[snowwindwaves]

They have dams!

Given the over provisioning required to be able to ensure a battery will be able to provide a guaranteed amount of energy, such as last say overnight in 5 years, and that batteries are good for a fixed number of cycles after which they have to be replaced, batteries were not competitive with pumped storage and all the civil works that entails on a project currently under construction.

[sergiosgc]

Correct. All of the large dams have been retrofitted with pumps. This involves creating the structures for pooling water downstream so you can pump it back up should the need arise.

Dams have many problems. They can only be built on certain topographies, they have an ecological impact (destroy an ecosystem, albeit creating a different one), and have a social impact. However, in the context of energy production, they are amazing. They can start and stop as fast as loaded thermal plants (without the readiness fuel consumption cost), they are 100% renewable, provide aquifers for collecting urban water and provide the best energy storage/temporal load balancing technology today.