Short answer

A battery at a mine does three jobs. It catches the dips when a cloud or a calm hits the solar or wind. It lets you run fewer engines, because the battery, not a spare engine, covers a sudden drop. And if it is big enough, it carries the mine through hours with every engine off.

Which of those jobs you need decides the size. Two numbers matter: power (MW), how hard the battery can push at once, and energy (MWh), how long it can keep pushing.

Power and energy, in plain words

Power is the size of the pipe. Energy is the size of the tank.

A mine needs enough power to cover the biggest sudden gap, for example when a cloud covers the solar field or when the mill starts. It needs enough energy to bridge that gap until an engine is up, or until the sun or wind is back.

Three real examples

Agnew gold mine, Western Australia (Gold Fields). Wind and solar with a 13 MW / 4 MWh battery. The battery's power is close to the mine's full load, but its tank is small. At full power, 4 MWh lasts under 20 minutes. The Australian Renewable Energy Agency (ARENA) reports that the battery buffers for about 15 minutes while gas engines start. Over a year the mine gets a bit over half its power from wind and sun, and more than 80% in good conditions. This is a battery sized for stability, not for the night.

Fekola gold mine, Mali (B2Gold). A 30 MW solar plant with a 15.4 MWh battery, added in 2021 to a mine that ran on heavy fuel oil. During the day, three of the six engines can be switched off, and up to 75% of daytime power comes from solar. The plant saves about 13 million litres of heavy fuel oil a year. This is a battery sized to let engines go off in daylight.

Bellevue gold mine, Western Australia. 27 MW of solar, 24 MW of wind and a 15 MW / 33 MWh battery, with engines as back-up. In May 2026 it ran 155 hours in a row with every engine off. Wind covers the evenings, and the bigger tank carries the gaps. This is a battery sized to replace engines for long stretches. More on this case in Solar and batteries for remote gold mines.

Same technology, three very different jobs. The tank went from 4 MWh to 33 MWh.

How to size it for your mine

Start with your load data, not with a battery catalogue. Five questions:

  1. What is the biggest sudden step in demand? Mill starts, hoists, a crusher tripping. The battery's power must cover it.
  2. How many engines do you want off, and when? Daytime only, like Fekola, or for long stretches, like Bellevue.
  3. How fast can your engines start? That sets how many minutes the battery must bridge.
  4. Is there a second renewable source? Solar alone stops at sunset. Wind or a much bigger tank is needed to cover the night.
  5. What does an hour of fuel cost you, delivered? This decides how far it pays to push.

Most mines start with a battery that smooths solar and lets some engines go off in daylight. It is the cheapest first step and it proves the system on site. A bigger tank can come later.

What it does not do

A battery does not make power. It moves power from when you have it to when you need it, and it reacts very fast. If there is not enough solar or wind to charge it, it cannot replace the engines. That is why storage and generation are sized together.

How GoSí works

GoSí Energy coordinates the project from feasibility to delivery: the load study, the sizing, the partners and the contract. Our EPC partners design, build and install the plant. Mines can buy the plant or pay only for the power through our Land + PPA model.

If you have a year of load data and your fuel bills, that is enough to start. Contact us.

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