Panauti Hydro Power Project

Introduction

Hydropower

Hydropower or water power is power derived from the energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as watermills, sawmills, textile mills, dock cranes, domestic lifts and paint making.

Since the early 20th century, the term is used almost exclusively in conjunction with the modern development of hydro-electric power, which allowed use of distant energy sources. Another method used to transmit energy used a trompe, which produces compressed air from falling water. Compressed air could then be piped to power other machinery at a distance from the waterfall. Hydro power is a renewable energy source.

Water's power is manifested in hydrology, by the forces of water on the riverbed and banks of a river. When a river is in flood, it is at its most powerful, and moves the greatest amount of sediment. This higher force results in the removal of sediment and other material from the riverbed and banks of the river, locally causing erosion, transport and, with lower flow, sedimentation downstream.

Hydro electricity

Hydro electricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation – 3,427 terawatt-hours of electricity production in 2010 and is expected to increase about 3.1% each year for the next 25 years.

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. There are now three hydroelectricity plants larger than 10 GW: the Three Gorges Dam in China, Itaipu Dam across the Brazil/Paraguay border, and Guri Dam in Venezuela

The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour. Hydro is also a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands. However, damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO₂) than fossil fuel powered energy plants

Types of Hydro Electricity power production

Conventional (dams)

Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. A large pipe (the "penstock") delivers water to the turbine.

Pumped-storage

This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale grid energy storage and improve the daily capacity factor of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.

Run-of-the-river

Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that the water coming from upstream must be used for generation at that moment, or must be allowed to bypass the dam. In the United States, run of the river hydropower could potentially provide 60,000 MW (about 13.7% of total use in 2011 if continuously available).

Tide

A tidal power plant makes use of the daily rise and fall of ocean water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be dispatch able to generate power during high demand periods. Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot waterwheels. Tidal power is viable in a relatively small number of locations around the world. In Great Britain, there are eight sites that could be developed, but they have the potential to generate 20% of the electricity used in 2012.

Underground

An underground power station makes use of a large natural height difference between two waterways, such as a waterfall or mountain lake. An underground tunnel is constructed to take water from the high reservoir to the generating hall built in an underground cavern near the lowest point of the water tunnel and a horizontal tailrace taking water away to the lower outlet waterway.

Working of hydropower plant

There are four parts of a typical hydropower plant which are:

Dams

The dam is made on a river to collect water. Whenever it rains, the water is collected into the dam so it serves as a water reservoir. The potential energy for further work is generated by the water level difference between the dams and the turbines because the water level in the dams is very high. Dams also control the water flow through penstocks.

Turbines

The next step is to convert this kinetic energy of water into mechanical energy. The water flows from a height throw the penstocks which are the channeled vessels to the turbines which have blades. The falling water has enough kinetic energy that when they strike hard with the blades of the turbines, they start spinning which means that the kinetic energy is converted into mechanical energy. The turbines resemble a lot with the windmills in which wind energy is used instead of water. But the turbines use potential and mechanical energy of falling water to convert into work.

Generators

The shafts of the turbines convert the mechanical energy into electric energy. Basically, the generators work on the principle of magnets which is that when you pass a magnet near a conductor, electric current flows through it.

AC Generator principle:

It is based on the principle of electromagnetic induction. When a coil rotates in a uniform magnetic field, the associated flux changes and an induced emf is generated according to faraday’s law of electromagnetic induction.

Suppose a coil of wire of area A is rotated in a uniform magnetic field of strength B. Suppose N is the number of turns of the coil. Let w be the uniform angular velocity with which coil is rotating inside a field. Suppose at instant t, ө be an angle between normal drawn to the plane of the coil and the direction at field B.

Now,Φ= normal component of B×A

= B.cosө × A

W e know, ө=wt

So, Φ= Bcos(wt) × A

According to Faradays law of electromagnetic induction,

Induced emf (E) = {-d (N Φ)}/dt ……………………….1

For N turns, = NΦ = NBAcos(wt) …………………2

So E = {-d(NBAcos(wt)}/d t= NBAw sin(wt)

Indiced emf becomes maximum whe n sin(wt) = +1

So, E₀ = +NBAw

So E = E₀sin(wt)

Construction:

AC generator consists of the following parts:

1. Armature:

It is a rectangular coil ABCD wounded over a soft iron core in large no. of turns. The soft iron core is used to increase the magnetic flux. The two ends of the coil are connected to slip rings C₁ and C₂ .The coil together with the rings can rotate in the magnetic field. The axis of rotation of the coil is in the plane of coil but perpendicular to the magnetic field.

2. Field Magnet:

It may be a permanent magnet or an electromagnet of concave poles which produces strong uniform magnetic field between the two poles.

3. Brushes:

Two graphite flexible brushes B₁ and B₂ are always I n contact with the slip rings. As the armature rotates, the slip rings C₁and C₂ slip against the b rushes so that the contact is kept all the time. These brushes are connected to two terminals P and Q and external load R_L.

Working:

The working of a generator can be described as follows:

1) Initially, when wt = 0, i.e. the plane of the coil becomes perpendicular to the field, emf = 0. So, E = E₀sin (wt) = E₀ sin0 = 0. The electric current flows through DCBA and from B₂and B₁ through R_L.

2) After time t = T/ 4, the coil becomes parallel to the magnetic field, wt = 90, E = E_0. The electric current flows through DCBA and from B₂ and B₁ through R_L.

3) After time t = T/2, the coil becomes inverted, wt = 0, E =0_. The electric current flows through ABCD and from B₁ and B₂ through R_L.

4) After time t = 3T/ 4, the coil becomes horizontal, wt = 90, E = E_0. The electric current flows through ABCD and from B₁ and B₂ through R_L.

5) After time t = T, the coil comes to original position, wt = 0, E = 0_. The electric current flows through DCBA and from B₂ and B₁ through R_L.

Thus the output emf is alternating in nature.

Rotor and stator

The rotor having field pole rotates on a specific speed. When it rotates it passes the field poles across the stator to make sure that it has the same effect of electric field. The water should keep on moving constantly to make sure that the amount of electricity produced is great. Static water cannot generate electricity.

Transmission lines

The electricity via power lines is transferred to substation which provides it to the consumers.

So, the process is of great importance. It should be performed in a right manner to ensure the great production of electricity. This process is not much costly as no fuels are produced and not much health hazardous chemicals are produced by it. But the research is still going on.

Panauti Hydro Power Station

Panauti Hydropower Station is the third hydropower station constructed in Nepal. It is a run-of-river scheme on Roshi Khola (river) having installed capacity of 2.4 MW with 3 units of 0.8 MW each. This power station lies at Khopasi of Kavre district located 35 km east of Kathmandu.

The power station was commissioned in the year 1965 A.D. with designed annual generation of 6.97 GWh. The project was completed with the assistance from USSR Government.

Some of the features of Panauti Hydro Power Station

Salient Features
Type : Peaking Run of the River
Designed Head : 60 meter
Installed Capacity : 2.4 MW
Discharge of Each Unit : 1.61m3/s
Length of Canal : 3.721 km.
Internal Diameter of Penstock : 1400 mm
Length of Penstock : 370 meter
Type of Turbine : Francis
Rated Voltage of Generator : 6.3 KV
Rated Speed : 1000 rpm
Turbine Generator Set : 3 Nos.
Turbine Capacity: 850 KW
Transmission Voltage: 33 KV
Step Up Transformer: 6.3/33 KV 2x 1.5 MVA
Project Inception Date: 2017 BS
Project Completion Date: 2022 BS
Project Financed by: USSR and Nepal Government
Project Construction Cost: NRs. 2.7 Cores

Methodology:

v For the completion of this project, we referred to different books and found out more about the topic

v We consulted the internet to gain further information on the topic.

v We asked our friends to tell us about the sites to find information to the topic.

v We requested my family members and friends to help me in different ways for the completion of the project.

Recommendations:

Panauti Hydropower station, although being the third hydropower stations in Nepal, is not producing as much current as it is expected to be.This is one of the causes for load-shedding in Nepal. It is the result of ill or no management of the water resources and the machines that get damaged with time. So, we strongly recommend the officials to repair these machines as soon and as well as possible because the cost of repairing these machines is definitely less than the economic loss Nepal faces each day due to the lack of electricity.

We would like to recommend to the government to take these measures to ensure the loss of water as it is the run of the rive type of hydro power and to produce the installed capacity of electricity.

Bibliography:

1) www.Google.com.np/Panauti Hydro Power Station.

2) Principles of Physics, Grade XII by Manu Kumar Khatry, Manoj kumar Thapa, Bhesa Raj Adhikari, Arjun Kumar Gautam and Parashu Ram Poudel, second(revised) edition, 2012.