Monday, October 22, 2012

Hydrokinetic Technologies - OTEC

The energy from the sun heats the surface water of the ocean. In tropical regions, the surface water can be much warmer than the deep water. This difference can be used to produce electricity. Ocean Thermal Energy Conversion, or OTEC, has the potential to produce more energy than tidal, wave, and wind energy combined, but it is a technology for the future.

The warm surface water is turned into steam under pressure, or used to heat another fluid into a vapor. This steam or vapor spins a turbine to produce electricity. Pumps bring cold deep water to the surface through huge pipes. The cold water cools the steam or vapor, turning it back into liquid form, and the closed cycle begins again. In an open system design, the steam is turned into fresh water, and new surface water is added to the system.

An OTEC system is only about 3 percent efficient. Pumping the water is a giant engineering challenge. In addition, the electricity must be transported to land. OTEC systems work best with a temperature difference of at least 20°C to operate. This limits its use to tropical regions where the surface waters are very warm. Hawaii, with its tropical climate, has experimented with OTEC systems since the 1970s.

Today, there are several experimental OTEC plants, but no big operations. It will probably be 15 to 20 years before the technology is available to produce energy economically from OTEC systems. OTEC will have the potential to produce non-polluting, renewable energy.

Hydrokinetic Technologies - Wave Energy

There is also tremendous energy in waves. Waves are caused by the wind blowing over the surface of the ocean. In many areas of the world, the wind blows with enough consistency and force to provide continuous waves. The west coasts of the United States and Europe and the coasts of Japan and New Zealand are good sites for harnessing wave energy.

There are several ways to harness wave energy. The motion of the waves can be used to push and pull air through a pipe. The air spins a turbine in the pipe, producing electricity. In Norway, a demonstration tower built into a cliff produces electricity for about four cents a kWh using this method. The wail of the fast-spinning turbines, however, can be heard for miles.

Another way to produce energy is to bend or focus the waves into a narrow channel, increasing their power and size. The waves can then be channeled into a catch basin, like tidal plants, or used directly to spin turbines.

There aren’t any big commercial wave energy plants, but there are a few small ones. There are wave-energy devices that power the lights and whistles on buoys. Small, on-shore sites have the best potential for the immediate future, especially if they can also be used to protect beaches and harbors. They could produce enough energy to power local communities. Japan, which must import almost all of its fuel, has an active wave-energy program.

Hydrokinetic Technologies - Tidal Energy

The tides rise and fall in eternal cycles. The waters of the oceans are in constant motion. We can use some of the ocean’s energy, but most of it is out of reach. The problem isn’t harnessing the energy as much as transporting it. Generating electricity in the middle of the ocean just doesn’t make sense -  there’s no one there to use it. We can only use the energy near shore, where people need it.

Tidal energy is the most promising source of ocean energy for today and the near future. Tides are changes in the level of the oceans caused by the rotation of the Earth and the gravitational pull of the moon and sun. Near shore water levels can vary up to 40 feet, depending on the season and local factors. Only about 20 locations have good inlets and a large enough tidal range—about 10 feet—to produce energy economically.

Tidal energy plants capture the energy in the changing tides. A low dam, called a barrage, is built across an inlet. The barrage has one-way gates (sluices) that allow the incoming flood tide to pass into the inlet. When the tide turns, the water flows out of the inlet through huge turbines built into the barrage, producing electricity. The oldest and largest tidal plant—La Rance in France—has been successfully producing electricity since 1966.

Tidal plants have very high development costs. It is very expensive and takes a long time to build the barrages, which can be several miles long. Also, tidal plants produce electricity less than half of the time. The seasons and cycles of the moon affect the level—and the energy—of the tides. The tides are very predictable, but not controllable.

On the other hand, the fuel is free and non-polluting, and the plants have very low operating costs. The plants should run for a hundred years with regularly scheduled maintenance.

Tidal power is a renewable energy source. The plants do affect the environment, though they produce no air pollution. During construction, there are major short-term changes to the ecology of the inlet. Once the plants go into operation, there can be long-term changes to water levels and currents. The plants in operation have reported no major environmental problems.

The United States has no tidal plants and only a few sites where tidal energy could be produced economically. France, England, Canada, and Russia have much more potential. The keys are to lower construction costs, increase output, and protect the environment.

Hydropower and the Environment

Hydropower dams can cause several environmental problems, even though they burn no fuel. Damming rivers may permanently alter river systems and wildlife habitats. Fish, for one, may no longer be able to swim upstream.

Hydro plant operations may also affect water quality by churning up dissolved metals that may have been deposited by industry long ago. Hydropower operations may increase silting, change water temperatures, and lower the levels of dissolved oxygen.

Some of these problems can be managed by constructing fish ladders, dredging the silt, and carefully regulating plant operations. Hydropower has advantages, too. Hydropower’s fuel supply (flowing water) is clean and is renewed yearly by snow and rainfall. Furthermore, hydro plants do not emit pollutants into the air because they burn no fuel. With growing concern over greenhouse gas emissions and increased demand for electricity, hydropower may become more important in the future.

Hydropower facilities offer a range of additional benefits. Many dams are used to control flooding and regulate water supply, and reservoirs provide lakes for recreational purposes, such as boating and fishing.

Economics of Hydropower

Hydropower is the cheapest way to generate electricity today. No other energy source, renewable or nonrenewable, can match it. Today, it costs less than one cent per kilowatt-hour (kWh) to produce electricity at a typical hydro plant. In comparison, it costs coal plants about four cents per kWh and nuclear plants about two cents per kWh to generate electricity.

Producing electricity from hydropower is cheap because, once a dam has been built and the equipment installed, the energy source—flowing water—is free.

Hydropower plants also produce power cheaply due to their sturdy structures and simple equipment. Hydro plants are dependable and long-lived, and their maintenance costs are low compared to coal or nuclear plants.

One requirement may increase hydropower’s costs in the future. The procedure for licensing and relicensing dams has become a lengthy and expensive process. Many environmental impact studies must be undertaken and as many as 13 state and federal agencies must be consulted. It takes up to seven years to get a license to build a hydroelectric dam or a relicense to continue operations.

Hydropower for Base Load Power

Demand for electricity is not steady; it goes up and down. People use more electricity during the day when they are awake and using electrical appliances and less at night when they are asleep. People also use more electricity when the weather is very cold or very hot.

Electric utility companies have to produce electricity to meet these changing demands. Base load power is the electricity that utilities have to generate all the time. For that reason, base load power should be cheap and reliable. Hydropower meets both of these requirements.

Generating electricity with hydropower is the cheapest way to generate electricity in the U.S., and the fuel supply—flowing water—is always available.

Hydro plants are more energy efficient than most thermal power plants, too. That means they waste less energy to produce electricity. In thermal power plants, a lot of energy is lost as heat. Hydro plants are about 90 percent efficient at converting the kinetic energy of the moving water into electricity.

Hydropower Production

How much electricity do we get from hydropower today? Depending on the amount of rainfall, hydro plants produce from five to ten percent of the electricity produced in this country (the most was 10.1 percent in 1997, and the least was 5.6 percent in 2001). In Oregon, Washington, and Idaho, hydropower accounts for more than half (55 to 76 percent) of each state's electricity generation.
Today, there is about 78,000 megawatts of conventional hydro generating capacity in the United states, and about 98,000 megawatts when including pumped storage. That's equivalent to the generating capacity of 80 large nuclear power plants. The biggest hydro plant in the U.S. is located at the Grand Coulee Dam on the Columbia River in northern Washington State. The United States also gets some hydropower generated electricity from Canada.
Some New England utilities buy this imported electricity. What does the future look like for hydropower? The most economical sites for hydropower dams in the U.S. have already been developed, so the development of big hydro plants is unlikely.
Existing plants could be modernized with turbine and generator upgrades, operational improvements, and adding generating capacity. Plus, many flood control dams not equipped for electricity production could be retrofitted with generating equipment. The National Hydropower Association estimates 60,000 megawatts of additional generating capacity could be developed in the United States by 2025.

Pumped Storage Systems

Some hydropower plants use pumped storage systems. A pumped storage system operates much like a public fountain does; the same water is used again and again.
At a pumped storage hydropower plant, flowing water is used to make electricity and then stored in a lower pool. Depending on how much electricity is needed, the water may be pumped back to an upper pool. Pumping water to the upper pool requires electricity so hydro plants usually use pumped storage systems only when there is peak demand for electricity.
Pumped hydro is the most reliable energy storage system used by American electric utilities. Coal and nuclear power plants have no energy storage systems. They must turn to gas and oil-fired generators when people demand lots of electricity. They also have no way to store any extra energy they might produce during normal generating periods.

Hydropower Plants

As people discovered centuries ago, the flow of water represents a huge supply of kinetic energy that can be put to work. Water wheels are useful for generating motion energy to grind grain or saw wood, but they are not practical for generating electricity. Water wheels are too bulky and slow.
Hydroelectric plants are different. They use modern turbine generators to produce electricity, just as thermal (coal, natural gas, nuclear) power plants do, except they do not produce heat to spin the turbines.

Storing Energy

One of the biggest advantages of a hydropower plant is its ability to store energy. The water in a reservoir is, after all, stored energy. Water can be stored in a reservoir and released when needed for electricity production.

During the day when people use more electricity, water can flow through a plant to generate electricity. Then, during the night when people use less electricity, water can be held back in the reservoir.

Storage also makes it possible to save water from winter rains for generating power during the summer, or to save water from wet years for generating electricity during dry years.

Head and Flow

The amount of electricity that can be generated at a hydro plant is determined by two factors: head and flow. Head is how far the water drops. It is the distance from the highest level of the dammed water to the point where it goes through the power-producing turbine.

Flow is how much water moves through the system - the more water that moves through a system, the higher the flow. Generally, a high head plant needs less water flow than a low-head plant to produce the same amount of electricity.

How a Hydropower Plant Works

A typical hydropower plant is a system with three parts:
  • a power plant where the electricity is produced;
  • a dam that can be opened or closed to control water flow; and
  • a reservoir (artificial lake) where water can be stored.
To generate electricity, a dam opens its gates to allow water from the reservoir above to flow down through large tubes called penstocks. At the bottom of the penstocks, the fast-moving water spins the blades of turbines. The turbines are connected to generators to produce electricity. The electricity is then transported via huge transmission lines to a local utility company.
  1. Water in a reservoir behind a hydropower dam flows through an intake screen, which filters out large debris, but allows fish to pass through.
  2. The water travels through a large pipe, called a penstock.
  3. The force of the water spins a turbine at a low speed, allowing fish to pass through unharmed.
  4. Inside the generator, the shaft spins coils of copper wire inside a ring of magnets. This creates an electric field, producing electricity.
  5. Electricity is sent to a switchyard, where a transformer increases the voltage, allowing it to travel through the electric grid.
  6. Water flows out of the penstock into the downstream river.

Hydro Dams

It’s easier to build a hydropower plant where there is a natural waterfall. That’s why both U.S. and Canada have hydropower plants at Niagara Falls. Dams, which are artificial waterfalls, are the next best way.

Dams are built on rivers where the terrain will produce an artificial lake or reservoir above the dam. Today there are about 84,000 dams in the United States, but less than three percent (2,200) have power-generating hydro plants. Most dams are built for flood control and irrigation, not electric power generation.

A dam serves two purposes at a hydropower plant. First, a dam increases the head, or height, of the water. Second, it controls the flow of water. Dams release water when it is needed for electricity production. Special gates called spillway gates release excess water from the reservoir during heavy rainfalls.

History of Hydropower

Hydropower has been used for centuries. The Greeks used water wheels to grind wheat into flour more than 2,000 years ago. In the early 1800s, American and European factories used the water wheel to power machines.

The water wheel is a simple machine. The water wheel is located below a source of flowing water. It captures the water in buckets attached to the wheel and the weight of the water causes the wheel to turn. Water wheels convert the potential energy (gravitational energy) of the water into motion. That energy can then be used to grind grain, drive sawmills, or pump water.

In the late 19th century, the force of falling water was used to generate electricity. The first hydroelectric power plant was built on the Fox River in Appleton, WI in 1882. In the following decades, many more hydroelectric plants were built. At its height in the early 1940s, hydropower provided 33 percent of this country’s electricity.

By the late 1940s, the best sites for big dams had been developed. Inexpensive fossil fuel plants also entered the picture. At that time, plants burning coal or oil could make electricity more cheaply than hydro plants. Soon they began to underprice the smaller hydroelectric plants. It wasn’t until the oil shocks of the 1970s that people showed a renewed interest in hydropower.


What is Hydropower?

Hydropower (from hydro, meaning water) is energy that comes from the force of moving water. The fall and movement of water is part of a continuous natural cycle called the water cycle.

Energy from the sun evaporates water in the Earth’s oceans and rivers and draws it upward as water vapor. When the water vapor reaches the cooler air in the atmosphere, it condenses and forms clouds. The moisture eventually falls to the Earth as rain or snow, replenishing the water in the oceans and rivers. Gravity drives the water, moving it from high ground to low ground. The force of moving water can be extremely powerful.

Hydropower is called a renewable energy source because the water on Earth is continuously replenished by precipitation. As long as the water cycle continues, we won’t run out of this energy source.

Sunday, October 21, 2012

BELO MONTE - Hydropower Project

The largest hydroelectric dam in Brazil and the third in the world


Name                                    Belo Monte

Country                                Brazil

Installed capacity             11,233 MW

Mean annual energy      40,042 GWh Energy equivalent energy 191,600 BEP day



Reasserting its condition of technological leader worldwide, IMPSA´s efficiency obtained in its hydraulic laboratory and offered to the winning consortium was superior to all other machinery that will be part of this provision.

In order to maximize local manufacture, IMPSA expanded its Production Center in Recife, in the state of Pernambuco, with state-of-the-art tool machinery so that high value-added turbine and generator components are fabricated in Brazil. To this end, some 500 local workers from different disciplines were hired. They are being trained to make the best transfer of technology to professionals and technicians.

To achieve sustainable development, Brazil has always prioritized the use of renewable energies. In this context, the Belo Monte project, in the state of Pará, northeastern Brazil, is one of the best options for expanding the country's power generation capacity. Not only for the amount of energy it can produce but also for the propitious conditions for integration into the interconnected national grid and.

Only the market leaders participated in bidding for the generation equipment. IMPSA obtained the supply of electromechanical equipment under “turnkey” conditions which includes four of the eighteen 620.2 MW Francis generating units with their respective speed governors and excitation systems, generator related equipment, penstocks for the 18 units and lifting equipment.


Technical characteristics


Hydraulic Design

Tests of the Belo Monte turbine scale model have been performed at the Hydraulics Laboratory of IMPSA's Technology Research Center in Argentina. The development process comprised:

·         Hydraulic design of turbine components.

·         Computational fluid dynamics (CFD): spiral chamber, stay ring, distributor, runner and draft tube.

·         Mechanical design of the reduced scale model.

·         Scale model test.

Project requirements, such as efficiency, cavitation, runaway speed, pressure fluctuations, hydraulic thrust and hydraulic torque of different components are checked using the tests performed on the model on the high head universal test rig of the Hydraulics Laboratory.

Mechanical Design

For mechanical design, a computerized 3D model is used to verify component stresses, deflections and natural frequencies using the finite element method (FEM).

The spiral case is made of welded steel plates designed for maximum operation pressure. The stay ring has two parallel plates welded onto 24 stay vanes. This component is tested at site at the design pressure.

The distributor has 24 wicket gates driven by two servomotors through an operating ring. The wicket gates are equipped with self-lubricating bushings.

The runner is made of casting in 13.4 stainless steel.

The shaft utilizes a thin-wall welded design. Because of its inertia, this solution increases the safety margin in the event of critical speeds and provides greater vibration stability and reduces manufacturing costs.



IMPSA's governor is of the digital electro-hydraulic type with PID control. The control electronics, composed of high-quality standard PLCs in a redundant “hot” stand-by configuration, is highly reliable and easy to maintain. The system architecture consists of both a main and a manual backup controller. This ensures high fault tolerance in the event of main controller failure and prevents the generating unit from shutting down; otherwise, the load would be rejected and the power system would be adversely affected. The software includes all speed and power control functions required for these types of units.

The oil pressure system (air/oil) has a pumping unit with three pumps to pressurize the system and an air/oil tank. The pumping unit and the air/oil tank were fully designed in 3D.



The units are three-phase, vertical shaft, salient pole synchronous machines, with a unit capacity of 679 MVA, 90rpm and a 18 kV rated voltage. With its 8.1 MVA specific power per pole, it is a piece of equipment of high technological complexity.

Integral dimensioning of the generator is performed with the ARGEN®, expert integrated system fully developed by IMPSA, which analyzes the equipment's behavior, both in steady and transient states as well as under normal and fault conditions. This tool synthesizes all the design fields required for this type of generator: electromagnetism, electrical and magnetic circuits, fluid mechanics and heat transmission, machine components, strength and fatigue of materials, tribology (lubricants-wear-bearings), shaftline stability, vibrations and oscillatory behavior.

Generators are designed with CAD (Computer Aided Design) and verification studies are carried out with tools developed by IMPSA and integrated into the PROGEN ® expert system, as well as with applications using FEM (Finite Element Method).

The stator's magnetic core is made from 0.5 mm non- oriented -grain magnetic steel sheets which are die-cut, varnished and stacked. The stator winding is mounted on the slots and the whole set is supported by the stator frame, a welded mechanical structure that directs the air from the core to the heat exchange units of the cooling system.

The rotor consists of a steel-welded spider, a rotor rim made of die-cut stacked segments (for radial ventilation) and the pole inductors that generate the rotating magnetic field in the machine's air gaps.

The shaft line arrangement includes a guide bearing on the generator's rotor, a combined bearing below the generator's rotor, and a guide bearing in the

turbine to maximize the rotor's dynamic stability.

Design characteristics include the lower support cone of the thrust bearing mounted on the turbine cover and a lower bracket which transmits radial stresses to the foundation minimizing the machine's length. This makes it possible to achieve significant savings in the project's civil structure.

The symmetric radial ventilation system uses the rotor to generate pressure for machine cooling.


Excitation System

The excitation system includes:

Digital regulation system: It is made up of two automated systems that actuate the manual/automatic regulation channels and of field current controllers linked to each SCR (thyristor) bridge rectifier. This 100% redundant structure ensures independent control at different levels: input/output, regulation channels and current controllers.

Power control system: It is made up of two bridge rectifiers in cold stand-by to ensure double power redundancy without jeopardizing the other SCRs in the event of a power failure near the bridge rectifiers. Each bridge rectifier has its own air/air heat exchange unit and protection system.

Field discharge: In the event of a normal shutdown, the system performs a fast DE excitation by delaying the trigger pulses in the rectifier without opening the field breaker. The energy stored in the rotor is returned to the excitation transformer. In the event of an emergency shutdown, the system performs a fast DE excitation by opening the field breaker and discharging the energy stored in the rotor into a non-linear resistor.

Excitation transformer: The epoxy-encapsulated winding is protected with its corresponding cell, which is connected to the segregated phase bus duct. It is specially designed to withstand harmonics generated by the bridge rectifier. Current transformers in the primary circuit provide protection against overcurrent’s.

Hydropower Conclusion

Reclamation is helping to meet the needs of our country, and one of the most pressing needs is the growing demand for electric power. Reclamation power plants annually generate more than 42 billion kWh of hydroelectric energy, which is enough to meet the annual residential needs of 14 million people or the energy equivalent of more than 80 million barrels of crude oil.

The deregulation of wholesale electricity sales and the imposition of requirements for open transmission access are resulting in dramatic changes in the business of electric power production in the United States. This restructuring increases the importance of clean, reliable energy sources such as hydropower.

Hydropower is important from an operational standpoint as it needs no "ramp-up" time, as many combustion technologies do. Hydropower can increase or decrease the amount of power it is supplying to the system almost instantly to meet shifting demand. With this important load-following capability, peaking capacity and voltage stability attributes, hydropower plays a significant part in ensuring reliable electricity service and in meeting customer needs in a market driven industry. In addition, hydroelectric pumped storage facilities are the only significant way currently available to store electricity.

Hydropower's ability to provide peaking power, load following, and frequency control helps protect against system failures that could lead to the damage of equipment and even brown or blackouts. Hydropower, besides being emissions-free and renewable has the above operating benefits that provide enhanced value to the electric system in the form of efficiency, security, and most important, reliability. The electric benefits provided by hydroelectric resources are of vital importance to the success of our National experiment to deregulate the electric industry.

Water is one of our most valuable resources, and hydropower makes use of this renewable treasure. As a National leader in managing hydropower, Reclamation is helping the Nation meet its present and future energy needs in a manner that protects the environment by improving hydropower projects and operating them more effectively.

Hydropower - From Past to Present

By using water for power generation, people have worked with nature to achieve a better lifestyle. The mechanical power of falling water is an age-old tool. As early as the 1700's, Americans recognized the advantages of mechanical hydropower and used it extensively for milling and pumping. By the early 1900's, hydroelectric power accounted for more than 40 percent of the Nation's supply of electricity. In the West and Pacific Northwest, hydropower provided about 75 percent of all the electricity consumed in the 1940's. With the increase in development of other forms of electric power generation, hydropower=s percentage has slowly declined to about 10 percent. However, many activities today still depend on hydropower.

Niagara Falls was the first of the American hydroelectric power sites developed for major generation and is still a source of electric power today. Power from such early plants was used initially for lighting, and when the electric motor came into being the demand for new electrical energy started its upward spiral.

The Federal Government became involved in hydropower production because of its commitment to water resource management in the arid West. The waterfalls of the Reclamation dams make them significant producers of electricity. Hydroelectric power generation has long been an integral part of Reclamation's operations while it is actually a byproduct of water development. In the early days, newly created projects lacked many of the modern conveniences, one of these being electrical power. This made it desirable to take advantage of the potential power source in water.

Power plants were installed at the dam sites to carry on construction camp activities. Hydropower was put to work lifting, moving and processing materials to build the dams and dig canals. Power plants ran sawmills, concrete plants, cableways, giant shovels, and draglines. Night operations were possible because of the lights fed by hydroelectric power. When construction was complete, hydropower drove pumps that provided drainage or conveyed water to lands at higher elevations than could be served by gravity-flow canals.

Surplus power was sold to existing power distribution systems in the area. Local industries, towns, and farm consumers benefited from the low-cost electricity. Much of the construction and operating costs of dams and related facilities were paid for by this sale of surplus power, rather than by the water users alone. This proved to be a great savings to irrigators struggling to survive in the West.

Reclamation=s first hydroelectric power plant was built to aid construction of the Theodore Roosevelt Dam on the Salt River about 75 miles northeast of Phoenix, Arizona. Small hydroelectric generators, installed prior to construction, provided energy for construction and for equipment to lift stone blocks into place. Surplus power was sold to the community, and citizens were quick to support expansion of the dam=s hydroelectric capacity. A 4,500-kW power plant was constructed and, in 1909, five generators were in operation, providing power to pump irrigation water and furnishing electricity to the Phoenix area.

Power development, a byproduct of water development, had a tremendous impact on the area=s economy and living conditions. Power was sold to farms, cities, and industries. Wells pumped by electricity meant more irrigated land for agriculture, and pumping also lowered water tables in those areas with waterlogging and alkaline soil problems. By 1916, nine pumping plants were in operation irrigating more than 10,000 acres. In addition, Reclamation supplied all of the residential and commercial power needs of Phoenix. Cheap hydropower, in abundant supply, attracted industrial development as well. A private company was able to build a large smelter and mill nearby to process low-grade copper ore, using hydroelectric power.

The Theodore Roosevelt Power plant was one of the first large power facilities constructed by the Federal Government. Its capacity has since been increased from 4,500 kW to more than 36,000 kW.

Power, first developed for building Theodore Roosevelt Dam and for pumping irrigation water, also helped pay for construction, enhanced the lives of farmers and city dwellers, and attracted new industry to the Phoenix area.

During World War I, Reclamation projects continued to provide water and hydroelectric power to Western farms and ranches. This helped feed and clothe the Nation, and the power revenues were a welcome source of income to the Federal Government.

The depression of the 1930's, coupled with widespread floods and drought in the West, spurred building of great multipurpose Reclamation projects such as Grand Coulee Dam on the Columbia River, Hoover Dam on the lower Colorado River, and the Central Valley Project in California. This was the Abig dam@ period, and the low-cost hydropower produced by those dams had a profound effect on urban and industrial growth.

World War II -- and the Nation=s need for hydroelectric power soared. At the outbreak of the war, the Axis Nations had three times more available power than the United States. The demand for power was identified in this 1942 statement on “The War Program of the Department of the Interior”:

“The war budget of $56 billion will require 154 billion kWh of electric energy annually for the manufacture of airplanes, tanks, guns, warships, and fighting material, and to equip and serve the men of the Army, Navy, and Marine Corps.”

Each dollar spent for wartime industry required about 2-3/4 kWh of electric power. The demand exceeded the total production capacity of all existing electric utilities in the United States. In 1942, 8.5 billion kWh of electric power was required to produce enough aluminum to meet the President’s goal of 60,000 new planes.

Hydropower provided one of the best ways for rapidly expanding the country=s energy output. Addition of more power plant units at dams throughout the West made it possible to expand energy production, and construction pushed ahead to speed up the availability of power. In 1941, Reclamation produced more than five billion kWh, resulting in a 25 percent increase in aluminum production. By 1944, Reclamation quadrupled its hydroelectric power output.

From 1940 through 1945, Reclamation power plants produced 47 billion kWh of electricity, enough to make:

·         69,000 airplanes

·         79,000 machine guns

·         5,000 ships

·         5,000 tanks

·         7,000,000 aircraft bombs, and

·         31,000,000 shells

During the war, Reclamation was the major producer of power in areas where needed resources were located -- the West. The supply of low-cost electricity attracted large defense industries to the area. Shipyards, steel mills, chemical companies, oil refineries, and automotive and aircraft factories . . . all needed vast amounts of electrical power. Atomic energy installations were located at Hanford, Washington, to make use of hydropower from Grand Coulee.

While power output of Reclamation projects energized the war industry, it was also used to process food, light military posts, and meet needs of the civilian population in many areas.

With the end of the war, power plants were put to use in rapidly developing peacetime industries. Hydropower has been vital for the West’s industries which use mineral resources or farm products as raw materials. Many industries have depended wholly on Federal hydropower. In fact, periodic low flows on the Columbia River have disrupted manufacturing in that region.

Farming was tremendously important to America during the war and continues to be today. Hydropower directly benefits rural areas in three ways:

·         It produces revenue which contributes toward repayment of irrigation facilities, easing the water users’ financial burden.

·         It makes irrigation of lands at higher elevations possible through pumping facilities.

·         It makes power available for use on the farm for domestic purposes.

Reclamation delivers 10 trillion gallons of water to more than 31 million people each year. This includes providing one out of five Western farmers (140,000) with irrigation water for 10 million farmland acres that produce 60% of the nation's vegetables and 25% of its fruits and nuts.

Some of the major hydroelectric power plants built by Reclamation are located at:

·         Grand Coulee Dam on the Columbia River in Washington (the largest single electrical generating complex in the United States)

·         Hoover Dam on the Colorado River in Arizona-Nevada

·         Glen Canyon Dam on the Colorado River in Arizona

·         Shasta Dam on the Sacramento River in California

·         Yellowtail Dam on the Bighorn River in Montana

Grand Coulee has a capacity of more than 6.8 million kW of power. Hydropower generated at Grand Coulee furnishes a large share of the power requirements in the Pacific Northwest.

Reclamation is one of the largest operators of Federal power-generating stations. The agency uses some of the power it produces to run its facilities, such as pumping plants. Excess Reclamation hydropower is marketed by either the Bonneville Power Administration or the Western Area Power Administration and is sold first to preferred customers, such as rural electric power co-cooperatives, public utility districts, municipalities, and state and Federal agencies. Any remaining power may be sold to private electric utilities. Reclamation generates enough hydropower to meet the needs of millions of people and power revenues exceed $900 million a year. Power revenues are returned to the Federal Treasury to repay the cost of constructing, operating, and maintaining projects.

Hydropower, the Environment, and Society

It is important to remember that people, and all their actions, are part of the natural world. The materials used for building, energy, clothing, food, and all the familiar parts of our day-to-day world come from natural resources.

Our surroundings are composed largely of the "built environment" - structures and facilities built by humans for comfort, security, and well-being. As our built environment grows, we grow more reliant on its offerings.

To meet our needs and support our built environment, we need electricity which can be generated by using the resources of natural fuels. Most resources are not renewable; there is a limited supply. In obtaining resources, it is often necessary to drill oil wells, tap natural gas supplies, or mine coal and uranium. To put water to work on a large scale, storage dams are needed.

We know that any innovation introduced by people has an impact on the natural environment. That impact may be desirable to some, and at the same time, unacceptable to others. Using any source of energy has some environmental cost. It is the degree of impact on the environment that is crucial.

Some human activities have more profound and lasting impacts than others. Techniques to mine resources from below the earth may leave long-lasting scars on the landscape. Oil wells may detract from the beauty of open, grassy fields. Reservoirs behind dams may cover picturesque valleys. Once available, use of energy sources can further impact the air, land, and water in varying degrees.

People want clean air and water and a pleasing environment. We also want energy to heat and light our homes and run our machines. What is the solution?

The situation seems straightforward: The demand for electrical power must be curbed or more power must be produced in environmentally acceptable ways. The solution, however, is not so simple.

Conservation can save electricity, but at the same time our population is growing steadily. Growth is inevitable, and with it the increased demand for electric power.

Since natural resources will continue to be used, the wisest solution is a careful, planned approach to their future use. All alternatives must be examined, and the most efficient, acceptable methods must be pursued.

Hydroelectric facilities have many characteristics that favor developing new projects and upgrading existing power plants:

-- Hydroelectric powerplants do not use up limited nonrenewable resources to make electricity.

-- They do not cause pollution of air, land, or water.

-- They have low failure rates, low operating costs, and are reliable.

--They can provide startup power in the event of a system wide power failure.

As an added benefit, reservoirs have scenic and recreation value for campers, fishermen, and water sports enthusiasts. The water is a home for fish and wildlife as well. Dams add to domestic water supplies, control water quality, provide irrigation for agriculture, and avert flooding. Dams can actually improve downstream conditions by allowing mud and other debris to settle out.

Existing power plants can be uprated or new power plants added at current dam sites without a significant effect on the environment. New facilities can be constructed with consideration of the environment. For instance, dams can be built at remote locations, power plants can be placed underground, and selective withdrawal systems can be used to control the water temperature released from the dam. Facilities can incorporate features that aid fish and wildlife, such as salmon runs or resting places for migratory birds.

In reconciling our natural and our built environments there will be tradeoffs and compromises. As we learn to live in harmony as part of the environment, we must seek the best alternatives among all ecologic, economic, technological, and social perspectives.

The value of water must be considered by all energy planners. Some water is now dammed and can be put to work to make hydroelectric power. Other water is presently going to waste. The fuel burned to replace this wasted energy is gone forever and, so, is a loss to our Nation.

The longer we delay the balanced development of our potential for hydropower, the more we unnecessarily use up other vital resources.

Future Potential of Hydropower

What is the full potential of hydropower to help meet the Nation=s energy needs? The hydropower resource assessment by the Department of Energy=s Hydropower Program has identified 5,677 sites in the United States with acceptable undeveloped hydropower potential. These sites have a modeled undeveloped capacity of about 30,000 MW. This represents about 40 percent of the existing conventional hydropower capacity.

A variety of restraints exist on this development, some natural and some imposed by our society. The natural restraints include such things as occasional unfavorable terrain for dams. Other restraints include disagreements about who should develop a resource or the resulting changes in environmental conditions. Often, other developments already exist where a hydroelectric power facility would require a dam and reservoir to be built.

Finding solutions to the problems imposed by natural restraints demands extensive engineering efforts. Sometimes a solution is impossible, or so expensive that the entire project becomes impractical. Solution to the societal issues is frequently much more difficult and the costs are far greater than those imposed by nature. Developing the full potential of hydropower will require consideration and coordination of many varied needs.

Tying Hydropower to Other Energy Forms

When we hear the term “solar energy,” we usually think of heat from the sun=s rays which can be put to work. But there are other forms of solar energy. Just as hydropower is a form of solar energy, so too is wind power. In effect, the sun causes the wind to blow by heating air masses that rise, cool, and sink to earth again. Solar energy in some form is always at work -- in rays of sunlight, in air currents, and in the water cycle.

Solar energy, in its various forms, has the potential of adding significant amounts of power for our use. The solar energy that reaches our planet in a single week is greater than that contained in all of the earth’s remaining coal, oil, and gas resources. However, the best sites for collecting solar energy in various forms are often far removed from people, their homes, and work places. Building thousands of miles of new transmission lines would make development of the power too costly.

Because of the seasonal, daily, and even hourly changes in the weather, energy flow from the wind and sun is neither constant nor reliable. Peak production times do not always coincide with high power demand times. To depend on the variable wind and sun as main power sources would not be acceptable to most American lifestyles. Imagine having to wait for the wind to blow to cook a meal or for the sun to come out from behind a cloud to watch television!

As intermittent energy sources, solar power and wind power must be tied to major hydroelectric power systems to be both economical and feasible. Hydropower can serve as an instant backup and to meet peak demands.

Linking wind power and hydropower can add to the Nation’s supply of electrical energy. Large wind machines can be tied to existing hydroelectric power plants. Wind power can be used, when the wind is blowing, to reduce demands on hydropower. That would allow dams to save their water for later release to generate power in peak periods.

The benefits of solar power and wind power are many. The most valuable feature of all is the replenishing supply of these types of energy. As long as the sun shines and the wind blows, these resources are truly renewable.

Hydropower Pumped Storage

Like peaking, pumped storage is a method of keeping water in reserve for peak period power demands. Pumped storage is water pumped to a storage pool above the power plant at a time when customer demand for energy is low, such as during the middle of the night. The water is then allowed to flow back through the turbine-generators at times when demand is high and a heavy load is place on the system.

The reservoir acts much like a battery, storing power in the form of water when demands are low and producing maximum power during daily and seasonal peak periods. An advantage of pumped storage is that hydroelectric generating units are able to start up quickly and make rapid adjustments in output. They operate efficiently when used for one hour or several hours.

Because pumped storage reservoirs are relatively small, construction costs are generally low compared with conventional hydropower facilities.

Peaking with Hydropower

Demands for power vary greatly during the day and night. These demands vary considerably from season to season, as well. For example, the highest peaks are usually found during summer daylight hours when air conditioners are running.

Nuclear and fossil fuel plants are not efficient for producing power for the short periods of increased demand during peak periods. Their operational requirements and their long startup times make them more efficient for meeting base load needs.

Since hydroelectric generators can be started or stopped almost instantly, hydropower is more responsive than most other energy sources for meeting peak demands. Water can be stored overnight in a reservoir until needed during the day, and then released through turbines to generate power to help supply the peak load demand. This mixing of power sources offers a utility company the flexibility to operate steam plants most efficiently as base plants while meeting peak needs with the help of hydropower. This technique can help ensure reliable supplies and may help eliminate brownouts and blackouts caused by partial or total power failures.

Today, many of Reclamation=s 58 power plants are used to meet peak electrical energy demands, rather than operating around the clock to meet the total daily demand. Increasing use of other energy-producing power plants in the future will not make hydroelectric power plants obsolete or unnecessary. On the contrary, hydropower can be even more important. While nuclear or fossil-fuel power plants can provide base loads, hydroelectric power plants can deal more economically with varying peak load demands. This is a job they are well suited for.

Friday, October 19, 2012

Low-head Hydropower

A low-head dam is one with a water drop of less than 65 feet and a generating capacity less than 15,000 kW. Large, high-head dams can produce more power at lower costs than low-head dams, but construction of large dams may be limited by lack of suitable sites, by environmental considerations, or by economic conditions. In contrast, there are many existing small dams and drops in elevation along canals where small generating plants could be installed. New low-head dams could be built to increase output as well. The key to the usefulness of such units is their ability to generate power near where it is needed, reducing the power inevitably lost during transmission.

Uprating Hydropower

The uprating of existing hydroelectric generator and turbine units at power plants is one of the most immediate, cost-effective, and environmentally acceptable means of developing additional electric power. Since 1978, Reclamation has pursued an aggressive uprating program which has added more than 1,600,000 kW to Reclamation's capacity at an average cost of $69 per kilowatt. This compares to an average cost for providing new peaking capacity through oil-fired generators of more than $400 per kilowatt. Reclamation's uprating program has essentially provided the equivalent of another major hydroelectric facility of the approximate magnitude of Hoover Dam and Power plant at a fraction of the cost and impact on the environment when compared to any other means of providing new generation capacity.

Hydropower Modern Concepts and Future Role

Hydropower does not discharge pollutants into the environment; however, it is not free from adverse environmental effects. Considerable efforts have been made to reduce environmental problems associated with hydropower operations, such as providing safe fish passage and improved water quality in the past decade at both Federal facilities and non-Federal facilities licensed by the Federal Energy Regulatory Commission.

Efforts to ensure the safety of dams and the use of newly available computer technologies to optimize operations have provided additional opportunities to improve the environment. Yet, many unanswered questions remain about how best to maintain the economic viability of hydropower in the face of increased demands to protect fish and other environmental resources.

Reclamation actively pursues research and development (R&D) programs to improve the operating efficiency and the environmental performance of hydropower facilities.

Hydropower research and development today is primarily being conducted in the following areas:

Fish Passage, Behavior, and Response

Turbine-Related Projects

Monitoring Tool Development


Water Quality

Dam Safety

Operations & Maintenance

Water Resources Management

Reclamation continues to work to improve the reliability and efficiency of generating hydropower. Today, engineers want to make the most of new and existing facilities to increase production and efficiency. Existing hydropower concepts and approaches include:

ü  Uprating existing power plants

ü  Developing small plants (low-head hydropower)

ü  Peaking with hydropower

ü  Pumped storage

ü  Tying hydropower to other forms of energy

Hydropower Turbines

While there are only two basic types of turbines (impulse and reaction), there are many variations. The specific type of turbine to be used in a power plant is not selected until all operational studies and cost estimates are complete. The turbine selected depends largely on the site conditions.

A reaction turbine is a horizontal or vertical wheel that operates with the wheel completely submerged, a feature which reduces turbulence. In theory, the reaction turbine works like a rotating lawn sprinkler where water at a central point is under pressure and escapes from the ends of the blades, causing rotation. Reaction turbines are the type most widely used.

An impulse turbine is a horizontal or vertical wheel that uses the kinetic energy of water striking its buckets or blades to cause rotation. The wheel is covered by a housing and the buckets or blades are shaped so they turn the flow of water about 170 degrees inside the housing. After turning the blades or buckets, the water falls to the bottom of the wheel housing and flows out.

How HydroPower is Computed

Before a hydroelectric power site is developed, engineers compute how much power can be produced when the facility is complete. The actual output of energy at a dam is determined by the volume of water released (discharge) and the vertical distance the water falls (head). So, a given amount of water falling a given distance will produce a certain amount of energy. The head and the discharge at the power site and the desired rotational speed of the generator determine the type of turbine to be used.

The head produces a pressure (water pressure), and the greater the head, the greater the pressure to drive turbines. This pressure is measured in pounds of force (pounds per square inch). More head or faster flowing water means more power.

To find the theoretical horsepower (the measure of mechanical energy) from a specific site, this formula is used:


THP = (Q x H)/8.8

where: THP = theoretical horsepower

Q = flow rate in cubic feet per second (cfs)

H = head in feet

8.8 = a constant

A more complicated formula is used to refine the calculations of this available power. The formula takes into account losses in the amount of head due to friction in the penstock and other variations due to the efficiency levels of mechanical devices used to harness the power.

To find how much electrical power we can expect, we must convert the mechanical measure (horsepower) into electrical terms (watts). One horsepower is equal to 746 watts (U.S. measure).

Transmitting Hydro Power

Once the electricity is produced, it must be delivered to where it is needed -- our homes, schools, offices, factories, etc. Dams are often in remote locations and power must be transmitted over some distance to its users.

Vast networks of transmission lines and facilities are used to bring electricity to us in a form we can use. All the electricity made at a power plant comes first through transformers which raise the voltage so it can travel long distances through power lines. (Voltage is the pressure that forces an electric current through a wire.) At local substations, transformers reduce the voltage so electricity can be divided up and directed throughout an area.

Transformers on poles (or buried underground, in some neighborhoods) further reduce the electric power to the right voltage for appliances and use in the home. When electricity gets to our homes, we buy it by the kilowatt-hour, and a meter measures how much we use.

While hydroelectric power plants are one source of electricity, other sources include power plants that burn fossil fuels or split atoms to create steam which in turn is used to generate power. Gas-turbine, solar, geothermal, and wind-powered systems are other sources. All these power plants may use the same system of transmission lines and stations in an area to bring power to you. By use of this "power grid" electricity can be interchanged among several utility systems to meet varying demands. So the electricity lighting your reading lamp now may be from a hydroelectric power plant, a wind generator, a nuclear facility, or a coal, gas, or oil-fired power plant … or a combination of these.

The area where you live and its energy resources are prime factors in determining what kind of power you use. For example, in Washington State hydroelectric power plants provided approximately 80 percent of the electrical power during 2002. In contrast, in Ohio during the same year, almost 87 percent of the electrical power came from coal-fired power plants due to the area=s ample supply of coal.

Electrical utilities range from large systems serving broad regional areas to small power companies serving individual communities. Most electric utilities are investor-owned (private) power companies. Others are owned by towns, cities, and rural electric associations. Surplus power produced at facilities owned by the Federal Government is marketed to preference power customers (A customer given preference by law in the purchase of federally generated electrical energy which is generally an entity which is nonprofit and publicly financed.) by the Department of Energy through its power marketing administrations.

Generating Hydro Power

In nature, energy cannot be created or destroyed, but its form can change. In generating electricity, no new energy is created. Actually one form of energy is converted to another form.

To generate electricity, water must be in motion. This is kinetic (moving) energy. When flowing water turns blades in a turbine, the form is changed to mechanical (machine) energy. The turbine turns the generator rotor which then converts this mechanical energy into another energy form -- electricity. Since water is the initial source of energy, we call this hydroelectric power or hydropower for short.

At facilities called hydroelectric power plants, hydropower is generated. Some power plants are located on rivers, streams, and canals, but for a reliable water supply, dams are needed. Dams store water for later release for such purposes as irrigation, domestic and industrial use, and power generation. The reservoir acts much like a battery, storing water to be released as needed to generate power.

The dam creates a "Ahead" or height from which water flows. A pipe (penstock) carries the water from the reservoir to the turbine. The fast-moving water pushes the turbine blades, something like a pinwheel in the wind. The waters force on the turbine blades turns the rotor, the moving part of the electric generator. When coils of wire on the rotor sweep past the generator=s stationary coil (stator), electricity is produced.

This concept was discovered by Michael Faraday in 1831 when he found that electricity could be generated by rotating magnets within copper coils.

When the water has completed its task, it flows on unchanged to serve other needs.

How Hydropower Works

Hydroelectric power comes from water at work, water in motion. It can be seen as a form of solar energy, as the sun powers the hydrologic cycle which gives the earth its water. In the hydrologic cycle, atmospheric water reaches the earth=s surface as precipitation. Some of this water evaporates, but much of it either percolates into the soil or becomes surface runoff. Water from rain and melting snow eventually reaches ponds, lakes, reservoirs, or oceans where evaporation is constantly occurring.

Moisture percolating into the soil may become ground water (subsurface water), some of which also enters water bodies through springs or underground streams. Ground water may move upward through soil during dry periods and may return to the atmosphere by evaporation.

Water vapor passes into the atmosphere by evaporation then circulates, condenses into clouds, and some returns to earth as precipitation. Thus, the water cycle is complete. Nature ensures that water is a renewable resource.

Hydroelectric Power - what is it?

It=s a form of energy … a renewable resource. Hydropower provides about 96 percent of the renewable energy in the United States. Other renewable resources include geothermal, wave power, tidal power, wind power, and solar power. Hydroelectric power plants do not use up resources to create electricity nor do they pollute the air, land, or water, as other power plants may. Hydroelectric power has played an important part in the development of this Nation's electric power industry. Both small and large hydroelectric power developments were instrumental in the early expansion of the electric power industry.

Hydroelectric power comes from flowing water … winter and spring runoff from mountain streams and clear lakes. Water, when it is falling by the force of gravity, can be used to turn turbines and generators that produce electricity.

Hydroelectric power is important to our Nation. Growing populations and modern technologies require vast amounts of electricity for creating, building, and expanding. In the 1920's, hydroelectric plants supplied as much as 40 percent of the electric energy produced. Although the amount of energy produced by this means has steadily increased, the amount produced by other types of power plants has increased at a faster rate and hydroelectric power presently supplies about 10 percent of the electrical generating capacity of the United States.

Hydropower is an essential contributor in the national power grid because of its ability to respond quickly to rapidly varying loads or system disturbances, which base load plants with steam systems powered by combustion or nuclear processes cannot accommodate.

Reclamation=s 58 power plants throughout the Western United States produce an average of 42 billion kWh (kilowatt-hours) per year, enough to meet the residential needs of more than 14 million people. This is the electrical energy equivalent of about 72 million barrels of oil. Hydroelectric power plants are the most efficient means of producing electric energy. The efficiency of today's hydroelectric plant is about 90 percent. Hydroelectric plants do not create air pollution, the fuel--falling water--is not consumed, projects have long lives relative to other forms of energy generation, and hydroelectric generators respond quickly to changing system conditions. These favorable characteristics continue to make hydroelectric projects attractive sources of electric power.

Saturday, October 6, 2012

Xiluodu Hydropower Project

Xiluodu Hydropower Project is situated on the Jinsha River reach. It is a huge hydropower project with comprehensive benefits of primary power generation, sediment controlling, flood controlling, downstream navigation improving. The controlled basin area is 454.4×103 km2, which is 96% of the whole Jinsha River basin area. The water level in normal storage is 600 m with a total reservoir capacity of 12.67 billion m3, active storage capacity of 6.46 billion m3 and flood control capacity is 4.65 billion m3. The key structures consist of dam, power conduit systems and power plants, flood discharge and energy dissipation structures etc. The type of dam is concrete double-curvature arch dam with a crest elevation of 610m and crest length of 700m. The maximum dam height is 278 m. Seven 12.5m×13.5m surface spillways, eight 6m×6.7m deep outlets are arranged on the arch dam body. There are five spillway tunnels both on the left and right banks separately. Two large underground power houses are laid on the both banks separately, each has 9 turbine units with the single capacity of 700MW, the total installed capacity of the project is 12600 MW, and the annual average power generation is 57.12 TWh. The power conduit systems are composed of intakes, headrace tunnels; main powerhouses, main transmission caverns, tailrace surge chambers and ground surface switch stations.
The construction of Xiluodu Hydropower Project began on Dec.26th, 2005. The total construction period is 12 years and 2 months. It is planned to realize river closure in 2008. The project static investment is 45.928 billion RMB based on the 2001’s price level.

Causes of Failure

The main reasons for lack of success with small water power developments are:

1.      Failure to realize how important full field data is for proper design.

2.      Failure of homemade equipment made with junked parts.

3.      Over-estimating the amount and constancy of the stream flow.

4.      Penstocks or flumes that are too small to allow the plant to operate at full capacity.

5.      Failure to anticipate the expense of keeping trash racks clear and machinery in good repair.

6.      Failure to design and plan for winter ice buildup.

7.      Overestimation of a proposed plant’s capability. The average home has demand peaks varying from 4 to 12 kilowatts.

Components: Turbines

The towering water wheel driving the old mill’s grinding stones creates a romantic image, but it is too slow and ponderous to efficiently convert water power to electric power. For example, a 5 foot diameter wheel that is 16" wide will generate only 300 watts or less. A compact turbine and generator is a better choice unless you are renovating an old mill site. Hydroelectric plants are available in capacities ranging from 1/2 KW to 12 KW.

A reaction turbine, either the Francis type or propeller wheel type, is turned by a mass of water falling through a duct encasing a wheel. Reaction-type generators are good choices if you have ample water supply but a low head. A reaction wheel is subject to greater friction losses than an impulse wheel; however, it has greater flexibility in installation.

An impulse (Pelton) turbine turns by the velocity of a jet of water striking the turbine’s wheel cups and can operate on as little as 1.5 cfm of water. In order to be most effective, a head of at least 50’ is required.

The type of facility you wish to provide with electrical service will largely determine whether you use an Alternating or Direct-Current generator. Lights and the universal motors that operate small appliances and tools will operate on DC. Larger motors, TV’s and many appliances require AC to operate. Alternating Current may be transmitted greater distances and on smaller wires than is possible with Direct Current; however, an AC installation does require an extra investment in governing equipment.

Direct Current generators are usually less expensive than AC generators but they do require expensive inverters to convert to AC. The potential of storing DC in batteries during low-usage periods and at times of uneven water flow is a compensation of such a system.

Components: Trash Racks and Head Gates

Even small streams can become torrents carrying large trees and other debris. Plan to protect the generator and water passages from debris by installing a trash rack at the head of the penstock. Set steel bars on edge to the flow of water and space about 1" apart. Normally trash racks are set on an incline to increase area so water velocity is less than 1.5 feet per second through the rack. An inclined rack is easier to clean with a rake. This feature is particularly important in the fall because leaves may blanket a rack in an hour or two.

A head gate or valve should be installed below the trash rack to control flow and to allow the turbine to be inspected and repaired.

Components: Penstocks

Friction in the pipe (penstock) or open channel that carries water to the generator is another cause of power loss. Most small hydroelectric sites have a small or moderate head, so it is very important to use large penstocks to reduce losses. 

If you are diverting a water source far up the hill, plastic or aluminum irrigation pipe and the heavier walled, pressure rated PVC plastic pipe make good penstocks. Table 2 shows head losses for typical plastic pipe. The flow rates to the right of the dashed lines have velocities that exceed 5 to 7 feet per second and are not recommended. Use a larger pipe instead.

For example, Table l shows a 2KW generator requires 0.6 cfs with a l00 foot head. Three hundred feet of 3" PVC pipe carrying 0.6 cfs from an upstream diversion has a head loss of 3 x 10.2 = 30.6 feet. Thus the diversion must be 100 + 30.6 = 130.6 feet above the generator to compensate for the friction or head loss in the pipe. A 6" pipe has only a 0.54 x 3 = 1.62 foot head loss.