An investigation into the DSM and energy efficiency potential of a modular underground air cooling unit applied in the South African mining industry
Van Eldik, Martin
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The South African mining industry is faced with the depletion of minerals and coal at current mining depths. This is forcing the industry to expand operations to greater depths where ample ore reserves are located. This expansion combined with the demand for increased production rates puts excessive strain on the ventilation and cooling systems of mines. The problem is that mining will eventually reach depths where current methods of ventilation and cooling will no longer be economical and practical to provide an acceptable working environment. To solve this problem new technologies or alternative cooling methods are required. One such concept is called spot cooling. This entails cooling the air in a remote location rather than cooling the entire environment leading up to that location. Until now spot cooling was primarily done using chilled water but a significant limitation of this approach is that the cooling effectiveness is proportional to the chilled water temperature. An alternative solution is the use of a localised refrigeration plant acting as a spot cooler. This is different from a standard underground refrigeration plant since it is modular with a smaller cooling capacity and is completely mobile so that it can be deployed at different locations as the need arises. The purpose of this study is to develop such a prototype modular air cooling unit (ACU) to establish a suitable working environment and to evaluate the techno-economic impact if it is applied on a wide scale for deep mine expansion. Furthermore, from an electrical supply side the potential of the ACU to contribute to energy efficiency (EE) and demand side management (DSM) initiatives is also investigated. A nominal 80kW prototype ACU was designed, manufactured and tested in both laboratory conditions and within an underground mining environment. A distinct advantage of the unit is that it can operate efficiently with high inlet water temperatures. This provides enhanced flexibility compared to existing technologies since it can utilise normal service water as heat sink as opposed to chilled water as a source of cooling. A system simulation model was developed to investigate the deep mining techno-economic impact as well as the EE and DSM potential of the ACU compared to existing chilled water technology. An investigation into the DSM and energy efficiency potential of a modular underground air cooling unit applied in the South African mining industry. School of Mechanical Engineering. North-West University Information and data from a case study mine were used to simulate different possible cooling configurations for deep mine expansion. From the results two configurations emerged that show the best potential for deep mine application, namely an underground chiller plant combined with chilled water cooling cars (CWCs) or a hot underground dam with ACUs. Of these two configurations only the ACU configuration holds significant EE and DSM potential due to a reduction in the total power requirement and it is also by far the most cost effective. This could provide substantial benefits for both the mining industry and the South African electrical supply utility, Eskom. From the results of this study it can be concluded that the ACU technology offers an energy efficient, cost effective and practical alternative to conventional cooling methods for deep mine expansion where the establishment of an acceptable working environment is a major concern.
- Engineering