Wind and solar make most of the headline renewable news, but they aren’t the only ones. If you’ve ever wondered about the alternative and renewable energy sources available in the United States and what it will mean for the future of available American energy supply, wonder no more. There’s been an option quietly in use for decades.

One of those is pumped-storage hydropower or PSH. This type of hydropower started in the U.S. around 1960, with most of the infrastructure in use now built between 1970 and 1990. Most people associated dams with hydropower, but that’s not always the case. That’s because not all dams are built to produce electricity. Dams are often built to control river flow to mitigate flooding, increase river flow during dry seasons and improve navigation of the waterways for flood plains.

So read on for an introduction to one of the oldest large-scale energy storage systems in the United States and how it’s making a comeback – we’ll at least through word of mouth.

How Does Pumped-Storage Hydropower Work?

Pumped-storage hydropower creates a system where water is pumped from an upper reservoir to a lower reservoir through a closed-loop hydraulic system or through an open-loop hydraulic pump system. Both work by forcing water to move between storage areas that activate a turbine, which produces electricity that is stored and sent to a power grid for distribution and consumption.

In essence, these systems pump water into their upper reservoirs when electricity demand is lower – usually in the evenings. During periods of high electricity demand, the stored water is released downhill through turbines which create electricity in the same manner as a conventional hydro station. The turbine can also act as a pump, moving water back uphill, and the process repeats itself.

An open-loop system utilizes a natural body of water and a dam. A closed-loop system acts like a siphon that consists of an upper and lower reservoir that does not connect to or rely on a naturally flowing river, stream, or waterway.

It is the oldest method of producing electricity on a large scale and a perfect addition to wind and solar power initiatives because it can pick up the slack seasonally and during periods of intermittency with wind and sun. Of all of the operating hydropower facilities, pumped storage accounts for 95% of all utility-scale energy storage in the country, according to the U.S. Department of Energy.

Benefits & Drawbacks of Pumped Hydropower Storage

As states start to mandate cleaner energy, policymakers, developers, and community members will evaluate costs, land availability, and other issues associated with the buildout and development of large-scale renewable projects. Like any energy source, hydropower comes with its own set of potential challenges in terms of the engineering mentioned above issues to control river flow, land use, local hydrology, and weather, as well as associated costs. These are also similar issues with other clean energy sources.

But the benefits are unquestionable. States with access to or can build hydropower facilities, or related transmission infrastructure will have an excellent large-scale sustainable renewable energy source. It can act on-demand to meet challenges posed by the seasonality and intermittency of solar and wind while improving grid reliability and mitigating other service disruptions.

Current and Developing Hydroelectric Facilities within the United States

The United States currently has over 2000 hydroelectric facilities that have produced approximately 37% of our nation’s renewable energy and have accounted for 7.3% of the total energy generated for our power grids. Until last year, hydropower was the leading source of renewable generation before wind surpassed it.

Even though approximately one-third of the potential for hydroelectricity is currently underway in the United States, there remains a lack of available land and water resources to construct large power plants. There is potential in the future for smaller hydroelectric plants to be built to serve individual communities, but that is still being considered. In the meantime, states which border Canada have considered new transmission projects that would supply clean hydropower into their energy mix in an attempt to meet their energy goals. People often forget how intertwined and dependent the Canadian and U.S. energy grid and markets are on one another. The U.S. has been importing energy and hydropower from Canada for over a century. Those clean energy imports make up a significant percentage of the electric mix in the Northeast and New England.

As a large consumer of electricity, the United States is currently expanding its renewable energy sources by utilizing a blend of technologies. Hydroelectric power can exponentially increase the use and availability of renewable energy at a large scale by providing a source of electricity that does not require home and landowners to install solar panels or wind turbines.

As we collectively work to find a diverse mix of energy solutions that are cleaner and more affordable to meet the demands of our communities, scientists, surveyors, and stakeholder groups, we will need to come together around hydroelectric infrastructure development. When they do, we will be poised to dramatically increase the percentage of renewable energy used nationwide and at home.

As the latest energy and climate debate continue, Consumer Energy Alliance remains an advocate for shining light on the challenges ahead for implementing various proposed state and federal renewable energy policy proposals and carbon reduction requirements in a manner that ensures that our grid remains reliable and will not put downward pressure on the budgets of families and small businesses.

Interestingly, while these ongoing renewable energy debates continue, there is an energy source that has been a hidden gem. Though it’s been around for almost 2,000 years, hydropower generation has been almost completely left out of most major renewable energy conversations.

So, why haven’t we talked more about it?

As its name refers, hydropower generation uses the flow of water, from a reservoir or river, to turn a turbine linked to a power generator. As water flows past the turbine, it turns a shaft leading to the generator and generates electricity. Thousands of years ago, people used hydropower to turn paddle wheels on rivers to grind grain, and prior to the availability of electricity in the U.S., mills were powered directly with hydropower.

In fact, hydropower was one of the first sources of energy used for electricity generation, and until 2019, hydropower was the largest source of total annual U.S. renewable electricity generation. In the U.S. in 2020, hydroelectricity accounted for about 7.3% of total U.S. utility-scale electricity generation and 37% of total utility-scale renewable electricity generation.

While the International Energy Agency (IEA) has stated that hydropower is expected to remain the world’s largest source of renewable energy generation, most Americans have probably seen some form of hydropower generation without even realizing it.

Where is Hydropower?

Since you need water for hydropower generation, the facilities are usually located on or near a water source. Conventional hydroelectric facilities include systems where the force of a river’s current applies pressure on a turbine to generate power or where water accumulates in a reservoir created by dams on streams and rivers and is released through the turbines to generate electricity. Meanwhile, pumped-storage hydropower facilities are a type of hydro-storage system where water is pumped from a water source up to a storage reservoir and is released from it to power hydro turbines located below. However, the electricity for pumping to storage may be supplied by hydro turbines or by other types of power plants including traditional fuel or nuclear power plants, when demand costs are low or peak electricity demand increases and power is needed. Pumped storage can be especially beneficial to provide on-demand energy to meet the intermittency and seasonality of renewables like solar and wind as well as dispatchable power to the grid during an outage or disruption.

There are currently about 1,450 conventional and 40 pumped-storage hydropower plants operating in the United States, with most hydropower generation capacity located in the Western part of the United States. However, there are conventional hydropower and hydroelectric facilities in nearly every state.

Most U.S. hydropower is produced at large dams on major rivers, and most of them were built before the mid-1970s by federal government agencies. The largest U.S. hydropower facility, and the largest U.S. electric power plant in generation capacity, is the Grand Coulee hydro dam on the Columbia River in Washington with 6,765 MW total generation capacity. New York has the largest conventional hydroelectricity generation capacity of all states east of the Mississippi River, followed by Alabama.

In 2020, the total U.S. conventional hydroelectricity net summer generation capacity was 79,946 megawatts (MW)—or about 80 million kilowatts. Almost two-thirds of the energy it took the Saturn V rocket to send a man to the moon.

Hydropower’s Outlook

The U.S. Energy Information Administration (EIA) projects that the share of renewables in the U.S. electricity generation mix will increase from 21% in 2020 to 42% in 2050 – which includes hydropower.

As policymakers continue to discuss sensible energy and environmental solutions for the future, large-scale hydropower will have to be included in the dialogue. A quick and cost-effective way to bring substantial supplies of emissions-free energy in the near term through additional hydropower capacity can help to ensure American families and small businesses have access to reliable, affordable power that can integrate and optimize with other long-term renewable energy options and technologies.

With so many clean and affordable energy choices – like hydropower – available to Americans, we hope you will join CEA’s discussion about common sense, solutions-oriented policies that are a win for consumers’ bottom lines, the electricity grid, and the environment.