The new pumped-hydro design leverages water to add more solar and wind power onto the grid. (Image Credit: NREL)
In a collaborative effort with the National Renewable Energy Laboratory (NREL) and other firms, Obermeyer Hydro Inc. designed a new pumped hydro system. The goal is to deploy the system in a time-efficient manner while cutting down on project costs and optimizing them for U.S. energy storage requirements. Obermeyer received a $1.18 million fund to develop the advanced closed-loop system as part of the U.S. Department of Energy Water Power Technologies Office’s HydroNEXT initiative.
This new design does not need an underground powerhouse, which is one of the more expensive, risky, and environmentally impactful aspects of pumped-storage hydropower construction. NREL researchers collaborated with Auburn University to perform an economic analysis of this new design. The research showed that abandoning the underground powerhouse results in a 33% decrease in project costs, with a 45% savings in construction costs.
The team also confirmed the computational fluid dynamics analysis of the pump-turbine performance. The round trip efficiency makes the technology extremely competitive in the energy storage technology field.
“We’re investigating ways to best meet large-scale grid storage needs while also tackling problems facing today’s electric power sector,” said Greg Stark, a principal investigator at NREL. “Obermeyer’s adjustable-speed pumped-storage hydropower system shows several significant advantages—it is highly scalable, adaptable to a number site types, and the design addresses project cost, timeline, and risk concerns.”
In this project, Obermeyer uses a new reversible pump-turbine design. Traditional pumped hydro designs have turbines that need to be buried deep below the tailwater surface elevation in an underground powerhouse to prevent destructive cavitation. Obermeyer’s turbine is installed in a vertical well=like structure, helping to reduce construction cost and eliminates project risk associated with an underground powerhouse.
Even though this method solved those problems, it created a new one. To replace an underground powerhouse with a “well,” Obermeyer needed to design a more compact turbine. A 180-degree meridional flow reversal made it possible to achieve this. “The entire project team expected an efficiency penalty due to this 180-degree flow reversal,” said Henry Obermeyer, Obermeyer Hydro, Inc.,’s president and chief engineer. “By comparison, the flow in a conventional Francis pump-turbine runner is only diverted 90 degrees. This novel arrangement required a coaxial diffuser, which unexpectedly outperformed a traditional scroll case diffuser and yielded a net efficiency bonus rather than the anticipated efficiency penalty.”
This new approach makes the 1-to 100-MW PSH projects more appealing from a site selection and a project economics standpoint. It could also create new opportunities for PSH.
“Only 3% of all dam infrastructure in the United States generates power,” said Katherine Obermeyer, strategic project manager of Obermeyer. “By tapping into nonpowered dams with our scalable and versatile solution, we can facilitate increasing amounts of renewable energy storage throughout the country.”
This new design could be utilized in closed-loop, and open-loop pumped storage projects, using underground and above-ground reservoirs, portable water storage and seawater. It can also be used in non-storage applications such as high-efficiency pumps for water supply and conveyance and premium-efficiency well pumps.
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