(16.12.20) Energy Storage Systems (ESS) are a necessary part of a local power generation with renewable energy sources in remote mines. Apart from enabling the transition to renewables, ESSs have additional technical benefits in mine operation.
Energy production in remote mines
Mining is a very energy-intensive industry. Driven both by pressure to decarbonize the industry (reference 1) and by the lowered production cost for electrical energy in photovoltaic and wind power plants (ref.2), among other renewable technologies, it is expected that mining industry will progressively transition into using these energy sources. According to Bloomberg NEF(ref.3), “Miners have contracted for 5.9GW of clean energy in the last decade – three quarters of which was signed up in the past two years.”
The transition to using renewable energy sources is not without some challenges to tackle. Many mines are located in remote sites, where the raw material to extract is plenty, but where no access to electricity from the grid infrastructure is available. To secure power production locally for the energy needs of the various processes, the mines are still heavily reliant on diesel generators.
Diesel generators consume fuel, whose total price in remote locations is considerably higher than the purchase price. The total fuel price also includes costs from the transportation, storage and guarding. The carbon footprint and particle emissions from burning fuel are also considerable compared to renewable energy sources, even if the footprint of their production is taken into account.
The initial capital investment for diesel generators may be lower than investing in local renewable production, but the fuel and O&M costs make up for it in the long run, and solar and wind power become cheaper per produced kWh. This, combined with the difference in emissions, makes a strong case for using renewable energy sources in local production. Note that this is not an either-or-situation: the best balance between cost-efficiency, carbon footprint and feasibility may be struck with a solution combining both generators and renewable production.
Note that Merus Power has done detailed payback calculations showing how a combination of a photovoltaic plant and an ESS can compete with investing to diesel generators.
Technical transition to renewables has challenges
Unfortunately, designing and maintaining an islanded electric network is not as simple as choosing an energy source and then plugging the mining machinery in. Replacing diesel generators with renewable energy technologies also requires addressing some technical challenges. Rotating generators have several important characteristics for an electric network:
- Their production can be controlled predictably (as opposed to renewables which are dependent on weather), as long as fuel is available.
- They are able to form an electric network and provide inertia
- They can provide short circuit current reliably to ensure that the network protections such as fuses and relays work correctly, and the network is thus safe for personnel
- With enough generators, the electric network becomes strong enough to absorb transient events (motors starting and stopping, consumption peaks) without losing stability.
Renewable energy sources can help in the above mentioned points, but they cannot produce a stable electric network and a continuous mining process alone. Mining machinery such as stone crushers, winders, conveyors, etc. need power even if the wind is not blowing or the sun is not shining. On the other hand, if the sun is up and the wind is fierce, it would be a waste to not capture this energy somehow even if the miners are on holiday.
To summarize, the production cannot necessarily be instantaneously matched with the mine process demand, which can cause stability issues in the grid. With diesel generators, power production can be matched with the demand by operating a certain number of generators according to the predicted demand.
Merus™ Energy Storage System as part of an islanded mine grid
The situation changes if local renewable production is coupled with an energy storage system, that can provide the system with a buffer between the production and consumption, that may take place at different times.
Energy storage systems can be based on various energy storage technologies. In this text, the case is made for lithium-ion batteries. Lithium-ion battery technology is proven and mature, and its advantages in mine applications are numerous:
- A lot of power and energy can be packed into a relatively small space with a relatively small mass. Lithium-ion batteries are very power- and energy dense. This makes it easier to transport and install them into any location.
- Likewise, because lithium-ion batteries are not dependent on any external factors such as geographical formations, they can be placed anywhere.
- The response time of the batteries is instantaneous. The power ramp rates for charging and discharging the battery are faster than with rotating machine.
To produce a stable grid, an ESS is designed with a suitable nominal power and nominal energy. The ESS nominal power can be designed to feed all the mine loads alone, or possibly optimized to work together with gensets or other sources of backup power.
The specification of the nominal energy of the Merus™ ESS, is a trickier question. How long does the ESS need to be able to feed the mine loads? Should the mine operator procure a battery that is able to feed all the mine loads for 24 hours or perhaps only a portion of the loads for 30 minutes?
The answer to the previous question would be different for each mine. A statistical study considering the mine load profile and typical energy production (with renewables and/or with other sources) profile should be carried out – what time is energy consumed and what time is it produced, and how much. Subsequently, these too profiles are compared, and where they don’t match, the battery is charged or discharged.
The process of study mentioned above only considers technical realities. It does not necessarily make sense to procure an ESS that can ensure that production and consumption are matched 100% of the year – for economic reasons, perhaps it would be more appropriate to procure an ESS that can guarantee that all loads stay connected “only” 99 % of the time, and during the 1 %, the least mission-critical loads are disconnected.
The possibilities for using an energy storage system in islanded microgrids are not limited to decoupling intermittent production from consumption. An ESS can produce many additional advantages, such as reactive power compensation at the same time while charging or discharging the battery, according to the operation strategy.
Merus Power is your preferred partner in designing islanded grid operation
The world is changing rapidly, and the decarbonization of industries is a worthy goal. Making the carbon footprint smaller by utilizing renewable energy sources in mines is a great leap in this direction, and Merus Power is there to help you all the way. Designing the automated operation strategy of an islanded grid and simultaneously maximizing its feasibility requires a good command of all the related technologies, which is Merus Power’s core knowhow.
Take the first step and contact us.
Sales Manager, Americas
Photo on top: Merus Power has extensive knowledge and experience from installations in rugged mine conditions. This picture is from a STATCOM installation in a gold mine. Read the success story from here.