Rising populations and economic development mean more people than ever will have easier access to power and technology that requires electricity. As such, global electricity demand is set to soar over the coming years.
Climate change and extreme weather conditions have put renewable energy center stage for meeting that demand. Meanwhile, 84.2% of worldwide energy comes from fossil fuels, releasing harmful emissions into the atmosphere.
But as the saying goes, still waters run deep. And lakes could be the answer to help balance our need for energy and our desire for clean energy sources.
Gravity and water could solve one of the world’s most perplexing energy puzzles. Here’s how pumped hydro storage is emerging as a crucial energy storage technology.
How Does Pumped Hydro Storage Work?
At the most basic level, pumped hydro storage requires:
- Two lakes or reservoirs at different elevations
- Turbines to produce electricity
- Water pumps
- Connection to an electric grid
An upper reservoir holds water. Hydro is the Greek word for water. This water stores energy as potential energy, ready to do work. In this case, that work means generating electricity.
The water rushes down penstocks, large pipes or channels, to a lower reservoir to create electricity. The speeding water turns turbines that produce electricity to export to the power grid, then fills the lower reservoir.
The “pumped” element to pumped hydro storage then kicks in. Pump turbines push water (hydro) from the lower reservoir back to the upper reservoir. Pumped storage projects with reversible turbines can use some of the electricity created by the turbines to pump water back to the upper reservoir.
A pumped storage power system’s energy storage capacity changes due to two primary factors. The more significant the height difference between the reservoirs, the more electricity it can generate. Similarly, a larger mass of water increases the pumped hydropower system’s electricity generation capabilities.
Pumped storage hydropower (PSH) is increasingly considered vital to the electricity supply.
Why Do We Need Pumped Hydro Storage?
Fossil fuel power stations offer dependable but slow-response electricity generating capacity. However, climate change means countries trying to hit net-zero emissions targets by 2050 must incorporate more renewable energy sources into their energy transition plan.
Solar power and wind energy offer clean electricity generation but can be intermittent. Sunny or windy days may result in excess electricity being wasted. Cloudy and windless days see renewable electricity production levels drop. Large-scale pumped storage facilities offer a grid-scale solution that can help grid reliability in those circumstances.
For example, it makes sense to pump water to the upper reservoir when there is either low demand for electricity or excess electricity generation on a very sunny or windy day. When there is a high demand on the power grid, the upper reservoir can release its water to create electricity to help the grid meet that demand. This grid balancing is called an ancillary service.
What Are the Advantages of Pumped Hydro Storage?
Pumped storage plants offer quickly accessible and clean energy. They can follow spikes and troughs in energy demand. Unlike battery storage, pumped hydro storage uses water as a fluid instead of chemicals and metals, reducing its environmental impact. Hydro plants may last 50 years or longer compared to 8 to 15 years for batteries.
Also, pumped hydro storage plants don’t often need their water levels topped up as rainfall usually exceeds evaporation. Once built, PSH is cost-effective with low operational costs, a long service life, and can run off sustainable and renewable power sources like solar and wind energy. They offer easily controllable power; a PSH can be switched on to help avoid a power outage, and are a long-duration energy storage system.
The surfaces of utility-scale reservoirs may be used for water sports and recreational activities, bringing a social benefit to the area. They can even help areas manage floods and water supplies. There are also PSH systems that use seawater.
Pumped Storage Hydropower: Closed-Loop or Open-Loop?
There are three types of pumped hydro storage plants:
- The water at a closed-loop plant doesn’t connect to any flowing feature nearby, such as a river. These self-contained units are considered to have less environmental impact.
- An open-loop system does feed into local water flows like rivers. This can affect local wildlife and the environment more than a closed-loop setup.
- A run-of-river system uses the water flow in rivers to produce megawatts of electricity.
How Big Is Pumped Hydro Storage Capacity Worldwide?
Around 96% of the world’s energy storage capacity is pumped hydro energy storage.
In 2020, there were more than 8,000 gigawatts (GW) of pumped hydro storage capacity globally. That is set to grow to almost 12,000 GWs by 2026.
The United States is the PSH powerhouse at present, accounting for around two-fifths of all installations in 2020. By 2026, India is expected to become the dominant global PSH stakeholder. In reality, China by far has the most significant potential for pumped hydro storage. On a day-to-day basis, Iceland uses more hydropower per person than any other nation on Earth.
According to the U.S. Department of Energy, some 93% of America’s utility-scale energy storage capacity comes from pumped hydro storage. There are 43 PSH plants, and the country has the potential to double that amount of PSH power plants.
Where Is It Best to Build Pumped Hydro Storage Plants?
Pumped hydro storage plants need an upper or lower reservoir to function, with space to add penstocks, turbines, and a connection point to the national grid.
Hilly and mountainous areas are ideal locations for PHS. Those regions with regular rainfall to replenish the reservoirs’ water are preferred to dry areas. Ideally, a renewable energy source will be nearby, like a solar or wind farm, to power the water pumps that push the water back to the upper reservoir.
How Long Does a Pumped Hydro Storage System Last?
Large-scale pumped hydro storage systems have a lifespan of 50-100 years. The Engeweiher plant in Switzerland is at 116 years of work, with at least another 29 years to go, making 145 operational years.
When Was Pumped Storage Hydropower Invented?
Italy and Switzerland pioneered PSH in the 1890s. Indeed, the oldest working pumped storage plant, built in 1907, is the Engeweiher in Switzerland. Its recent refurbishment means it will be operating until at least 2052.
What Are the Disadvantages of Pumped Hydro Storage?
Pumped hydro storage plants are not a panacea to all ills. Here are some of its drawbacks.
High Capital Costs
PHS power plants need to be big to achieve low-cost electricity generation. That means enormous capital costs to build a facility; smaller pumped hydro plants won’t supply affordable electricity to power grids.
Interestingly, the U.S. Department of Energy states that new pumped hydro storage plans will produce electricity at around $165 per kilowatt-hour (kWh). That compares to $362 per kWh for Li-ion batteries in 2025.
Environmental Impact
Building reservoirs impacts local wildlife and their habitats. Migratory routes could change, as could prey available for native species. Flora, fauna, and landscapes transform after constructing a large pumped hydro storage plant.
Local water flows may be interrupted and degrade the water quality available to local populations. Constructing a PHS plant has a considerable CO2 footprint, from cement, roads to remote sites, and tailpipe emissions of workers and delivery trucks.
Methane, one of the most potent greenhouse gases, builds up behind dam walls and reservoirs. Decaying organic matter releases methane, a gas that is more than 30 times more damaging than carbon dioxide during its 100-year journey through the atmosphere. Estimates suggest up to 8% of all the world’s methane emissions may soon come from reservoirs.
Energy Losses and Climate Change
Pumped hydro storage plants are not infallible. A drought or severe leak can lead to a lack of water and shutdown. The facility also uses electricity to work, albeit they are around 80% efficient per cycle.
Political Turmoil
Water is a precious commodity and will only become more so as populations and pressure on natural resources increase. Reservoirs and dams may cause issues around borders when one country’s hydroelectric plan affects another’s.
Is Hydroelectric the Same as Pumped Hydro Storage?
Hydroelectric power differs from pumped hydro storage, although they share some features.
Hydroelectric plants usually sit at the head of a dammed river or lake. They store energy in the water behind the dam. Water is released on demand through penstocks to drive turbines to create electricity, just like at pumped hydro storage plants.
The crucial difference is a hydroelectric plant’s water flows into a river and away from the dam; the water is lost and doesn’t return. The hydroelectric plant can only use the water once to create electricity. In contrast, a pumped hydro storage plant captures the water. It pumps it back to the original upper reservoir for as many uses as are required over the PHS plant’s lifetime.
A hydroelectric plant also requires a river and rainfall to replenish, reducing its efficiency during droughts. A pumped hydro storage plant needs only rain to keep its water levels topped up. However, they also suffer during shortages due to evaporation.
Fun Facts About Pumped Hydro Storage
Here are some amazing facts about pumped hydro storage:
- The biggest pumped hydro station in the world is in Bath Country, Virginia, with a 3 GW capacity, enough to power 6,000 homes every year.
- China is building an even bigger PSH with a 3.6 GW capacity at Fengning, set for completion this year.
- Switzerland creates around 57% of its electricity from pumped hydro storage plants.
- South Africa’s Drakensberg Pumped Storage Scheme uses not one but four dams to generate electricity in the Drakensberg Mountains.
- It takes just three minutes for France’s Grand Maison PSH plant to supply its total 1.8 GW capacity to the national grid.
Marrying Pumped Hydro Storage to the Renewable Revolution
Pumped hydro storage is a relatively simple concept that could form the core of humankind’s transition to clean energy.
Stored water in an upper reservoir flows through pipes to a lower reservoir, turning electricity-generating turbines during its journey. This electricity flows into the power grid. The water is pumped back to the upper reservoir to repeat the process.
Pumped hydro storage power plants respond quickly to energy spikes, sometimes reaching total capacity within three minutes. They can pump water to the upper reservoir when excess electricity is created or during times of low demand to maximize how we use energy.
Marrying energy storage creation to avoid waste is vital to an energy-efficient future. Solar or wind power can pump the water back to the upper reservoir, making a circular green and clean energy source.
Battery storage, pumped hydro storage’s leading energy storage competitor, requires manufacturing and processing many materials. Lithium-ion batteries require lithium, mined in energy-intensive and potentially polluting ways. In contrast, PHS power plants use water as their primary fluid.
That’s not to say PHS comes without problems; its huge reservoirs can dramatically alter the landscape, wildlife, and water of their locations. However, high startup costs cannot disguise its long-term benefits as a clean, low-cost electricity source.
The rise of renewables needs a storage solution that keeps emissions as low as possible. The renewable energy that is pumped hydro storage brings much to the table to solve that puzzle.
Brought to you by amigoenergy
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