Energy Management: OceanaGold; Macraes Goldmine

Energy NZ has undertake two compressed air audits of OceanGold's Macreas gold mine, with the first saving it 57% in compressed air energy in 2016 and the second consolidating air compressor operations and estimating a total saving of 75% or $220,000 per annum if recommendations are heeded.

Energy NZ’s first in-depth compressed air audit of New Zealand’s largest gold mine in Central Otago in 2010 showed the possibility of significant compressed air energy savings via compressed air leaks, alternative tank aeration, improved multi-compressor control and improved air quality.

The audit was carried out by Energy NZ’s accredited compressed air auditors and certified ultrasonic leak detection engineers.

OceanaGold followed Energy NZ’s audit recommendations and proceeded to execute systematic improvements to the mine’s compressed air system over the next six years, including installing blowers to offset compressed air use, improving air quality, repairing compressed air leaks and switching off compressors.

As a result of the success of this endeavour OceanaGold contracted Energy NZ to revisit its compressed air system at a later date.

The objectives of the second audit's assessment included quantifying the savings made after the first audit, recalculating the remaining compressed air efficiency and identifying opportunities for increased efficiency.

The assessment revealed that the site’s compressed air energy use had been reduced by a staggering 57%, exceeding Energy NZ’s initial estimation and resulting in a cost reduction of approximately $180,000 per annum. Significant reductions in maintenance costs were also achieved.

Currently OceanaGold is implementing NZ Energy's remaining compressed air recommendations, which it conservatively estimates could result in a total energy saving of 75% ($220,000 per annum).   

Once complete, the site will operate on a single 55 kW variable-speed drive compressor as opposed to three air compressors totalling 410 kW in capacity.