Pelton turbine

Pelton Hydro Turbine  for high water head Project

The Pelton turbine is widely used in hydropower station with the heads from 80-1000m.
Pelton turbine is consisted of runner, turbine case, nozzles assembly, inlet pipe, deflector etc. The runner is assembled in the shaft of the generator, torque transmission by ping.
lt utilizes the dynamic power of high pressure water flow to rotate the runner and force the rotor work, The centre line of the jet is in the same plane as the runner while rotating.
Pelton turbine has the advantages of compact construction, stable running and easy operation. Normally, Small pelton turbine always arranged with horizontal shaft and one or two nozzles,   Medium size and larger Pelton turbines are most often arranged with vertical shaft, and equip four or six nozzles to obtain more power.

1. Runner

The runner is the principle part of the turbine. It has influence over the characteristic of the turbine. The runner consists of vanes, the hub and the outer ring of runner. The shape of vane is three dimension cambers. The outer ring applies to strengthen the runner and to reduce the loss of wind.

The runner disc and buckets are CNC machined from and integrally forged 13%Cr 4% Ni steel, the faces of buckets which are in contact with water must be CNC machined and ground to a smooth surface with a maximum surface roughness of 0.8 Microns. The buckets  must be controlled by a coordinate measuring machine via a certified measuring company and must be submitted for approval. The center line allowance between the buckets is 0.57mm

Additional tests for material must be completed according to specification for Inspection of steel castings for hydraulic machines CCH 70.3. A detailed chemical analysis, Ultrasonic tests UT70.3, magnetic particle tests MT 70.3, and dye penetrant tests PT70.3 must be performed via a certified company and results should be submitted for approval.

Runner must be statically balanced according to ISO 1940/1 class G6.3 and G2.5.

2. The case and the cover of the case

The case used is a fine gradewelding steel with a minimum yield strength of 550 Mpa (St52 or equivalent), it has enough intensity and is convenient for maintenance. There is trachea on the case, which should be connected to the ventilating pipes from the tailrace channel and shall not use air from the power house. it is for complementing the air the jet takes, avoid vacuum in the house, keep the circulation, and there is a gate in the unit for overhauling, between up cover and down seat there is o-washer for overhauling.

3. Jet deflectors

Deflectors be manufactured from a monolithic stainless steel. Deflectors be

designed to withstand maximum discharge from the nozzle without vibration. The deflectors

be controlled by a double acting servomotor located outside the turbine casing.

4. Nozzle

The nozzle is components of the distributor of the pelton turbine.The intake pipe conduits pressure water flow to the nozzle via the guide support which is used to support the needle stem to provide against a vortex. In practice the nozzle is just a needle valve; however the valve plays a role of shut off and of transform energy in impulse turbine. The pressure water flow enters the nozzle body. Then the velocity of water flow shall be increased rapidly at the nozzle tip and the water flow is formed a jet to inject to the vanes of runner.

 So pressure energy of the flow changes to velocity energy and the runner does a work. The opening of nozzle shall be adjusted by nozzle control mechanism which is consisted distributing valve, the servomotor of needle and by combination mechanism. The operation oil pressure is 6.3Mpa, it used internal control structure, the opening of the needle is 75%~85% on the full-load. The server-motor piston and the piston rod is made of 35 steel welding.

Allowance of the position of the jet center line and the rotor pitch circle is ±1.2mm. Allowance of the position of the jet center line and the pelton watershed edge is ±1.2mm as per the IEC standards.

5. Needle control mechanism

The needle control mechanism includes a jet deflector; the jet deflector is also called deviator. It is used to deflect the jet on a sudden load rejection in order to avoid run away of the unit and pressure over rise for excessive water hammer in the penstock.

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

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

Renewable energy--Hydropower

Hydropower has always been considered the cleanest form of power generation,Hydropower is the leading source of renewable energy. It provides more than 97% of all electricity generated by renewable sources. Other sources including solar, geothermal, wind, and biomass account for less than 3% of renewable electricity production. Hydropower is clean. It prevents the burning of billions gallons of oil or millions tons of coal each years. Hydropower is the most efficient way to generate electricity. Modern hydro turbine generator units can convert as much as 90% of the available energy into electricity. The best fossil fuel plants are only about 50% efficient. The dams and hydropower plants also play an important role in water resource planning, in preventing flooding, making rivers navigable, solving irrigation problems and creating recreation areas.

Hydropower is using water to power machinery or make electricity. Water constantly moves through a vast global cycle, evaporating from lakes and oceans, forming clouds, precipitating as rain or snow, then flowing back down to the ocean. The energy of this water cycle, which is driven by the sun, can be tapped to produce electricity or for mechanical tasks like grinding grain. Hydropower uses a fuel—water—that is not reduced or used up in the process. Because the water cycle is an endless, constantly recharging system, hydropower is considered a renewable energy.

When flowing water is captured and turned into electricity, it is called hydroelectric power or hydropower. There are several types of hydroelectric facilities; they are all powered by the kinetic energy of flowing water as it moves downstream. Turbines and generators convert the energy into electricity, which is then fed into the electrical grid to be used in homes, businesses, and by industry.