Climate change is one of the most challenging issues facing the world today, impacting the stability of energy grids around the globe and increasing demand whilst extreme weather events are accelerating. Central to this challenge is the need for a rapid transition of the electricity sector from fossil fuels to low-carbon sources of power. Strengthening grid resilience and reliability alongside energy security are also key objectives of the clean energy transition.

There is no doubt that we can and will deploy wind and solar power at a huge scale. But what happens when the sun does not shine and the wind does not blow? These technologies need a low carbon back-up or communities will fall back on fossil fuels or simply have to get used to blackouts. Flexible electricity systems are needed to mitigate against these risks, and stable, reliable storage solutions that can support the grid and avoid curtailing renewable energy when they produce more than the system requires.

One critical source of system flexibility is energy storage that can “charge” when there is too much wind, and “generate” when the sun goes down. Consensus is growing that long-duration energy storage is needed and a lot of it, and to use all the tools at our disposal to deploy, including PSH as a provable, bankable and dependable storage asset.

The primary source of stored energy on electricity grids today – at well over 90% of energy stored – is pumped storage hydropower (PSH) but despite being proven and cost-effective, the deployment of PSH is not keeping pace with the increased demand for both long duration storage and the other services that are needed to provide system flexibility. Additionally, while there is significant potential for scaling up global pumped hydro capacity, the flexibility and storage services provided by pumped storage hydropower are not yet adequately valued in many countries reducing investment and holding back new projects.

To secure net zero ambitions and avoid grid incidents, governments around the world need to address the obstacles to the development of pumped storage hydropower. Planning and permitting need to be accelerated and attracting private investment and financing for deployment of PSH requires market arrangements that provide long term revenue visibility.