Achieving energy efficiency with medium voltage variable speed drives for ventilation-on-demand in South African mines

Abstract

The sustainability of the mining industry is contingent on the industry's ability to improve upon the status quo of operational efficiency. The advancement of energy efficient technologies coupled with modern strategies have resulted in large industrial energy efficiency improvements, lowering emissions and wastage. Mine ventilation fans in South Africa were identified as large energy consumers with potential for efficiency improvements, with the installation of medium voltage variable speed drive technologies. An extensive energy audit was conducted on ten mine ventilation networks to calculate the feasibility inter alia cost savings, energy savings and greenhouse gas emission reductions under varying airflow conditions. Two ventilation-on-demand applications were considered namely, constant speed reduction- and dynamic applications. The financial indicators revealed it is economically viable for the implementation of medium voltage variable speed drives as part of the ventilation-on-demand applications. The energy audit revealed that a total annual electrical energy saving of 179 421 MWh could be achieved with the implementation of the ventilation-on-demand applications. The resulting cost saving is estimated at US$11.57-million with an average payback period of 9 months. The average greenhouse gas emission reduction is calculated as 53% per annum. The feasibility of installing medium voltage variable speed drives on South African mine ventilation fans as part of ventilation-on-demand applications to improve efficiency and lower emissions was proven. The results emphasise the importance of such audits to illustrate the underutilised resources available to increase mine sustainability and subsequently profitability.