Renewable energy in mining: A practical application for active operations

By Jocelyn Zuliani and Joel Guilbaud for Canadian Mining Journal - org pub 1 August 2020

Historically, mines have been powered using fossil fuels, a costly endeavor when you consider the high price of transportation and storage, not to mention the amount of greenhouse gases (GHG) emitted into the atmosphere — a very high cost to the natural environment. Recently, several mine operators have set ambitious targets to significantly reduce emissions, with aspirations of achieving net-zero operations within the next 25 to 30 years. Their strategy: incorporate green technologies for power generation, as well as energy storage capabilities whenever and wherever possible. So, the question remains, how do we get there?

The mine of the future will need to generate nearly 100% of its energy requirements  for powering the mine and supplying the vehicle fleet  with emission-free energy. Currently, there are many technologies in development to help us achieve mass electrification in mining. This includes high-efficiency renewable generation, low-cost energy storage for both short duration and longer duration, high-density battery and hydrogen-powered vehicles, combined heat and power generation from solar-enclosed technologies, and small modular nuclear reactors (SMRs).

One of the most appealing use cases to date lies in a hybrid microgrid approach. Several mines have started down this path, integrating wind or solar photovoltaic (PV) generation with short-duration lithium-ion batteries. These configurations typically generate 10-25% of a mine’s total electricity needs. In these low penetration microgrids, the microgrid continues to be controlled by the diesel gen-sets with renewables acting as a reduction to the overall mine load, while short-duration lithium-ion batteries are utilized to reduce the variability that stems from renewable generation. The batteries essentially act as an operating reserve and will either generate or store electricity if there is a significant drop or increase in renewable generation, that is until a diesel gen-set can be safely ramped up or down. This approach allows for fewer gen-sets to remain online at any given time, reducing both fuel consumption and operating costs.

Today, many mining operations are targeting medium renewable penetration, aiming for 40-60% of the total electricity generated from renewable sources. Continually reducing costs and improving the performance of wind and solar PV, as well as innovations to support reliable operations in extreme climates have made these generation sources more attractive. However, in order to achieve medium to high renewable penetration, the dispatch of the diesel gen-sets must be modified. The renewable generator’s contribution to the microgrid is significant and can no longer be treated as a simple reduction in load. Energy storage integration is a must, allowing all diesel gen-sets to be turned off for several hours. During these short periods, the wind or solar PV generation is high enough to cover the mine’s electricity needs. When the gen-sets are off, the energy storage will control the grid, maintaining power quality, and controlling the variability of the renewable generation.

In the future, as more aggressive and higher renewable penetration targets are set, aiming for near 100% renewable penetration, a significant shift in operating strategies is required. In this scenario, diesel gen-sets will only be operated during extended periods of low renewable generation. This will require both high- power energy storage to smooth short-duration intermittency and long-duration energy storage to support the supply of renewable generation, shifting it over several hours of the day. Long-duration storage is key to enabling this operating mode and there are many technologies being developed to support this requirement, including flow batteries, zinc batteries, geothermal and thermal storage, compressed gas storage, and hydrogen storage.

As mines reach higher renewable penetration, there will be excess power available at virtually no cost. The amount of excess renewable power available depends on both the mine’s location and the technologies adopted, with up to 50% of the total renewable generation available for heat demand and truck charging. Battery-powered trucks are expected to dominate the market for 100 tonnes of production or less. Heavy payload trucks of 300 tonnes and above will be hydrogen-powered and refilled with green hydrogen, mostly produced with excess power from the mine’s renewable generation output. In sunny locations, heat-intensive mining processes will use solar-enclosed technologies to produce both heat and power with a single generation technology. Lithium mines require a large amount of process steam and will benefit the most from solar-enclosed heat and power technologies. This will consequently lead to the decarbonization of the entire lithium mining processes, further accelerating the uptake of lithium-based batteries for renewable integration and electric vehicles.

And finally, SMRs are another highly anticipated technology pathway for remote mining. SMRs can be factory-produced and meet scaleable power demands, giving the mine the flexibility to add modules based on current and future power demand. SMRs can produce megawatt-scale baseload power that can be complemented by other traditional renewable and storage technologies to meet the mine and fleet energy demand. In Canada alone, a dozen companies have pre-licensing engagements with the Canadian Nuclear Safety Commission. Once a successful demonstration is achieved, the mining sector is set to be a primary target for commercialization, due to its high reliance on expensive diesel fuel in remote areas.

It’s no secret that off-grid mines are faced with electricity generation challenges, but with all of these technologies in the commercial development pipeline, we have an incredible opportunity to drastically curb climate change impacts in mining. The time is now!

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