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Len Rosen's picture
Principal Author and Editor, 21st Century Tech Blog

Futurist, Writer and Researcher, now retired, former freelance writer for new technology ventures. Former President & CEO of Len Rosen Marketing Inc., a marketing consulting firm focused on...

  • Member since 2018
  • 196 items added with 185,073 views
  • Feb 9, 2023

A novel use of abandoned coal mines is to turn their vertical mineshafts into sources of kinetic energy to power Underground Gravity Energy Storage batteries.

Roger Arnold's picture
Roger Arnold on Feb 11, 2023

The authors of the paper estimate gravity batteries like the one above could operate at a cost of between USD $1 and $10 per Kilowatt-hour with the capacity to generate from 10 to 70 Terrawatt-hours of electricity.


That's got to be wrong. An operating cost of $1 to $10 per kWh produced -- it that's what it's supposed to mean -- isn't remotely competitive. The cost per kWh produced needs to be at most a few cents more than the cost of the electricity used to store the energy. OTOH, if it's meant to refer to the capital cost of storage capacity, I have a hard time believing it could possibly be as low as $1 per kWh of storage capacity. Even $10 would be low enough to revolutionize the energy storage market.

As to the figure of 10 to 70 TWh of storage capacity, I could believe that if it's the projected total for all abandoned mines in the US. Gravity storage of this type should be good for about 6 kWh of storage capacity per cubic meter of tunnel volume per kilometer of shaft depth. Few coal mines have shaft depths greater than 2 km. That would mean ~12 kWh per cubic meter of tunnel volume at that depth. It would require a billion cubic meters, or one cubic kilometer, of tunnel volume at 2 km depth to give 12 terawatt-hours of storage capacity.

One hundred thousand kilometers of tunnels, if the average tunnel cross section is 10 m^2. That would be one hellofa coal mine.

Julian Silk's picture
Julian Silk on Feb 12, 2023

Given the risk of flooding, wouldn't it be reasonable to see which of these mines could be converted to pumped storage hydroelectric facilities?

Len Rosen's picture
Thank Len for the Post!
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