How Gas Turbine Power Plant Work ?

Gas Turbine Power Plant

Gas turbine power plant:-

A generating station which employs gas turbine as the prime mover for the generation of electrical energy is known as a gas turbine power plant.

How Gas Turbine Power Plant Work?

In a gas turbine power plant, air is used as the working fluid. The air is compressed by the compressor and is led to the combustion chamber where heat is added to air, thus raising its temperature. Heat is added to the compressed air either by burning fuel in the chamber or by the use of air heaters. The hot and high-pressure air from the combustion chamber is then passed to the gas turbine where it expands and does the mechanical work. The gas turbine drives the alternator which converts mechanical energy into electrical energy.

In a gas turbine power plant we use high pressure and temperature air instead of high pressure and temperature steam to rotate the turbine.

In a gas Turbine Power Plant compressor, gas turbine and the alternator are mounted on the

same shaft so that a part of mechanical power of the turbine can be utilised for the operation of the compressor. Gas turbine power plants are being used as standby plants for hydroelectric stations, as a starting plant for driving auxiliaries in power plants etc.

Advantages

(i) It is simple in design as compared to steam power station since no boilers and their auxiliaries are required. (ii) It is much smaller in size as compared to steam power station of the same capacity. This is expected since gas turbine power plant does not require boiler, feed water arrangement etc.

(iii) The initial and operating costs are much lower than that of equivalent steam power station. (iv) It requires comparatively less water as no condenser is used. (v) The maintenance charges are quite small. (vi) Gas turbines are much simpler in construction and operation than steam turbines. (vii) It can be started quickly form cold conditions. (viii) There are no standby losses. However, in a steam power station, these losses occur because boiler is kept in operation even when the steam turbine is supplying no load.

Disadvantages

(i) There is a problem for starting the unit. It is because before starting the turbine, the compressor has to be operated for which power is required from some external source. How-ever, once the unit starts, the external power is not needed as the turbine itself supplies the necessary power to the compressor. (ii) Since a greater part of power developed by the turbine is used in driving the compressor, the net output is low. (iii) The overall efficiency of such plants is low (about 20%) because the exhaust gases from the turbine contain sufficient heat. (iv) The temperature of combustion chamber is quite high (3000℉) so that its life is compara-tively reduced. 

What is Load Curve ? | Daily Load Curve & Important Factor

 What Is Load Curve?

The curve showing the variation of load on the Power station with respect to (w.r.t.) time is known as a load curve.

The load on a power station is never constant; it varies from time to time. These load variations during the whole day (i.e., 24 hours) are recorded half-hourly or hourly and are plotted against time on the graph. The curve thus obtain known as daily load curve as it shows the variations of load w.r.t time during the day. Figure below shows a typical daily load curve of a power station.

 Note:-  IN EASY WAY TO UNDERSTANDING

1.These load variations during the whole day are recorded half hourly or hourly and are plotted against time on the graph. The curve thus obtained is known as daily load curve.

2.The monthly load curve can be obtained from the daily load curves of that month.

➢ For this purpose, average values of power over a month at different times of the day are calculated and then plotted on the graph.

➢ The monthly load curve is generally used to fix the rates of energy.

3. The yearly load curve is obtained by considering the monthly load curve of that particular year.

➢ The yearly load curve is generally used to determine the annual load factor.

Important Terms:

(i) Connected load:  It is the sum of commences ratings of all the equipment’s connected to supply system.

(ii) Maximum demand: It is the greatest demand of load on tire power station during a given period.

(iii) Demand factor:  It is the ratio of maximum demand on the power station to its connected load i.e. 

The value of demand factor is usually less than 1. It is expected because maximum demand on the power station is generally less than the corrected load.

(iv) Average load:  The average of loads occurring on the power station in a given period (day or month or year) is known as average load or average demand.

(v) Load factor:  The ratio of average load to the maximum demand during a given period is known as load factor i.e.,

Load factor is always less than 1 because the average load is smaller than the maximum demand. Higher the load factor of the power station, lesser will be the cost per unit generated.

(vi) Diversity factor:  The ratio of the sum of individual maximum demands to the maximum demand on power station is known as diversity factor i.e.,

(vii) Plant capacity factor: It is the ratio of actual energy produced to the maximum possible energy that could have been produced during a given period i.e.,

(viii) Plant use factor: It is ratio of kWh generated to the product of plant capacity and the number of hours for which the plant was in operation i.e.,

How Diesel Power Station Works | Electricalk4u

Diesel Power Station

A generating station in Which diesel engine is used as the prime over for the generation of electrical energy is known as diesel power station.

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 the alternator which converts mechanical energy into electrical energy.

Diesel Power Station Important Parts 

(i) Fuel supply system. 

It consists of storage tank, strainers, fuel transfer pump and all day fuel tank. The fuel oil is supplied at the plant site by rail or road. This oil is stored in the storage tank. From the storage tank, oil is pumped to smaller all day tank at daily or short intervals. From this tank, fuel oil is passed through strainers to remove suspended impurities. The clean oil is injected into the engine by fuel injection pump.

(ii) Air intake system. 

 This system supplies necessary air to the engine for fuel combustion. It consists of pipes for the supply of fresh air to the engine manifold. Filters are provided to remove dust particles from air which may act as abrasive in the engine cylinder.

(iii) Exhaust system.

  This system leads the engine exhaust gas outside the building and dis-charges it into atmosphere. A silencer is usually incorporated in the system to reduce the noise level

(iv) Cooling system. 

The heat released by the burning of fuel in the engine cylinder is partially converted into work. The remainder part of the heat passes through the cylinder walls, piston, rings etc. and may cause damage to the system. In order to keep the temperature of the engine parts within the safe operating limits, cooling is provided. The cooling system consists of a water source, pump and cooling towers. The pump circulates water through cylinder and head jacket. The water takes away heat form the engine and itself becomes hot.The hot water is cooled by cooling towers and is recirculated for cooling.

(v) Lubricating system. 

This system minimises the wear of rubbing surfaces of the engine. It comprises of lubricating oil tank, pump, filter and oil cooler. The lubricating oil is drawn from the lubricating oil tank by the pump and is passed through filters to remove impurities. The clean lubricating oil is delivered to the points which require lubrication. The oil coolers incorporated in the system keep the temperature of the oil low.

(vi) Engine starting system. 

This is an arrangement to rotate the engine initially, while starting, until firing starts and the unit runs with its own power. Small sets are started manually by handles but for larger units, compressed air is used for starting. In the latter case, air at high pressure is admitted to a few of the cylinders, making them to act as reciprocating air motors to turn over the engine shaft. The fuel is admitted to the remaining cylinders which makes the engine to start under its own power.

Advantages:

1.  The design and layout of the plant are quite simple.

2.  It occupies less space as the number and size of the auxiliaries is small.

3.  It can be located at any place. 

4.  It can be started quickly and can pick up load in a short time.

5.  There are no standby losses.

6.  It requires less quantity of water for cooling.

7.  The overall cost is much less than that of steam power station of the same capacity.

8.  The thermal efficiency of the plant is higher than that of a steam power station.

Disadvantages:

1.  The plant has high running charges as the fuel (i.e., diesel) used is costly.

2.  The plant does not work satisfactorily under overload conditions for a longer period.

3.  The plant can only generate small power.

4.  The cost of lubrication is generally high.

5.  The maintenance charges are generally high.

Nuclear Power Plant or Nuclear Power Station

Nuclear Power Plant or Nuclear Power Station 

Nuclear Power Station:-

A generating station in which nuclear energy is converted into electrical energy is known as a nuclear power station.

Nuclear Reactor:

➢ In a nuclear reactor, the energy is released because of nuclear fission. This energy is absorbed by the hot coolant. The heat exchanger is used for converting water into steam using the coolant and this steam is sent to the turbine for power generation.

Moderator:

➢ It is used to reduce speed of the neutron. The material used as a moderator has low molecular weight. In case of enriched plants, ordinary water is used as a moderator. In case of natural uranium plant, the material graphite, heavy and light water, Beryllium and its oxide is used.

Control Rod:

➢ It is used for absorbing acess neutrons produced during chain reaction. Materials cadmium Boron and Hafnium are used as control rod.

Coolant:

➢ It transfers heat produced inside the reactor to the heat exchanger for conversion of Water to steam.

➢ Materials: Water, Heavy Water, Liquid Sodium, Helium, Co2 or Sodium- potassium alloy is liquid form.

Heat Exchanger:

➢ The coolant gives up heat to the heat exchanger which is utilized in raising the steam. After giving up heat, the coolant is again fed to the reactor.

Note:

1. Complete fission of 1kg of Nuclear Fuel (U235)can produce as much energy as can be

produced by the burning of 275 tons (2,75,000kg) of high grade coal.

2. Nuclear Fuel

➢ Enriched Uranium – U92238– 99.3% of fuel

➢ Natural Uranium – U92235– 0.07% of fuel

➢ Thorium – Th90232

Selection of site for Nuclear Power Station:

1. Availability of Water

2. Disposal of Water

3. Distance from Populated area

4. Transportation Facilities

Advantages

(i) The amount of fuel required is quite small. Therefore, there is a considerable saving in the cost of fuel transportation.

(ii) A nuclear power plant requires less space as compared to any other type of the same size.

(iii) It has low running charges as a small amount of fuel is used for producing bulk electrical energy.

(iv) This type of plant is very economical for producing bulk electric power.

(v) It can be located near the load centres because it does not require large quantities of water and need not be near coal mines. Therefore, the cost of primary distribution is reduced.

(vi) There are large deposits of nuclear fuels available all over the world. Therefore, such plants can ensure continued supply of electrical energy for thousands of years.

(vii) It ensures reliability of operation.

Disadvantages

(i) The fuel used is expensive and is difficult to recover.

(ii) The capital cost on a nuclear plant is very high as compared to other types of plants.

(iii) The erection and commissioning of the plant requires greater technical know-how.

(iv) The fission by-products are generally radioactive and may cause a dangerous amount of

radioactive pollution

(v) Maintenance charges are high due to lack of standardization. Moreover, high salaries of

specially trained personnel employed to handle the plant further raise the cost.

(vi) Nuclear power plants are not well suited for varying loads as the reactor does not respond to the load fluctuations efficiently.

(vii) The disposal of the by-products, which are radioactive, is a big problem. They have either to be disposed off in a deep trench or in a sea away from sea-shore.

Hydro-electric Power Plant or Hydro-electric Power Station

Hydro-electric Power Plant or (Hydro-electric Power Station)

Hydro-electric Power Station:-

A generating station which utilizes the potential energy of water at a high level for the generation of

electrical energy is known as a hydroelectric power station.

Principle:-

➢A Dam is a barrier which stores water and creates water head. The type and arrangement

depends upon the topography of the site, foundation conditions, local materials and transportation available, occurrence of earthquake and other hazards.

➢ A spillway is used to protect the dam from the floods in the water level is beyond capacity of the

dam it is used as safety valve to the dam.

➢ A surge tank is used in medium and large head plants with closed conduit type penstocks. It is used to protect penstocks form water hammering effect.

➢ Surge Tank is also used to supply additional water in case of sudden load demands.

➢ Penstocks are open or closed conduit which carry water from reservoir to the turbines.

➢ Concrete penstocks are suitable for low heads (<30m) as greater pressure causes rapid

deterioration of concrete.

➢ The steel penstocks can be designed for any head the thickness of the penstock, increase with the

head or working pressure.

➢ The area of rainwater collected for storing of water in the dam is called catchment area.

➢ The amount of percentage of water which is converted into streams/river after evaporation

and filtration by land is called yield factor.

Types of Turbine:

(a) Based on Water Head (H) :-

Head	Turbine
< 15m	Kaplan (or) Movable Vane Propeller
15 to 70m	Kaplan (or) Francis
70 to 500 m	Francis (or) Pelton
> 500 m	Impulse (or) Pelton

(b) Based on Water in Penstocks:

Turbine	Water in Penstock
Pelton	8m/sec
Francis	4m/sec
Kaplan	2m/sec

(c) Based on speed (RPM):

Turbine	Speed (RPM)
Pelton	13 – 70
Francis	70 – 400
Kaplan	400 – 1000

Choice of site for Hydro-electric Power Station

1. Availability of Water

2. Storage of Water

3. Cost and type of land

4. Transportation Facilities

Advantages

(i) It requires no fuel as water is used for the generation of electrical energy.

(ii) It is quite neat and clean as no smoke or ash is produced.

(iii) It requires very small running charges because water is the source of energy which is available free of cost.

(iv) It is comparatively simple in construction and requires less maintenance.

(v) It does not require a long starting time like a steam power station. In fact, such plants can be put into service instantly.

(vi) It is robust and has a longer life.

(vii) Such plants serve many purposes. In addition to the generation of electrical energy, they also help in irrigation and controlling floods.

(viii) Although such plants require the attention of highly skilled persons at the time of construction, yet for operation, a few experienced persons may do the job well.

Disadvantages

(i) It involves high capital cost due to construction of dam.

(ii) There is uncertainty about the availability of huge amount of water due to dependence on

weather conditions.

(iii) Skilled and experienced hands are required to build the plant.

(iv) It requires high cost of transmission lines as the plant is located in hilly areas which are quite

away from the consumers

Thermal Power Plant or Thermal Power Generation(Steam Power Station)

Thermal Power Plants 

Electrical Power Generation Station

Electrical Power Generation:-The conversion of energy available in different forms in nature into electric energy is called a generation of electrical energy.

Electrical Power Generation Plant 

Conventional                                                   Non-Conventional

1.Thermal Power Plant                                         1.Hydro-electric Power Plant

2.Nuclear Power Plant                                          2.Wind Power Plant

3.Gas Power Plant                                                 3.Solar Power Plant

4.Diesel Power Plant                                             4.Geothermal Power Plant

                                                                               5.Tidal Power Plant

Steam Power Station (Thermal Station):-

A generating station which converts heat energy of coal combustion into electrical energy is known as a steam power station.

Principle:

➢ Thermal plants work on the principle of Rankine cycle, in which, steam is reheated for improvement of thermal efficiency.

➢  From the coal storage plant, coal is delivered to the coal handling plant where it is pulverized (i.e.crushed into small pieces) in order to increase its surface exposure, thus promoting rapid combustion without using large quantity of air.

➢ The coal is burnt in the boiler and the ash product after the complete combustion of coal is removed to the ash handling plant and then delivered to the ash storage plant for disposal.

➢De-mineralized (DM) water is used to protect the boiler tubes from corrosion effect.

➢ Deaerator is used for removing air bubbles inside the water for protecting the boiler tubes.

➢ BFP (Boiler Feed Pump) is the highest pressure generating pump in thermal plant. It generates pressure upto 165kg and consume power upto 4MW.

➢ The steam produced in the boiler is wet and is passed through a super heater where it is dried and super heated (i.e. steam temperature increased above that of boiling point of water) by the flue gases on their way to chimney, which increases overall efficiency and prevent turbine blades from corrosion.

➢ Economizer is used to absorb heat from flue gas to increase the feed water temperature, which improves thermal efficiency.

➢ An Air preheater (APH) is used for increasing the temp. of the air supplied for coal burning by deriving heat from flue gas.

➢ Turbo separator are used inside the drum for separating water and steam.

➢ A condenser is a device which condens the steam at the exhaust of turbine. It serves two important functions. Firstly, it creates a very low pressure at the exhaust of turbine, thus permitting expansion of the steam in the prime mover to a very low pressure.

➢ This helps in converting heat energy of steam into mechanical energy in the prime mover.

➢ Vacuum pump and steam ejector are used in a condenser for absorbing steam from the turbine to the condenser.

➢ Most of the energy is wasted for conversion of steam into water inside the condenser so that thermal efficiency is between 35-40%

➢ Using cooling Tower, circulating water temperature is reduced.

➢ Primary Air (PA) fan is used to send coal powder from the coal mill to the boiler.

➢ Forced Draught (FD) fan is used to supply oxygen to the boiler for proper combustion.

➢ Induced Draught (ID) Fan is used to take flue gases from the boiler and released to the atmosphere through chimney.

➢ Electrostatic Precipitator (ESP) is used to collect ash particles from the flue gas. It works on the principal of electrostatic field.

➢ Natural water usually has pH value between 6.5 and 7.5 pH.

➢ A common recommendation is to maintain boiler water is 8.5 pH.

Choice of site for Steam / Thermal Power Plant:

1. Supply of fuel

2. Availability of Water

3. Transpiration facility

4. Coat and type of lands

5. Nearness to load center

6. Distance from populated area

Efficiency of Thermal Power Plant:

The overall efficiency of steam power station is quite low (about 35-40%) due mainly to two reasons

1. A huge amount of heat is lost in the condenser and

2. Heat losses occur at various stages of the plant

1. Thermal Efficiency:

➢ The ratio of heat equivalent to the mechanical energy transmitted to the turbine shaft to the heat of combustion of coal is known as thermal efficiency of thermal power plant.

Note:-

➢ More than 50% of total heat of combustion is lost in the condenser. The other/remaining heat losses occur in flue gases, radiation, ash etc.

2. Overall Efficiency:

➢ The ratio of heat equipment of electrical output to the heat of combustion of coal is known as overall efficiency of thermal power plant.

➢ Overall Efficiency = Thermal Efficiency X Electrical Efficiency

Advantages

(i) The fuel (i.e., coal) used is quite cheap.

(ii) Less initial cost as compared to other generating stations.

(iii) It can be installed at any place irrespective of the existence of coal. The coal can be transported to the site of the plant by rail or road.

(iv) It requires less space as compared to the hydroelectric power station.

(v) The cost of generation is lesser than that of the diesel power station.

Disadvantages

(i) It pollutes the atmosphere due to the production of large amount of smoke and fumes.

(ii) It is costlier in running cost as compared to hydroelectric plant.