1. Power plants convert thermal energy from fossil fuels into electrical energy through thermodynamic cycles like the Brayton, Rankine, and Otto cycles. They use prime movers like steam and gas turbines to power electrical generators. 2. Common types of power plants include fossil fuel plants, hydroelectric, nuclear, and renewable plants. Fossil fuel plants burn coal, natural gas, or oil. Alternative energy sources help address environmental concerns of fossil fuels. 3. Thermodynamic cycles determine power plant categories. The Brayton cycle powers gas turbines, Rankine cycle powers steam turbines, and Otto and Diesel cycles power reciprocating engines. Combined cycle plants boost efficiency by combining gas and steam cycles.

1. Power Plant
And
Thermodynamic
cycles
Syed Salman Haider Naqvi
Mechanical Engineering
NED University of Engineering and Technology

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
Power Plants____________________
Power plants or power stations are industrial facility that produces Electric Power. A power
station is equipped with mechanical equipment running on Thermodynamic cycle converting
Thermal Energy into Electrical Energy by the virtue of rotational motion of the prime mover.
The engines installed in a Power Station harvest energy from the fossil fuels which in exchange
produces Electric Power
Fossil Fired Power Station
A Fossil fired Power Station is a power station which burns fossil fuel such as coal, natural gas or
petroleum to produce electricity. Fossil-fuel power stations have machinery to convert the heat
energy of combustion into mechanical energy, which then operates an electrical generator. The
prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating internal
combustion engine. All plants use the energy extracted from expanding gas, either steam or
combustion gases.
Alternative Energy Harvesting Stations
Alternatives to fossil fuel power plants include nuclear power, solar power, geothermal power,
wind power, tidal power, hydroelectric power and other renewable energies. Some of these are
proven technologies on an industrial scale.
Environment Hazards
The world's power demands are expected to rise 60% by 2030. World organizations and
international agencies, like the IEA, are concerned about the environmental impact of burning
fossil fuels, and coal in particular. The combustion of coal contributes the most to acid rain and
air pollution, and has been connected with global warming. Modern day coal power plants
pollute less than older designs due to new "scrubber" technologies that filter the exhaust air in
smoke stacks; however, emission levels of various pollutants are still on average several times
greater than natural gas power plants. In these modern designs, pollution from coal-fired power
plants comes from the emission of gases such as carbon dioxide, nitrogen oxides, and sulfur
dioxide into the air.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
Types of Power Plants
On the basis of thermodynamic cycles or working mechanism, power plants can be categorized
as followed
 Thermal Power Plant
 Hydro-Electric Power Plant
 Nuclear Power Plant
 Renewable Energy Plants
Commissioning of a Power Plant is a multi-Million Dollar Project. Furthermore, the venue of the
plant and its type adds further into the budget. I.e. Solar Plant is a costly project compared to
Simple Cycle Power Plant. But in long run Solar is found expensive and less energy is harvested.
Whereas, Simple Cycle Plant can run 24/7 provided supply of fuel is not compromised.
Following chart displays facts and figures of different types of Power Station.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
Thermodynamic Cycles – Power Plant______
One of the most important application of Thermodynamics is Power Generation. The devices
or systems used to produce a net power output are often calledengines, and the thermodynamic
cycles they operate on are called power cycles.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
 Gas cycles, the working fluid remains in the gaseous phase throughout the entire cycle.
 Vapor cycles the working fluid exists in the vapor phase during one part of the cycle and
in the liquid phase during another part.
Otto Cycle – SI Engines
Otto Cycle is the only thermodynamic cycle used
today in SI engines was first developed in
Germany in 1876 by Nikolaus A. Otto. The 4-
Stroke SI engines comprise of four mechanical
process and two revolutions of the Crankshaft
Assuming the piston is at TDC1 at start-up, all
valves are closed. The piston travels downwards
towards BDC2, during the process inlet valve
opens and fresh charge3 enters the cylinder, this
is the Intake Stroke. Soon after reaching BDC inlet
valve closes and piston travels to TDC
compressing the freshly entered charge, this is
the Compression Stroke. The Spark-plug situated
at TDC ignites the charge to produce the Power
Stroke, the piston is forced downwards to BDC.
The piston then returns to TDC, while exhaust
valves are open, this is the Exhaust Stroke.
1 Top dead center TDC is the position of the piston when it forms the smallestvolume in the cylinder.
2 BDC Bottom Dead Center is the position of the piston when itforms the largestvolume in the cylinder.
3 Charge is the air-fuel mixtureentering the IC engine.
Thermodynamics
Cycles
Gas Cycles Vapor Cycles

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
The actual and ideal process diagrams are shown in figure.
1-2 Isentropic compression
2-3 Constant-volume heat addition
3-4 Isentropic expansion
4-1 Constant-volume heat rejection
There exist2-Stroke Gasolineengines but they aren’t popular now due to their inefficiencies.Low
thermal and net efficiency. They work on the same principle and thermodynamic process as 4-
Stroke engines. The MEP4 and Compression Ratio5 “r” for a Gasoline engine are also a major
factor to consider. In SI engines compression ratio ranges from 6-10 before Auto-Ignition and
knocking.
Diesel Cycle – CI Engines
Diesel Cycle is the only thermodynamic cycle used today
in CI Engines.During 1890s Rudolph Dieselproposed the
Diesel Cycle which is used today in modern Diesel
engines. Different from SI engines, CI engines have
Glow-plug and Fuel Injector in against to Spark-plug and
Carburetor in SI engines. The compression ratios are
higher in CI engines due to the elimination of knocking6
phenomenon and auto-ignition 7since only air is
compressed in the cylinder. The compression is high
enough to reach the self-ignition temperature of the
fuel. Thus at the end of compression stroke fuel is
injected through the nozzle into the compressed air
stream having temperatures higher then self-ignition
temperature of the fuel (self-ignition temperature of
Diesel is 256oC). The compression ratios in CI engines
ranges from 12-24. The function of the glow-plug is to
preheat the air in the cylinder at start-up only.
4 Mean Effective Pressureis a fictitiouspressurethat,if it acted on the piston duringthe entire power stroke,
would produce the same amount of net work as that produced duringthe actual cycle.
5 Compression ratio r of an engine is the ratio of the maximum volume formed in the cylinder to the minimum
(clearance) volume.
6 is the audiblenoiseoccurringin the engine because of auto-ignition,the premature ignition of the fuel.
7 Auto-ignition is the premature ignition of the fuel that produces an audiblenoise,which is called engineknock.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
The Thermodynamic process as shown in fig(a) is elaborated as followed.
1-2 Isentropic Compression
2-3 Constant Pressure Heat Addition
3-4 Isentropic Expansion
4-1 Constant Volume Heat Rejection
The higher efficiency and lower fuel costs of diesel engines make them attractive in applications
requiring relatively large amounts of power, such as in locomotive engines, emergency power
generation units, large ships, and heavy trucks.
The EDG (emergency diesel generator) used in BQPS II – K-Electric is a 1.8MW V-16 CI Engine.
Brayton Cycle – GT Engines
Brayton Cycle on a Gas Turbine was first
proposed by George Brayton and his first
development came into existence in 1870.
Gas Turbines operate on an open cycle as shown
in fig. 9-29. Fresh Air at ambient8 conditions is
sucked into the compressor where it’s
temperature and pressure are raised. The
compression ratio ranges from 15-40 in modern
GTs. The compressed air then travels to the
combustion chamber where the burners are
present and fuel is injected and burned at
constant pressure. The high temperature and
pressure gases then expands in the turbine
section where it’s pressure is reduced back to
ambient or atmospheric pressure.
8 Ambient conditions arethe liveatmospheric temperature and pressurereadings.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
The Thermodynamic Brayton cycle as closed cycle is as
followed.
1-2 Isentropic compression 9(in a compressor)
2-3 Constant-pressure heat addition
3-4 Isentropic expansion (in a turbine)
4-1 Constant-pressure heat rejection
The T-s and P-v diagrams of an ideal Brayton cycle are shown
in Fig. 9–31.
The two major application areas of gas-turbine engines are
aircraft propulsion and electric power generation. When it is
used for aircraft propulsion, the gas turbine produces just
enough power to drive the compressor and a small generator
to power the auxiliary equipment. The high-velocity exhaust
gases are responsible for producing the necessary thrust to
propel the aircraft. Gas turbines are also used as stationary
power plants to generate electricity as stand-alone units or in
conjunction with steampower plants on the high-temperature
side.In these plants,the exhaust gases of the gas turbine serve
as the heat source for the steam.
There are 3 GTs General ElectricPG9171E - 129.1 MW installed
in BQPS II K-Electric.
9 Isentropic process is an internally reversibleand adiabatic process.In such a process theentropy remains
constant.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
Rankine Cycle – ST Engine
Rankine Cycle is a type of Vapor cycle, based on
closed cycle configuration. An Ideal Rankine
Cycle involves the following thermodynamic
processes.
1-2 Isentropic compression in a pump
2-3 Constant pressure heat addition in a boiler
3-4 Isentropic expansion in a turbine
4-1 Constant pressure heat rejection in a
condenser
The saturated water in entered into the pump at
state 1 where its compressed and pressure is
increased to boiler operating pressure. The temperature is also raised in the isentropic
compression process from state 1 to state 2. The saturated compressed water is then entered in
the boiler region where it exits as a high temperature and pressure Super-Heated Vapor at state
3. The energy required for phase
transformation is provided through a nuclear
reactor, Coal or Natural Gas burner or through
the exhaust of GT in HRSG. The super-heated
vapor at about 90-100bar pressure then enters
into the turbine section where it drives the
Steam Turbine, from state 3 to state 4. The low
pressure wet steam at the exit of the turbine is
then drawn into the condenser, where pressure
is maintained below atmospheric pressure. The
condenser acts as a heat sink where all the heat
of wet steam is extracted and saturated water
is re-produced from state 4 to state 1.
The ST’s used in conjunction with GTs have a net efficiency of 45%, installed in BQPS II K-Electric.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
Combined Cycle Power Plants
The conquest to produce more power brings us to
mechanical limit, where more energy was at expense
of material design and metallurgy. Here Combined
Cycle was introduced, boosting the relative efficiency
to 45% and in some cases 60%for Advanced Combined
Cycle Power Plants.
A combined cycle is a junction of Gas cycle and Vapor
Cycle. Brayton and Rankine cycle and junction
together to give higher work output.
The Exhaust of aGT is a very high temperature gas.The
temperature of exhaust ranges from 500-700oC+.
Since over time the metallurgy of the material used in
GT has improved and is more temperature resistant
was ceramic coating and can bear upto 1500oC+
temperature, resulting in higher exhaust temperature.
The exhaust gases then are sent to heat exchangers
HRSG (heat regenerative steam generation), here the
heat of exhaust is exchanged with the boiler water.
This results in high super-heated vapor formation for
running a ST. The pressure of super-heated vapor is
maintained at 90-100bar before sending it to the ST.
The efficiencies of a CCPP is 45% at average. The
evolution of mechanical design and calibration has
resulted into a more productive and lower cost energy
production.
The two cycles in the combined cycle system are
independent, with the syncing medium is a heat
exchanger HRSG.
A 560MW CCPP Bin Qasim Power Station II K-Electric
was commissioned in 2012 and is fully operational.

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Syed Salman Haider Naqvi ME-305 Batch 2013-17 Mechanical Department
Submitted to Dr. Prof. Ahmed Hussain NED University of Engineering and Technology
References
1. Gas Turbine Engineering Handbook – Meherwan P. Boyce 2nd Edition
2. Thermodynamics an Engineering Approach – Yunus A. Cengel
3. Internal Combustion Engines – G.W. Ganeson
4. https://en.wikipedia.org/wiki/Power_station
5. https://en.wikipedia.org/wiki/Fossil-fuel_power_station