Scientists at Oak Ridge National Laboratory (ORNL) and the University of Tennessee, Knoxville (UTK), have unveiled an algorithm designed to forecast electric grid stability by harnessing signals from pumped storage hydropower (PSH) projects. This innovation emerges as a crucial tool in navigating the grid's transition towards intermittent renewable energy sources.

Hydropower is a renewable energy source directly connected to the grid, providing inertia as water spins large turbines. Pumped storage hydropower draws electricity from the grid to pump water from a lower to an upper reservoir in times of low power demand to create an energy storage bank. In times of high demand, the projects generate electricity as water is routed back to the lower reservoir through the turbines.

When the pumps shut down, they almost always stop at a fixed power level, said Yilu Liu, lead for the project and UT-ORNL Governor’s Chair for power grids. “That’s a very defined signal on the grid that can help us calculate overall inertia,” Liu said.

Inertia, denoting the kinetic energy sustained by the rotating components of large power plants, serves to uphold the grid's equilibrium amidst the flux of power supply and demand. However, renewables like solar and wind, linked to the grid via inverters, offer minimal inertia due to the conversion of direct current to alternating current, rendering grids susceptible to sudden disruptions.

To address this challenge, Liu and her team devised an algorithm that integrates the PSH signal with data gleaned from FNET/GridEye, a cost-effective grid sensing and measurement system devised by ORNL and UTK. This amalgamation yields a real-time, precise assessment of grid inertia.

The resultant visualization interface empowers grid operators to monitor inertia seamlessly, enabling proactive measures against potential grid instability. Validated with the assistance of utilities and regulatory bodies in the western and eastern US where pumped storage hydropower is most prevalent, the method showcases its efficacy in bolstering grid resilience.

“What we’re providing will become more and more important for grid situational awareness as the system grows increasingly reliant on renewables,” Liu said. The visualization tool is being demonstrated to utilities and grid coordinating authorities such as the North American Electric Reliability Corporation.

“Through this project we can demonstrate how important inertia is, and how pumped storage hydro can contribute to it, especially as we are looking at more intermittent renewable energy sources added to the grid,” said Shih-Chieh Kao, manager of the Water Power Program at ORNL.

The project was supported by the Water Power Technologies Office of the Department of Energy’s Office of Energy Efficiency and Renewable Energy as part of WPTO’s HydroWIRES initiative to leverage hydropower for greater grid reliability and resilience. FNET/GridEye was developed with support from DOE’s Office of Electricity.

ORNL and UT researchers created a new method to calculate the power grid’s inertia in real time, using signals from pumped storage hydropower facilities such as TVA’s Raccoon Mountain project, pictured here. Credit: Tennessee Valley Authority