Can pumped storage fuel a more sustainable future?
Integrating renewables with pumped storage can build a resilient and sustainable energy future
Hydroelectric projects use the pressure of water flowing downstream to move turbines which generate electricity for consumers.
A pumped storage project adds the capability to pump water uphill when there is excess electricity on the grid. The excess electricity powers pumps that move the water uphill to release later when more generation is needed.
Often referred to as a large “water battery,” pumped storage can store excess electricity produced by other sources of renewable energy.
How does a pumped storage system work?
By Kathleen King and Craig Scott
Reservoirs are connected by pipelines that pass through a powerhouse.
Pumped storage has been used as a means of energy storage since the early 1900s. It is the largest source of energy storage both in terms of capacity and number of plants.
These projects can both produce a lot of power (megawatt-capacity) and store it for long periods of time (megawatt-hours). This stands out amongst other energy storage options.
Challenges for new pumped storage plants include size, capital cost, reliance on specific geographies like mountains, and prolonged development timelines. In recent years, developers and experts are revisiting these challenges with a new enthusiasm exploring potential sites outside of the typical geography and involving new technologies.
Pumped Storage Today
As energy consumers, we might take for granted that at every instant, grid operators are balancing the supply of electricity with the demand.
The significant expansion of solar and wind energy pose even greater challenges for these grid operators, who can’t control when the sun is shining or the wind is blowing. A very sudden change in supply—for example, the drop of solar power at sunset—means other generation sources must quickly make up the difference.
In places with significant solar power production—like California—when you plot the difference between total electricity demand and the amount of solar power over the course of a day, it can resemble the shape of a duck. The “neck” of the duck shows a dramatic increase in electricity production needed over a short period of time as the sun sets while the total electricity demand is still high. The neck of the duck is a problem for the grid.
While it’s difficult for some types of generators to respond quickly enough to keep the grid reliable, pumped storage excels at rapidly bringing large amounts of generation online to fill the gap.
Combining with renewables for a sustainable future
Pumped storage has the unique ability to provide energy reserves and grid reliability. An estimated 36 GW of new pumped storage capacity could be added to the grid. Both operators and consumers see pumped storage as a proven and sustainable solution to our energy storage needs.
Pumped storage projects have two reservoirs close together with a significant elevation difference.
Global energy storage capacity installed
Pump storage plants operating in the United States
Potential for new pumped storage capacity in the US
Steady growth in renewable generation, such as wind and solar, creates demand for grid-scale energy storage. Pumped storage hydropower is a proven, reliable, and sustainable answer to our energy storage needs.
When demand is low, excess renewable energy from wind and solar can be used to pump water from the lower reservoir to the upper, storing the energy for later use.
Former mine sites could become pumped storage projects using mined areas as lower reservoirs.
The duck curve shows electricity production needed after accounting for solar power production to meet demand. A sharp rise in electricity production needed around sunset is a problem for the grid that pumped storage can help solve.
When power is needed, water is released from the upper reservoir producing energy that can be quickly added to the power grid.
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The powerhouse contains reversible pump-turbines which can generate electricity while in turbine mode and store energy while in pump mode.