The control of rock winders for maximum demand management on deep South African mines
Bosman, Petrus Hendrik
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In South Africa, electrical energy is taken for granted. The low electricity price has helped electricity intensive industries to be competitive. Unfortunately it has also prevented industries to become energy efficient. During the National Electrification Programme, more than 3.1 million homes were supplied with electricity. This has mainly increased the peak demand for electricity supplied by Eskom. Projections show that peak demand will be higher than Eskom's current generating capacity by as early as 2007. In order to curb this growth in electricity demand, Eskom launched a Demand Side Management programme in accordance with regulations drawn up by the Department of Minerals and Energy and the National Energy Regulator. The main purpose for this programme is to reduce electrical energy usage during evening peak demand times, as well as to encourage an energy efficient society. One way of implementing this evening peak reduction is to shift the load to other times of the day. An inherent problem with this method is the possible increase of an electrical energy user's maximum demand. Such an increase could incur additional costs to an electricity user. In order to limit this maximum demand, certain systems could be shut down when the electrical energy use is on the verge of reaching peak levels. It will be shown that rock winders are the most suitable of all the systems used on a mine to manage the maximum demand. All underground mines make use of winders to extract excavated ore. Winder motors are usually large electrical energy consumers. As such, they provide an efficient and fast means of limiting the maximum demand. It is intended to switch off winder motors whenever the overall electricity demand of the mine reaches a peak level - as long as production is not influenced. This system was successfully implemented at Anglo Gold Ashanti's Kopanang gold mine in South Africa. During the first month of installation, the system managed the mine's maximum demand at a level of 88 MVA. A calculated annual saving of R137 000 was achieved, with a maximum potential saving of R349 000. This research showed that rock winders can be successfully used to manage a mine's maximum demand. It can be implemented on most deep level mines that use rock winders. Suitable sites include gold, platinum and diamond mines.
- Engineering