Low-Cost, Modular Pumped-Storage That Can Be Installed Anywhere—ORNL GLIDES Project Nears Commercial Readiness

ORNL concluded a 4-year research, testing, and analysis project investigating a new lab-developed PSH technology, and results indicate promising cost and commercialization potential. The Ground-Level Integrated Diverse Energy Storage (GLIDES) project concluded R&D of a new form of PSH targeting the gap between small-scale batteries and large grid-scale PSH options. Throughout 2019–2020, ORNL completed modeling and simulation of GLIDES to verify its viability as a storage option for a number of scales in utility and behind-the-meter applications, and completed market analysis that confirmed the technology’s ability to provide essential reliability services across diverse U.S. electricity markets. To cap off the project, ORNL evaluated the economic value of co-locating GLIDES within a run-of-river hydropower plant and co-optimizing their joint operations to reduce systemwide energy costs and open up new opportunities to participate in ancillary markets, a capability traditionally unavailable for run-of-river facilities.

GLIDES is a modular, scalable energy storage technology designed for a long life (>30 years), high round-trip efficiency (ratio of energy put in compared to energy retrieved from storage), and low cost. The technology works by pumping water from a reservoir into vessels that are prepressurized with air (or other gases). As the liquid volume inside the pressure vessel increases, the liquid acts as a piston and compresses the gas in the vessel, storing energy. When electricity is needed, a valve opens and the compressed gas in the pressure vessel pushes the high-head water through the GLIDES system’s hydraulic turbine to generate electricity.

Over the course of the multiyear (2016–2020) project, ORNL focused on validating the GLIDES system performance, reducing the capital cost of the pressure vessels, which account for 75%–90% of total system costs, and evaluating revenue potential through market participation. The researchers built and demonstrated two proof-of-concept prototypes at ORNL using carbon steel and carbon-fiber pressure vessels and supplied air and water as the working gas and liquid. To study the behavior of the prototype systems, the research team developed and validated physics-based and techno-economic models using experimental data from the prototypes. Round-trip efficiencies as high as 82% were achieved in the experiments, and ORNL identified multiple pathways for increasing GLIDES system performance and minimizing capital costs. Market analyses conducted in 2019 also showed the technology can provide essential reliability services across diverse U.S. electricity markets. A case study performed for a grid-scale 60-megawatt-hour (MWh) system demonstrated that GLIDES can produce yearly revenues of as much as $10 million by providing ancillary services such as arbitrage, operating reserve, and regulation services. Based on the estimate of annual revenue and capital costs, the expense of a 60-MWh GLIDES system can be recouped in as little as 3 years.

Complementary to the lab’s earlier analysis, during 2019–2020 ORNL was also able to conduct additional simulated studies for GLIDES leveraging available hydropower data from INL’s Integrated Hydropower Storage Systems project. The objective was to evaluate the financial performance of GLIDES when incorporated within four cascading run-of-river hydropower plants. As these types of facilities are typically not configured to have an impoundment, they have limited operational control and ancillary services. Because GLIDES is a form of energy storage, ORNL saw an opportunity to evaluate the technology as part of an integrated hydropower and energy storage system to not only provide energy but also participate in ancillary markets and thus create more revenue streams. The Integrated Hydropower Storage Systems project had previously evaluated the financial performance of these four cascading run-of-river hydropower plants when combined with other types of energy storage, including flywheels and Lithium-ion batteries. Partnering with the integrated team allowed for an apples-to-apples comparison of the potential benefits of hybridizing run-of-river hydropower plants with different types of energy storage.

In the case study, each run-of-river plant was assumed to be equipped with a 1-MW, 4-hour-duration GLIDES system. Researchers then estimated the annual profit based on typical selected days using the collected downstream water flow rate data and a price profile generated by the integrated team. The simulation looked at scenarios wherein it was more efficient to use the generation from the run-of-river plants to charge GLIDES versus when it was more optimal to sell to an energy market directly. Results showed that, when incorporated into the run-of-river system, GLIDES could be highly profitable within a 4- to 6-year payback period, with each megawatt-hour of energy or ancillary service provided by the integrated hydropower energy storage system to the power grid reducing energy production costs, including decreased transmission congestion and losses.

For additional information, contact Brennan T Smith.