Conversion of mines to hydroelectric batteries
A group of researchers from Michigan Technological University (MTU) say a fully renewable energy grid could be achieved if the United States converts mines into hydroelectric batteries. Such mines could pave the way for “the most ambitious” renewable energy goals in much of the country.
The need for more energy storage has become “absolutely urgent” as renewable energy sources have developed, said Associate Professor Timothy Scarlett, archaeologist with the MTU research team. Wind and solar power generation exceeds our ability to use or store it, creating bottlenecks of pent-up energy that can lead to wasted energy and brownouts.
Scarlett explains that converting mines to act as batteries would stabilize a grid powered by wind and solar power, absorb excess energy and compensate for shortages at times when there is too much or too little energy. .
What are the opportunities and barriers to converting decommissioned mines into pumped underground hydroelectric storage (PUSH) facilities? This question has been explored at MTU’s Keweenaw Energy Transitions Lab (KETL), which has as its primary objective to explore, investigate and develop pathways to transform past environmental and economic liabilities into clean energy productive assets for the benefit sustainable and thriving communities.
The PUSH study focuses on a disused iron ore mine in Negaunee, Michigan, but it doesn’t stop there. Building on the data collected, the team extends the results to consider the applicability of PUSH on a national scale.
Funded by a grant from the Arthur P. Sloan Foundation, the KETL team is exploring the potential for adapting an abandoned mine in Michigan’s Upper Peninsula (UP) into an energy storage facility. Michigan’s UP has copper and iron mining chains filled with abandoned mines, which present ecological and economic challenges. Researchers found 968 suitable mines, mostly in the west and on the Upper Peninsula, using a government database. Many of these mines are very large, giving them enormous energy potential as batteries for the power grid.
The communities that live with these historic mines, however, maintain complex relationships with them, valuing their symbolic role as heritage monuments, places of memory and tourist resources. Given these contexts, the KETL study focused on much more than renewable energy applications.
Instead, the researchers asked the question, “Can PUSH installations be designed to enhance heritage values while transforming the energy system?” The report concludes that PUSH can help economically disadvantaged areas transform into thriving hubs of economic development – because of, not despite, their heritage.
“Pumped storage is the best solution, and underground pumped storage is the most elegant of the best solutions,” Scarlett describes. (To note: Scarlett reached out to Clean Technica following an article we published in 2019 about the first steps of their project.)
The National Renewable Energy Laboratory said the United States needs 120 gigawatts of storage to have an 80% renewable energy grid by 2050; the country had about 23 gigawatts in 2020.
The technology behind hydroelectric batteries
PUSH is a type of closed-loop pumped hydro-storage (PSH) technology where the upper tank is located above or below the ground surface, while the lower tank and turbomachinery are built entirely underground.
This closed-loop PSH application is capable of providing essential network services while mitigating and remediating environmental damage caused by past mining activities and providing sustainable economic development opportunities for post-mining communities. These attributes of PUSH can alleviate the complexities of the licensing and permitting process and improve the economic feasibility of PUSH installations.
The case study in Negaunee, Michigan showed that the mine could provide very long-term storage, providing continuous food for 30,000 people for 3.5 months – at a profit – once built.
The team accumulated data from a variety of sources: community outreach; historical documents from local archives, including documents such as maps of surface and underground works and other company documents; and oral histories of mining operations and community life. Each was instrumental in analyzing mine dimensions, structural integrity, soil and water contamination, property rights and design considerations.
A PUSH installation can be developed using mature technological systems – materials and machines – used by conventional PSHs. In what they call a conservative estimate, the researchers determined that the United States has between 137 and 285 gigawatts of storage capacity in nearly 1,000 likely PUSH-suitable mines.
Based on their analyses, the team made several high and low volume reservoir and load estimates, which resulted in 5 fully and partially underground PUSH designs.
Using these designs, the team calculated the nameplate and energy storage capacities for several scenarios under 3 models.
- The first model calculated the maximum nominal installed capacity with a discharge time of 7 hours for partially and completely underground PUSH installations using the upper and lower volume estimates of the available upper and lower tanks. The main purpose of this model is to demonstrate the potential of a system requiring high power output. The team does not believe this model contains realistic options for the location of the case study, as current market conditions and transmission and distribution infrastructure are highly unlikely to accommodate facilities with these nominal capacities.
- The second model simulates daily energy storage scenarios based on the site characteristics shown above. This template features the most realistic design options that can be developed on the site.
- The third model extends the second model to explore the potential of PUSH as a long-term energy storage solution. The third model scenarios have the largest storage capacities for a fully and partially underground PUSH facility. Although this model is similar to the first model, it appears to be more practical as it is not constrained by the limitations of the first model, and it is not likely to require the construction of additional wells.
Managing potentially contaminated mine water during the dewatering and mining stages is likely to be a challenge, the researchers note.
Thanks to their study“Improving the power grid and community resilience by converting disused mines into underground pumped storage facilities“, KETL researchers have determined that opportunities in the transition to renewable energy are available and in the public interest through problem-solving approaches such as energy storage, state of mines and rural economic development. Together, these elements can help achieve greater energy justice.
By analyzing the technical, economic, legal, regulatory, water quality, social and community engagement dimensions of PUSH, the team came to see their work as an opportunity to bring sustainable economic resources to communities. that have been abandoned by mining as they struggle. with refurbishment and revitalization.
Projects of this type are already underway in Europe. Last year, Finland invested 26.3 million euros to convert one of the continent’s deepest mines into energy storage.
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