Power Plant 1

DME603
Power Plant Engineering
Diploma VI Semester
LNCT & S, Bhopal

Introduction of Power Plant Engineering
 A power plant is an industrial facility used to generate electric power with
the help of one or more generators which converts different energy sources
into electric power.
 A power plant or a power generating station, is basically an industrial
location that is utilized for the generation and distribution of electric power
in mass scale, usually in the order of several 1000 Watts. These are generally
located at the sub-urban regions or several kilometers away from the cities
or the load centers, because of its requisites like huge land and water
demand, along with several operating constraints like the waste disposal etc.
 Electricity is produced at a an electric power plant. Some fuel source, such as
coal, oil, natural gas, or nuclear energy produces heat. The heat is used to
boil water to create steam. The steam under high pressure is used to spin a
turbine.

Types of Power Plants
A power plant can be of several types depending mainly on the type of fuel
used. A power generating station can be broadly classified in to 5 types
mentioned below.
Thermal Power Plants
Diesel Engine Power Plants
Gas Turbine Power Plants
Nuclear Power Plants
Hydro Electric Power Plants

Energy Scenario
Energy is one of the major inputs for the economic development of any
country. In the case of the developing countries, the energy sector assumes a
critical importance in view of the ever- increasing energy needs requiring huge
investments to meet them.
Energy can be classified into several types based on the following criteria:
 Primary and Secondary energy
 Commercial and Non commercial energy
 Renewable and Non-Renewable energy

Commercial and Non commercial Energy
The energy sources that are available in the market for a definite price are
known as commercial energy. By far the most important forms of commercial
energy are electricity, coal and refined petroleum products. Commercial
energy forms the basis of industrial, agricultural, transport and commercial
development in the modern world.
Examples: Electricity, lignite, coal, oil, natural gas etc.
The energy sources that are not available in the commercial market for a price
are classified as non-commercial energy. Non-commercial energy sources
include fuels such as firewood, cattle dung and agricultural wastes, which are
traditionally gathered, and not bought at a price used especially in rural
households. These are also called traditional fuels. Non-commercial energy is
often ignored in energy accounting.
Examples: Firewood, agro waste in rural areas; Solar energy for water heating.

Renewable and Non-Renewable Energy
Renewable energy is the energy obtained from regenerative or virtually in
exhaustible sources of energy occurring in the natural environment like solar
energy, wind energy etc. This is also referred as non-conventional sources of
energy.
Nonrenewable energy is the energy obtained from static stores of energy that
remain bound unless released by human interaction. Examples are fossil fuels
of coal, oil and natural gas and nuclear fuels. This type of energy is al so called
finite energy or conventional sources of energy.

Renewable and Non-Renewable Energy

LO3: Contents
Hydro power plant: General arrangement & its operation, classification,
advantages and disadvantages, technical data of hydro power plants in India,
Diesel power plant: General arrangement & its operation, classification,
advantages and disadvantages, technical data of diesel engine power plants in
India
Nuclear power plant: General arrangement & its operation, classification,
criteria for selection of installation of nuclear power plant, advantages and
disadvantages, technical data of nuclear power plants in India, safe disposal of
nuclear waste

Hydro Power Plant
 Hydro-energy is known as traditional renewable energy source. It is based on
natural circulating water flow and its drop from higher to lower land surface
that constitutes the potential.
 In order to convert this potential to applicable electric energy, water flow
should be led to and drive a hydraulic turbine, transforming hydro energy
into mechanical energy, the latter again drives a connected generator
transforming the mechanical energy into electric energy.
 When water is at a height, it has potential energy stored in it. When this
water flows down, its potential energy is first converted to kinetic energy and
then to mechanical energy with the help of turbines. With the use of a
generator, the mechanical energy is transformed into electrical energy.
Hydropower is essential only next to thermal power.
 Hydropower plants meet nearly 20% of the total power of the world.

Classification of Hydropower Plants
As such there are no hard and fast rules to classify Hydro power plants. Some
of the basis are as follows:
 Based on Hydraulic Characteristics
 Based on Head
 Based on Capacity
 Based on Turbine Characteristics
 Based on Load Characteristics
 Based on Interconnection

Main Parts of Hydro Power Station
Most of the hydro schemes in hilly areas in India are the high head and
medium head and have the same basic and common components of a
hydroelectric head. The major components of a hydro electric are;
1. Catchment area
2. Reservoir
3. Dam
4. Spillways
5. Conduits
6. Surge tanks
7. Draft tubes
8. Power house
9. Switchyard for power evacuation

Dam
Develops a reservoir to store water.
Builds up head for power generation.
Spillway
To safeguard the dam when water level in the reservoir rises.
Conduits
Headrace is a channel which lead the water to the turbine.
Tailrace is a channel which carries water from the turbine.
A canal is an open waterway excavated in natural ground following its contour.
A flume is an open channel erected on a surface above ground.
A tunnel is a closed channel excavated through an obstruction.
A pipeline is a closed conduit supported on the ground.

Intake
Contains trash racks to filter out debris which may damage the turbine
Forebay
Enlarged body of water just above the intake
Penstocks
Penstocks are closed conduits for supplying water “under pressure” from head
pond to the
turbines.
Surge Tank
A surge tank is a small reservoir in which the water level rises or falls to reduce
the pressure
swings so that they are not transmitted to the penstock.

Water Hammer
Load on the turbine is suddenly reduced
Governor closes turbine gates
Sudden increase of pressure in the penstock
Negative Pressure
Load on the generator is suddenly increased
Governor opens the turbine gates
Tends to cause a vacuum in the penstock
 When the gates are closed, water level rises in the surge tank and when the
gates are suddenly opened, surge tank provides the initial water supply.

Draft Tubes
The function of the draft tube is;
To reduce the velocity head losses of the water
To allow the turbine to be set above the tailrace to facilitate inspection and
maintenance
Scroll Casing
Takes the water from penstock to turbine blades
Tailrace
A tailrace is required to discharge the water leaving the turbine into the river.
The design of the tail race should be such that water has a free exit.

Power House Switchyard
1. Hydraulic turbines 1. Step up transformers
2. Electric generators 2. Instrument transformers
3. Governors 3. Transmission lines
4. Gate valves
5. Relief valves
6. Water circulation pumps
7. Air ducts
8. Switch board and instruments
9. Storage batteries
10. Cranes

Advantages and disadvantages
Advantages
Rainwater is stored in the dam. Thus, it is considered to be a renewable source
of energy.
The construction of dams helps in providing irrigation of the local farmers; it
also helps in controlling floods.
This method of electricity generation does not produce any pollution.
Their operational cost is very low.
Disadvantages
Hydropower plants require high capital with a low rate of return.
Dams can only be built at specific locations.
A Large area of agriculture is submerged underwater.

Nuclear Power Plant
 A nuclear power plant is a thermal power station in which the heat source is
one or more nuclear reactors. As in a conventional thermal power station the
heat is used to generate steam which drives a steam turbine connected to a
generator which produces electricity.
 Nuclear power plants are usually considered to be base load stations, which
are best suited to constant power output.
 Electric power has become an important and essential resources, it is used
for all the purposes. Without electric power, a single day cannot move
further. Keeping in mind the above problem, the R & D of government
departments are establishing different modes of power generation plants.
Nuclear power plant is one of the mode of the power generation.

Nuclear Power Reactors
A nuclear reactor produces and controls the release of energy from splitting
the atoms of elements such as uranium and plutonium. In a nuclear power
reactor, the energy released from continuous fission of the atoms in the fuel as
heat is used to make steam. The steam is used to drive the turbines which
produce electricity (as in most fossil fuel plants).
There are several components common to most types of reactors:
Fuel: Usually pellets of uranium oxide (UO2) arranged in tubes to form fuel
rods. The rods are arranged into fuel assemblies in the reactor core.
Moderator: This is material which slows down the neutrons released from
fission so that they cause more fission. It is usually water, but may be heavy
water or graphite.
Pressure Vessel or Pressure Tubes: Usually a robust steel vessel containing the
reactor core and moderator/coolant, but it may be a series of tubes holding
the fuel and conveying the coolant through the moderator.

Nuclear Power Reactors
Control Rods: These are made with neutron-
absorbing material such as cadmium, hafnium
or boron, and are inserted or withdrawn from
the core to control the rate of reaction, or to
halt it. (Secondary shutdown systems involve
adding other neutron absorbers, usually in the
primary cooling system.)
Coolant: A liquid or gas circulating through the
core so as to transfer the heat from it. In
light water reactors the moderator functions
also as coolant.
Steam Generator: Part of the cooling system
where the heat from the reactor is used to
make steam for the turbine.

Classification on the basis of different criteria:
On the Basis of Neutron Energy
 Fast Reactor: In these reactors, fission is effected by fast neutrons without
any use of moderators.
 Thermal Reactors: In these reactors, fission is effected by fast neutrons are
slowed down with the use of moderators. The slow neutrons are absorbed
by the fissionable fuel and chain reaction is maintained.
On the Basis of Fuel Used
 Natural Fuel: In this reactor, natural Uranium is used as fuel and generally
heavy water or graphite is used as moderator.
 Enriched Uranium: In this reactor, the Uranium used contains 5 to 10% U235
and ordinary water can be used as moderator.

Classification on the basis of different criteria:
On the Basis of Moderator Used
 Water moderated
 Heavy water moderated
 Graphite moderated
 Beryllium moderated
On the Basis of Coolant Used
 Water cooled reactors
 Gas cooled reactors
 Liquid metal cooled reactors
 Organic liquid cooled reactors

BOILING WATER REACTOR (BWR)
The BWR uses demineralized water (light water) as a coolant and neutron
moderator. Heat is produced by nuclear fission in the reactor core, and this
causes the cooling water to boil, producing steam. The steam is directly used
to drive a turbine, after which is cooled in a condenser and converted back to
liquid water. This water is then returned to the reactor core, completing the
loop. The cooling water is maintained at about 75 atm (7.6 MPa) so that it
boils in the core at about 285°C. In comparison, there is no significant boiling
allowed in a PWR because of the high pressure maintained in its primary loop -
approximately 158 atm (16 MPa, 2300 psi).

Description of Major Components and Systems
Feed water: Steam exiting from the turbine flows into condensers located
underneath the low pressure turbines where the steam is cooled and returned
to the liquid state (condensate). The condensate is then pumped through feed
water heaters that raise its temperature using extraction steam from various
turbine stages. Feed water from the feed water heaters enters the reactor
pressure vessel (RPV) through nozzles high on the vessel, well above the top of
the nuclear fuel assemblies (these nuclear fuel assemblies constitute the
“core”) but below the water level.
The feed water enters into the down comer region and combines with water
exiting the water separators. The feed water sub cools the saturated water
from the steam separators

Control Systems: Reactor power is controlled via two methods: by inserting or
withdrawing control rods and by changing the water flow through the reactor
core. Positioning (withdrawing or inserting) control rods is the normal method
for controlling power when starting up a BWR. As control rods are withdrawn,
neutron absorption decreases in the control material and increases in the fuel,
so reactor power increases.
As control rods are inserted, neutron absorption increases in the control
material and decreases in the fuel, so reactor power decreases. Some early
BWRs and the proposed ESBWR (Economic Simplified BWR) designs use
only natural circulation with control rod positioning to control power from
zero to 100% because they do not have reactor recirculation systems.
Changing (increasing or decreasing) the flow of water through the core is the
normal and convenient method for controlling power.

Steam Turbines: Steam produced in the reactor core passes through steam
separators and dryer plates above the core and then directly to the turbine,
which is part of the reactor circuit. Because the water around the core of a
reactor is always contaminated with traces of radionuclides, the turbine must
be shielded during normal operation, and radiological protection must be
provided during maintenance.
The increased cost related to operation and maintenance of a BWR tends to
balance the savings due to the simpler design and greater thermal efficiency of
a BWR when compared with a PWR. Most of the radioactivity in the water is
very short-lived (mostly N-16, with a 7-second half-life), so the turbine hall can
be entered soon after the reactor is shut down.

Advantages and disadvantages of BWR
Advantages
 The reactor vessel and associated components operate at a substantially
lower pressure.
 Pressure vessel is subject to significantly less irradiation and so does not
become as brittle with age.
 Operates at a lower nuclear fuel temperature.
 Fewer components due to no steam generators and no pressurizer vessel.
(Older BWRs have external recirculation loops, but even this piping is
eliminated in modern BWRs, such as the ABWR.)
 Lower risk (probability) of a rupture causing loss of coolant and lower risk
of a severe accident should such a rupture occur. This is due to fewer pipes,
fewer large diameter pipes, fewer welds and no steam generator tubes.

 Measuring the water level in the pressure vessel is the same for both normal
and emergency operations, which results in easy and intuitive assessment of
emergency conditions.
 Can operate at lower core power density levels using natural circulation
without forced flow.
 A BWR may be designed to operate using only natural circulation so that
recirculation pumps are eliminated entirely. (The new ESBWR design uses
natural circulation.)

Disadvantages
 Complex calculations for managing consumption of nuclear fuel during
operation due to “two phase (water and steam) fluid flow” in the upper part
of the core. This requires more instrumentation in the reactor core. The
innovation of computers, however, makes this less of an issue.
 Much larger pressure vessel than for a PWR of similar power, with
correspondingly higher cost. (However, the overall cost is reduced because
a modern BWR has no main steam generators and associated piping).
 Contamination of the turbine by short-lived activation products. This means
that shielding and access control around the steam turbine are required
during normal operations due to the radiation levels arising from the steam
entering directly from the reactor core.

Diesel Power Plant
 In a diesel power station, diesel engine is used as the prime mover. The
diesel burns inside the engine and the products of this combustion act as the
working fluid to produce mechanical energy. The diesel engine drives
alternator which converts mechanical energy into electrical energy.
 As the generation cost is considerable due to high price of diesel, therefore,
such power stations are only used to produce small power. Although steam
power stations and hydro-electric plants are invariably used to generate bulk
power at cheaper costs, yet diesel power stations are finding favour at places
where demand of power is less, sufficient quantity of coal and water is not
available and the transportation facilities are inadequate.
 This plants are also standby sets for continuity of supply to important points
such as hospitals, radio stations, cinema houses and telephone exchanges.

Schematic diagram of a diesel power plant

Different components used in a diesel power plant
 Diesel engine
 Air intake system
 Exhaust system
 Cooling water system
 Fuel supply system
 Lubrication system
 Diesel engine starting system
Diesel Engine: A diesel engine is the main component of a diesel power plant.
It is used to generate mechanical power in form of rotation energy with the
help of the combustion of diesel. An alternator is connected to the same shaft
as the diesel engine.

 There are two types of diesel engines; one is Two-stroke engines & other one
is Four-stroke engines.
 In two-stroke engines, every revolution of the crankshaft, one power stroke
is developed. And in four-stroke engines, one power stroke is developed
every two revolutions of the crankshaft.
 Compared to four-stroke engines, two-stroke engines have a low weight-to-
power ratio, are more compact, easy to start, and have low capital cost. But
the thermodynamic efficiency of a two-stroke engine is less compared to
four-stroke engines. Two-stroke engines require more cooling water and
consume more lubricants.
The required capacity of a diesel power plant can be calculated by the below
equation.
Capacity of Plant = (Connected Load × Demand Factor) / (Diversity Factor)

Air Intake System: Large diesel engine power plant requires air in the range of
4-8 m3/kWh. In natural air, lots of dust particles are available which may
damage the cylinders of engines. Therefore, air filters are used in the air intake
systems.
The air filters are made of cloth, wood, or felt. In some cases, oil bath filters
are used. In oil bath filters, the dust particles are oil-coated. The design of an
air intake system is done in such a way that it causes minimum pressure loss
during airflow.
If the pressure losses are high, it may increase fuel consumption and reduce
engine capacity. To avoid clogging, the air filters must be cleaned periodically.
In a large capacity power plant, a silencer is used between the engine and
intake system to reduce noise pollution.

Exhaust System: While combustion of diesel, gases are produced. The system
that is used to remove these gases is known as an exhaust system. The exhaust
system aims to discharge gases from the engine into the atmosphere.
The exhaust systems are designed in such a way that they will remove gases
without losing pressure. If pressure releases, it requires more work to do to
exhaust gases. And it will increase fuel consumption and reduce the power
output of diesel engines.
To reduce the noise level, the exhaust system must be provided with mufflers
and silencers. With the help of flexible exhaust pipes, the vibration must
isolate from the plant.
The exhaust system is needed to cover by asbestos to avoid heat transfer and
it must be cleaned periodically.

Cooling Water System: The IC engine works by burning fuel with air and the
percentage utilization of energy is as below;
a. 30-37% – useful work
b. 30-35% – carried by exhaust gases
c. 0-12% – lost by radiation, convection, and conduction
d. 22-30% – heat energy flows from gases to cylinder walls
Therefore, in an IC engine, 22-30% of energy is lost in form of heat energy. And
to avoid overheating of the engine, it requires a cooling system. There are two
types of cooling systems;
a. Direct cooling
b. Indirect cooling

Fuel Supply System: In a diesel power plant, as the name suggests, diesel is
used as a fuel. The fuel supply system has to perform the below functions.
 Depending upon the capacity of the engine and supply hours, the storage
tank is required to store the diesel.
 Before supplying fuel to the engine, the fuel must be filtered and it does not
contain any impurities.
 Metering of fuel is necessary.
 According to the load in each cycle, it must inject the exact quantity of fuel.
 Provide return path to unused fuel.
 In a multi-cylinder engine, it is required atomization of fuel and even
distribution of fuel to each cylinder.
Types: Common rail system, Individual pump system, Distributor system

Lubrication System: In the IC engine, the piston-cylinder arrangement is
referred to a very large variation of temperature. It works at a maximum
temperature of around 2000˚ C or higher than this. At such a high
temperature, the lubricating material may convert into gummy material. And it
results in sticking piston rings.
The engines run on high load conditions and cause friction loss in case if the
lubrication system fails. Therefore, the lubrication system is necessary for the
IC engine and it requires an adequate quantity of oil reach to all parts of the
engine.
The lubrication system prevents direct contact between two metals and will
reduce the wear and tear in moving parts. The below-listed components of the
IC engine must be lubricated;

The lubrication system prevents direct contact between two metals and will
reduce the wear and tear in moving parts. The below-listed components of the
IC engine must be lubricated;
 Piston and cylinder
 Main crankshaft bearings
 Cam, camshaft, and its bearings
 Ends of bearings at connecting rod
There are three types of lubricating systems;
 Mist or charge lubricating system
 Wet sump injection system
 Dry sump injection system

Diesel Engine Starting System: At the time of starting, the temperature and
pressure of the cylinder are not sufficient to initiate the combustion. Hence,
starting of the engine is not conductive for initiation of combustion. There are
several methods introduced to start a diesel engine. Some of these methods
are listed below.
 Hand or kick-starting
 Electrical starting
 Compressed air
 Auxiliary petrol engine
 Hot bulb ignition
 Special cartridge starting

Form these methods, the electrical starting method is the most popular
method to start a diesel engine. In this method, a battery is used with a series-
wound motor (starting motor). This arrangement is designed to operate on a
large current at low voltage. The starting motor is connected with the engine
flywheel through gears and supplies torque till the engine starts.

Site Selection of Diesel Power Plant
The factors affecting a selection of a location for diesel power plant are listed below.
 Bearing capacity: The diesel engine is placed on a foundation. If the bearing
capacity of selected land is high then it does not require high depth for a
foundation. And it will save the initial cost of a power plant.
 Transportation facility: The plant requires heavy pieces of machinery. Hence, the
selected site must have an adequate transportation facility.
 Labor: Large capacity diesel power plant requires several labors.
 Availability of water: The diesel power plant requires water for cooling purposes.
 Future expansion: There is some extra land available for future expansion.
 Availability of fuel: This plant requires a high volume of fuel (diesel). So, a site
should be selected where fuel is available easily.
 Distance from the populated area: The operation of a diesel engine pollutes
nearby areas. Hence, it is located far from populated area.
 Distance from load center: To avoid transmission loss, the site should be selected
near the load center.

Advantages & Disadvantages of Diesel Power Plants
Advantages
 It can start and stop quickly when required.
 This plant can be located at any place and it is easy to install for a small capacity
power plant.
 It does not require more space.
 For varying loads, this plant responds quickly.
 The water is required only for cooling purposes. So, a very little quantity of water is
required.
 The thermal efficiency of this plant is higher than a steam power plant.
 The diesel power plant can be efficiently used up to 100 MW.
 Less manpower is required.
 It can burn a wide range of fuel.
 Fewer fire chances.

Advantages & Disadvantages of Diesel Power Plants
Disadvantages
 The generation cost per unit is very high. As the operation of this plant
depends on the price of diesel. And diesel prices are high.
 The capacity of a diesel power plant is less compared to a steam power plant
and hydroelectric power plant.
 It creates noise pollution and carbon pollution by the combustion of diesel.
 It requires high maintenance and lubrication costs.
 This plant is not capable to meet continuous overload demand.
 The life of this plant is less compared to other power plants.

Power Plant 1

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