Francis Turbine

Horizontal Francis Hydro Turbine / Francis Water Turbine with Water Head From 20m to 300m

Francis turbines are most widely used among water head from 20m to 700mm. A Francis turbine has a runner with fixed blade, usually nine or more. Water is introduced just above the runner and all around it and then falls through, causing it to spin. Besides the runner, the other major components are the spiral case, wicket gates, and draft tube. Most small Francis turbine are horizontal shaft and metallic spiral case, it has two bearing assembled on the generator seat.

Water flows through penstock of the power station, Butterfly valve, expansion pipe, inlet tube, spiral case and wicket gates into the runner, and then it drives the runner to revolve and convert hydraulic energy into mechanical energy and drives the rotor of generator revolution by the force of the main shaft of turbine, thus converting the mechanical energy into electric energy.

Franics Turbine runner compose of the  blade, upper crown, bend and cone.
The whole rotating part is mainly composed of the runner, main shaft, flywheel and main sealing assembly etc. The main shaft is laid in horizontal or vertical  position. The runner cone is keyed on the end of the main shaft, and locked with bolt, The other  end of the main shaft is connected to the flywheel. The runner is the principal component of the turbine convert hydraulic energy into mechanical energy. The main sealing assembly adopts polyethylene packing structure to prevent water leaking out, and should be connected the clean and pressure water which pressure is 0.15~0.25MPa.

Spiral case

The spiral casing is the largest part of the hydraulic turbine and erecting bench- mark. It is made of steel-welding structure. Together with spiral casing and stay ring. Some stay vanes are equipped on the inner of stay ring. A pressure gauge is equipped to measure the pressure of the inlet water there. On the top of the spiral casing, it presents an air-discharge valve, which is used to expel out the residual air in the shell, when the shell is filled with water before starting up the turbine.

Distributor
The distributor consists of wicket gates, guide vane arms, shear pins, regulating ring, head cover, bottom ring etc.
 The wicket gates  function is to regulate the discharge of water flow. so as to suit the regulation on various loads.
 The opening of wicket gates can be regulated by the governor servomotor, to guarantee the revolving speed constant when the load changes. When the turbine is shut down all openings between the wicket from flowing into the runner. Each wicket gate swivels in bushing along, the axial line of its stem. The lower bushing seats in the head cover, the middle and upper bushing seat in the bottom ring. The connecting rod mechanism is equipped between the wicket gates and regulating ring in order to transfers their move and force.
Also the  shear pins are equipped on the distributor. When the turbine is shut down if the closing of the wicket gates exists obstacles, the shear pin related to the opening will be shorn so that the other pats of distributor many not be damaged. The regulating ring is connected with the servomotor by way of the connecting rod.

The draft tube  consists of draft tube, draft tube cone and draft tube bend etc. It’s function is to guide water current and receive some hydraulic energy.

Hydropower project

       Types of Hydropower

There are three types of hydropower facilities: impoundment, diversion, and pumped storage. Some hydropower plants use dams and some do not. The images below show both types of hydropower plants. Impoundment The most common type of hydroelectric power plant is an impoundment facility. An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level. Diversion A diversion, sometimes called run-of-river, facility channels a portion of a river through a canal or penstock. It may not require the use of a dam Pumped Storage When the demand for electricity is low, a pumped storage facility stores energy by pumping water from a lower reservoir to an upper reservoir. During periods of high electrical demand, the water is released back to the lower reservoir to generate electricity. Sizes of Hydropower Plants Facilities range in size from large power plants that supply many consumers with electricity to small and micro plants that individuals operate for their own energy needs or to sell power to utilities. Large Hydropower Although definitions vary, we define large hydropower as facilities that have a capacity of more than 50 MW. Medium Hydropower Although definitions vary, we define medium hydropower as facilities that have a capacity of 10 MW to 50 MW. Small Hydropower Although definitions vary, we define small hydropower as facilities that have a capacity of below 10 MW. Advantages and Disadvantages of Hydropower Hydropower offers advantages over other energy sources but faces unique environmental challenges. Advantages Hydropower relies on the water cycle, which is driven by the sun, thus it's a renewable power source. Hydropower is a fueled by water, so it's a clean fuel source. Hydropower doesn't pollute the air like power plants that burn fossil fuels, such as coal or natural gas. Hydropower is generally available as needed; engineers can control the flow of water through the turbines to produce electricity on demand. Hydropower plants provide benefits in addition to clean electricity. Impoundment hydropower creates reservoirs that offer a variety of recreational opportunities, notably fishing, swimming, and boating. Most hydropower installations are required to provide some public access to the reservoir to allow the public to take advantage of these opportunities. Other benefits may include water supply and flood control. Disadvantages Fish populations can be impacted if fish cannot migrate upstream past impoundment dams to spawning grounds or if they cannot migrate downstream to the ocean. Upstream fish passage can be aided using fish ladders or elevators, or by trapping and hauling the fish upstream by truck. Downstream fish passage is aided by diverting fish from turbine intakes using screens or racks or even underwater lights and sounds, and by maintaining a minimum spill flow past the turbine. Hydropower can impact water quality and flow. Hydropower plants can cause low dissolved oxygen levels in the water, a problem that is harmful to riparian (riverbank) habitats and is addressed using various aeration techniques, which oxygenate the water. Maintaining minimum flows of water downstream of a hydropower installation is also critical for the survival of riparian habitats. New hydropower facilities impact the local environment and may compete with other uses for the land. Those alternative uses may be more highly valued than electricity generation. Humans, flora, and fauna may lose their natural habitat. Local cultures and historical sites may be impinged upon. Some older hydropower facilities may have historic value, so renovations of these facilities must also be sensitive to such preservation concerns and to impacts on plant and animal life.

How Hydropower Power Plant Works

Hydropower power plant generates at least 20% of the world electricity supply. Also, according to the hydropower facts by the National Renewable Energy Laboratory, there are more than 2,000 of hydropower station operating in USA. It provides about 10% of the USA electricity, making water power as the biggest renewable energy resource in the country. But do you really know how the hydropower power plant able to generate electricity?

Well, the hydro power plant is utilizing the energy of the flowing water. A hydro power plant usually made up of several devices like turbine, generator, and transformer. These devices can capture the kinetic energy of water and convert it into electricity.

Continue reading this article to know the clear concept of how a hydropower station works and the description of each of its components function.

Hydropower power plant schematic

The schematic of hydropower station above show how the water flow can be used to produce electricity. For more information see the explanation of each component below:

Dam – most of conventional hydropower power plant use dam to block the water and keep them in the reservoir. If the dam built correctly, the reservoir should be able to used for recreational purpose like fishing or rafting.

Intake – the gates of the dam that only open to let the water flow through the penstock.

Penstock – the pipeline that leads the water flow to the turbine

Turbine – set of blades that shaped like a propeller. These large blades are connected to a generator by a shaft. Unless these blades are turning, the generator cannot produce the electricity.

Generator – when the turbine blades are rotating, so do the magnets inside the generator. This huge magnet rotates past a copper coil, causing a moving electron that generates the alternates current (AC).

Transformer – as the generator generates the AC, transformers convert it to a higher voltage current so the electricity current is strong enough to be transmitted through the power lines.

Power lines – a set of wires that are used to transmit the electricity. Usually consists of four wires; one is used as the grounding wire while the other three are used for the transmission.

Outflow – a pipeline that leads the used water flowing back to river.

The explanation of how hydropower power plant works

The reservoir stores the water. As the intakes opened, the water is flowing through the penstock. When the water flows through the penstock, it builds up a pressure that strikes the turbine and its kinetic energy turns the blades of the turbine. This process is causing the generator to turns as well, so it can produce the electricity. Transformers strengthen electricity and then they are transmitted through the power lines. The amount of generated electricity depends on the volume of the water flow and the height difference between the reservoir surface and the turbines.

What happen to the water that used to turns the turbine? They had finished their task, so now it is time to return them to where they belong: the river. The water is directed back to the river stream through the outflow, until the natural evaporation process brings them back to replenish the reservoir through the rain. This starts the cycle of hydropower power plant again to produce electricity.

XIANGJIABA hydropower station

Xiangjiaba hydropower station

China's third largest hydropower station

-XIANGJIABA  hydropower station

Project total investment:43.4 Billion Yuan

 Engineering period: 2008-2015

Xiangjiaba hydropower station located in downstream of Jinsha river, Yuannan Fushui county (right bank) and Sichuan Yibin County (Left Bank) . Where is the junction of the two provinces. 157km away from Xiluodu hydropower station. Static investment 43.4 billion Yuan.

Xiangjiaba hydropower station installation capacity 6000 megawatt,( total 8 unit, each one 750 megawatt), reservoir normal storage water level 380m,guarantee output power 2.009 million KW, average annual generating capacity of 30.747 billion KWH. reservoir area 95.6 sq.km, the reservoir is gorge type, total reservoir volume 5.163billion cubic meter. Backwater length 156.6 km. control drainage area 458.8 thousand sq.km. 97% of Jinsha river drainage area.

The project closure on 2008, and the first unit put into operation on 2012, complete project finished on July.2014.

The project use gravity dam, crest elevation 383m, crest length 909.3m, max. Dam height 161m.

Xiangjiaba hydropower station also use vertical Francis hydro turbine, installed 8 unit 800MW turbine generator set. it has the world largest unit installed capacity Francis turbine generator, also the first 800MW Francis turbine generator in the world.

The turbine key parameter below:(world's largest hydro turbine)

Installed capacity:8x800MW,

Max. Water head: 114.2m,

Min.water head:86.1m,

Rated water head: 100m

Runner inlet diameter:10360mm

Runner outlet diameter: 9300mm

Runner max. Diameter:10527mm

Rated output power:812MW

Turbine rated speed:71.4r/min

XILUODU hydropower station

China's second largest hydropower station

-XILUODU hydropower station

Project total investment:79.2 Billion Yuan
Engineering period: 2005-2015

Xiluodu hydropower station is located in Qinghai-Tibet Plateau, Yunnan-Guizhou Plateau to the Sichuan Basin transition zone, located in Xiluodu Gorge, where bordering Leibo County, Sichuan Province and Yongshan County, Yunnan Province,  Xiluodu Hydropower Station is the largest of the four giant hydropower station on Jinsha River, Capacity quite with the Itaipu,the world's second largest hydropower station.total installed capacity is 12.6 million kilowatts, Annual generation capacity ranked third in the world,is 571.2 billion KWh, equal to Itaipu hydropower station, and three and a half of the Gezhou Dam, is the second largest hydropower station in China.

Xiluodu hydropower station is the closest key power of China “west to east power transmission project” on Jinsha river, also the largest hydropower station on Jinsha river.

Jinsha river is upper stream of Yangtze river,total length 3364 kilometer, drainage area 473.2 thousand sq.km. Jinsha river has abundant water resources, reserves energy reached 112.4 million kilowatts,  accounted for 1/6 of the total hydropower in China.

This project located in Xiluodu Gorge, where bordering Leibo County, Sichuan Province and Yongshan County, Yunnan Province, downstream of Jinsha river. The project use concrete double curvature arch dam,dam height 278m, normal storage water level 600m, total storage 11.57 billion cubic meters,

Regulation storage 6.46 billion cubic meters, installed capacity 12.6 million KW, average annual generating capacity of 57.12 billion KWH, the project static investment 45.928 billion Yuan, total 79.234 billion Yuan. Project feasibility design finished on Dec. 2001, start building on Dec.2005, on Jun.2013, the first set of generator put into operation, and whole project completed on 2015.

Xiluodu Hydropower station use vertical Francis hydro turbine, manufacturer Voith, rated water head 197m, max. Head 229.4m, min. Head 154.6m, weighted average of the head 223.48m, rated flow 430.5 cubic meter per second, rated output power 784 Megawatt, rated speed 125 r/min,suction head HS=-10.81m, installation elevation 359m. Francis runner diameter is 7.4m, max. Outer diameter 7.755m, height 3.462m, each runner weight 179 ton.

Material is stainless steel 0Cr13Ni4Mo.  

  

When Xiluodu hydropower plant was fully connected to the grid in June 2014, it started with a nominal capacity of 13.86 gigawatts. All in all, 18 machine units are in operation. This made it the world's third largest hydropower plant. The plant will help to reduce air pollution thanks to the renewable electricity production of Xiluodu: The annual consumption of coal will be cut down by 41 million tons. In addition to that, exhaust gas emissions will be reduced by nearly 150 million tons of CO2, 480,000 tons of nitrogen dioxide and 850,000 tons of sulfur dioxide per year.

Another advantage of Xiluodu is the ability to deliver base load in large quantity. Xiluodu can produce as much energy around the clock as 14 large thermal or nuclear power plants. As a matter of fact, hydropower technology can bridge the gap between the enormous demand of electricity, and, on the other hand, meet the emission targets our societies have committed themselves to.

panoramic photo of Construction site:

Closure photo of the Xiluodu Dam

Dam photo:

 Spiral case photo:

 spiral case welding:

 Draft tube tunnel construction

 spiral case installation

 Francis turbine runner

 generator rotor isntallation

 generator stator assembly

night scene of XILUODU

Three Gorges Hydropower Project

In 2012, the Three Gorges Dam in China took over the #1 spot of the largest hydroelectric dam (in electricity production), replacing the Itaipu hydroelectric power plant in Brazil and Paraguay. The Three Gorges Dam has a generating capacity of 22,500 megawatts (MW) compared to 14,000 MW for the Itaipu Dam. But, over a year-long period, both dams can generate about the same amount of electricity because seasonal variations in water availability on the Yangtze River in China limit power generation at Three Gorges for a number of months during the year.

The height of Three Gorges is about 594 feet (181 meters (m)) and the length is about 7,770 feet (2, 335 m). The dam creates the Three Gorges Reservoir, which has a surface area of about 400 square miles (1,045 square kilometers) and extends upstream from the dam about 370 miles (600 kilometers).

In the United States, the Grand Coulee Dam on the Columbia River, Washington, is the largest, with a generating capacity of about 6,800 MW (5th overall worldwide).

Three Gorges power station had installed 32 units of 700MW turbines,which is the largest capacity, largest size of Francis generator set. The Francis turbine runner diameter is 10.05m,height 5.99m, total weight 445 ton, 15 blades, each blades weight 17.6 ton. The runner use stainless steel 0Cr13Ni4Mo, weld structure. The turbine design water head 85m.

Hydroelectric power water use

Hydroelectric power must be one of the oldest methods of producing power. No doubt, Jack the Caveman stuck some sturdy leaves on a pole and put it in a moving stream. The water would spin the pole that crushed grain to make their delicious, low-fat prehistoric bran muffins. People have used moving water to help them in their work throughout history, and modern people make great use of moving water to produce electricity.

Hydroelectric power for the Nation

Although most energy in the United States is produced by fossil-fuel and nuclear power plants, hydroelectricity is still important to the Nation, accounting for about 7% of total energy production. Nowadays, huge power generators are placed inside dams. Water flowing through the dams spin turbine blades (made out of metal instead of leaves) which are connected to generators. Power is produced and is sent to homes and businesses.

World distribution of hydropower

· Hydropower is the most important and widely-used renewable source of energy.

· Hydropower represents about 16% (International Energy Agency) of total electricity production.

· China is the largest producer of hydroelectricity, followed by Canada, Brazil, and the United States (Source: Energy Information Administration).

· Approximately two-thirds of the economically feasible potential remains to be developed. Untapped hydro resources are still abundant in Latin America, Central Africa, India and China.

Producing electricity using hydroelectric power has some advantages over other power-producing methods. Let's do a quick comparison:

Advantages to hydroelectric power:

· Fuel is not burned so there is minimal pollution

· Water to run the power plant is provided free by nature

· Hydropower plays a major role in reducing greenhouse gas emissions

· Relatively low operations and maintenance costs

· The technology is reliable and proven over time

· It's renewable - rainfall renews the water in the reservoir, so the fuel is almost always there

Read an expanded list of advantages of hydroelectric power from the Top World Conference on Sustainable Development conference, Johannesburg, South Africa (2002)

Disadvantages to power plants that use coal, oil, and gas fuel:

· They use up valuable and limited natural resources

· They can produce a lot of pollution

· Companies have to dig up the Earth or drill wells to get the coal, oil, and gas

· For nuclear power plants there are waste-disposal problems

Hydroelectric power is not perfect, though, and does have some disadvantages:

· High investment costs

· Hydrology dependent (precipitation)

· In some cases, inundation of land and wildlife habitat

· In some cases, loss or modification of fish habitat

· Fish entrainment or passage restriction

· In some cases, changes in reservoir and stream water quality

· In some cases, displacement of local populations

Hydropower and the Environment

Hydropower is nonpolluting, but does have environmental impacts

Hydropower does not pollute the water or the air. However, hydropower facilities can have large environmental impacts by changing the environment and affecting land use, homes, and natural habitats in the dam area.

Most hydroelectric power plants have a dam and a reservoir. These structures may obstruct fish migration and affect their populations. Operating a hydroelectric power plant may also change the water temperature and the river's flow. These changes may harm native plants and animals in the river and on land. Reservoirs may cover people's homes, important natural areas, agricultural land, and archaeological sites. So building dams can require relocating people. Methane, a strong greenhouse gas, may also form in some reservoirs and be emitted to the atmosphere. (EPA Energy Kids)

Reservoir construction is "drying up" in the United States

Gosh, hydroelectric power sounds great -- so why don't we use it to produce all of our power? Mainly because you need lots of water and a lot of land where you can build a dam and reservoir, which all takes a LOT of money, time, and construction. In fact, most of the good spots to locate hydro plants have already been taken. In the early part of the century hydroelectric plants supplied a bit less than one-half of the nation's power, but the number is down to about 10 percent today. The trend for the future will probably be to build small-scale hydro plants that can generate electricity for a single community.

As this chart shows, the construction of surface reservoirs has slowed considerably in recent years. In the middle of the 20th Century, when urbanization was occuring at a rapid rate, many reservoirs were constructed to serve peoples' rising demand for water and power. Since about 1980, the rate of reservoir construction has slowed considerably.

Typical hydroelectric powerplant

Hydroelectric energy is produced by the force of falling water. The capacity to produce this energy is dependent on both the available flow and the height from which it falls. Building up behind a high dam, water accumulates potential energy. This is transformed into mechanical energy when the water rushes down the sluice and strikes the rotary blades of turbine. The turbine's rotation spins electromagnets which generate current in stationary coils of wire. Finally, the current is put through a transformer where the voltage is increased for long distance transmission over power lines. (Source: Environment Canada)

Hydroelectric-power production in the United States and the world

As this chart shows, in the United States, most states make some use of hydroelectric power, although, as you can expect, states with low topographical relief, such as Florida and Kansas, produce very little hydroelectric power. But some states, such as Idaho, Washington, and Oregon use hydroelectricity as their main power source. in 1995, all of Idaho's power came from hydroelectric plants.

The second chart shows hydroelectric power generation in 2012 for the leading hydroelectric-generating countries in the world. China has developed large hydroelectric facilities in the last decade and now lead the world in hydroelectricity usage. But, from north to south and from east to west, countries all over the world make use of hydroelectricity—the main ingredients are a large river and a drop in elevation (along with money, of course).

Source: Energy Information Administration (EIA):
http://www.eia.gov/cfapps/ipdbproject/IEDIndex3.cfm

http://water.usgs.gov/edu/wuhy.html