No description available.

No description available.

Eskom, the sole supplier of electricity in South Africa is facing an energy crisis. This is due to the steady increase in demand for electricity in South Africa. Low electricity prices in South Africa have helped the energy intensive industries of South Africa to be more competitive. Unfortunately this has resulted in poor energy efficiency practices and has hampered incentives to save energy. To address this problem, Eskom initiated a Demand Side Management (DSM) programme. DSM is beneficial to both Eskom and the client. However, due to the high cost of implementing such projects, it is feasible to implement it only on sites where the load shift potential is high enough for Eskom to benefit. The mining industry has been targeted for DSM programmes. This is due to the existence of a large mining sector in South Africa and to its energy intensive nature. Most mining operations require large amounts of water which is used to cool the underground environment and so ensure productivity and the safety of the workers. Due to the large amounts of water needed for mining, the electricity usage of these pumping systems is very high. If the use of this electricity can be optimised by implementing DSM principles, this will result in the long term savings of costs for the mines involved. The majority of pumping systems found on mines are single shaft systems. Individually these systems have a very high DSM potential. However, if multiple shaft systems can be used for DSM, the benefits will be far greater. Furthermore, combining several sites with an interconnected water pumping system will increase the potential for DSM and enable sites where individually the potential is too low to be feasible for a DSM project to raise their potential. This will result in more sites where DSM projects can be implemented and more clients who can benefit from the DSM programme. The purpose of this study is to investigate and implement a DSM project on an intricate multi-shaft mine pumping system which will be controlled from a single point. The project required a detailed investigation of the pumping systems on each shaft and how the water system is interlinked between the shafts. This project was carried out on Beatrix Mine Shafts 1, 2 and 3. The pumping systems were analysed and simulated according to the specific constraints and requirements that were specified by the mine. During the investigation and implementation of this project, possible efficiency improvements on certain pump stations were discovered and implemented. The improvements enabled both an increase in water flow to the surface and a decrease in power consumption. Due to this load reduction, the savings achieved were higher than those found in most load shifting projects. Moreover, additional infrastructures were installed to ensure communication between pumping systems. Once the simulation and optimisation of the control system was completed, the pumping system network was automated. The load shift resulted in a ± 3.5 MW shift in the morning peak demand period and a ± 6.0 MW shift in the evening peak demand period. This load shift has resulted in an average cost saving of R 80 000 per month during summer tariff period, and R 300 000 per month during winter tariff period. This saving result was calculated by taking load reduction into account. This project has shown that a DSM project can be implemented successfully, given the necessary historical data and expertise, on a pumping system that is interconnected between multiple shafts. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.

Eskom, the sole supplier of electricity in South Africa is facing an energy crisis. This is due to the steady increase in demand for electricity in South Africa. Low electricity prices in South Africa have helped the energy intensive industries of South Africa to be more competitive. Unfortunately this has resulted in poor energy efficiency practices and has hampered incentives to save energy. To address this problem, Eskom initiated a Demand Side Management (DSM) programme. DSM is beneficial to both Eskom and the client. However, due to the high cost of implementing such projects, it is feasible to implement it only on sites where the load shift potential is high enough for Eskom to benefit. The mining industry has been targeted for DSM programmes. This is due to the existence of a large mining sector in South Africa and to its energy intensive nature. Most mining operations require large amounts of water which is used to cool the underground environment and so ensure productivity and the safety of the workers. Due to the large amounts of water needed for mining, the electricity usage of these pumping systems is very high. If the use of this electricity can be optimised by implementing DSM principles, this will result in the long term savings of costs for the mines involved. The majority of pumping systems found on mines are single shaft systems. Individually these systems have a very high DSM potential. However, if multiple shaft systems can be used for DSM, the benefits will be far greater. Furthermore, combining several sites with an interconnected water pumping system will increase the potential for DSM and enable sites where individually the potential is too low to be feasible for a DSM project to raise their potential. This will result in more sites where DSM projects can be implemented and more clients who can benefit from the DSM programme. The purpose of this study is to investigate and implement a DSM project on an intricate multi-shaft mine pumping system which will be controlled from a single point. The project required a detailed investigation of the pumping systems on each shaft and how the water system is interlinked between the shafts. This project was carried out on Beatrix Mine Shafts 1, 2 and 3. The pumping systems were analysed and simulated according to the specific constraints and requirements that were specified by the mine. During the investigation and implementation of this project, possible efficiency improvements on certain pump stations were discovered and implemented. The improvements enabled both an increase in water flow to the surface and a decrease in power consumption. Due to this load reduction, the savings achieved were higher than those found in most load shifting projects. Moreover, additional infrastructures were installed to ensure communication between pumping systems. Once the simulation and optimisation of the control system was completed, the pumping system network was automated. The load shift resulted in a ± 3.5 MW shift in the morning peak demand period and a ± 6.0 MW shift in the evening peak demand period. This load shift has resulted in an average cost saving of R 80 000 per month during summer tariff period, and R 300 000 per month during winter tariff period. This saving result was calculated by taking load reduction into account. This project has shown that a DSM project can be implemented successfully, given the necessary historical data and expertise, on a pumping system that is interconnected between multiple shafts. / Thesis (M.Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2007.

No description available.

The interaction between drainage from the variably saturated zone above the water table, and the response of an unconfined aquifer to pumping has been the source of debate for many decades. While various field tests (Nwankwor et al., 1992 and Moench et al., 2001) have supported the concept that variably saturated flow processes delay drainage above a falling water table, Neuman (1972, 1974, 1975), has asserted that the impact is minimal, delay in response of the water table is due to elastic storage effects, and instantaneous yield above the water table is a reasonable assumption in unconfined aquifer analysis. This assumption results in exceedingly low estimates of specific yield in comparison to other analysis techniques (Neuman, 1987). A 7-day pumping test by Bevan et al. (2005) in the unconfined aquifer at Canadian Forces Base Borden has highlighted the complexity in drainage from above the water table during pumping, as the tension saturated zone was found to increase in thickness as a function of both proximity to the pumping well, and elapsed pumping time. This extended thickness persisted for the 7-day pumping duration. Analytical analysis of the test by Endres et al. (2007) resulted in significant underestimates of specific yield in comparison to laboratory values for most solutions. Narasimham (2007) suggested that the use of numerical simulators which include variably saturated flow may provide the most accurate representation of the test results. An attempt to replicate test results using a numerical simulation of variably saturated flow by Moench (2008) could not provide a complete physical mechanism for the extension observed by Bevan et al. (2005). This study provides a detailed investigation on the effect of heterogeneity, hysteresis, and entrapped air on drainage during unconfined pumping tests using numerical simulations, field experiments, and laboratory observations. The results of the Bevan et al. (2005) pumping test are used as a standard for comparison. Three variably-saturated groundwater flow numerical codes were evaluated for their ability to replicate the variations in soil moisture content observed during pumping by Bevan et al. (2005). Results of the numerical simulations were also analyzed for their similarity to the peak and subsequent decrease in vertical gradients observed during pumping in the Borden aquifer. While the models generated vertical gradients through the capillary fringe during pumping, these gradients dissipated significantly before 1000 min. of pumping. No gradients in the saturated zone generated by the numerical model would be capable of shifting the pressure head sufficiently to cause an apparent capillary fringe extension following the first few hours of pumping. Significant gradients were persistent throughout the test at locations where saturation was less than 85%. Accounting for the formation of vertical gradients, no simulation was able to replicate the soil moisture distributions observed by Bevan et al. (2005). Based on these results, heterogeneity, hysteresis, and entrapped air were proposed as processes with the potential to significantly affect drainage from above the water table during pumping, as their investigation may provide the physical mechanism for the observed capillary fringe extension. Compaction of the aquifer material was dismissed as a potential mechanism based on the results of a proctor test. The effect of heterogeneity on drainage from the Borden aquifer during pumping was investigated numerically using geostatistical methods. A log-normal saturated hydraulic conductivity distribution was used to represent the Borden aquifer. Brooks and Corey parameters were used to describe the pressure-saturation-relative conductivity relationships. The air-entry pressure parameter was scaled to the saturated conductivity using the scaling relationship for Borden sand proposed by Keuper and Frind (1991). The Brooks and Corey lambda parameter was kept constant. A Monte Carlo analysis was performed on the results. While several realizations of the hydraulic conductivity distribution resulted in the formation of perched water during drainage, the ensemble capillary fringe thickness was unchanged from the thickness generated using a homogeneous conceptual aquifer model. No single realization produced a capillary fringe extension in which the magnitude was a function of elapsed pumping time, or distance from the pumping well. Approximation of the effect of air-entry barriers on drainage did not increase the estimated capillary fringe thickness. The presence and location of finer grained layers appeared to have a much greater impact on the thickness of the capillary fringe than the drawdown induced by pumping. Ensemble results for the hydraulic head drawdown provided improved matches to the field observations in comparison to the homogeneous numerical model during intermediate and late times in the pumping test. A mild degree of heterogeneity appears to have sufficient effect on drainage from above the water table during pumping to impact hydraulic drawdown. The effect would be magnified with the greater degree of heterogeneity that is more typical of natural aquifer systems. A 24-hour pumping test was conducted at CFB Borden to gain a better understanding of the nature of drainage during a pumping test. Due to the wet site conditions prior to the test, the moisture profile during pumping was significantly influenced by hysteresis. The hydraulic head drawdown generated during the test was insufficient to generate any drainage due to the lowering of the top of the saturated zone, and the formation of perched lenses could not occur. Hysteresis in the moisture profile was a controlling factor in this result. Although there was no significant drainage initiated due to the lowering of the top of the saturated zone, an inflection point was still apparent in the time-drawdown curve for the four monitoring wells observed. Vertical gradients measured throughout the saturated zone, including the capillary fringe, remained low throughout the duration of pumping, and no significant increase was apparent in the transition from saturated to tension-saturated conditions. Hysteresis has the potential to increase the delay in drainage as the water table falls during pumping. A laboratory tank apparatus was used to determine the effect of entrapped air, grain size distribution, and horizontal gradient on drainage in a primarily horizontal flow regime. The tank was packed on three separate occasions, once with a coarse well sorted silica sand, and twice with sand from the Borden aquifer. For each packing, the tank was drained twice, using two different horizontal gradient magnitudes. Results show that horizontal gradient magnitude has no impact on soil moisture distributions during drainage. Air-entry pressure was elevated in comparison to gravity drainage derived pressure head – saturation curves. This elevation was not transient, nor dependant on gradient or grain size distribution. The increase in air-entry pressure does not appear to be due to insufficient equilibration time between water level drops or flow redistribution around the TDR Rods. Results of this study support a conceptual model of unconfined aquifer response in which drainage from above the water table is a complex and time dependant process. Individually, heterogeneity and hysteresis have been shown to cause a time delay between the lowering of the water table and the subsequent drainage of the tension saturated zone during intermediate to late pumping times. The magnitude and duration of this delay varies by process and is a function of the degree of heterogeneity, moisture conditions in the aquifer prior to pumping, and the drawdown rate of the water table. While no individual process tested could produce the capillary fringe extension observed by Bevan et al. (2005), the investigation of each has led to an improved conceptual understanding of the response to pumping in unconfined aquifers. Due to the complex interaction of these processes it is unlikely that pumping test results, even those which include moisture content observations, could be used to accurately predict unsaturated flow parameters. Storage parameter (i.e. specific yield) estimates made using analytical solutions may not be appropriate unless delayed drainage from above the water table is properly accounted for.

Thesis (M.S. - Civil Engineering and Engineering Mechanics)--University of Arizona, 1985. / Includes bibliographical references (leaves 59-60).

Thesis (Ph.D.)--University of Tulsa, 1994. / Includes bibliographical references (leaves 169-172).

Thesis (Ph.D.)--University of Tulsa, 1988. / Bibliography: leaves 232-239.

Thesis (BSc. (Hons))--Australian National University, 2002. / Available via the Australian National University Library Electronic Pre and Post Print Repository. Title from title screen (viewed Feb. 18, 2003). "A thesis submitted as partial fulfillment of the requirements for the degree of Bachelor of Science with Honours in theoretical physics at the Australian National University" Includes bibliographical references.