Water (Hydro) Power

Mills driven by waterwheels are the oldest sources of mechanical power, along with windmills and tidal mills.   A waterwheel converts the potential gravitational energy of a height of water into rotational mechanical energy to do work.   The falling water strikes the blades of the wheel and forces them to rotate.   Although it is very inefficient, converting about 5% of the available energy into useful work, that mattered little in a country abounding in rivers and creeks with free water, and it was more efficient, cheaper and easier than using human and animal muscle.

Mills and factories used waterwheels to grind grain, roll iron bars into plates, full woolen fibers, and saw lumber.   Furnaces that separated metals from their ores used it to operate bellows.   Forges used it to drop hammers onto metal in forming operatings.   Its size and complexity required a large investment to build and a large sales revenue to recoup this investment, so it was always located in areas that could reach customers or be reached by them without incurring prohibitive transportation costs.   A nearby waterfall was required to propel the waterwheel, which was attached to a wooden axle that delivered the power through a gear system to the final end grinders, saws, and hammers located in the mill.   The waterfall was provided naturally or, more commonly, by a dam that gave sufficient height above the waterwheel.   Water was shunted via a "race" (a small canal) from the waterfall to the waterwheel.   The disadvantage of a waterwheel is that when the water is frozen or low, mill operations are slowed or stopped until water conditions become more favorable.   Water wheels were made of wood, which made them susceptible to rot.   After iron became cheaper, it was used for waterwheels, but by that time, water turbines, all made of iron and steel, replaced waterwheels.

Water turbines differ from water wheels.   Water falls on the vanes of a waterwheel under the force of gravity.   The wheel turns at a constant rate.   In a water turbine, water is forced into the hub of the wheel and then moves out along the vanes.   The water forces the wheel to move faster, which forces more water into the hub and onto the vanes.  A water turbine can deliver much more power than a water wheel for the same amount of water supplied, thus improving the productivity of the driven machinery.   Falling water in older days provided the energy to rotate waterwheels, which are obsolete.   Later, by means of a water turbines, the water drove blades on shafts which were connected to gears and pulleys to produce mechanical power.   These are also obsolete today.   Today, water turbines drive electric generators in a hydropower plant that produce electrical power.   Water turbines differ from waterwheels in that the water swirls horizontallly around the turbine rotor, thus converting more water kinetic energy to mechanical energy than a water wheel, which converts only some the vertical water kinetic energy, the rest of the energy being lost.   Therefore, water turbines are much more efficient than water wheels.   Water turbines are of two types: impulse and reaction.   When the potential energy of the water is converted into kinetic energy within the delivery tube leading to the turbine blade runners, it is an impulse turbine.   When the potential energy of the water is converted into kinetic energy in the turbine blade runners, it is a reaction turbine.   Impulse turbines require a high head of water to be effective, so they are not as common as reaction turbines.   Water turbines can be 90% efficient, compared to the 5% efficiency of waterwheels.   Water turbines are smaller than water wheels for comparable power.   They also turn faster, thus reducing the need for more gearing to increase the rotating speed.   Here are some examples of old reaction water turbines used to convert the kinetic energy of water into mechanical energy of a rotating shaft, which would be connected to other gears and machines.   The completion of a hydropower plant is described under Niagara Power, which in 1895 delivered more power than any one place in the world.   The most extensive power installation in 1934, will be described under Tennessee Valley Authority.

The major advantage of hydroelectricity is elimination of the cost of fuel.   The cost of operating a hydroelectric plants is nearly immune to increases in the cost of fossil fuels such as oil, natural gas or coal.   Hydroelectric plants tend to have longer economic lives than fuel-fired generation, with some plants now in service having been built 50 to 100 years ago.   Operating labor cost is usually low since plants are automated and have few personnel on site during normal operation.   Where a dam serves multiple purposes, a hydroelectric plant may be added with relatively low construction cost, providing a useful revenue stream to offset the costs of dam operation.   It has been calculated that the sale of electricity from the Three Gorges Dam will cover the construction costs after 5 to 7 years of full generation. ^{Wiki n.p.}

Reservoirs created by hydroelectric schemes often provide facilities for water sports, and become tourist attractions in themselves.   In some countries, farming fish in the reservoirs is common.   Multi-use dams installed for irrigation can support the fish farm with relatively constant water supply.   Large hydro dams can control floods, which would otherwise affect people living downstream of the project.   When dams create large reservoirs and eliminate rapids, boats may be used to improve transportation.   Since no fossil fuel is consumed, emission of carbon dioxide, a greenhouse gas, from burning fuel is eliminated.   While some carbon dioxide is produced during manufacture and construction of the project, this is a tiny fraction of the operating emissions of equivalent fossil-fuel electricity generation. ^{Wiki n.p.}

Hydroelectric projects can be disruptive to surrounding aquatic ecosystems.   For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed.   Salmon spawn are also harmed on their migration to sea when they must pass through turbines.   This has led to some areas transporting smolt downstream by barge during parts of the year.   Turbine and power-plant designs that are easier on aquatic life are an active area of research.   Generation of hydroelectric power changes the downstream river environment.   Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of river beds and loss of riverbanks.   Since turbines are often opened intermittently, rapid or even daily fluctuations in river flow are observed.   For example, in the Grand Canyon, the daily cyclic flow variation caused by Glen Canyon Dam was found to be contributing to erosion of sand bars.   Dissolved oxygen content of the water may change from pre-construction conditions.   Water exiting from turbines is typically much colder than the pre-dam water, which can change aquatic faunal populations, including endangered species.   Some hydroelectric projects also utilize canals, typically to divert a river at a shallower gradient to increase the head of the scheme.   In some cases, the entire river may be diverted leaving a dry riverbed.   A further concern is the impact of major schemes on birds.   Since damming and redirecting the waters of the Platte River in Nebraska for agricultural and energy use, many native and migratory birds such as the Piping Plover and Sandhill Crane have become increasingly endangered. ^{Wiki n.p.}

Hydroelectricity eliminates the flue gas emissions from fossil fuel combustion, including pollutants such as sulfur dioxide, nitric oxide, carbon monoxide, dust, and mercury in the coal.   Compared to the nuclear power plant, hydroelectricity generates no nuclear waste, nor nuclear leaks.   Unlike uranium, hydroelectricity is also a renewable energy source.   Compared to wind farms, hydroelectricity power plants have a more predictable load factor.   If the project has a storage reservoir, it can be dispatched to generate power when needed.   Hydroelectric plants can be easily regulated to follow variations in power demand.   Unlike fossil-fueled combustion turbines, construction of a hydroelectric plant requires a long lead-time for site studies, hydrological studies, and environmental impact assessment.   Hydrological data up to 50 years or more is usually required to determine the best sites and operating regimes for a large hydroelectric plant.   Unlike plants operated by fuel, such as fossil or nuclear energy, the number of sites that can be economically developed for hydroelectric production is limited; in many areas the most cost effective sites have already been exploited.   New hydro sites tend to be far from population centers and require extensive transmission lines.   Hydroelectric generation depends on rainfall in the watershed, and may be significantly reduced in years of low rainfall or snowmelt.   Utilities that primarily use hydroelectric power may spend additional capital to build extra capacity to ensure sufficient power is available in low water years. ^{Wiki n.p.}

To 1790

The ancient waterwheel mill, introduced into Europe probably from Asia in the 13th century, was the largest and most complicated power-producing mechanism used in America from the earliest settlements through the 19th century, being gradually replaced by stationary steam engines from about 1800 on.

1790-1799

1800-1809

1810-1819

1820-1829

In 1827, a French engineer, Benoît Fourneyron, built a water turbine that delivered 6 horsepower and later one that delivered 50 horsepower. ^{Asimov 321}

1830-1839

1840-1849

1850-1859

1860-1869

1870-1879

1880-1889

In 1880, Lester Pelton invented a type of impulse water turbine called the Pelton Wheel or Pelton Turbine. ^{Asimov 321}

1890-1899

Niagara Falls hydroelectric power, the largest hydroelectric installation in the world at the time, went on line in Niagara Falls in 1895 and in Buffalo in 1896.

1900-1909

1910-1919

1920-1929

1930-1939

1940-1949

1950-1959

1960-1969

1970-1979

1980-1989

1990-1999