Energy efficiency through variable speed drive control on a cascading mine cooling system

An ever-expanding global industry focuses on energy supply and use. Cost-effective electrical energy production and reduced consumption pave the way for this expansion. Eskom´s demand-side management (DSM) initiative provides the opportunity to reduce electricity consumption with cost-effective implementations for their respective clients. South African gold mines extend their operations to up to 4000 m below the surface to remain profitable. Deep-level mining therefore requires large and energy-intensive cooling installations to provide safe working conditions. This paper investigates the improved energy efficiency and control of a South African gold mine´s cascade cooling plant. Variable speed drives (VSDs) were installed on the chiller evaporator and condenser water pumps to provide variable flow control of the water through the chillers. This results in reduced motor electricity usage and improves chiller efficiencies. The results indicate that effective control and utilisation of energy efficient technology can produce substantial electricity cost savings. This indicates the potential for reducing energy inefficiencies and operating costs on technologically outdated machinery.