This centuries-old technique could be the best means of long-term economical storage of wind and solar energy

To drastically reduce greenhouse gas emissions, we need a lot more solar and wind power generation, and a lot of cheap energy storage. Pumped hydroelectricity is a solution for this.

Wind and solar energy vary throughout the day, so energy storage is essential to provide a continuous flow of electricity. But today’s batteries are usually quite small, storing enough energy for a few hours of electricity. To become more dependent on wind and solar power, we also need more overnight and longer-term storage.

Although batteries are all the rage, there is a simple and proven long-term storage technique that has been used in many parts of the world for over 100 years.


Storage of hydroelectric energy by pumping.

It involves pumping water upstream from a reservoir to an upper reservoir for storage and, when power is needed, releasing the water to flow downward through turbines, generating electricity on its way to the lower reservoir.

Pumped hydro storage is often overlooked due to concerns about the impact of hydropower on rivers. But most of the best hydroelectric storage places are not in rivers.

This global atlas of potential sites for closed-loop pumped storage power plants, systems that do not include a river, includes thousands of good potential sites around the world. Although many of these sites, which are located by satellite, are located in rugged terrain and may be unsuitable for geological, hydrological, economic, environmental or social reasons, it is estimated that only a fraction of them are necessary for support an electrical system. 100% renewable.

Solar and wind energy require long-term storage.

To function properly, power grids must be able to match incoming power supply to power demand in real time, failing which they risk shortages or overloads.

There are several techniques grid operators can use to maintain this balance with variable sources such as wind and solar. Among them are the sharing of energy across large areas through high voltage transmission lines, demand side management and the use of energy storage.

Batteries installed in homes, power stations and electric vehicles are preferred for storing energy for a few hours. They are able to handle the surge of solar energy at noon, when the sun is at its zenith, and release it when power demand peaks at night.

pumped hydroelectricFor its part, allows larger and longer storage than batteries, and this is essential in an electrical system dominated by wind and solar power. It’s also cheaper for overnight and long-term storage.

Storage of hydroelectric energy pumped out of the river.

Globally, the energy storage share of pumped storage power plants accounts for approximately 99% of the energy storage volume.

Pumped hydropower projects can be controversial, especially when they involve building dams on rivers that flood land to create new reservoirs and can affect ecosystems.

Creating closed-loop systems that use pairs of existing lakes or reservoirs instead of rivers would obviate the need for new dams.

A pumped-off-river hydroelectric system consists of a pair of reservoirs separated by several kilometers with an elevation difference of 200 to 800 meters and connected by pipelines or tunnels. Reservoirs can be new or use old mining operations or existing lakes or reservoirs.

We can talk about a few examples, such as the coal mine in Kentucky, which will become a giant energy storage project in the form of a “water battery”. Or the Linthal hydroelectric power station, one of the most impressive underground infrastructures in Europe.

On sunny or windy days, water is pumped into the upper reservoir. At night, the water goes back down through the turbines to recover the stored energy.

A pair of 100-hectare reservoirs with an altitude difference of 600 meters and a depth of 20 meters can store 24 gigawatt hours of energy, which means the system could provide 1 gigawatt of energy for 24 hours, enough for a city ​​of one million people.

Water can circulate between the upper and lower reservoirs for a hundred years or more. Evaporation suppressors, small objects that float on water to trap moist air, can help reduce water evaporation.

In total, the amount of water needed to maintain a 100% renewable electricity system is approximately 3 liters per person per day, which is equivalent to a 20 second morning shower. That’s a tenth of the water that evaporates per person per day in the cooling systems of fossil fuel power plants.

A few days ago, the Fengning pumped storage power station was inaugurated, which is not only the largest pumped storage power station in China, but also the largest in the world.

Switching from electricity to renewables and subsequent electrification of vehicles and heating can eliminate most human-made greenhouse gas emissions. The world has great potential for storing hydroelectricity by pumping off rivers to help with this, and it will need it as wind and solar power expand.

Around this centuries-old technique, new developments are emerging, such as AirBattery, a new solution for storing renewable energy in a combination of pumped hydroelectricity and compressed air. Or the world’s first pumped hydroelectric plant with desalination, powered by renewable energy, at an affordable price.

What is clear is that the rapid increase in wind and solar generation is making cheap and efficient storage even more necessary, and pumped hydropower can be part of the solution.


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