Pumped Storage Hydropower is America’s Energy Storage
Everything old is new again. Hydropower is making its comeback, and not just as a generation source. Water can act as a battery, too. It’s called pumped storage and it’s the largest and oldest form of energy storage in the country, and it’s the most efficient form of large-scale energy storage.
Hydropower was America’s first renewable power source. It is often mistakenly considered a tapped resource, but according to the U.S. Department of Energy’s 2016 Hydropower Vision report, hydropower’s capacity can sustainably add 50 new gigawatts by 2050 — 36 GW of which is pumped storage.
The Ultimate Water Battery: Unleashing the Power of Hydropower
Energy Storage
NHA Unveils 2024 Pumped Storage Report
The National Hydropower Association (NHA) released the 2024 Pumped Storage Report, which details both the promise and the challenges facing the U.S. pumped storage hydropower industry.
As the global community accelerates its transition toward renewable energy, the importance of reliable energy storage becomes increasingly evident. Among the various technologies available, pumped storage hydropower (PSH) stands out as a cornerstone solution, ensuring grid stability and sustainability. This report explores the substantial benefits, challenges, and strategic pathways for advancing PSH in North America, emphasizing its vital role in a renewable energy future.
According to the International Hydropower Association’s (IHA) 2024 World Hydropower Outlook, global PSH capacity grew by 6.5 GW in 2023, reaching 179 GW. Projections by the International Renewable Energy Agency (IRENA) to meet a global net-zero scenario by 2050 indicate that over 420 GW of PSH will be required, which means about 10 GW/year of new installed capacity or an annual installed capacity growth rate of approximately 3.3 percent. For the United States to meet its corresponding share of the global net zero goals, it would require an average of about 1000 MW of new PSH installed yearly.
The United States needs new pumped storage to meet its long-duration energy storage needs and support its federal and state renewable energy targets. This report provides an analysis of PSH’s evolution and technological advancements and suggests strategic actions to overcome existing barriers specific to the United States. In the United States, 67 new PSH projects are planned across 21 states, representing over 50 GW of new storage capacity. The future of energy is one where reliability, sustainability, and resilience are all paramount. PSH is uniquely positioned to deliver on all these fronts, making it an indispensable component of our energy strategy.
Pumped storage today makes up 97 percent of utility-scale energy storage in the United States at 42 sites with a total of 23 GW of capacity.
Pumped Storage Explained
Pumped storage facilities are built to push water from a lower reservoir uphill to an elevated reservoir during times of surplus electricity. In pumping mode, electric energy is converted to potential energy and stored in the form of water at an upper elevation, which is why it is sometimes called a “water battery”. Pumping the water uphill for temporary storage “recharges the battery”.
From there, gravity takes care of the rest .During periods of high electricity demand, the stored water is released back through the turbines and converted back to electricity in generating mode like a conventional hydropower facility.
Illustration source: U.S. Department of Energy Hydropower Vision Report
Pumped Storage Enables More Wind and Solar
Pumped storage hydropower enables greater integration of other renewables (wind/solar) into the grid by utilizing excess generation, and being ready to produce power during low wind and solar generation periods. It also has the ability to quickly ramp electricity generation up in response to periods of peak demand.
As the capacity of available firming resources continue to be stretched to their limit to support the growth of
variable renewable energy resources, the U.S. electric industry is moving more toward the deployment of emission-free energy storage resources. Pumped storage provides predictable, consistent generation.
Pumped storage facilities are like sponges; they can suck up this excess energy from the grid and store it for later.
Pumped Storage and the Grid
Other renewables, like wind and solar generation, while less variable with adequate geographic diversity, can present new
challenges for the U.S. grid. The power output in variable generation resources can fluctuate widely as weather patterns change and, while the changing weather patterns may be well understood, the magnitude of renewable energy generation ramps (in particular, when not in correlation with changing load) can be challenging to grid operators when renewable energy resources are a large component of their generation portfolio. This variable output can lead to frequency and voltage fluctuations, which adversely affect grid stability.
Pumped storage, however, meets increased transmission system demands for reliability and system reserves. It shifts, stores, and reuses energy generated until there is the corresponding demand for system reserves and variable energy integration.
This shifting, when performed at a grid-scale, can also avoid transmission congestion periods (i.e., absorb or consume surplus generation to levels consistent with transmission transfer capability), to help more efficiently manage the electric grid (e.g., quick access to significant and sustained energy ramping), and to avoid potential interruptions to energy supply (e.g., supply operating reserves, spinning inertia, etc.). Advanced adjustable speed technology also allows pumped storage to provide an even greater range of fast ramping, both up and down, and frequency regulation services in both the generation and pumping modes.
