With the increasing pace of electrification, energy storage is becoming a natural part of energy systems. Utilized to store energy in electric vehicles, to increase small scale solar electricity self-consumption, in microgrids as backup power, as part of a larger power grid for congestion management or to manage variations in renewable energy production. There are multiple applications for energy storage.

With Swedish battery producer Northvolt teaming up with among others the Swedish automotive industry represented by Scania and Volvo, and several initiatives being presented by the automotive industry, one could think that the Swedish industry is all about putting energy storage in vehicles. But as the Swedish automotive industry is focusing on putting electric vehicles on the ground, another large industry in Sweden, namely the mining industry, might want to pay extra attention to what is happening below ground.

In a research project started in 2020, a concept for underground pumped hydro storage (UPHS) is tested by Swedish company Pumped Hydro Storage in an abandoned underground mine on the island of Åland. The storage concept is intended to be able to support frequency regulation, which is not such a common application for conventional pumped hydro storage, as these have traditionally been relatively slow and primarily acted as intraday energy storage.

Globally pumped hydro storage represents 94% of all energy storage capacity. Sweden has some conventional pumped hydro storages (PHS), the largest with a capacity of 55 MW, but in relation to other parts of the world, PHS has not been that widespread in the country. However, underground pumped hydro storage is getting increased attention worldwide as it is claimed to have a smaller environmental footprint compared to conventional PHS and in addition, it is not limited to certain topographies.

The project on Åland is not the only one on UPHS in Sweden. Swedish distribution system operator Ellevio announced in 2021 that they will join forces with Mine Storage that operate in the UPHS segment, to test underground mines as storage for large scale solar and wind parks. Mine Storage is currently looking for suitable mines in the distribution grid area of Ellevio. The company emphasises the large potential for underground pumped hydro storage worldwide claiming that there are at least 500,000 abandoned mines worldwide where their technology can be deployed. In Sweden, there are more than 300 abandoned mines, according to the Swedish Environmental Protection Agency. How many of these are suitable for UPHS has to this date not yet been explored.

In addition to abandoned mines, Sweden also hosts several underground mines in operation and a number of these energy storages are also finding new applications. Epiroc, a supplier of rock excavation equipment, has already released their battery-driven electric mining vehicles that can reduce both environmental and health impacts in underground mines. In 2021, the Swedish mining giant LKAB will have a couple of battery-driven Epiroc machines as well as some autonomous electric wheel loaders from Sandvik in operation. LKAB hopes that new vehicles can support the development of fossil-free mining operations.

There are certainly exciting things happening when you leave no stone unturned looking for new opportunities in the era of electrification.

This article was written by Anna Nilsson, Project Manager at IVL Swedish Environmental Research Institute. 


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