial population and structure can be identified by the combined use of culture-based, microscopic and molecular techniques. Overall, the process is affected by bio-digester design, operational factors and manure characteristics. The purpose of anaerobic digestion is the production of a renewable energy source (biogas) and an odor free nutrient-rich fertilizer. Conversely, if animal wastes are accidentally found in the environment, it can cause a drastic chain of environmental and public health complications.

The effect of reduced shunt resistance and shading on photovoltaic module performance

In analyzing , the effects of low shunt resistance and temporary partial or complete shading are often neglected. These factors can however be detrimental to the performance of these modules and specifically, shading may cause irreversible cell damage if the module is not electrically protected. In this study the effects of reduced shunt resistance and shading on PV module performance were investigated. Furthermore, the effect of shading is analyzed for various cell shunt resistances. The ultimate objective of the study is therefore to quantify the inter-dependence of the effect of reduced shunt resistance and shading on PV module performance. This paper investigates the effect of reduced shunt resistance, R/sub sh/, on PV module performance, the effect of shading on module performance and finally discusses the correlation between the effects of reduced shunts and shading. Results obtained indicate that there exists such a correlation.

Computer Simulation of the Mass and Energy Balance during Gasification of Sugarcane Bagasse

This paper investigated the mass and energy balance of the gasification of sugarcane bagasse using computer simulation. The key parameters and gasifier operating conditions were investigated in order to establish their impact on gas volume and conversion efficiency of the gasification process. The heating value of sugarcane bagasse was measured and found to be 17.8 MJ/kg which was used during calculation of the conversion efficiency of the gasification process. Fuel properties and gasifier design parameters were found to have an impact on conversion efficiency of the gasification process of sugarcane bagasse. The moisture content of sugarcane bagasse was varied by 1.14%, 15%, and 25%, respectively. Optimum conversion efficiency was achieved at low moisture content (1.14%) after computer simulation of the gasification process. The volume of carbon monoxide increased at low moisture content. It was also found that maximum conversion efficiency was achieved at reduced particle diameter (6 cm) and at reduced throat diameter (10 cm) and throat angle (25°), respectively, after these parameters were varied. Temperature of input air was also found to have an impact on the conversion efficiency of the gasification process as conversion efficiency increased slightly with increasing temperature of input air.

An Overview of the Control of Bacterial Pathogens in Cattle Manure

Cattle manure harbors microbial constituents that make it a potential source of pollution in the environment and infections in humans. Knowledge of, and microbial assessment of, manure is crucial in a bid to prevent public health and environmental hazards through the development of better management practices and policies that should govern manure handling. Physical, chemical and biological methods to reduce pathogen population in manure do exist, but are faced with challenges such as cost, odor pollution, green house gas emission, etc. Consequently, anaerobic digestion of animal manure is currently one of the most widely used treatment method that can help to salvage the above-mentioned adverse effects and in addition, produces biogas that can serve as an alternative/complementary source of energy. However, this method has to be monitored closely as it could be fraught with challenges during operation, caused by the inherent characteristics of the manure. In addition, to further reduce bacterial pathogens to a significant level, anaerobic digestion can be combined with other methods such as thermal, aerobic and physical methods. In this paper, we review the bacterial composition of cattle manure as well as methods engaged in the control of pathogenic microbes present in manure and recommendations that need to be respected and implemented in order to prevent microbial contamination of the environment, animals and humans.

Temperature Stability of Traditional and Low-cost Modern Housing in the Eastern Cape, South Africa

The aim of this study is to compare the thermal comfort of traditional (Xhosa) huts and low-cost modern houses built under the reconstruction development program (RDP) and the influence of fly ash on brick properties and the indoor environment. A mixing proportion of 50% fly ash produces a brick with lower thermal conductivity and water absorption but with a higher compressive strength, while the clay plasticity decreases with the increase in fly ash. The results indicate that traditional huts offer better thermal comfort than low-cost modern houses, while the fly ash brick house (FABH) has a better thermal performance than the RDP house.

Monitoring current-voltage characteristics of photovoltaic modules

The aim of the study was to build a system to monitor the current-voltage (I-V) characteristics of photovoltaic (PV) modules subjected to outdoor conditions at the University of Port Elizabeth, South Africa. The monitoring of I-V characteristics, module temperature, ambient temperature, and irradiance will enable an analysis of module performance, degradation and or failure. In this paper the design of a low-cost system built to sequentially measure I-V characteristics of seven modules at regular intervals is discussed and an analysis of data obtained is presented.

An Investigation into the Impact of Reaction Temperature on Various Parameters during Torrefaction of Sugarcane Bagasse Relevant to Gasification

Torrefaction of sugarcane bagasse was conducted in an electric muffle furnace at 200, 250, and 300°C in order to establish the impact of heat treatment temperature on various parameters and as a method to improve sugarcane bagasse characteristics for the purpose of gasification. The results show that weight loss of bagasse reduced as temperature of torrefaction increased due to excessive devolatilization. A reduced moisture and volatile matter content as well as improved calorific value were also achieved with increasing temperature of torrefaction. The torrefaction progress was again followed by elemental analysis of the material which showed the presence of C, H, and O in varying proportions depending on torrefaction temperature. The decrease in the weight percentages of O2 and H2 as torrefaction reaction temperature increased resulted in the accumulation of C in the solid product. The thermogravimetric analysis conducted established the maximum reactivity temperature of the torrefied material and revealed that the degradation of torrefied sugarcane bagasse was accelerated by thermal treatment of the material prior to analysis. Finally, the study established that torrefaction at 300°C led to a much more degraded material compared to the lower torrefaction reaction temperatures of 200 and 250°C, respectively.

Inactivation of Selected Bacterial Pathogens in Dairy Cattle Manure by Mesophilic Anaerobic Digestion (Balloon Type Digester)

Anaerobic digestion of animal manure in biogas digesters has shown promise as a technology in reducing the microbial load to safe and recommended levels. We sought to treat dairy manure obtained from the Fort Hare Dairy Farm by investigating the survival rates of bacterial pathogens, through a total viable plate count method, before, during and after mesophilic anaerobic digestion. Different microbiological media were inoculated with different serial dilutions of manure samples that were withdrawn from the biogas digester at 3, 7 and 14 day intervals to determine the viable cells. Data obtained indicated that the pathogens of public health importance were 90%–99% reduced in the order: Campylobacter sp. (18 days) < Escherichia coli sp. (62 days) < Salmonella sp. (133 days) from a viable count of 10.1 × 103, 3.6 × 105, 7.4 × 103 to concentrations below the detection limit (DL = 102 cfu/g manure), respectively. This disparity in survival rates may be influenced by the inherent characteristics of these bacteria, available nutrients as well as the stages of the anaerobic digestion process. In addition, the highest p-value i.e., 0.957 for E. coli showed the statistical significance of its model and the strongest correlation between its reductions with days of digestion. In conclusion, the results demonstrated that the specific bacterial pathogens in manure can be considerably reduced through anaerobic digestion after 133 days.

Analysis of photovoltaic module energy output under operating conditions in South Africa

South Africa does not have any industry standard methodology to evaluate photovoltaic (PV) modules for energy production. The aim of this study is to characterize the energy production of PV modules deployed outdoors at the University of Port Elizabeth (UPE), Summerstrand, South Africa, with the view of facilitating such a standard. The system developed for this study was designed to monitor the energy production of seven PV modules under normal operating conditions. An analysis of energy production of three of the PV modules under test, while operating under prevailing outdoor conditions, is given. Measured energy output is also compared with that predicted using an energy model.

Comparative study of a directly cooled PV water heating system to a naturally cooled module in South Africa

Efficiency of a photovoltaic (PV) solar module is largely affected by high temperatures. High temperatures reduce the efficiency of a module, while lower temperatures contribute towards a higher efficiency. If a module operates under high temperatures it degrades fast and its output and lifespan gets altered. Higher conversion efficiencies were obtained on the directly cooled module as compared to the naturally cooled module. The directly cooled module operated at low temperatures for the entire sunny day reaching a maximum temperature of 34.34°C while the naturally cooled module reached a maximum of 58.64°C. A maximum thermal efficiency of 15.26% was obtained from an un-insulated system.