A New Energy Storage Solution For Wind And Solar Power

---

Support CleanTechnica’s work through a Substack subscription or on Stripe.

---

This year’s sharp U-turn in federal energy policy is a head-scratcher for any number of reasons. Wind and solar are out, but other renewables are in. For example, hydropower made the list of favored resources, which means that pumped hydropower systems are on the table, too. On the down side, traditional pumped hydro systems are massive, expensive pieces of infrastructure with limited opportunities for siting. However, solutions are emerging….

In The US, Pumped Hydropower Is The Hero Of Energy Storage

Pumped hydropower means just what it says. Water is pumped from a low-lying river or reservoir, into a reservoir located at a higher elevation. When electricity is needed, gravity does all the the heavy lifting. The water flows downhill to a generating station, where it runs turbines to produce electricity.

Pumped storage systems predate the renewable energy transition, but they are an ideal match for today’s utility-scale wind and solar farms. For all the improvements in battery-type energy storage systems and new long-duration storage systems, pumped hydro still accounts for about 95% of the bulk-quantity, long-duration energy storage capacity in the US.

During periods when electricity demand is low but the sun is shining and/or the wind is blowing, the excess capacity from wind turbines and solar panels can be put to work at a pumped hydropower facility. If electricity is needed at night-time or during periods of slack wind, the pumped hydro system can be called into play.

A New Model For Pumped Hydro Energy Storage

The US does offer some opportunities for constructing new pumped hydro facilities, but then the cost factor kicks in. The long construction timeline is another inhibiting factor.

Alternative pathways are beginning to emerge. A Texas startup, for example, is repurposing old oil wells for pumped storage. Other solutions involve deploying water pressure in the ocean.

The latest example to cross the CleanTechnica radar comes from the Italian startup Sizable Energy. “Sizable Energy’s patented offshore pumped hydro system stores energy by pumping saturated sea salt brine (heavier than seawater) from the seabed to a surface reservoir, leveraging the depth of the ocean for efficient energy storage,” Sizable explains.

The company’s website is a little thin on detail, except to note that the system is fairly straightforward and can be assembled through local supply chains. The lower reservoir is fixed to the ocean floor and the upper reservoir floats on the surface, with a connecting pipe in between. Reversible pumps move the saturated brine from one reservoir to another.

Sizable has already passed the system through tank tests, followed by trials at sea. The next step is a pilot-scale facility, already underway off the coast of Reggio Calabria, Italy. “This pilot will validate all key floating components, demonstrate the full-scale assembly and deployment process, setting the stage for a multi-MWh demonstration plant in the Mediterranean Sea off the coast of Italy,” Sizable notes.

The company does not intend to let the grass grow beneath its feet. “With this milestone approaching, the company is preparing for commercial project development in 2026 across multiple global sites, in partnership with local manufacturers, governments, and energy providers,” the company added.

More Energy Storage For Wind & Solar Power

In a press statement, Sizable Energy board member Bruce Leak drew the connection between pumped storage and renewable energy. “As a society, we’ve proven that wind and solar can deliver the cheapest electrons. Now we urgently need a long duration energy storage solution that can be economically deployed at massive scale,” said Leak, who is also a partner in the California-based energy transition investment firm Playground Global.

“Ocean depth is a practically unlimited resource, and Sizable Energy is leveraging it to deliver long-duration energy storage at a fraction of the cost of batteries,” Leak added. “Their gravity-based approach is the clear path to enabling energy abundance.”

Heads Explode As Pumped Storage Meets Marine Energy

Leak’s firm was the lead investor in a new $8 million funding round aimed at taking the Sizable Energy solution to market. Energy-thirsty coastal cities would be a good place to start. Utility-scale solar farms are difficult to wedge into crowded coastal regions, but, the booming global offshore wind industry provides an alternative source of clean kilowatts.

Except, of course, here in the US. Upon taking office earlier this year, US President Donald Trump made good on his oft-repeated promise to dismantle the US offshore wind industry. Though not a complete setback, the war against offshore wind has put a crimp in the renewable energy aspirations of coastal communities.

Still, a new Wood Mackenzie report indicates that the domestic offshore wind industry has enough wind in its sails, so to speak, to sustain itself for several years. By then perhaps federal energy policy will take another tack, smoothing the way for offshore energy storage solutions to pair up with the copious offshore wind resources of the US.

Another offshore angle to consider is the emerging marine energy industry, meaning devices that harvest kinetic energy from waves, tides, and currents. The technology challenges are formidable and scale-up is years away, so marine energy is not necessarily a near term solution. In an interesting twist, though, marine energy falls into the category of renewable energy resources protected by the “American Energy Dominance” policy, alongside biomass and geothermal energy as well as hydropower.

Marine energy was not specifically named by the White House when the new policy launched in January. However, since then the Energy Department has indicated that marine energy fits the reliable, 24/7 power generation standard described by “American Energy Dominance.”

As for why the new policy doesn’t recognize that modern battery systems and advanced grid management tools that provide wind and solar with the same level of reliability as other renewables, that’s a good question. By way of explanation, Interior Secretary Doug Burgum has suggested that energy storage is not even a thing that exists.

That’s one answer. If you can think of any others, drop a note in the comment thread.

Photo: A new, floating pumped hydropower system aims to cut the cost of utility-scale energy storage for wind and solar farms (cropped, courtesy of Sizable Energy via businesswire.com).