Blueprint Underway for Commercial Mine Energy Storage Facility in Sweden 

A blueprint for what could become the world’s first commercial underground mine storage facility has garnered financial backing from Swedish Mining Innovation, a joint agency overseen by Sweden’s Innovation Agency, government research council Formas, and Sweden’s Energy Agency. An international consortium comprising mining and energy companies is now poised to compile the next steps to build the facility in the historical mining area of Bergslagen in Sweden.

The blueprint, which will include all steps in the process—from initial landowner and authority approval, to a grid-connected energy storage and supply facility—will eventually be presented in a European Union application. Mine Storage, a Swedish grid-scale energy storage company, will lead the consortium, which will also comprise Swedish mining companies Boliden and Lovisagruvan, energy company Mälarenergi, global hydropower equipment manufacturer Voith Hydro, and engineering and design company AFRY. The grant from Vinnova, as part of the agency’s Swedish Mining Innovation initiative, “is a clear indication of the increased interest in the global potential of using abandoned mines for energy storage,” said Thomas Johansson, co-founder and CEO of Mine Storage.

Reutilizing Abandoned Mines as Massive Batteries

The concept explores revitalizing abandoned mines as massive “batteries” to help balance soaring shares of intermittent generation, essentially creating a “cross-sectional” project that solves several sustainability issues. According to Stefan Sädbom, a long-time exploration geologist with decades of experience in the mining and metals industry, and who currently acts as an advisor to Mine Storage, “many countries have thousands of abandoned underground mines.”

Large-scale and long-duration energy storage is also becoming essential in the face of rapid electrification and volatile energy prices. “The world needs to store produced energy and control the energy supply to a much greater extent than today,” Johansson said. More than 90% of energy storage today is provided by pumped storage hydropower, owing to its established technologies to allow for quick response with flexibility to fluctuations in energy demand. However, “most countries lack the height differences required in the landscape for storage facilities above ground,” he noted. “This is where mine storage comes in.”

1. Mine Storage’s concept explores revitalizing abandoned mines as massive “batteries” to help balance the grid. The powerhouse consists of both turbine and pump equipment. Energy from the grid is stored by pumping water to the higher elevation. Energy is fed back to the grid when water is released to the lower reservoir passing the turbine in the powerhouse. Courtesy: Mine Storage

Since being founded in 2020, Mine Storage has floated a solution that essentially replicates traditional pumped storage with upper and lower reservoirs in underground mines (Figure 1). “Closed mines are filled with water (groundwater) naturally. We look into a wide range of mines, from those closed since decades to mines still in operation,” Johansson told POWER. “In some cases, existing underground caverns and volumes may be sufficient, in others we may need to expand to get sufficient volumes.”

To assess a site’s suitability, Mine Storage conducts an in-depth assessment on a potential site’s geotechnical conditions, such as rock steadiness; hydrological prerequisites, such as head and mine design; environment; and operational questions, such as need for draining and water quality. It also conducts several other assessments, including to survey grid-connections, construction needs, health and safety, and water supply; a commercial assessment, which involves preliminary financial estimates of the business case; a rights and regulatory part, which includes discussions with land and concession holders, and assessing the legislative and permitting prerequisites; and a market assessment to gauge beneficial policies, regulation, incentives, potential partners, customers, preliminary revenues, and local acceptance levels.

A High-Value Prospect

Johansson acknowledged the concept requires a long-term undertaking, which could present a significantly higher capital cost than batteries. However, because Mine Storage’s pumped storage plants under development range from 15 MW to 400 MW in power output and 30 MWh to 800 MWh in energy for one discharge, the projects may have a competitive levelized cost of storage. “A mine storage is an infrastructure/energy investment with very high sustainable value and our financial calculations show profitability that should attract investors,” said Johansson.

The concept’s potential business case has so far won Mine Storage several notable backers. Among them is Voith Hydro, a company heavily invested in pumped hydropower technology and hydropower flexibility. Mine Storage in June 2021 forged an alliance with Voith Hydro to explore early project development at two specific sites in Sweden to develop the necessary technical solutions. Last summer, Mine Storage also entered into a collaboration agreement with Ellevio, one of Sweden’s largest regional grid operators, to evaluate how a mine storage system could eliminate bottlenecks on the grid. In the fall, the company said it successfully closed an oversubscribed seed round, ramping up the capital and experience the company needs to scale up.

—Sonal Patel is a POWER senior associate editor (@sonalcpatel, @POWERmagazine).