Tech Insights

Design Guidance for Critical Hydro Systems

April 18, 2024 by John Nieman

Pumped storage hydropower systems can offset renewable energy fluctuations and protect grid stability. A Department of Energy study explores how to scope out ideal sites for hydropower systems and which geomembrane liners offer improved efficiency for their operation. 

The shift to clean energy is in full swing, and the vast strides made by solar power, wind energy, and the electric vehicle market are center stage in this shift. Hydropower's role is critical, especially because pumped storage hydropower (PSH) systems can protect the grid from unforeseen failures. When an excess of energy is available, PSH systems can pump water into an elevated reservoir, thus creating a readily available reserve during sudden decreases in the power supply from intermittent solar and wind sources. 

The U.S. Department of Energy’s (DOE) Argonne National Laboratory recently completed several studies to help advance PSH technology. They examined Alaskan topography to map ideal sites for PSH systems and studied geomembrane liners, which optimize the systems’ performance by reducing leakage and promoting efficiency.  

 

Pumped storage hydropower system in operation.

Pumped storage hydropower system in operation. Image used courtesy of DOE 

 

Grid Impacts of Unstable Wind and Solar

Although wind and solar power significantly contribute to energy for the grid, natural energy sources are not controllable in the same manner fossil fuels have been manipulated. 

As years pass, renewable sources of electricity like solar and wind are growing steadily, and fossil fuel use is decreasing in equal measure.

 

The sources of our electricity

The sources of electricity. Image used courtesy of the Energy Information Administration

 

Even though these trends are steady, they will have to accelerate substantially in the coming years to meet energy mandates. Various national and international regulations are swiftly moving toward net zero emissions and the significant expansion of wind and solar to meet these goals. 

However, as dependence on these energy sources grows, the grid will become increasingly vulnerable to their natural fluctuations

Variable input renewable energies can cause serious problems for large electrical systems because they are simply not controllable and thus subject to unexpected variations. Shifts to other energy sources must compensate. Recent California heat waves and the infamous 2021 winter storm in Texas caused grid failures and blackouts connected to underperforming wind and solar power sources. Additionally, 1.1 million consumers in Britain faced a blackout when the Hornsea 1 offshore wind facility experienced a sudden failure.

Other seemingly mundane drops in wind speed can also lead to unexpected power problems, such as the occurrence in Europe in 2021, when unseasonably light winds contributed to power scarcity, leading to skyrocketing electricity prices. 

 

PSH Systems Store Energy for High-Demand Periods

Given the risks associated with the expanding solar and wind power sectors, complementary energy systems are needed to stabilize unexpected shifts in supply. The studies just finished by the DOE’s Argonne National Laboratory are designed to help facilitate the implementation of critical, value-adding PSH systems. They focused on streamlining the site selection process and advancing technology associated with the geomembrane liners to improve efficiency once more systems are built. 

Often overlooked, PSH systems provided an astounding 96% of stored grid-scale energy in 2022. With the projected growth of wind and solar projects, supporting PSH growth is essential to shore up fluctuation vulnerabilities.  

The studies focused on rural communities in Alaska, which still relied on fossil fuels for 68% of the state’s electricity. Such rural communities are common throughout the U.S., so this research sets a precedent for aiding the development of PSH systems in other rural regions vulnerable to grid failures. 

The study found that smaller-scale PSH projects with prefabricated components are more useful in remote locales than larger projects, which depend on infrastructure likely to be insufficient in rural places. This research will help stakeholders make future decisions about evaluating sites and analyzing site-specific characteristics to maximize investments in PSH construction. 

The study also evaluated geomembrane lining systems for the PSH reservoirs. These geomembrane systems have been in use for some time. Extensive guidelines exist for their use in other applications, like dams, but design guidance for their use in PSH systems is lacking.

 

Visualization of a textured geomembrane at various threshold heights

Visualization of a textured geomembrane at various threshold heights. Image used courtesy of DOE

 

The report found no superior material for these geomembrane linings but recommended further research to help establish formulas for selecting the best lining based on myriad contextual variables. Researchers advised additional work on cost analysis and reference design to ensure optimal performance of geomembrane linings used in PSH applications. 

This DOE research will help other engineers develop more PSH systems, which will play a central role in stabilizing the electrical grid as it becomes ever more dependent on renewable sources of power subject to unexpected weather oscillations.