Dee Finnegan & Kiersten Warning
Water constantly moves through a vast global cycle driven by the sun. Water evaporates from lakes and oceans, forms clouds, precipitates as rain or snow, and flows back down to the ocean.1 This cycle has been harnessed for power for millennia. In 3000 BCE, Egyptian and Mesopotamian peoples used waterwheels to draw stream or well water to irrigate crops. By 100 BCE, Greek waterwheels powered gristmills for wheat and corn. Mills spread to China by 100 CE where metallurgists adapted it for their use by 300 CE. The waterwheel spread to most areas of the world by 500-1200 CE, including all of Europe.2
Today, hydropower is the world's leading source of renewable energy and produces over 95% of sustainably generated electricity.3 While fossil fuel plants convert 50% of raw material to electrical power, modern hydropower turbines can convert 90% of water's energy into electricity. To produce energy from water costs 1/3 as much as the cost to produce energy from fossil fuels.4 So why not produce power only from water? This paper attempts to answer that question by exploring the uses, history, and future of water as a source of energy.
"Hydro" is Greek for water or liquid. The moving or falling of water can be used to do work. The ability to do work is energy or power.5
Hydropower production needs certain geography: hills and mountains provide the drop necessary to generate kinetic energy for capture and conversion to electric or mechanical power. Norway, with its mountains and waterfalls generates 99% of its electricity from hydropower6; Brazil with rivers like the Amazon, generates 83% of its electricity with hydropower7. Large rivers with healthy tributaries and reliable rainfall are ideal for dams like the Three Gorges Dam, the world's largest hydroelectric dam, on the Yangtze River in China.8 Large bodies of water like lakes and oceans produce tides and waves that can be captured to produce energy. France, China, U.S., Russia, Canada, Japan are some countries exploring wave and tide power.9
Water spills over a waterfall or rushes through a dam with tremendous power. The distance water drops to the point where humans retrieve its energy – with a waterwheel or hydropower turbine – is called a head. The longer the drop, the greater the head. Flow is the amount of water that falls. A wide, deep river has significant flow which means much force.10 Dams stop the flow of a river and often form reservoirs behind the dam or send the river directly through a hydroelectric power plant or powerhouse.11 A decrease in the amount of water in a river can dramatically decrease the ability to produce hydropower; for example, a 10% runoff drop in the Colorado River means a 36% hydroelectric power production drop.12
Interestingly, only 3%, or 2,400 of the 80,000 U.S. dams produce electricity. Other uses include 35% recreation, 18% stock ponds, 15% flood control, 12% public water supply, 11% irrigation.13
Figure 1: Old Mill, Hatsfield, Massachusetts
Source: Creative Commons, http://www.flickr.com/photos/29936458@N05/3460335916/
Sitting in a stream or at a narrow point below a waterfall, a waterwheel traps water flowing over the fall in the cups of the wheel. The force of the water presses on the cups and turns the wheel slowly. This large wheel connects to a smaller wheel that turns much faster. Called gearing, this is similar to bicycle gears that enable a rider to pedal more powerfully up hills or faster on flat surfaces. If a river is fast but flat, a pipe called a penstock can carry water downhill, forcing it through a nozzle that shoots a very hard stream of water at a turbine. A turbine, like a small, fast waterwheel, powers electric generators directly, without gears.14
A fall of 10-15 feet of a moderate amount of water from streams could power the waterwheels of milldams in prior to the American Revolution. Millwrights diverted water into channels called headraces or dug shallow ditches from ponds upstream of a waterfall to the mill's wheelpit or built small (less than 5 feet) dams of wooden cribs, frames or even branches and tree trunks to ensure water supply during dry periods.15
Figure 2: Three Gorges Dam, China
Source: Creative Commons, http://www.flickr.com/photos/pvcg/3412711352/
Most hydropower plants have three parts: 1) a reservoir stores water above a drop, to create a head; 2) a dam opens and closes to control water flow; 3) a power plant transforms the moving energy of water into electricity or mechanical energy. When the dam opens, water flows from the reservoir through a large pipe called a penstock that ends at turbines. The swiftly flowing water presses against the blades inside a turbine and makes it spin. The spinning turbine turns a shaft connected to the generator. The energy from the spinning shaft turns the rotor. The rotor's electromagnetic spin is inside the tight copper coil of the stator, the nonmoving part of a rotor that incubates electricity production from the copper coils. The motion moves electrons, creating an electric field between the coil and the magnets. Electricity leaves the generator as electric current, traveling through high-voltage power cables to a local utility company that distributes it to homes and businesses.16
Figure 3: Wave installation in Norway
Source: Creative Commons, http://www.flickr.com/photos/blomstereng/350320429/
Oceans cover over 70% of the Earth's surface and contain enormous energy in their tides and waves. Tapping this chaotic energy source is a greater challenge than capturing the power of rivers. The oldest and simplest sea power generators use the surge and suck of waves close to shore. They grab waves on the way up the beach and let the sea suck them back through a waterwheel or a turbine. Newer mechanisms catch waves at their peak height and position them above large funnels. On the way down the beach, a wave rushes through the narrow neck of the funnel and powers a turbine.17 This technology is still being developed and is not widely employed to date.
Figure 4: TEES Tidal Barrage
Source: Creative Commons, http://www.flickr.com/photos/31422712@N04/2969092927/
Unlike wind-driven waves, tides rise and fall on a schedule. Deep bays and estuaries isolate large sections of water from the ocean and can produce 50-foot tides. To create tidal power stations, barriers are built across beaches or rivers. The tide rises, forcing water one-way through a two-way turbine. This creates electricity and carries a large volume of water behind the barrier. A gate drops to hold the water in place. When the tide recedes, the gate lifts and water flows back through the turbines, creating electricity in the other direction.18 Tidal power stations are possible in very few areas: Canada's Bay of Fundy, Great Britain's Severn Estuary, France's La Rance Estuary, and Mexico's Gulf of California. The La Rance produces over 500 megawatts of electricity, the most of any tidal power station in the world.19
Figure 5: Turbines under the Sea
Tidal currents of 2-3 knots can be captured in tide farms that resemble underwater wind farms. The first built was in 2003 near Hammerfest, Norway.
Figure 6: How Tidal Lagoons Generate Electricity
Tidal lagoons are created by building walls in the sea to create artificial estuaries. Lagoons need shallow and large tidal ranges. The U.K., for example, requires a tidal lagoon equal to the size of the U.K to generate cost-efficient electricity.20
Thirty-three percent of the world's countries generate at least 50% of their power from water:
The U.S. produces 7-10% of its energy from hydropower; in high rainfall states like Oregon and Washington, up to 85% of electricity is generated from water.22
Top producers of hydropower as a percentage of consumption include
Water powered much of the U.S. Industrial Revolution, marking a transition from hand and home production to factories perched on rivers and streams. European mill technology was implemented in the U.S., enabling mass production of goods to support growing U.S. cities.24 Congress began regulating hydroelectric construction after the first hydroelectric station was built in 1882 in Appleton, Wisconsin. In 1901, it enacted the first Water Power Act to streamline a previously cumbersome plant-by-plant permit process requiring a separate act of Congress for each hydroelectric installation. As westward expansion ensued, in 1902, the Reclamation Act created the Bureau of Reclamation and authorized the Secretary of the Interior to develop irrigation and hydropower projects in 17 western states with scarce water resources.
In 1918, WWI prompted President Wilson to authorize a munitions plant in Muscle Shoals, Alabama that was to be powered by hydroelectricity from the Wilson Dam. This dam is one of the earliest federal dam projects. In 1920, the Federal Power Commission gave the Secretaries of War, Agriculture, and the Interior power to grant licenses to private hydropower developers on major rivers and government lands, as most dams were privately owned. This changed in 1928 with the federal Boulder Canyon Project which authorized the construction of the Hoover Dam and ushered in the era of big dam construction under President Franklin Delano Roosevelt that included the Grand Coulee Dam on the Columbia River in Washington State, the Central Valley Project in California, the Tennessee Valley Authority, and the Bonneville Project. The Public Utility Act of 1935 expanded the FPC's jurisdiction to include setting wholesale electricity rates; consumer rates remained regulated by state utility commissions.
The Flood Control Act of 1944 allowed the Secretary of the Interior to market power from Army Corps of Engineers projects and authorized the Pick-Sloan Missouri Basin Program which implemented a comprehensive water use plan that included conservation, use, and power generation. Due to WWII power demands, the federal government began construction and control of the largest hydropower projects, largely through the Army Corps of Engineers. The Corps is now the largest single producer of hydroelectric power in the U.S., operating 75 dams with an installed capacity of 21,000 megawatts, enough power to fulfill the annual energy needs of over 61 million individuals.25
The 1946 Fish and Wildlife Coordination Act ensured consideration of wildlife in federal actions for the first time. The 1968 Wild and Scenic Rivers Act first addressed environmental concerns by "protecting rivers in their natural state by excluding them from consideration as hydroelectric generation sites." In 1986, the Electric Consumers Protection Agency required the Federal Energy Regulatory Commission to entertain recommendations from national and local fish and wildlife agencies. Today the U.S. government officially requires FERC to prioritize environment concerns (and civilian recreation) alongside the potential for energy when it makes power-development decisions.26
The United States participates in the United Nations' Convention on Environment and Development, the World Summit on Sustainable Development, and the World Commission on Dams. These bodies create ecology-friendly policies that call governments, consultants, and non-governmental organizations to work with affected populations to institute hydropower installments that are sustainable.27
Figure 7: Appleton Hydropowered Streetcar
The Fox River in Appleton, Wisconsin became the site for the world's first hydroelectric station which began operation in 1882. Henry J. Rogers, a paper mill manager inspired by Thomas Edison's plans for a steam powered power plant in New York, built the plant to power the Appleton Paper and Pulp Company, the Vulcan Paper Mill, and his personal residence. Appleton is also the site for the first hydroelectrically lighted college building, Lawrence's Ormsby Hall, and the first "western" lighted hotel, the Waverly House. Hydroelectricity also drove the city's electric trolley system from 1886 to 1930 until it could no longer compete with gasoline-powered automobiles.28
While proponents argue that hydroelectricity is efficient, renewable, sustainable, and low-cost, the building of large dams and of the infrastructure to support them causes significant environmental and social problems both at the site of the dam and the surrounding region, especially downstream. The Hoover Dam disturbed the natural process of the Colorado River transfer of silt to Mexican forests. This area, once able to support farmers, a variety of birds, and wildlife species became a desert.29
Hydropower also alters the natural flow of rivers and streams that affect the aeration and temperature of the water further disturbing and fragmenting wildlife habitats. Dams often kill fish directly or indirectly by creating uninhabitable water or preventing spawning. According to the National Food and Agricultural Organization, dams on tropical rivers have resulted in 10% of tropical deforestation.
Although promoted as "greenhouse gas free", stagnant hydroelectric dam reservoirs release methane, a greenhouse gas, from accumulated vegetative matter.30 However methane capture and utilization as a renewable energy source may be possible in the future.31
The construction of major dams dislocates people and destroys livelihoods. We are just starting to address these ramifications. In 2005, for example, U.S. Congress passed legislation to compensate the Spokane Indian tribe for loss of lands and fishing livelihood resulting from the construction and operation of the Grand Coulee Dam in 1942.32 We may see further future legal action to compensate, for example, those who lost their livelihoods when dams converted California's once-lush Central Valley into a desert.33
The environmentalist John Muir was one of the first to object to dams when plans developed in 1903 to dam the Tuolumne River in California's Yosemite National Park. Although Muir lost his battle, it served to bring attention to dam building in National Parks.34 In the 1960s, environmental groups rallied against the construction of Glen Canyon Dam, fueled by popular media such as Edward Abbey's The Monkey Wrench Gangand Eliot Porter's coffee table photography book The Place No One Knew.35 Although the dam was built in 1963, the project marked a turning point of attitudes towards massive dam building projects, sparking federal regulatory action that mandates consideration of environmental concerns in all major hydropower installations.
The expected lifespan of dams is around 50-75 years. 5,000 dams around the world are now over 50 years old; U.S. dams' average age is 40 years. Prohibitive maintenance costs often force owners to abandon them. Washed out dams create erosion problems, sediment deposits, and habitat destruction. Decommissioning, from simply stopping operation to removal, is common and necessary.36
Like many other states, Wisconsin actively reviews aging dams and is one of the leaders in dam removal as the most feasible solution to the crumbling structures. Over sixty dams Wisconsin dams were removed between 1967 and 2003.37 The central Wisconsin dam at Baraboo Creek was removed in 2002. Today, the area has started to stabilize. The quick river movement has created a rare "riffle" environment – small, shallow and gravelly areas of streambed with quick current that is ideal for some forms of small aquatic life and fish spawning. Recreational opportunities have increased for anglers and canoeists and kayakers who appreciate the increased challenge of a swifter river. Native small mouth bass have returned to make this river their home.
Water power has a place in the future of energy production. "The challenge…is to learn to treat water and the world as a precious interconnected whole." – Allison Stark Draper38
Freestanding, damless turbines are currently being developed. Another design resembles an underwater wind sock to capture the highest concentration of stream flow.39
Figure 8: Drawing of an Oscillating Water Column
It is possible to retrieve wave energy through the use of an oscillating water column (OWC). A wave hits an OWC, compresses the air inside it, and forces the air through air turbines. Ideally, these columns produce energy as the air goes in and out of the column. OWC's are still experimental.40
Open-water "salter ducks" milk the power of wind-driven waves. Salter ducks are linked floats that come in chains of 25. As each of the floats bobs up and down independently of its neighbors, the alternating motion powers a pump. The salter duck system shows a lot of potential to generate energy but it lacks precision because its bobbing floats are at the mercy of harsh weather.
In contrast, moored systems attach securely to the ocean floor. They look like large, floating funnels. The swelling waves of rough seas travel through their wide mouths, into narrow tubes that house turbines. The problem is that while waves are constant, they are not of uniform size. Moored systems can provide power for rough tasks like crushing, milling, and grinding. They do less well generating electricity, which demands a smooth flow of energy. In addition, marine life are harmed by such open-water systems.41
Experiments with sea currents use large underwater wheels that fly sails similar to those on windmills. The currents push the sails and turn the wheels but also endanger large sea creatures like whales and dolphins. Smaller creatures, like barnacles, can grow on the equipment and damage it. As with any open-ocean system it is expensive to build cables hundreds of miles to shore but creative transport solutions are being developed.42
The future may see an increasing divide between the large scale of industrial power and the small scale of householders running their homes on renewable resources of solar, wind, and hydropower.43 Small (<10 megawatts) to micro (<100 kilowatts) installments may be the future of hydropower. The 1978 Public Utility Regulatory Policies Act encourages small-scale power production facilities, exempts certain hydroelectric projects from federal licensing requirements, and requires utilities to purchase – at "avoided cost" rates – power from small production facilities that use renewable resources. Small hydro is usually a "run of the river" system which does not require a dam and does not disrupt a stream's natural flow. These systems are less expensive to build and have fewer environmental effects.
Micro systems are most common in small, rural communities where farmers with water sources sometimes create their own hydroelectric systems to provide low-cost, personal power "off the grid". While in the U.S. dropping off the grid is voluntary, in some countries large regions have no access to an electrical grid. In 1998, the Indonesian government began a project to provide 18,600 villages with power using small hydropower systems. In Vietnam, 3,000 small systems will create power for 2 million households. Hilly, river-laced Nepal has an installed micro hydropower capacity of about 8.7 megawatts with a potential of 42MW. China raises its small hydro capacity by one gigawatt a year in rural areas.44
The modern American community demands immense energy, but for daily life, most people need and use small amounts of power. Production of power by its users is both efficient and sensible. In May 2001, inventor Robert Komarechka of Canada patented a liquid shoe sole that uses tiny turbines to generate hydropower. A steady walk produces a steady flow of electricity that users can access through a socket on the shoe or a device on a belt. Hydroelectric shoes will generate enough energy for mobile phones, GPS receivers, and portable computers.45
Power to the People.
Draper, Allison Stark. Hydropower of the Future: New Ways of Turning Water into Energy. New York: The Rosen Publishing Group, Inc., 2003.
Hay, Duncan. Hydroelectric Development in the United States, 1880-1940. Washington, D.C.: Edison Electric Institute, 1991.
International Rivers Alliance: http://www.internationalrivers.org
River Alliance of Wisconsin: http://www.wisconsinrivers.org
World Energy Council: http://www.worldenergy.org
Billington, David P. and Donald C. Jackson. Big Dams of the New Deal Era: A Confluence of Engineering and Politics. Norman, OK: University of Oklahoma Press, 2006.
Cech, Thomas V. Principles of Water Resources: History, Development, Management, and Policy. 2nd Edition. New York: John Wiley & Sons, Inc., 2005.
Draper, Allison Stark. Hydropower of the Future: New Ways of Turning Water into Energy. New York: The Rosen Publishing Group, Inc., 2003.
Edwards, Brian K. The Economics of Hydroelectric Power. Northampton, MA: Edward Elgar Publishing Limited, 2003.
"Ending a Damned Nuisance." The Economist. February 19, 2008.
Hjort-af-Ornas, Anders. Turning Hydropower Social: Where Global Sustainability Conventions Matter. Berlin: Springer-Verlag, 2008.
MacKay, David J. C. Sustainable Energy – Without the Hot Air. Accessed September 1, 2009 at www.withouthotair.com .
Malloy, Peter M. "Nineteenth-Century Hydropower: Design and Construction of the Lawrence Dam, 1845-1848." The Henry Francis du Pont Winterthur Museum, 0084-1416/1504-0003, 1980.
McKinnon, Shaun. "At Age 50, Dam Still Generates Love, Hate." The Arizona Republic. May. 28, 2007.
Nye, David E. Consuming Power: A Social History of American Energies. Cambridge, MA: MIT Press, 2001 .
Ruby, Robert H. and John Arthur Brown. The Spokane Indians: Children of the Sun. Norman, OK: University of Oklahoma Press, 2006.
Walter, Robert C. and Dorothy J. Merritts. "Natural Streams and the Legacy of Water-Powered Mills." Science 319, 299 (2008).
2 Walter 2008.
3 Draper 2003: 5.
4 Id.: 13.
9 Draper 2003: 39.
10 Id.: 9-10.
12 Id.: 52.
13 Draper 2003: 26.
14 Id.: 9-10.
15 Malloy 1980: 315.
16 Draper 2003: 11.
17 Id.: 35-36.
18 Id.: 38-39.
19 Id.: 39.
20 MacKay 2009: 85.
21 Edwards 2003: 1.
22 Draper 2003: 46.
24 Nye 1998.
25 For details on how to convert energy production to consumption, see http://www.wvic.com/index.php?option=com_content&task=view&id=8&Itemid=45.
26 Draper 2003; Edwards 2003; Hjort-af-Ornas 2008.
27 Hjort-af-Ornas 2008: 2-3.
28 Cech 2005.
29 Draper 2003.
32 Ruby and Brown 2006.
33 For more information on the effects of dambuilding on the West, see Marc Reisner's Cadillac Desert: The American West and Its Disappearing Water. New York: Viking Penguin, Inc., 1986.
34 Billington and Jackson 2006.
35 McKinnon 1997.
38 Draper 2003: 56.
39 "Ending a Damned Nuisance." The Economist. February 19, 2008.
40 Draper 2003: 36.
41 Id.: 37.
42 Id.: 38.
43 Id.: 47-48.
44 Id.: 47-48.
45 Id.: 49.