“Get used to blackouts or risk reverting to fossil fuels” is the stark warning from the International Forum on Pumped Storage Hydropower. Unless the world scales up investment in water batteries to support the accelerating deployment of solar and wind power, this is the future we will face.

The International Forum on Pumped Storage Hydropower was formed in November 2020. It is a coalition of 13 governments led by the US Department of Energy, the International Hydropower Association with more than 70 multilateral banks, research institutes, NGOs, and public and private companies. Its ambition is to research practical recommendations for governments and markets to address the urgent need for green, long duration energy storage in the clean energy transition.

According to the IHA, pumped storage installed capacity is set to more than double in the coming years. However, this still remains well short of the energy storage requirements of electricity grids increasingly reliant on solar and wind power for generation. By the end of 2020, there was 160GW of pumped storage hydropower installed globally, comprising 95 per cent of total installed energy storage.

“There is no doubt that that we will deploy wind and solar power at a huge scale. However, there is an ignored crisis within the crisis,” the pumped storage forum stated. “What happens when the sun does not shine, and the wind does not blow? These technologies need a low carbon back-up, or we will fall back on fossil fuels or simply have to get used to blackouts. We need flexible electricity systems to mitigate against these risks.”

Best alternative

Former Australian Prime Minister Malcom Turnbull is a co-chair of the forum. “We understand the red alert we face to address global warming. We understand the consequences of our to-date inadequate responses to it, and the even direr consequences of inadequate action in the future,” he said. “When we talk about the transition to zero emission energy systems, we often overlook long duration storage. That’s why this forum is such an important initiative because we have a real problem. On the one hand, variable renewable wind and solar are getting cheaper and cheaper all the time. And that’s fantastic…they are so much cheaper than we ever thought they would be,” Turnbull enthused. “But while the cost of variable renewable energy is decreasing it still remains variable. It remains intermittent and we have to be able to provide reliability. Without long duration storage you cannot make renewables reliable.

“The best alternative,” Turnbull continued, “is pumped storage. It’s an old technology, over 100 years old, but it absolutely works, and it works at large scale. The problem is we’re not building enough of it.”

During his time as Prime Minister of Australia from 2015-18, Turnbull spearheaded the development of pumped storage, specifically the 2000MW Snowy 2.0 scheme.

“The penny dropped for me in 2016 when I realised that we had this temporal asymmetry that we were rolling out more and more variable renewables, which you can build very quickly,” he explained, “but a pumped storage scheme takes many years – even if it is fast tracked. That’s why you’ve got to plan ahead now.”


In September 2021 the pumped storage forum held a panel discussion at the World Hydropower Congress, where its three working groups released a series of final reports. These focused on:

  • Policy and market frameworks. This was led by GE Renewable Energy and developed a global position paper to identify the current market and investment barriers and opportunities for pumped storage development, as well as recommendations to de-risk investment.
  • Sustainability -led by EDF, aims to provide guidance and recommendations on mitigating adverse impacts that may occur in the development of pumped storage to ensure that it can best support the clean energy transition in the most sustainable way.
  • Capabilities, costs and innovation. Led by Voith Hydro, this seeks to raise awareness on the role of pumped storage in addressing the needs of future power systems and deepen understanding about its potential.

As Malcom Turnbull stated: “All the talent of the hydropower world has been brought together to tackle this question of how do we ensure that we give pumped storage the priority and urgency that it needs, to ensure we have a successful transition to a zero emission energy future?”

The International Forum on Pumped Storage Hydropower has put forward seven major recommendations for governments around the world to avert the risk of policymakers and grid operators falling back on fossil fuels to provide clean energy storage. These are:

  • Assess long-term storage needs now, so that the most efficient options, which may take longer to build, are not lost.
  • Ensure consistent, technology neutral comparisons between energy storage and flexibility options.
  • Remunerate providers of essential electricity grid, storage, and flexibility services.
  • Licensing and permitting should take advantage of internationally recognised sustainability tools.
  • Ensure long-term revenue visibility with risk sharing to deliver the lowest overall cost to society.
  • Assess and map for pumped storage hydropower among potential existing hydropower assets and prospective sites.
  • Support and incentivise pumped storage hydropower in green recovery programmes and green finance mechanisms.

United Nations Special Envoy on Climate Action and Finance, Mark Carney, said: “I welcome the findings of the international forum and underscoring the need for ambitious solutions to decarbonise at rapid scale.”

He believes “there is a central role for pumped storage” in addressing the climate crisis and that it is the only form of large-scale duration, green energy storage in the world. He adds that it is increasingly important, complements the growth of intermittent renewables and can provide unique services that other batteries cannot.

There are “three fundamental drivers to get us to where we need to go”, Carney said. These include country commitment and policy, mainstreaming of climate finance, and large-scale renewable grids that are fully reliable.

“I do some work with Brookfield Asset Management, and one of the schemes we operate is a 2.1GW pumped storage scheme in the UK,” Carney explains. “With the challenges of power markets over the past few weeks, effectively that market has become islanded. So, the proportion of the power that is provided by intermittent renewables has gone up, and pumped storage activity is at its highest level in over 60 years.

“This just provides a bit of visibility of what will happen to other markets as renewable penetration increases,” he continued. “And this is why we need to plan ahead. Pumped storage is capital intensive and that underscores the importance of implementing solution-orientated measures of having credible and predictable government policy so we can build the pumped storage we need to complement rapid scaling of [variable] renewable energy.”

Thomas Östros, Vice President of the European Investment Bank, added: “We stand ready as a bank to support electricity storage through financing and advisory services. Among storage technologies we see pumped storage hydropower as one of the most mature, reliable and versatile large-scale solutions for grid flexibility and security, promoting intermittent renewables in a cost-effective, safe and sustainable manner. In fact, pumped storage hydropower has the potential to remain the most competitive green storage solution at scale over the next decade….We stand ready to be one of the key actors in this field.”

Power of hydro

“It’s clear that we need pumped storage but the point is that very often people don’t understand the technical reasoning behind it,” Uwe Wehnhardt, President and CEO of Voith Hydro said. In his role as a representative of equipment suppliers he says he feels compelled to give “more memorable technical arguments” for pumped storage.

“We need pumped storage hydropower. These facilities provide essential grid services such as rotating inertia and reactive power and provide a means to respond quickly to the risk of blackouts,” he said; giving the example of how Austrian pumped storage recently helped to overcome the risk of blackouts across southern Europe.

“Decarbonisation of power systems, coupled with the partial phasing out of nuclear power, is progressing rapidly. This development will be scaled up further over the next few years and can provoke potential instability,” Wehnhardt explained. “As we move away from coal and nuclear energy, the most stable baseload in the grid will gradually disappear – and we have to understand this. When using pumped storage facilities grid operators can react quickly. And that’s the power of hydro.”

As Yves Giraud, CEO of EDF Hydro added: “Pumped storage hydropower projects should be better acknowledged for all the services they bring to the electric system – such as the flexibility and ancillary services needed to develop variable renewable energies like wind and solar. In my opinion, in Europe and many countries worldwide, there should be a new market design to integrate storage facilities. Pumped storage hydro is highly valuable and a key enabler of the energy transition. We have all the tools to develop it in a sustainable way, so that it can play this major and vital role in the decarbonisation of electricity.”

US experience

Kelly Speakes-Backman is the Acting Assistant Secretary at the US Department of Energy, and co-chair of the International Forum on Pumped Storage Hydropower. She shared the US’ experience which has a long history of hydro in the grid.

Pumped storage in the US accounts for about 550GWh and 22GW of grid scale energy storage. Forty-four pumped storage plants currently operate and provide 93% of grid scale energy storage by capacity. In the past decade US pumped storage capacity grew by about 1300MW – nearly as much installed capacity as all other energy storage types combined.

“Pumped storage is a very important aspect of our clean energy future,” Speakes-Backman stated. “It can and will continue to play a crucial role in our fight against climate change. That’s why we must continue our investment and innovation into pumped storage hydro.”

Speakes-Backman said the DoE is working hard to drive the research and development, demonstration and deployment of the innovative technologies required to achieve US energy and climate goals. It is also making sure that opportunities in the clean energy economy benefits everyone and that no communities are left behind.

“Decarbonising our future is also imperative for social and economic justice and that’s why at DoE we commit our work to empowering disadvantaged communities with clean renewable and resilient energy. We are working to ensure 40% of overall benefits of relevant federal investments in clean energy are delivered to disadvantaged communities,” Speakes-Backman said. ”Every step of the way we are considering the environmental justice and equity impacts in everything we do, and that includes our work on pumped storage hydropower.

“As we shift how we power our countries and economies, the need to scale up and recognise the value of pumped storage has never been greater. As variable renewable energy deployment is increasing, energy grids worldwide need to adapt to incorporate these resources.”

The Doe also announced in July 2021 its new goal to reduce the cost of grid-scale, long duration energy storage by 90% within the decade

“We have to break down the barriers to advancing more deployment of pumped storage and other forms of long duration storage,” Speakes-Backman said. “We need cheaper and more efficient storage to make it easier to capture and store higher penetrations of renewable clean energy for use when energy generation is unavailable or lower than demand.”

Chinese ambitions

China has been responsible for most of the global growth in pumped storage over recent years. Zheng Sheng’an is the President of the China Renewable Energy Engineering Institute and said that, as of the end June 2021, China had 34 large and medium sized pumped storage plants in operation, with a total capacity of 32.49GW. There is an additional capacity of 55GW under construction.

China’s experience shows that the keys in driving pumped storage development are location identification, holistic planning and a revenue guarantee mechanism.

Sheng’an explained that China has also been conducting research to promote pumped storage development and has issued guidance on how pricing should be determined. There was a clear call for enhancing a two-tier pricing system and costs sharing.

“That is to say there will be a guarantee on the price in order to ensure that the initial investment in construction can be recouped more predictably. This will lay the foundation for further development of pumped storage in China,” said Sheng’an.

Jobs, jobs, jobs

As the international forum highlights, more pumped storage hydropower capacity will be crucial to the clean energy transition.

“You cannot affect the clean energy transition with variable renewable energy alone,” Turnbull said. “You cannot get there just with solar panels and wind turbines. You’ve got to be able to store the electricity when the sun is blazing and the wind is blowing so that you can use it when they’re not. We’ve got to get on and build pumped hydro.”

Jennifer Granholm, US Secretary of Energy added: “There is a resurgence of interest in starting projects to add more pumped storage capacity to the energy system. And that means three things: jobs, jobs and jobs. So we need to put people to work to get these projects off the ground. Not just researchers and scientists but engineers, construction workers, dam operators and maintenance workers.”

One such example of new projects is Coire Glas which is the first pumped storage projects to be built in the UK for over 30 years.

“Long duration pumped storage is a key part of the transition to net zero. We currently have about 4GW of storage capacity in the UK,” said Ian Innes, Project Director for Coire Glas pumped storage at SSE Renewables. In their future energy scenarios the National Grid has indicated that we will need around 40GW. Coire Glas is a 1500MW scheme that will make a significant contribution to that increase and capacity required.”

“We have to seize the momentum,” Pascal Radue, President and CEO of Hydro Solutions at GE Renewable Energy, said. “Policymakers should assess the long-term storage needs of their future power system now, so that the most efficient options, which may take longer to build, are not lost. Now is the time for us as an industry to demonstrate what is needed so that we can ultimately bring the necessary capacities online to contribute to the success of the energy transition.”
The reports from each of the International Forum on Pumped Storage Hydropower’s working groups are available online at https://pumped-storage-forum.hydropower.org/