New Long Duration Energy Storage System Deploys Underground Hydropower

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As any natural gas industry insider will tell you, a whole new fleet of natural gas power plants is needed to make sure the nation’s supply of electricity keeps up with demand. That opinion is clearly separated from reality. The domestic wind, solar, and storage industries have already proven they can get the job done, and new developments on the energy storage scene make the case for renewables all the more compelling.

Who Needs New Long Duration Energy Storage Systems?

If you’re wondering why something new and different is needed for wind and solar storage when lithium-ion battery technology is widely available, that’s a good question. Diversifying the energy storage supply chain is one significant consideration. Onshoring the supply chain is another benefit, as is de-risking the supply chain to avoid toxic materials and ethical entanglements.

The key benefit of alternative storage systems, though, is to provide high volume, long duration storage for wind and solar energy. Li-ion batteries do a good job of handling variations in wind and solar for a few hours at a time. They can deal with daily grid balancing chores and smooth over short-term emergencies, too. However, a more robust energy storage platform is needed for the grid of the future, saturated as it will be with wind and solar energy and beset with more climate-related emergencies.

The US Department of Energy has spent a long time and a lot of taxpayer dollars encouraging innovators to explore new long duration solutions capable of delivering power for 10 hours or more — and ideally for days, months, and seasons. Nevertheless, the oldest technology on the books still dominates the scene, that being pumped hydropower. Despite all the innovator activity, pumped storage systems still account for about 95% of long duration storage in the US.

The Geomechanical Solution

Signs progress have finally begun emerging in recent years.The Texas firm Quidnet, for example, has come up with a new twist on the hydropower angle. Instead of relying on the above-ground reservoirs used in conventional pumped storage systems, Quidnet has leveraged know-how from the oilfield services industry to develop a cost-shaving subsurface system it calls Geomechanical Energy Storage.

“Quidnet pumps water underground and stores it in-between layers of rock. The natural elasticity of the rock performs like a spring and holds the water under pressure until it is needed, at which time it is released through a hydroelectric turbine to produce electricity and send back to the grid,” the company explains.

That sounds simple enough, but the devil is in the details. Quidnet launched in 2013 with a plan to develop a new kind of injector-generator that serves as a modular hydropower system, capable of deployment in unused oil and gas wells in addition to purpose-built locations.

Quidnet surfaced on the CleanTechnica radar in 2019, when it earned funding from the US Department of Energy to develop the GES system for commercial use. Last year we caught up with Quidnet again, after it nailed down a $10 million, 300-megawatt strategic partnership with Hunt Energy Network.

Quidnet has received Energy Department funds from two offices, the Water Power Technologies Office and ARPA-E, which is the office tasked with supporting transformational innovation in the energy field. ARPA-E is supporting a Quidnet project for the Texas municipal utility CPS Energy. In the most recent development, on June 25 Quidnet announced a successful test of the CPS project. The GES system clocked a discharge of 35 megawatt-hours after storing energy for six months.

That’s not a typo. It was six months, not hours, days, or weeks. To ice the long duration cake, the GES system lost no power during six months of sequestration. That’s a sharp contrast with battery-type systems, which lose charge when idled for long periods.

More Data Centers, More Energy Storage, Less Gas

The GES system is designed to leverage excess energy on the grid. That may include gas and/or coal power plants in some regions, but ideally the system would recharge when more excess wind and solar are available. In a press statement on June 25, Quidnet put gas stakeholders on notice, drawing attention to GES’s ability to meet the “firm power demands of the growing AI data center sector.”

Further underscoring the ability of GES to compete with new gas power plants, Quidnet had this to say:

At a time when a substantial backlog of large-scale generation projects threatens the country’s grid, Quidnet’s GES technology leverages a uniquely unconstrained supply chain to meet hyperscale power demand with rapidly deployable and reliable power capacity.

That thing about “unconstrained supply chain” is a not-so-subtle dig at gas power plant developers, who are facing long delays partly due to a global turbine backlog reportedly stretching up to seven years.

Wait…Hunt Energy Network?

If you caught that thing about Hunt Energy Network, that’s where things get interesting. That’s Hunt, as in the Ray L. Hunt family business Hunt Consolidated, which has been pickled in the oil business since the 1930s.

They’re not about to give up on that any time soon, but they did launch HEN in August of 2024 as a new venture in their portfolio, in order to cash in on the Texas market for energy storage. The opportunity also attracted the attention of Manulife Investment Management, which is backing the HEN venture under an arrangement for the John Hancock Life Insurance Company.

As for why Texas, that’s easy. Texas is a perfect storm of opportunity for long duration energy storage innovators. That includes the renewable energy side. Texas is a longtime, perennial leader in wind-driven electricity generation, and it is giving California a run for the money as the nation’s #1 producer of solar power as well.

That status is out of whack with the state’s iconic position in the oil and gas industry, but there are reasons (#ERCOT) for that. Texas energy planners have been in a mad scramble to exploit any and all in-state energy resources ever since the 1990s, when state lawmakers decided they would not enroll Texas in a new, regionally organized electricity-sharing scheme under the purview of federal regulators.

A pox on those pesky federal regulators. As a result of that decades-old decision, Texas is largely cut off from outside help when its grid is stressed. On the plus side, grid managers are eager to exploit the state’s copious wind and solar resources to the fullest extent possible, and that’s where energy storage comes in.

To be clear, energy storage systems, including Quidnet’s, are typically source-agnostic. CPS Energy, for example, includes natural gas, nuclear, and coal in its power generation portfolio alongside wind, solar, and landfill gas.

In addition, the Republican-lead state legislature has been muddying the waters for wind and solar development in Texas. Still, Texas is not the only state where new energy storage systems can put down stakes. Hold on to your hats…

Photo (cropped): The US startup Quidnet has successfully tested a new long duration energy storage system for six months without loss of power, leveraging water pressure in underground reservoirs to conserve excess electricity from the grid (courtesy of Quidnet).