Hydroelectric power doesn’t get much attention in today’s discussions of how to generate electricity, particularly in a world looking to boost renewable technologies such as wind and solar. But the oldest form of electricity generation—the original renewable—has plenty of life.
Hydroelectric generation—using water to turn turbines—is the Rodney Dangerfield of renewable energy. The late American comedian had a well-known catchphrase: “I don’t get no respect.”
But what some have viewed as a politically incorrect form of electric generation—due to its environmental impacts—is the dominant source of low-carbon dioxide renewable energy on the planet, as well as the oldest source of power. According to the International Energy Agency (IEA), “Hydropower is the largest source of renewable electricity in the world, producing around 16% of the world’s electricity from over 1,200 GW of installed capacity.”
1. The International Hydropower Association compiles data on hydropower installations worldwide. The group this year said China has the most installed hydro generation capacity, at 341 GW, followed by the U.S., Brazil, and Canada. Courtesy: 2018 Hydropower Status Report, International Hydropower Association
The International Hydropower Association (IHA) this year said China leads the world with 341 GW of installed hydro capacity, followed by the U.S. with 103 GW, Brazil with 100 GW, and Canada with 81 GW (Figure 1).
Hydro’s position in the U.S. mirrors the IEA world assessment. The U.S. Department of Energy’s (DOE’s) Energy Information Administration (EIA) says that “conventional hydroelectric” generation—high-head dams—totaled 300.353 TWh of generation in 2017, compared to 254.303 TWh for wind, 50.017 TWh for solar photovoltaic, 41.152 TWh for wood and wood-derived fuels, and 15.927 TWh from geothermal.
Wind and solar have boomed, but they started from a smaller base. An analysis from the anti-hydro group Rivers without Boundaries noted that worldwide in 2017, solar added 98 GW of nameplate capacity, wind 52 GW, coal 35 GW, natural gas 38 GW, large hydro 19 GW, and nuclear 11 GW.
IEA’s 2018 hydro assessment says, “Annual net capacity growth has slowed in recent years, due to fewer large projects being developed in China and Brazil. However, cumulative capacity is still expected to increase by an additional 125 GW by 2023.” By 2050, according to a 2012 IEA analysis, hydro could double its generation to more than 7,000 TWh, and “prevent annual emissions of up to 3 billion tonnes of CO2 from fossil fuel plants.”
It appears that this old generating dog has new tricks.
A Deep History of Water Power
Hydroelectricity dates to the 19th century, when both Pelton and Francis turbines were invented, based on water wheels that ground grain for 2,000 years (see sidebar). Legendary British scientist Michael Faraday in 1831 demonstrated the basis of hydropower: electromagnetic induction.
Hydro Turbine Technologies
Hydro turbines generally come in two types: impulse turbines and reaction turbines. According to the U.S. Department of Energy (DOE), “The type of hydropower turbine selected for a project is based on the height of the standing water—referred to as the ‘head’—and the flow, or volume of water at the site. Other deciding factors include how deep the turbine must be set, efficiency, and cost.”
Impulse Turbines. According to the DOE, “The impulse turbine uses the velocity of the water to move the runner and discharges to atmospheric pressure. The water stream hits each bucket on the runner. There is no suction on the down side of the turbine, and the water flows out the bottom of the turbine housing after hitting the runner. An impulse turbine is generally suitable for high-head, low-flow applications.”
An example is the Pelton turbine used in the Bieudron Hydroelectric Power Station in the Swiss Alps, which went into service in 1998. The plant features three Pelton turbines rated at 423 MW each. The Pelton turbine was originally developed and refined in the 1870s.
Another impulse technology is the cross-flow turbine, also known as a Banki turbine. These designs are suited for small projects, such as run-of-river or conduit projects that capture energy from larger water flows and lower heads.
Reaction Turbines. These machines generate power from both the pressure and the energy from moving water. According to the DOE, “The runner is placed directly in the water stream flowing over the blades rather than striking each individually. Reaction turbines are generally used for sites with lower head and higher flows than the impulse turbines.”
The Francis turbine, according to the DOE, “has a runner with fixed buckets (vanes), usually nine or more. Water is introduced just above the runner and all around it and then falls through, causing it to spin.” Invented in the 1850s, the Francis turbine is suited for applications ranging from several kW up to several GW. They are the most common hydro turbines. The Grand Coulee Dam on the Columbia River in Washington state, with two powerhouses developed in the 1930s and a third in 1974, employs Francis turbines with a total capacity of 6.8 GW.
In 1881, a dynamo at Niagara Falls, New York, generated electricity for nearby street lighting, the first commercial hydroelectric generation. By 1886, 50 hydro plants were online or under construction in the U.S. and Canada. By the turn of the 20th century, hydro was rapidly becoming the source of most U.S. electricity. The 1902 Reclamation Act gave the federal government’s Interior Department authority to develop large-scale hydro on public land.
2. Hoover Dam was built in the 1930s. It is located near Boulder City, Nevada, and provides power to customers in Nevada, Arizona, and California. The plant has 17 turbines, with a generation capacity of about 2,080 MW. Water is pulled from Lake Mead behind the dam. The lake, which covers nearly 250 square miles and is nearly twice the size of Rhode Island, has a capacity of more than 1 trillion cubic feet of water. Courtesy: Creative Commons / Kuczora
The 1930s saw hydropower take off, with the Boulder (renamed Hoover) Dam (Figure 2) on the Colorado River, the creation of the Power Authority of the State of New York and its Niagara River generation, the establishment of the Tennessee Valley Authority and its major hydro program, and the construction of the Grand Coulee and Bonneville dams in the Pacific Northwest.
3. The Glen Canyon Dam near Page, Arizona, created Lake Powell, one of the top recreational destinations in the U.S. The dam has brought lots of backlash from environmentalists who have called for draining Lake Powell, getting rid of the dam, and restoring the Colorado River to its natural flow. Hydropower from Glen Canyon serves 4 million customers from Arizona to Wyoming. The power plant has eight 165-MW turbines. Courtesy: Creative Commons / Mark Byzewski
By the 1960s, hydro galvanized a nascent environmental movement. Opponents began challenging the lakes created by high dams, as the water inundated enormous amounts of land, sometimes destroying unique ecosystems and beautiful natural features. That was the case with the 1960s-era, 710-foot-high Interior Department Glen Canyon Dam (Figure 3) on the Colorado River in Arizona. It created Lake Powell, with a 161,000-acre surface area. That project energized the Sierra Club, then mostly a California-based hiking group. It turned environmental activist, the late David Brower, into an icon of environmentalism. Brower later founded Friends of the Earth, which cut its political teeth on opposition to hydro.
Today, hydro is evolving away from the conventional big dams with high water heads. In the U.S., sites for large-scale hydro now appear limited, except perhaps in Alaska.
But newer hydro technologies may have a bigger role in keeping water power in the generating mix. These include run-of-river hydroelectricity; smaller low-head projects of 10 MW or less, often with no manmade reservoirs; conduit and canal generation; wave and tidal power; and, perhaps most important, pumped storage.
Hydro has tangible virtues. Able to provide baseload power, hydro can also follow load, so it can be dispatched economically. Hydro also offers spinning reserves, reactive power and voltage support, and black-start capability. Hydro can provide power storage, an increasingly valuable service as intermittent generation from wind and solar begins to capture much new generation in a world looking for low- and zero-carbon dioxide generating sources.
A Pumped-Storage Future?
Pumped storage dates to the 1930s. It may be the most attractive future hydro application. According to the EIA, 97% of installed electric storage capacity in the U.S. today is pumped storage.
The concept is simple: Surplus electricity from conventional generation pumps water uphill. Then operators release the water to generate power when the grid needs more electricity.
The development of nuclear power gave impetus to pumped storage. By federal regulation—and U.S. plant designs—U.S. nuclear plants don’t follow load. They operate 24 hours a day, every day of the year, in the ultimate definition of “baseload.” But often—particularly in the dead of night—the power nuclear plants generate can’t be used. It is dumped, a wasted resource. Generating utilities saw pumped storage as a way to store that formerly unwanted power for when it was needed, helping to recover costs.
The U.S. has more than 13 GW of pumped-storage capacity in projects greater than 1,000 MW. The Federal Energy Regulatory Commission (FERC), which licenses hydroelectric projects, said, “Most of these projects were authorized more than 30 years ago.” As nuclear power faded and the connection linking pumped storage to nuclear plants weakened, utility interest in the technology waned.
The rise of intermittent power generation, particularly from wind and solar, has revitalized interest in pumped-storage technology. Worldwide, according to IEA data, pumped-storage capacity today is about 150 GW, with about another 75 GW in the development pipeline.
The National Hydropower Association (NHA), the Washington, D.C., lobby for the domestic hydro industry, said in a 2018 report on pumped storage: “A technology exists that has been providing grid-scale energy storage at highly affordable prices for decades: pumped storage hydropower. While batteries, compressed air, flywheels and other emerging technologies often capture the headlines, pumped storage hydropower has continued to advance its capabilities as the leading grid storage solution allowing for even more optionality in the effort to integrate intermittent renewable energy in a reliable and cost-effective manner.”
Given new opportunities for energy storage, pumped-storage purveyors have upped their game. The NHA noted that pumped storage “has continued to advance its technology in recent years, including the capability for very fast response to grid signals, and an increased flexibility for development in broader, less traditional geographies with the application of ‘closed loop’ systems.” According to FERC, closed-loop pumped-storage systems “are not continuously connected to a naturally flowing water feature.” That reduces their environmental impact. There are no closed-loop systems currently operating in the U.S.
4. The Gordon Butte pumped-storage project in Montana is a closed-loop, 400-MW facility. The project has upper and lower closed-loop reservoirs connected by an underground concrete and steel-lined hydraulic shaft. Each reservoir is sized at about 4,000 acre-feet of water. Courtesy: Absaroka Energy
The DOE in December said it had picked two proposed pumped-storage projects for analysis of their “long-term value”: GridAmerica Holdings’ conventional 1,200-MW Goldendale project on the Washington-Oregon border, and Absaroka Energy’s 400-MW closed-loop, Gordon Butte project (Figure 4) in Montana. DOE said that while pumped-storage hydro was “initially built to balance the electricity system between periods of high demand during the day and low demand at night, increases in variable renewable generation have changed how plants are operated and the value they provide to the grid.”
POWER magazine in May 2017, citing the IHA, reported that “about 6.4 GW of pumped storage systems were installed worldwide in 2016—more than twice the 2.5 GW installed in 2015. The surge in pumped storage system installations is in tandem with soaring interest in energy storage technologies to support the integration of variable generation and support grid stability.”
While often dismissed, hydro has not run out of steam (or water). As a DOE analysis recently concluded, “Even after a century of proven experience with the reliable renewable resource, significant opportunities exist to expand the nation’s hydropower resources through non-powered dams, water conveyance systems, pumped storage hydropower, and site development.” ■
—Kennedy Maize is a long-time energy journalist and frequent contributor to POWER.