Abandoned oil wells could revolutionize energy storage

Transitioning from fossil fuels to renewable energy, such as wind and solar, comes with a challenge: how to store energy for use when the sun isn’t shining or the wind isn’t blowing.

One possible solution is compressed-air energy storage (CAES), a system that compresses air and stores it underground when energy demand is low, then releases the air to generate electricity when demand is high.

While CAES has promise, high startup costs have slowed its adoption.

A new role for abandoned wells

Researchers at Penn State have explored a way to make CAES more efficient by tapping into natural geothermal heat in abandoned oil and gas wells.

The U.S. Environmental Protection Agency estimates there are around 3.9 million such wells across the country.

According to the study, repurposing these wells for CAES could improve energy efficiency by 9.5% over current methods, making the technology more viable for widespread use.

“This improvement in efficiency can be a game changer to justify the economics of compressed-air energy storage projects,” said Arash Dahi Taleghani, a professor of petroleum and natural gas engineering at Penn State.

“And on top of that, we could significantly avoid the upfront cost by using existing oil and gas wells that are no longer in production. This could be a win, win situation.”

Geothermal heat boosts energy storage

Depleted oil and gas wells provide access to hot rock formations deep underground. Gases, like compressed air, increase in pressure as temperatures rise, meaning these wells could store more energy.

When electricity is needed, the heated, compressed air is released to drive a turbine, generating power more efficiently than traditional CAES systems.

“Without taking advantage of the geothermal setup, you could not get enough encouraging numbers,” Taleghani explained.

The researchers used numerical modeling simulations to study the effect of placing CAES systems inside abandoned wells. They found that the geothermal heat significantly increased air temperature within the system.

“And on top of that, drilling new wells may not justify the economics of this type of storage. But by combining these two factors, and by going back and forth through modeling and simulation, we found this could be a very good solution.”

A crucial step toward clean energy

Energy storage is a key component of the clean energy transition. Renewables are inherently intermittent – there’s no sun at night, and wind speeds fluctuate – so storing excess energy and releasing it when needed is essential for grid stability.

“The problem is that sometimes when we need energy, there is no sunshine or there is no wind,” Taleghani said.

“That’s a big barrier against further expansion of most of the renewable energy that is available to us. That’s why it’s very important to have some storage capacity to support the grid.”

Environmental and economic benefits

Beyond improving energy efficiency, repurposing abandoned oil and gas wells could help address environmental concerns.

Many orphaned wells, if not properly sealed, can leak methane into the atmosphere and groundwater. Pennsylvania alone has hundreds of thousands of these wells, posing potential risks.

“If we use existing wells, we are basically hitting two birds with one stone,” Taleghani said.

“First, we are sealing these wells. That stops any potential leaks. And then if we are repurposing these wells for energy storage, we are still using the infrastructure that is in place in these communities. It can potentially maintain employment in the area and allow communities to be part of the energy future.”

This approach could create new job opportunities in regions that were historically reliant on the fossil fuel industry.

By converting old infrastructure into an asset for renewable energy, communities can participate in the clean energy transition while preserving local employment levels.

The future of energy storage

With improved efficiency and the potential to repurpose existing wells, CAES could become a more attractive option for large-scale energy storage.

While further research and investment are needed, this study highlights a promising way to bridge the gap between renewable energy supply and demand, without the heavy costs of drilling new wells.

As the world moves toward cleaner energy, innovative solutions like this could help reshape how we store and use power, making renewable energy more practical and reliable for the future.

The full study was published in the journal Journal of Energy Storage.

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