THE MOST ECONOMICAL STORAGE TECHNOLOGY FOR LONG DISCHARGE DURATION

Pumped Hydro Storage

ENABLING THE ENERGY TRANSITION

Centralized synchronous plants will be less dominant in the future energy mix and with the massive penetration of intermittent renewables such as wind and solar and their impact on the grid reliability is huge. Supply of energy is variable and services to maintain voltage or frequency of the grid cannot be met by inverter-based resources.

Hydropower can play a defining role in the energy transition thanks to the balancing and system services to the grid that facilitate the integration of variable renewables. With higher needs for storage and grid support services, Pumped Hydro Storage is the natural large-scale energy storage solution. It provides all services from reactive power support to frequency control, synchronous or virtual inertia and black-start capabilities. It brings support that was previously managed by fossil-fueled power plants but with even more reactivity and in a sustainable manner without CO2 emissions.

For years, Pumped Hydro Storage has offered a cost-effective way to provide reliable large-scale balancing and grid services. New pumped hydro storage technologies—such as variable speed capability—give plant owners even more flexibility by providing grid frequency support in both directions (in turbine and pump modes) as well as quicker response times.

The high inertia of rotating machines can also stabilize the grid in case of disturbances, which influences grid frequency, enabling low-inertia renewable energies, such as wind and solar to enter the grid and allowing their power to be transmitted over great distances.

Hydro storage technology is an enabler for the transition and modernization of 21st century power generation. It provides production, storage and grid stabilization. Moreover, it brings a critical benefit that distinguishes it from the others—water management.

How does Pumped Hydro Storage work?

Pumped hydro storage plants store energy using a system of two interconnected reservoirs with one at a higher elevation than the other. Water is pumped to the upper reservoir in times of surplus energy and, in times of excess demand, water from the upper reservoir is released, generating electricity as the water passes through reversible Francis turbines on its way to the lower reservoir. The process is then repeated with an overall cycle efficiency of about 80%.

With fixed speed pumped storage plants, power regulation is possible while the plant is generating electricity but with the state-of-the-art variable speed technology, power regulation in specific ranges is possible while generating and while pumping, providing additional flexibility to support the grid stability.