Pumped Storage Hydropower
Pumped Storage Hydropower is a modified use of conventional hydropower technology.
To store and manage electricity in a PSH facility, two large basins of water are required: one at the top of a hill and the other at the bottom.
The distance between the two basins can range between 30 meters and 700 meters, with 100 meters being a common design.
There are two key advantages of this storage technology:
First, some PSH operations can supply reserve power for up to 18 hours, while the most common storage timeframe for a grid battery facility is only 4 to 6 hours;
Second, PSH facilities can have a lifetime exceeding 50 or 60 years.
The disadvantages of PSH include its high initial capital cost and long construction times.
We need to go inside a PSH facility to see how it works.
PSH – How It Works
During off-peak hours when electricity is cheap, typically weekday and weekend nights, a powerful motor-generator set acts as a motor to power large water pumps.
Water is pumped to the upper basin from the lower one, using a 6- to 8-meter diameter tunnel or pipeline, often called a penstock.
The upper reservoir is sometimes referred to as a “water battery”; and pumping water uphill “recharges the battery.”
During periods of high electricity demand, the flow is reversed, and stored water is released downhill back through the turbine.
The motor-generator switches to generator mode to produce electricity, very similar to a conventional hydropower station.
Two key mechanisms in this facility are:
● A gigantic ball-valve to enable the penstock flow to reverse direction, and
● A transformer to raise the generated voltage to that required by the grid
PSH Market Outlook – Europe
The International Energy Agency estimates that PSH installations currently account for over 95% of the energy storage capacity worldwide.
Europe is the one of the largest zones, with 57 GW of capacity, accounting for about 15% of renewable generation.
However, the average European pumped storage plant is more than 30 years old, with two-thirds of the plants built between 1970 and 1990. Conditions are ripe for new capacity construction.
With the UN Paris Accord renewable targets, many EU member states have introduced economic support programs for energy storage, using what are called feed-in tariffs. This type of tariff guarantees that customers with renewable generation, such as roof-top solar will receive a set price from their utility for the electricity they generate and provide to the grid.
In this context, PSH systems could expand.
European PSH opportunities are focused on mountainous regions in Switzerland, Austria, Germany, Spain and Portugal.
One interesting facility, under construction in the Sinai Peninsula in Egypt, has a capacity of 2.4 GW.
It will be the first PSH plant in the Middle East designed solely to generate electricity, and is due for completion in 2024.
PSH Market Outlook – US
In the US, the Pumped Storage Hydropower fleet consists of 42 plants with about 22 GW of capacity, or 97% of the total utility-scale electricity storage capacity.
Construction of new PSH facilities stalled in the mid-1980s. A major economic limitation is that the PSH storage type is not properly valued in the energy wholesale market.
This ultimately stifled new projects, unlike the more progressive EU feed-in tariff initiatives.
With the right regulatory framework, the US Department of Energy planning models forecast an economic potential for 35 GW of additional PSH capacity to be installed by 2050.
A major project being considered is the 2.5 GW Navajo Energy Storage Station that would use water from Lake Powell in Arizona, with a new reservoir added on a plateau above the lake.
This plant would use solar and wind power to pump water to the upper reservoir, and then release it to generate 10 hours of peak demand electricity each day.
PSH Challenges
Pumped storage technologies are especially feasible for long-term energy storage capacity higher than 50 megawatts.
However, several challenges impact their expanded use, including:
● High capital costs and extended timelines for construction
● Suitable land and terrain for two massive water basins
● A potential negative impact on local communities
● Environmental and ecological effects – similar to any large hydropower project
● High maintenance costs to control erosion – when soil builds up in the basins, it reduces the “battery” capacity of the installation
Summary: Pumped Storage Hydropower, or PSH
Our summary of the Pumped Storage Hydropower renewable is as follows:
- In a PSH facility there are two huge basins of water – one at the top of a hill and the other at the bottom.
- The International Energy Agency estimates that PSH installations currently account for over 95% of the world’s energy storage capacity.
- Some PSH facilities can supply reserve power for up to 18 hours, versus only 4 to 6 hours for grid-scale batteries.
- Numerous PSH projects are being considered around the world. However, there are very high capital costs and numerous environmental challenges.