Helmo Preuss
Pumped storage hydropower (PSH) is the best solution for long-duration energy storage (LDES), Eddie Rich, the CEO of the International Hydropower Association (IHA), told the Pre-Assembly Day of the Fifteenth session of the International Renewable Energy Agency (IRENA) Assembly in Abu Dhabi.
The theme of the event was: Accelerating the Renewable Energy Transition – The Way Forward (Energy security, Socio-economic development and Financing options). Participants in the round table discussion highlighted the importance of grid and storage solutions for accelerating the energy transition and their crucial role in achieving renewable energy and storage targets by 2030, which amounted to 1 500 Gigawatts (GW) of energy storage and 25 million kilometres of transmission lines.
PSH uses off-peak power to pump water to an upper dam and then releases this water to a lower dam to generate power during peak periods, so essentially it becomes a water battery.
The main cost of pumped storage is the capital cost, as two dams have to be constructed, the tunnels and powerhouse have to be excavated, the turbine/pumps have to be installed, and the high-voltage transmission lines have to be linked to the rest of the national grid.
The operational cost is minimal; the efficiency loss of electricity is only 20% as it takes 20 hours to fill the upper dam, which can provide 16 hours of power. The IHA currently estimates that PSH projects globally store up to 9,000 Gigawatt hours (GWh) of electricity or around a third of the 24,638 GWh South Africa lost to load shedding in 2023.
Rich also highlighted the need for PSH to cope with the rapid growth in variable renewable energy (VRE) sources such as solar and wind, as these power sources require stable, reliable, and flexible storage solutions that can operate at utility scale.
The flexibility that PSH provides through its storage and ancillary grid services is seen as increasingly important in securing stable power supplies as PSH offers services such as system inertia, frequency control, voltage regulation, storage and reserve power with rapid mode changes, and black-start capability.
All of these are vital to support the ever-growing proportion of variable renewables, but he said that at the moment utilities and governments did not know how to price these services to encourage investors to provide the capital that ensures an adequate return.
The current grid constraints mean that some wind and solar power is “wasted” as it exceeds the ability of the grid to handle the power, so this power is curtailed and is not used. PSH can help in avoiding curtailment, reducing transmission congestion, and reducing overall costs and emissions in the power sector.
“Pumped storage is currently experiencing a renaissance, with world leaders recognising it as a flexible, reliable, and renewable long-duration energy storage option, but we need to get the pricing and regulatory framework correct to encourage more investment,” Rich said.
The 2024 World Hydropower Outlook reported that 214 GW of PSH, or around four and a half times Eskom’s current capacity, are currently at various stages of development.
“The potential of pumped storage is enormous as recent atlases compiled by the Australian National University identify 600,000 identified off-river sites which excluded wildlife reserves, suggesting almost limitless upside,” Rich noted.
In addition, Rich said that there is increasing research and evidence for the benefits of retrofitting disused mines, underground caverns, non-powered dams, and conventional hydropower plants into PSH plants, so PSH could provide a solution for the world’s need to transition into a greener energy future.
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