In this era of energy management, there is an opportunity for cutting energy costs and energy usage in mine cooling systems by operating refrigeration plants at night, outside of peak usage times at night when refrigeration plants operate more efficiently and there is greater availability of electricity. BBEnergy have designed, developed and constructed the following three different types of thermal storage for use on mine cooling systems. These include thermal storage by:
- Ice mass storage
- Thermal stratification
- Bladder separation
Ice mass thermal storage operates by placing ice in a storage dam on surface, ice can be made at night and stored until required. Refrigeration machines are more efficient at night because it is cooler. In the daytime, the refrigeration machines can be turned off once enough ice has been made. During this period, cooling is provided by melting ice in the ice dam. Overall, on a 24-hour cycle, the ice thermal storage system uses less power than a conventional water cooling system, and the added benefit is that the system runs at night when the cost of power is lower. BBE has demonstrated the effectiveness of this technology at the recently completed 800 ton ice thermal storage at AngloGold Ashanti’s Mponeng mine, located near Carletonville. BBE is now constructing ice thermal storage systems at Anglo Platinum’s Townlands mine, AngloGold Ashanti’s Tau Lekoa mine and AngloGold Ashanti’s Moab Khotsong mine.
Thermal storage by thermal stratification operates by storing both warm and cold water in a common dam. Warm water is lighter than cold water and can ‘float’ naturally above cold water in a tall dam where the inlet and outlet manifolds have been carefully designed to minimise turbulence. The density differences between warm and cold prevents the water masses from mixing. Thermal storage by thermal stratification can be retrofitted to an existing surface dam but is only suited to tall narrow dams. BBEnergy have designed and commissioned energy management systems incorporating thermal storage by thermal stratification at Impala Platinum Shafts No.9, No.11 and No.14
A flexible membrane or bladder can be used to separate warm and cold water masses in a common dam. Bladder thermal storage can be retrofitted to almost any existing surface dam. BBEnergy have designed and commissioned energy management systems incorporating thermal storage by bladder separating at Impala Platinum Shafts No.1 and No.12.