In a diesel engine power plant, a combination of diesel engine (act as prime-mover) and alternator generates electricity. In the diesel engine, fuel burns and the gaseous product of the combustion process generates mechanical energy. The alternator converts this mechanical energy into electrical energy and generates electricity. There are various parts in the diesel power plant, some of the significant components of the diesel power plant, for example, diesel engine, fuse system, compressor, etc. are explained here with the application and advantages of the diesel power plant.
How to Select Site for Power Plant
- Availability of land: We need land to set-up the power plant. Land should be available at a reasonable price. If the land cost is high then capital post will increase that result in increased electricity cost.
- Availability of water: Enough amount of water should be available near the plant cooling system.
- Availability of fuel: Fuel should be available nearby the plant location. Because of this the transportation and operating cost will reduce.
- Transportation facility: Transportation facility like road/train services should be available near the plant. Otherwise, it will be difficult to transport fuel and other materials and components of a diesel power plant to the plant site.
- Distance between the power plant and load: Diesel engine power plant should be near to load so that energy dissipation will be less.
- Neighbourhood of power plant: Power plant should not be near the populated area, because of the noise and the polluted exhaust from the plant.
Layout of Components of Diesel Power Plant
Diesel Engine
It is one of the most important components of a diesel power plant. There are two types of engines four-stroke engine and two-stroke engine:
- Four-Stroke Engine: It takes two cycles (two strokes in each cycle) to complete a full cycle of an engine operation. In backward cycle, suction/intake and compression take place while in the forward cycle expansion and exhaust takes place. In suction process cylinder takes the air, piston receding towards crank end of the cylinder. The piston moves towards the cover end of the cylinder till it reached an extreme position in compression. After that at the end of the compression step, fuel is injected in atomized form. This results in the ignition and increases the pressure of the gas in the cylinder. The increased pressure in the cylinder causes the piston to move backwards. After that, in exhaust piston again moves forward and expelled gaseous products of composition.
- Two-Stroke Engine: In the two-stroke engine, the operation of the engine gets completed in one cycle. In it, power and exhaust completed when the piston moves backwards in the forward cycle intake and compression takes place. The two-stroke engine developed more power at the same speed and cost less, while the four-stroke engine has higher efficiency, low fuel consumption and effective lubrication.
Ignition may be through compression or spark plug. The combustion starts by spontaneous ignition of fuel and air because of high temperature by compression of air while in spark it uses a spark plug to ignite the fuel-air mixture.
Fuel System
Fuel tanks are located outdoors in the plant. These bulk tanks stores fuel and small tanks/pumps deliver the oil from these tanks based on the requirement(daily or at suitable intervals). The function of the engine fuel admission system is to supply the correct amount of fuel to each cylinder in advance of working strokes at the proper time even with varying load conditions.
Air Intake System
Air is drawn from outside and delivered to the inlet through air filters which remove dust and other impurities. Filter type includes dry, oil bath, or electrostatic precipitation filtering. In cold intake air is heated by the energy of exhaust gases before injection.
Engine Cooling System
The cooling system includes cooling pumps, cooling towers, spray ponds, and water treatment. Its main purpose is to carry out the heat from the engine cylinder and maintain the temperature of cylinders within safe limits. The pump circulates water through the source pump and jacket to carry heat away. If the temperature of exiting cooling water is too high then lubrication oil burns, so the temperature of exiting water is around 70oC.
Engine Lubrication System
High pressure and small clearance require a good lubrication system. Lubrication not only lubricates moving parts but also removes heat from the cylinder and helps the piston ring seal gases. Good lubrication improves the life of the engine components and the efficiency of the system. The lubrication oil cost of a diesel plant is around 30% of the fuel cost.
Exhaust System
The function of the exhaust system is to discharge the engine exhaust to the atmosphere outside of the building. A good exhaust system should keep noise at a low level and exhaust well above the ground. An exhaust pipe is provided with a muffler to reduce pressure in the exhaust line which eliminates most of the noise.
Compression Air System
The compression air system mostly used compressed air from the air tank. It compresses the air at about 20 times atmospheric pressure and admitted it to a few engine cylinders, making them work like a reciprocating air motor to turn the engine shaft. A motor-driven compressor supplies air into the compressed air tank.
Alternator
Diesel engine alternator is generally salient pole construction type. The number of poles and capacity of the motor varies from 6 to 28 and 25 to 5000KVA at 0.8 pf lagging(power factor). It is directly coupled to the engine and is provided with an automatic voltage regulator. This automatic voltage regulator permits close voltage regulation and satisfactory parallel operation.
What are the Advantages of Diesel Power Plant
- Design and installation are simple and cheap.
- Quickly procured, installed and commissioned.
- Start and put on load quickly.
- Having good efficiency of about 45-50%.
- Less space for fuel storage.
- Free from ash handling problem
- Capital cost per KW of capacity is low.
- Locate very near to load.
What are the Disadvantages of Diesel Power Plant
- Used only in small size.
- High operating cost due to the high cost of fuel as compare to thermal power plant and gas turbine power plant.
- Its life is very short of about 5-7years.
- Suitable for small load capacity.
- Unlike hydroelectric Power Plants, diesel-engine power plants pollutes the environment.
- Because of high repair and maintenance cost, the electricity cost will increase.
Where to use Diesel Engine Power Plant
- Diesel engine power plant is suitable for a remote location.
- It can be used as a peak-load and stand-by plant.
- In steam power station it is used as starting auxiliaries.
- Due to the small size, it can be move from one place to another place and can be used as a mobile plant.
- Usages of diesel engine plant are very common during the construction of thermal and hydroelectric power plant.
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