Obermeyer Hydro and its project partners NREL, Microtunneling, Inc., and Small Hydro Consulting found that, compared to conventional pumped-storage resources, Obermeyer’s novel PSH system could reduce initial capital costs by 33%, increase the number of potentially viable sites, decrease potential environmental impacts of PSH projects, and reduce geologic risks of underground powerhouse construction. Geological surprises can make the complex underground excavation and construction associated with PSH susceptible to unexpected costs and delays; therefore, risks can be mitigated by reducing the volume and complexity of such excavations. The company’s configuration is uniquely designed to only require construction of a vertical shaft to position a submersible pump-turbine/motor-generator sufficiently deep, instead of an elaborate underground cavern that would involve much larger excavation. By providing the PSH pump-turbine in a shaft instead of an underground powerhouse, Obermeyer’s technology will help reduce costs and time of construction for future deployments.

To enable broader development of PSH, both cost and scale reductions are important. To help shorten deployment times and reduce project costs and other vulnerabilities, WPTO awarded funding to Obermeyer Hydro, Inc., to design a cost-effective, small-scale, adjustable-speed PSH system optimized for U.S. energy storage requirements. According to WPTO’s Hydropower Vision report, the United States has the potential to add 36 GW of PSH by 2050—more than doubling the country’s current capacity. But since 2000, only one new PSH project has been constructed in the United States. Historically, PSH projects must be very large to justify the high fixed costs associated with engineering complex underground structures that come with inherent geological risk. Reversible-pump turbines have strict, design-specific submergence requirements and are typically installed in a large, excavated underground powerhouse—but such facilities are also expensive and require suitable geology.

Obermeyer’s project focused on the design of an adjustable-speed PSH motor-generator and also took a lens to the integration of several subsystems, including electromagnetic and mechanical components and weights, into a complete PSH system design while developing a breakdown of estimated costs. The required subsystems include the pump turbine itself, the motor-generator, the power converter, the control system, and the water conveyance structures, including penstock, draft tube, shaft with liner access cover, and pressure relief valve. The novel permanent-magnet motor-generator with heat pipe cooling promises higher power density than traditional permanent-magnet designs. Hydraulic efficiencies of 94%–95% were achieved through computational fluid dynamics modeling and independent verification of the system.

A publication capturing these results, methodologies, and further data is expected to be released in early 2021.

For additional information, contact Henry Obermeyer.

Obermeyer’s PSH configuration.
In Obermeyer’s PSH configuration, a turbine-generator is placed at the bottom of a shaft with a lifting mechanism to facilitate future maintenance.
Courtesy of Obermeyer Hydro, Inc.

Grid Reliability, Resilience, & Integration Success Stories