Let’s work with the gravity. Australian National University study identifies more than 600 000 sites and 23 000 TWh worth of locations for pumped hydro electricity storage.
Turns out that 1% of that would be enough for three days (72h) worth of global electricity. Worldwide electricity production was 28466 TWh 2021.
Annually the 1% could provide 9100 TWh of electricity assuming a modest storage capacity-to-production ratio of 39. In that ratio I mean how many times the whole reservoir is totally utlized during the year.
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Potential pumped hydro storage (PHS) sites in Spain and Portugal.
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This highlights the pumped hydro storage as a viable option for the NZE energy system. Pumped hydro should get more attention. It is 1. conventional, 2. long-term, 3. highly efficient, and 4. cost-effective compared to many other energy storage methods.
Latest developments includes an opening of Tâmega gigabattery in Portugal which deploys 1160 MW power and 40 GWh of storage capacity. That is 20% of the Portugal's average electricity production power of 5,8 GW for 35 hours. With the growing amount of renewable electricity production, electricity storage methods are becoming more important.
For a reference, many of the developments in the United States, were build in 70s and 80s such as Ludington Pumped Storage Power Plant built in 1973 but it has been quiter since then. Ludington plant utilizes a natural 32 meter elevation difference on the bank of lake Michigan and a 3,6km long artificial lake. It's installed production capacity is 2172 MW and the artificial lake contains 19,5 GWh worth of electricity.
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| Ludington Pumped Storage Power Plant (1973). |
China has been dominating the list of the new pumped storage facilities since the beginning of the 21st century. It has the most available capacity but even more importantly by far the most planned capacity under construction, although the Wikipedia list seems to be somewhat outdated.
Out of 74 sites under construction 69 are in China. These Chinese locations have a total planned generation capacity of 93 GW. Perhaps it would be a high time to do something with the pumped hydro in the Old Continent too.
Cost estimates
Pumped storage is one of the storage options for electricity and it can be a cost-effective in between stationary battery storage options that are often feasible for couple of hours, and a likely long-term storage options such as biofuels.
PHS (PHES) market share and cost estimates depend on many aspects but in today's market PHES is the lowest cost option for 2-64 hour of storage variations according to this study which has been widely cited.
Same study estimates that the PHES market potential will remain and to be between 12-64 hour storage by 2040. Batteries have will likely take a larger share of the electricity storage markets in between the 0-12 hours options.
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| Electricity storage options cost estimates. |
When comparing the 80 year lifetime costs between pumped hydro storage (PHS) and other storage methods, PHS is approximately 4-times cheaper than hydrogen and 5-times cheaper than li-ion batteries according to Pumped Storage Hydropower Capabilities and Costs, 2021 lifetime estimate.
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| Lifetime cost estimate of different storage methods. |
Their study also estimates that the capex cost per PHS site is around 207€ (220 usd) per constructed kWh but it seems quite high compared to referenced estimates on actual pumped hydro sites.
The nine referenced PHS sites that I found accurate investment costs vary between 9-175 €/ kWh.
Excluding the USA 1970-1980s PHS sites and the variation drops between 9-75 €/kWh. There seems to be a correlation between investment costs and the storage capacity size. In other words the reservoir size and its gravitational potential differnce between the lower and upper-reservoir.
Out of the most recent developments Tâmega pumped hydro plant costed 37,5€/kWh in Portugal with the reservoir of 40 GWh. Chinese Fenging PHS site with the similar reservoir size costed approximately the same (44€/kWh).
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| Pumped hydro storage plant cost estimates. |
We are lacking data between the Snowy 2.0 PHS development in Australia (350 GWh), and the other storage capacity sizes between 20-40 GWh, but seems that increasing the storage size decreases the cost/kWh significantly. More data and locations are needed for comprehensive analysis. Nevertheless the Pumped Storage Hydropower working group paper 200€/kWh estimate seems quite excessive based on these actual investment costs. Even the most expensive recent development, Nant de Drance in Switzerland costed only 75€/kWH completed in 2022. That is more than 60% less than the working paper assessment for the pumped hydro storage cost.
Snowy 2.0 reservoir in Australia is by far the most cost-effective with the average cost of 9,2 €/kWh (14,6 Australian dollars) under construction with a 350 000 MWh storage capacity and the planned cost estimate of
5,1 billion Australian dollars.Round-trip efficiency
Another important indication of the PHS potential is the energy round-trip efficiency. PHS and most of the battery solutions can achieve an energy-in and energy-out efficiency of around 80-90%. Hydrogen's electricity storage round-trip efficiency is only around 25%.
Due to this round-trip energy inefficiency and the higher long-term cost, Hydrogen should be considered as an electricity storage option only if other options are unavailable. It's 4-times more expensive in the long-term and 3-times less efficient than pumped hydro storage for storing electricity.
Storage to capacity ratio
Storage-to-capacity ratio, which I mentioned in the beginning of the blog, indicates what is the actual electricity production of different pumped hydro power plants in relation to their electricity storage size. This value is an indication of how many times the whole reservoir storage capacity is utilized annually.
According to preliminary research, the storage capacity size indicates not only the cost per kWh which was analysed previously, but also how many times the the whole capacity is used.
For example a Vianden pumped storage plant in Luzemburg utilizes its 4,9 GWh storage almost daily, 336 times in a year. Larger 40 GWh PHS Fenging in China uses its storage only 86 times in a year according to annual production data that we have about
the power plant.
According to this preliminary dataset, it seems that the newer PHS locations utilizes their storage more often than the older locations. The lowest utilization rates of 39 are for the two PHS plants in the United States which were built in 1970-1980s. This is also an indication of pumped hydro storage utilization rates that we can expect from the future PHS locations.
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| PHS production/ storage capacity ratio and the indication of relationship. |
In practise this storage to capacity ratio means that if the one percent (1%) of the Australian National University 23 000 TWh PHS locations is utilized, these sites would generate around 9100 TWh of electricity per year with a modest utilization rate of 39.
That would be 32% of the global electricity generation 2021.
For the three following potential pumped hydro plant locations an utilization rate of 100 is assumed based on the most recent PHS location rates from Fenging, China (86) and Nant de Drance, Switzerland (125).
Potential pumped hydro storage locations
Serfaus, Austria
Capacity: 150 GWh. Elevation difference: 792 meters
Adequate for 17,5h of Austria's average power demand (2021). With an annual 100- reservoir utilization rate, Serfaus plant could provide up to 20% of the Austrian electricity demand annually.
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| Serfaus PSH location. |
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| Upper reservoir. |
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| Lower reservoir. |
Semelano di Sotto, Italy
Capacity: 150 GWh. Elevation difference: 490 meters
Adequate for 4,2h of Italy's average electricity demand (2021). With an annual 100- reservoir utilization rate, Semelano di Sotto plant could provide up to 5% of the Italian electricity demand annually.
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| Semelano di Sotto PSH location. |
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| Lower reservoir. |
Cabo, Spain
Capacity: 150 GWh. Elevation difference: 790 meters
Adequate for 5,3h of Spain's average electricity demand (2021). With an annual 100- reservoir utilization rate, Cabo plant could provide up to 6% of the Spain electricity demand annually.
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| Cabo PSH location. |
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| Lower reservoir. |
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| Upper reservoir. |
Needles to say that environmental aspects must be carefully managed and considered locally when the pumped hydro plant locations are planned but the potential is too large to ignore. Environmental evaluations must be equal and just.
These three country specific pumped hydro locations with the 150 GWh, which was randomly chosen would be plenty for the each of the country to begin with. In the Australian National University global atlas there are hundreds of these potential locations more in each specific country. Make it three times more and storage requirements would be met for quite some time.
Obviously threre's not a fair share between low-altitude countries and the countries with more altitude variation but the Ludington Pumped Storage Power Plant by the lake Michigan shows that even smaller altitude variations can be utilized with appropriate planning.
Pumped hydro plant technology is conventional, cost-effective, and efficient. We have decades of experience but we lack some of the information about investment cost estimates for the larger reservoirs which might be a potential solution for long-term electricity storage. If the cost estimates are between the Tâmega and the Snowy 2.0 projects, these plants should be implemented immediately, and we could see them completed in around the early 2030s.
Even the smaller reservoirs can be highly valuable in balancing the grid demand and supply with the increasing share of intermitted energy supply from the cost-effective renewable energy sources.
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Potential pumped hydro storage and plant locations in Italy and Central-Europe.
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Australian National University pumped hydro location atlas :
https://re100.eng.anu.edu.au/index.html
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