7.13 Energy conservation gains renewed impetus in the South Africa region
In its drive to conserve energy - primarily from a cost and environmental perspective - the South Africa region's engineering department has focused on two areas: developing and implementing renewable energy sources on the one hand and ensuring efficient use of energy on the other.
Renewable energy relies on natural resources such as the sun, the wind, water, the earth's heat, and plants. Renewable energy technologies turn these fuels into usable forms of energy - most often electricity.
Says Keith Arnold, energy engineer, "The South African operations make use of the depth (up to 3,800 metres) at which we operate to generate power from the water used for our mining process. Water is already gravitated underground for cooling the working areas, for dust suppression and used in some underground equipment."
At Mponeng mine in the West Wits area electricity is generated underground via Pelton Wheel turbines. These produce about 6% of the mine's power requirement. The generators are synchronised with the power system so other loads operating on the distribution network absorb the energy generated. At times the generation is more than that part of the mine can absorb, in which case it is exported into the national network and the utility passes a credit to AngloGold Ashanti.
At the Kopanang mine, in the Vaal River area, the Pelton Wheel turbines are coupled to pumps. The pumps are then used to transport 'hot' used water to surface for re-cooling through the surface refrigeration plant for re-use underground as a cooling medium.
Tau Lekoa mine, also in the Vaal River area, uses its depth to drive hydro-powered drills and other equipment in the stopes. Tau Lekoa is the only gold mine in the country to be powered largely by water.
Moab Khotsong will implement a demand side management project in late 2005/early 2006 whereby water supply down the mine will be used to displace the water coming out of the mine through a three chamber pipe feeder system. The only power required will be to overcome the friction losses in the system. Studies are being undertaken to indicate expected savings, but previous figures suggested that 32 MW of pumping would be replaced by only 10 MW using the chamber pipe feeder system. Four systems will come into operation and each system will have the capacity to displace 318 litres per second.
Says Keith, "We are also active in the Demand Side Management initiative implemented by the National Electricity Regulator, and which is managed by Eskom DSM and funded by all consumers of electricity. The overall aim of the initiative is to reduce the national system peak demand, which occurs in the evening between 18:00 and 20:00. Projects are focused on shifting load out of this time into other times of the day. This will result in delaying Eskom's capital expenditure for new Peak Generating plants, which will in turn escalate the cost of power. These projects also save AngloGold Ashanti money as the cost of energy in these peak hours is more per unit than other hours of the day."
As from the 2005/2006 business planning cycle, each business unit will be required to submit life-of-mine energy plans. While energy consumption has always been part of the budgetary process, energy conservation objectives has now given it added emphasis.
During 2004, AngloGold Ashanti together with Anglo American plc completed a technology strategy with the objective of reducing the group's energy intensity year-on-year. AngloGold Ashanti has selected TauTona at West Wits as the pilot operation. A number of projects have been identified and are being investigated.
Another aspect addressed is the moni-toring of pump efficiency through special pump coatings, achieving sustained efficiency over longer periods
One of the challenges is to ensure that such worthy efficiency initiatives are shared by other operating regions to the benefit of the entire company.