Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
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RENEWABLE ENERGY 60 E&MJ; • APRIL 2016 www.e-mj.com remote DeGrussa copper mine in Western Australia. The largest of its kind in the world, the system includes a 10.6-MWp pho- tovoltaic (PV) facility covering 20 ha, and 4 MW (6 MWp) of lithium-ion battery storage, integrated into the mine's 19 MW of diesel generating capacity. Benefts for Sandfre include cheaper electricity, especially in the long term, no more volatility in electricity prices, better electricity quality, no capex (since the plant is provided by Neo- en), and 5 million liters of diesel savings a year, Desrousseaux claimed. Construction began last July, with commissioning scheduled for March. During the day, 80% of the mine's 12-MW demand will come from the PVs, with diesel generation powering the operation at night. The battery capacity is used as a spinning reserve, rather than for load leveling. Desrousseaux admitted there are a num- ber of challenges, including adapting to the health and safety requirements of the mining sector, and integrating the various sources of power supply. In addition, PVs cannot handle sudden changes in demand; hence the need for battery storage. Costs for a stand-alone off-grid system will be higher than those for government-supported projects, so mining companies have to have a long-term commitment, and the motivation, to achieve the biggest benefts from using an on-site IPP company. Lastly in this session, Duncan Stevens from Gold Fields in South Africa reported on the company's two-year evaluation of the potential for solar power to supplement its needs at the South Deep mine. With a life of more than 70 years, South Deep has an average demand of 55 MW, peaking at 75 MW, with energy accounting for 13% of its operating costs. Stevens explained that Gold Fields is aiming for at least 20% renewables at each new mine in its portfolio, with the company focusing on optimized, rather than maximized, solar input at South Deep. Gold Fields has been working on its renewables projects with the Denver-based Carbon War Room-Rocky Mountain Insti- tute. The organization's CEO, Jules Kortenhorst, described its involvement, with its "Sunshine for Mines" project aiming to have 15% of the mining industry's power needs run from renew- ables by 2025. Gold Fields is now looking at a 40-MW photovoltaic plant for South Deep, with its initial request for expressions of interest having generated around 75 responses. A request for proposals resulted in 28 responses, with 10 companies then submitting bids. As Stevens noted, some of those proposals claim to meet Eskom price parity today, and most trend favorably with infa- tion over the term of the prospective power purchase agreement. Energy storage technologies also appear to be on par with the current cost of diesel generation, he added. Economics Stack Up The message throughout the meeting was consistent: "Oil may be cheap now, but price volatility is inevitable. Renewables offer better long-term stability." The challenge is to convince a traditionally conservative industry to take the next step, and to develop new mechanisms for fnancing renewable energy supply systems. From the German solar power developer, Belectric, Nir Dekel described a conceptual hybrid solar-storage-diesel system for use at a southern African open-pit gold mine. With capex of $29 million, this could offer $1.7 million in annual energy savings, he suggested, with fxed power supply costs of $0.26/kWh for 24% solar input compared to $0.31/kWh for the 76% provided by diesel gensets. What is more, the entire solar system could be relocated to another site should the mine life be shorter than that of the PV panels. However, it is not just solar energy that has potential for powering mines. As Jennie Thomas, environmental services manager at ICL's Boulby potash mine in England, explained, the company has been evaluating a range of possibilities for off- setting its energy bills, especially in its ore-treatment plant. These have included geothermal, heat recovery from the mine ventilation exhaust and brines, hydropower using the shafts, and wind turbines. There is no question that renewables will play an increas- ing role in supplying mine energy requirements. However, not- ed ICMM's CEO, Tom Butler, during a panel discussion, there is still plenty of unpredictability. "Funding is neutral on power plants, with money going to where returns are good and the risk is least," he said. "We are at the early stages of an energy transition," added Matthew Bateson from Rio Tinto. "The future will be exciting for people who enjoy technical challenges." Chris Moscardelli, director of energy project fnance at Société Générale, discussing ways of unlocking fnance for mining-sector renewables. Keith Ainsley of Knight Piésold describing Banro Corp.'s hydro projects in the DRC.