Carbon taxes and high fuel costs nudge mining companies to consider employing renewable energy alternatives, said experts at a recent webinar
Mining companies in Chile, a country which placed a carbon tax of $5 per ton on heat and power in the electricity and industrial sectors last year, are attracted to the cost savings of replacing diesel fuels with concentrating solar heat (CSH) says Antonio Moreno, regional director of Abengoa in the Middle East. Having set up a CSH powered mining project in Chile, Abengoa is now exploring where CSH can provide similar savings in other regions.
As CSH technology starts to take off in Chile, the Australian extractives sector is also taking note, with a view to capitalizing on the technology once it becomes more established, according to Graham Nathan, director of the Centre for Energy Technology at the University of Adelaide.
Progress in Chile
Moreno sees multiple applications for CSH across the energy intensive mining process, including in the melting and separation of solvents. Solar thermal is also versatile as it offers a steam supply for heat process, electricity generation and energy storage, he says.
Abengoa constructed South America’s first solar thermal project in the Atacama Desert in Chile four years ago. Currently in operation, the parabolic trough plant is integrated into a copper mine operated by Minera El Tesoro, a subsidiary of Antofagasta Minerals, where it provides thermal energy for a 24-hour electro-mining process unit. 24,445 MWh·th is generated annually via 1,280 parabolic trough (PT-1) modules, using water for thermal energy storage and as a heat transfer fluid. Abengoa reports that the plant enables Minera El Tesoro to reduce diesel fuel usage by 60%, while reducing annual emissions of CO2 by approximately 10,000 tons, including from the reduction of fuel transport by 125 trucks per year.
Minera el Tesoro CSH plant – key facts
The project powered two heaters, needed to drive temperatures of 55-80 ºC. Abengoa ran analysis and used meteorological data to see how much oil could be displaced and what hourly flow rate and water inlet temperature was required. They explored different annual performance models to come up with the most optimized design, resulting in building a 21,000 m2 solar field and storage volume of 400 m3 of water, creating a water temperature rising to 80-85 ºC to transfer heat to the copper solution. It’s a reliable supply with fully integrated storage, it can run around the clock and it solves the problem of using diesel in remote locations, says Moreno, whilst also reducing the risk and cost of operating the plant on diesel as well as saving carbon emissions.
CSH in the mining sector
Nathan sees significant potential for CSH application in high temperature process industries, such as mining. Global carbon emissions projections currently show that the industrial sector is on course to reduce emissions much slower than other sectors, he says, which opens a window for renewable energy to offer low carbon solutions.
Low, medium and high temperature CSH all have important commercial uses, including ore concentration and digestion at 180-300 ºC and iron and copper reduction at above 400 ºC, says Nathan. High solar resources also coincide with Australian mining sites where high temperature processes are being applied, according to CSIRO mapping.
The challenges of commercializing CSH in mining include the need for smaller solar thermal systems in the tens of megawatts, with storage capacity to accommodate for continuous energy use, he says. Remote sites offer obvious scope for cost savings as they run on LPG, a more expensive fuel compared natural gas. But it may cost more to maintain a small system and other energy sources might be needed as part of a hybrid system, he adds.
CSH technology needs to be demonstrated first in a retrofit project within the mining sector to prove itself in Australia, says Nathan. Abengoa’s Moreno agrees that solar thermal can be used effectively and efficiently within a hybrid mix of energy technologies, which can also provide extra reliability. The biggest challenge currently facing CSH uptake in the mining sector, Moreno says, is finding clients willing move away from more traditional methods.