Solving The Pumped Hydro Energy Storage Problem

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Pumped hydropower energy storage systems have a problem. They can provide long-lasting, large-scale storage for wind and solar power, but they are massive pieces of expensive infrastructure. They also require specific topography, and they can easily run into opposition on environmental grounds. If only someone, somewhere, could figure out a way to resolve all three issues at once — oh, wait.

Deploying Buildings For More Pumped Hydro Energy Storage

The solution to the pumped hydro problem is staring you in the face, if you live or work near a skyscraper. Simply attach a pumped hydro energy storage system to a tall building, and you can reduce the infrastructure expense while practically eliminating the potential for running afoul of sensitive environmental or cultural sites.

Leveraging the built environment for new pumped hydro systems also evaporates the topography problem. Conventional pumped hydro systems rely on an upper reservoir and a lower water source, which can be either another reservoir or a running river. When excess renewable energy is available, water is pumped from the lower level to the reservoir above. When electricity demand rises, the water is released from the upper reservoir to run downhill to a power generating station.

A similar (but different) gravity-based principle is at work in the elevated water towers commonly used to regulate water system pressure in many communities, so it was only a matter of time before someone applied the idea to buildings and power generation.

Leveraging Tall Buildings For Energy Storage

Of course, the devil is in the details, but the Swiss firm Energy Vault has a headstart. CleanTechnica took note of the company a few years ago, when it introduced an energy storage system that can be described as a waterless pumped hydro system. The Energy Vault system deploys excess renewable energy to run mechanical systems that raise and lower a solid weight (see our Energy Vault archive here).

In an interesting twist, back in 2021, Energy Vault also proposed recycling old wind turbine blades to provide the weights for its system.

Recycled turbine blades or not, the idea seems to be catching on. Energy Vault lists China among its clients, with 3.7 gigawatts’ worth of energy storage projects announced. The company also notes that it has projects in the pipeline in Egypt, Greece, and the 16-member South African Development Community.

In the meantime, Energy Vault has been applying its gravity know-how to pumped hydro systems, and that’s where the buildings angle comes in.

Earlier this week, Energy Vault announced a new partnership with the A-list architecture firm SOM (short for Skidmore, Owings & Merrill), aimed at incorporating its new suite of gravity storage systems into buildings, including pumped hydro as well as mechanical systems.

As described by Energy Vault, SOM is known for notable skyscrapers around the world, including Burj Khalifa, Tianjin CTF Finance Centre, Willis Tower, and One World Trade Center.

The Pumped Hydropower Energy Storage Statement

Considering the growing availability of both renewable energy and standalone energy storage systems, it’s fair to ask why anyone would want to incorporate a pumped hydro system into their building.

Since tall buildings are all about making a statement, making an even bigger statement is probably reason enough for some developers to consider incorporating a pumped hydro system into their plans.

“This partnership with Energy Vault is a commitment not only to accelerate the world’s transition away from fossil fuels, but also to explore, together, how the architecture of renewable energy can enhance our shared natural landscapes and urban environments,” SOM partner Adam Semel explained in a press statement.

Energy Vault is accommodating that market with its new EVc product, which it bills as the first to integrate a large scale pumped hydropower energy storage system within a building.

The EVc is designed primarily as a standalone system, but Energy Vault notes that it is compatible with buildings designed to accommodate the company’s new EVu mechanical system.

“EVc’s cylindrical shape is an optimized design to withstand environmental factors such as wind and seismic events,” the company also notes.

More Gravity Energy Storage On The Way

In addition to the EVc and EVu systems, Energy Vault is also rolling out another gravity system. Called EVy, this one relies on existing topography, but requires less infrastructure than conventional pumped hydro systems.

Rounding out the roster is EV0, which Energy Vault describes as an alternative to concrete-based pumped hydro systems. “EV0 allows for all of the technical and economic benefits of traditional pumped hydro storage, while eliminating negative consequences associated with concrete production and disruption to existing wild-life eco-systems,” Energy Vault explains.

“This innovative, ‘modular pumped hydro’ system leverages a unique and low cost fabric vessel (the “Water Tree”) to store the water in pre-manufactured modules that can be deployed quickly while leveraging proven pump-turbines and penstock designs for existing pumped hydro systems,” the company adds.

More Pumped Hydro Energy Storage For The USA

As for the US, finding sites for new pumped hydro energy storage facilities is not a cakewalk. However, there are some opportunities to get the ball rolling without running into a brick wall of opposition.

The Energy Department, for example, has been funding a pumped hydropower system that leverages water pressure in underground rock formations to minimize above-ground infrastructure.

Another example is taking place in Kentucky, where plans are in the works to convert an abandoned coal mine for pumped hydro energy storage.

Repowering the nation’s stockpile of existing pumped hydro facilities is another way to squeeze more clean kilowatts out of the technology without investing in all-new infrastructure.

The Energy Department is also determined to make the case for new closed loop pumped hydro systems. Closed loop systems recirculate the same water between two reservoirs, instead of releasing it to a running river.

The question is how closed loop systems stack up against other energy storage technologies in terms of lifecycle greenhouse gas emissions. In March, the Energy Department came up with the answer, based on an analysis of the design of closed loop systems at 35 proposed sites in the US.

“Researchers found that PSH [pumped storage hydropower], on average, offered the lowest GWP [global warming potential] when compared to compressed-air energy storage, utility-scale lithium-ion batteries, utility-scale lead-acid batteries, and vanadium redox flow batteries,” the Energy Department stated.

“These results demonstrate that enabling renewable electricity deployment by adding PSH to the grid will result in lower climate change impacts and contribute more to achieving the country’s clean energy goals compared to other grid-scale energy storage technologies,” they concluded.

That seems pretty definitive. If you have any thoughts about that, drop us a note in the comment thread.

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Image: Rendering of a gravity-based, building-integrated energy storage system (courtesy of Energy Vault via businesswire.com).