BBE – the first South African company to introduce the ice storage concept to the local mining industry – has commissioned an innovative facility at a refrigeration plant 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 (providing 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 t 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. These schemes have become an integral part of BBE’s expertise and competency. BBE is a registered ESCO (Energy Services Company) with the South African national power supply company, Eskom. This is a recognition of BBE’s technical competency and an acknowledgement of the company’s work in the field of energy saving and load-shift management for mine cooling and ventilation systems. Being an ESCO, BBE is able to initiate these projects in conjunction with an enthusiastic mine who provides a letter of intent with which BBE can then apply to Eskom for funding through the DSM (demand side management) programme. BBE guarantees the performance of the system, while the mine contracts to operate the system as required.
BBE has carried out many other types of energy efficiency projects, making optimum use of energy recovery devices such as turbines, hydro-displacement devices, hydro-power, as well as designing control systems for the active ongoing control of ventilation and cooling equipment components. The company is very proud of its innovative ice thermal storage systems, which have resulted in significant capital operating cost savings in a variety of mines.