A techno-economical assessment of micro vs localised hydropower drilling systems for deep-level gold mines

Compressed air handheld rockdrills have historically enabled efficient blasthole drilling in South African narrow reef gold mines. However, as operations matured and production moved further from shafts, their efficiency declined. Rising electricity tariffs have further reduced profitability, necessitating the adoption of alternative drilling technologies. Hydropower rockdrills present a viable solution, yet adoption has been limited due to uncertainty regarding their economic benefits. This study provides an impartial techno-economic assessment of two hydropower configurations, micro and localised systems, evaluated over 12 months against a compressed air baseline. Although compressed air systems require no additional capital, their high operating cost (US $14.23/t) makes them the least economical option. The localised hydropower system demonstrates clear advantages, with 47% lower capital cost than micro systems and the lowest operating cost (US $2.41/t). Over a 5-year period, the total cost of ownership is significantly reduced (US $215,700 vs US $983,520 for compressed air), yielding savings of approximately US $767,820. Productivity improvements are also notable, with localised systems achieving 1693 t/month and a superior ROI of 323%, with payback within one month. Overall, localised hydropower systems offer the most cost-effective, productive, and safer alternative to compressed air drilling.