BBE has commissioned an innovative ice thermal storage scheme at a refrigeration installation, at AngloGold Ashanti’s Moab Khotsong mine near Klerksdorp, which provides cooling for chilled service water and air cooling for the mine.
The refrigeration machine for the ice maker operates outside of peak tariff periods, when the availability of electricity is more reliable and electricity is cheaper and particularly at night when the outside temperature is lower and the refrigeration machines operate more efficiently. Ice is formed on the outside of submerged coils in an existing surface water dam and stored until required. In peak tariff periods, all the refrigeration machines, which provide some 40 MWR of cooling, can be turned off and cooling is then provided by melting ice in the dam. Overall, in a 24 hour cycle, the ice thermal storage system uses less power than a conventional water cooling system and the system operates outside of Eskom peak tariff periods.
This turnkey project, awarded to BBE in 2008, included engineering design, procurement, construction, management and commissioning. It is the second installation of its kind for AngloGold Ashanti, the first being an 800 tonne ice mass thermal storage system at Mponeng mine near Carletonville. The Moab Khotsong installation is a third generation design where the ice is formed directly on refrigerant carrying coils.
Ice thermal storage schemes are an ideal response to the critical need for power and energy management in the arena of mine ventilation, refrigeration and cooling systems.