Kaplan turbine

Axial Flow Turbine Kaplan Hydro Turbine / Kaplan Water Turbine for Water Head 2m - 70m Hydropower Project

The Kaplan (axial-flow) turbine for low head from 2m to 70m. This type of turbine is mostly suitable for hydropower stations with low water head and big flow.
lts feature is that the water flow passes through the runner axially. The axial-flow turbine can be classified into two forms according to the runner construction: one is fixed blades (Propeller) for small variation of head and power, the other is movable blades (Kaplan) for large variation of head and power.
The kaplan turbine with vertical shaft arrangement , with three types as open flume, pressure flume, and seal off (concrete spiral case).
Generally, Kaplan turbine is composed of distributor, guide vane, runner, draft tube etc. 

Main Structure of Kaplan Water Turbine

This hydraulic turbine is axial flow turbine with a vertical shaft. And its spiral case is made of metal or concrete.
The water flows through the channeling pipe, and then into the spiral case, which ensure that the water enter the turbine circumferentially and symmetrically, forming certain circumfluence quantum.
The water flows through the stay ring into the distributor, whose guide vanes can regulate the turbine discharge and the flow direction and thus make the water flow into the runner circumferentially and symmetrically. Consequently, the runner revolves and converts hydraulic energy into mechanical energy and then drives the rotor of the generator revolve by the force of the main shaft of the hydraulic turbine, thus converting the mechanical energy into electrical energy. The water, which has gotten out of the runner, flows to the downstream of river through the draft tube.
Because of the restoration of the draft tube, the energy of the water flowing out of the outlet, is partly reused, thus loss is reduced and efficiency is improved.

Main structures of the hydraulic turbine are described in the following.

Draft tube assembly

It includes draft tube straight cone and metal bend tube. Because of the restoration of the draft tube, the energy of the water flowing out of the outlet is partly reused, thus loss is reduced and efficiency is improved.

Rotating parts assembly

Rotating department is mainly composed of a runner, main shaft, radial turbine bearing and seals of main shaft. Runner with the blades of stainless steel of 06Cr13Ni4Mo assembled and welded. After having been mould into shape, all the  blades must be processed to the required degree of roughness and precision.
To ensure the stable operation of runner, a test for still balance is performed in the manufactory. Shared by the hydraulic turbine and hydro generator, the vertical main shaft, connects the runner with pins. The main shaft seal is of the type with soft graphite packing
The radial turbine bearing is water-lubricating elastic metal-plastics bearing,clean water,0.15~0.2Mpa.

kaplan turbine runner

Distributor assembly

Distributor consists of head cover, bottom ring, guide vanes, the regulating ring, transmission departments and any other parts. They are divided into two parts. One part includes guide vanes and supporters of three parts of shaft sleeves, namely bottom ring and head cover. The other part includes guide vane arm, conjunction rod, regulating ring, and pull-push rod of transmission departments.

distributor

a. Guide vane and its supporting parts.

There are  guide vanes spreading in a circle equally.

Guide vane is standard blade-shaped with positive curvature This enables the guide vanes to have the virtues of little hydraulic loss and high degree of strength as guide vanes’ opening varies. The Guide vanes are made of 20SiMn.On the bottom of guide vane, shaft sleeves are fixed with the bottom ring and they are self-lubricating bearings of thin plates of Fluon. In the head cover, shaft sleeves are fixed with the bottom ring and they are self-lubricating bearings of thin plates of Fluon.

Guide vanes

b. Transmission department.

Control ring is welded with steel plates, supported by head cover. On the joint surface are anti-grinding plates of nylon, which are used for guide in direction. There is pressing plate so that control ring won’t go up. On the top, control ring are connected with two connecting rods. Below, there are 24 holes to pins, spreading in a circle equally. Control ring is connected with guide vanes through pins, connecting plates and guide vane arms.

The shear pins between the guide vane arms and connecting plates are the weakest part in the transmission department of guide vane. If guide vanes close with great difficulty, the shear pins are immediately sheared to protect other parts. Consequently the signaling equipment is sheared, and signal is sent.

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.

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