Pumped Storage Hydro: the storage giants

When all eyes are on Li-Ion batteries and other alternative technologies, many are surprised by the fact that more than 90% of the world’s energy storage capacity is pumped hydro, a technology with more than 100 years of history and still at the centre of pharaonic projects all over the world.


According to 2020 data, there are 160 GW of pumped storage hydro (PSH) capacity while in batteries, we do not reach 30 GW. But the big difference lies in storage capacity, with an estimated 8,500 GWh of capacity in pumped-hydro storage stations, giving an average of 53 hours of storage per installation, a big difference with batteries, which do not exceed 4 hours of storage.


According to Wikipedia, the world’s largest pumping station is the Fening in China, with a dizzying capacity of 3,000MW/40,000MWh or the equivalent of storing 13h of the equivalent supply of 3 nuclear power plants.


Some countries are accelerating pumped storage planning, such as India, which recently issued a tender for 12 sites with a total of 13.8 GW of capacity.


But not everything is rosy in the world of hydraulic pumping. The projects are pharaonic, with exorbitant deadlines and costs. In addition, suitable pumping sites are few and far between and complex because of the unevenness required.


Recently, two of the world’s most spectacular PSH projects have been in the news, with the circumstance that they are the two faces of this type of project: Snowy 2.0 in Australia is an example of a project with delays and cost overruns that it is not known when and how it will be completed, while Iberdrola’s Alto Tamega in Portugal is, on paper, a success story that is already in operation.


When things go wrong: Snowy 2.0

It was 2017 and in Australia, one of the most spectacular hydraulic pumping projects in history was proposed: Snowy 2.0.


Their figures were colossal: 2,200 MW and 350,000 MWh of storage capacity, which, according to official figures, meant 175 hours*! These were impressive figures at a time when battery projects were still in their infancy, and where the largest installation was the famous Hornsdale with 100MW/129MWh (just over 1h of storage), although the average installation does not exceed 20 MW. By the way, Hornsdale was the project that began to take shape through the old Twitter, but that’s another story.



Going back to Snowy 2.0, not only the dimensions of the project were impressive. So was the engineering behind it. Basically, it involved digging a 27 km tunnel to connect two reservoirs at different heights and building the pumping station at a depth of 1 km in between.



As usual with Australian projects, the information available is immense and the project website has a wealth of educational and technical materials explaining the project. The short introductory video is well worth watching.


But what was originally going to be a $2bn project that would be up and running by 2025, is already $12bn under budget and is not expected before 2029. Clearly, this totally changes the picture of the business case. Moreover, the abysmal difference that existed in 2017 between PSH projects and batteries is becoming less and less. In terms of CAPEX, batteries require much less investment and in terms of capacity, we already see 6-hour batteries and 1000 MW of power. In 2029 we will probably see durations of 8-10h, so the gap is narrowing.


But it is in the timeframe where batteries have a big advantage. Today it is feasible to install a large battery in less than 2 years while PSH projects have lead times (and problems) that are closer to those of large infrastructures such as nuclear power plants.


A success story: Gouvaes-Alto Tamega


If in Snowy 2.0 we see the problems of these macro-projects, the Alto Tamega complex in Portugal, developed by Iberdrola, seems to be the other side of the coin.


The complex includes the Gouvaes reversible pumped-storage power plant with a capacity of 880 MW and a storage capacity of 24 hours. It does not reach the figures of Snowy 2.0, but it is equivalent in power to one mega-battery and in capacity to more than 5.



The project has not been easy: 8 years of implementation but it is now in operation. Once again, we see that even successfully completed projects have lead times of close to a decade. In terms of costs we do not know as it is a private project but with the duration of the work, it is more than likely that it has suffered deviations.


In the following video you can get a glimpse of the colossal work that the complex has involved.




Given the very different project profiles between PSHs and Li-Ion batteries, it makes no sense to put them as competitors. It is clear that they are complementary but that due to their complexity and limited locations, PSHs will increasingly be large one-off projects to complement the large volume of gigabattery Li-Ion we will see in the coming years. But be that as it may, we will always enjoy the engineering wonders of such colossal projects.