Improving existing DSM initiatives on mine refrigeration systems for sustainable performance

Mining is done at great depths in South Africa and the high virgin rock temperatures at these depths result in refrigeration systems being one of the largest electricity consumers on mines. The general operation, control and equipment stance of the refrigeration systems are, however, inefficient and overdesigned and, as a result, several demand-side management (DSM) initiatives have previously been implemented on mine refrigeration systems. Although significant electricity cost savings were realised from these initiatives, DSM project deterioration occurs over time thus eroding the viability of sustained electrical cost savings. It is therefore critical to identify the factors affecting the performance of DSM initiatives in order to develop a performance strategy that includes measures to improve the existing DSM initiatives on mine refrigeration systems for sustainable and optimised performance. The feasibility of such a strategy was proven using case studies. This was done by analysing the post-implementation effects of said strategy on two underperforming, deteriorating refrigeration systems situated at two separate gold mines with previously existing DSM initiatives. The studies showed that a sustainable average daily power saving of 1.8 MW was achieved during the course of 15 months for Mine A; with a sustainable average daily power saving of 1.62 MW over the course of 17 months for Mine B. As a result, the average electrical cost savings, according to the 2015/2016 Eskom electricity tariffs, amounted to R11.9 million for Mine A and R12.1 million for Mine B.