Introduction of Diesel Power plant
The diesel power plants are installed where the supply of coal and water is not available in sufficient quantity or where power is to be generated in small quantity or where standby sets are required for continuity of supply such as in hospitals, telephone exchanges, etc.
These plants in the range of 2 to 50 MW capacity are used as central stations for small supply authorities and works.
There are basically two main types of diesel power plants combustion engines categorized by the type of fuel used: gasoline or diesel. The vast majority of those engines power automobiles, but they have been also used for ships, boats, agricultural processing machinery, and many other industrial applications.
During the last quarter of the twentieth-century abundant fossil fuel production and distribution made possible commercial application of diesel-powered electricity generation for several applications.
Definition of Diesel Electric Power Plant
A generating station in which a diesel engine is used as the prime mover for the generation of electrical energy is known as a diesel power plant. For generating electrical power, it is essential to rotate the rotor of an alternator by means of a prime mover.
The prime mover can be driven by different methods. Using a diesel engine as the prime mover is one of the popular methods of generating power. When the prime mover of the alternators is a diesel engine, the power station is called a diesel power station.
The mechanical power required for driving alternators comes from the combustion of diesel. As the diesel costs are high, this type of power station is not suitable for producing power on large scale in our country. But for small-scale production of electric power, and where, there are no other easily available alternatives of producing electric power, a diesel power station is used.
How Electrical Power Produce using Diesel Power Plant?
In a diesel power station, the 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 an alternator that converts mechanical energy into electrical energy.
As the generation cost is considerable due to the high price of diesel, therefore, such power stations are only used to produce small power.
Although steam power stations and hydroelectric plants are invariably used to generate bulk power at cheaper costs, yet diesel power stations are finding favors at places where the demand for power is less, sufficient quantity of coal and water is not available and the transportation facilities are inadequate.
These plants are also standby sets for continuity of supply to important points such as hospitals, radio stations, cinema houses, and telephone exchanges.
Selection of Site for a Diesel Power Station
- Near to Load Center: As far as possible the plant should be installed near to load center, to reduce transmission & distribution cost of electrical energy.
- Availability of Land: For erection of diesel power plant, land should be available near to load center at low cost.
- Availability of Water: The soft water is freely available for the purpose of cooling.
- Foundations: As we know that, the diesel engines or a machine produces vibrations. So, provide good foundation to erect the diesel engine.
- Fuel Transportation: The diesel plant is far away from fuel mines. So, to provide fuel to the plant arrange good transportation facility like road, rail etc.
- Local Conditions: For increasing the demand of power & future expansion space available.
- Noise Pollution: The plant should away from populated areas, because it produces noise.
Main Components of Diesel Electric Power Plant
The essential components of a diesel-electric power plant are as follow:
- Diesel Engine
- Engine Fuel Supply System
- Engine Air Intake System
- Engine Exhaust System
- Engine Cooling System
- Engine Lubrication System.
- Engine Starting System.
- AC or DC Generators
1. Diesel Engine
It is the main component used in diesel-electric power plants for developing mechanical power. This mechanical power we use to run the generator & produce electrical energy. For producing electrical energy, the diesel engine is mechanically coupled to a generator.
When the diesel fuel burning inside the engine, it starts to produce mechanical power. The combustion of diesel fuel produces increased temperature & pressure inside the engine. Due to this pressure gases are formed, this gas pushes the piston inside the diesel engine, and then mechanical power is produced. With the use of this mechanical power, the shaft of the diesel engine starts rotating.
2. Engine Fuel Supply System
It consists of Fuel Storage Tank, Fuel Filter or Strainer, Fuel Transfer Pump, Day Tank, Heaters & Connecting Pipes.
First of all with the help of transportation facilities available (road, rail, etc.) the diesel fuel is stored in a storage tank. Then this diesel fuel transfer today tank, the function of day tank is how much quantity of diesel required for 24 hours in the store.
If the day tank is full or overflow occurs, then excessive diesel is returned to the storage tank. The filter or strainer is used to purify diesel. With the help of a fuel transfer pump, the diesel is transfer to the day tank.
3. Engine Air-Intake System
This System includes air filters, air tank, compressor & connecting pipes. The air filters are used to supply fresh air to diesel engines for the purpose of combustion. The engine required fresh air because dust particles in the air entering into the engine will cause a disastrous effect to the valve, cylinder & pistons.
The compressor or Supercharger is used to increase the pressure of the air supplied to the engine. This will help to increase the output power.
4. Engine Exhaust System
These systems consist of silencers & connecting ducts. As the temperature of the exhaust gases is sufficiently high, it is used for heating the fuel oil or air supplied to the diesel engine. The exhaust gas is removed from the engine to the atmosphere by means of an exhaust system.
A silencer is normally used in this system to reduce the noise level of the engine.
5. Engine Cooling System
The Diesel Engine Cooling System Consist of coolant pumps, water cooling towers or spray pond, water treatment or filtration plant & Connecting Pipe Works. The heat produced due to internal combustion drives the engine. But some parts of this heat raise the temperature of different parts of the engine.
High temperatures may cause permanent damage to the machine. Hence, it is essential to maintain the overall temperature of the engine to a tolerable level. The cooling system of the diesel power station does exactly so.
The cooling system is required to carry heat from the diesel engine to keep its temperature within safe limits. The water pump circulates water to the cylinder of the diesel engine to carry away the heat. The cooling tower is used for the same water reused.
The cooling system requires a water source, water pump, and cooling towers. The pump circulates water through the cylinder and head jacket. The water takes away heat from the engine and it becomes hot. The hot water is cooled by cooling towers and is re-circulated for cooling.
The cooling system can be classified into two types:
- Open Cooling System: A Plant near the river may utilize the river water for cooling & discharging again the hot water into river. This type of cooling system is known as open cooling system.
- Closed Cooling System: The Cooling Water is circulated again & again and only water lost due to leakage, evaporation etc. is made up by taking make up water from supply source.
6. Engine Lubrication System
Engine lubrication system consists of lubricating oil pump, oil tanks, filters, coolers, purifiers & connecting pipes. This system provides lubricating oil to moving parts of the system to reduce the friction between the wear & tear of the engine parts.
This system minimizes the water of the rubbing surface of the engine. Here lubricating oil is stored in the main lubricating oil tank. This lubricating oil is drawn from the tank by means of an oil pump. Then the oil is passed through the oil filter for removing impurities.
From the filtering point, this clean lubricating oil is delivered to the different points of the machine where lubrication is required the oil cooler is provided in the system to keep the temperature of the lubricating oil as low as possible. It is then cooled through a heat exchanger by means of cold water and then it is fed to the engine.
7. Engine Starting System:
The function of the starting system is to start the engine from a standstill or cold conditions by supplying compressed air.
For starting a diesel engine, initial rotation of the engine shaft is required. Until the firing starts and the unit runs with its own power. For small DG sets, the initial rotation of the shaft is provided by handles but for the large diesel power stations. Compressed air is made for starting.
This system includes storage compressed air tank, self-starter, auxiliary engines & electrical motors (battery), etc.
1. Starting of Small Engine: Small sets or small capacities of diesel engines are started manually.
2. Starting with the help of Auxiliary Engine: When it is started by the auxiliary engine, the auxiliary engine is disengaged by the main engine & started by hand. When it is warmed up, it is geared with the main engine so that it will start to rotate. After that within, few seconds auxiliary engine disengaging.
3. Starting with the help of batteries: To start the electrical motor batteries are used, the motor is geared with a diesel engine, it will start rotating with the motor & will start in few seconds & as it picks up the speed the motor gets disengaged automatically. In some cases, the motor works as a generator, this will further help to charge the batteries.
4. Starting with the help of compressed air: A large capacity (above 75kW) capacity diesel engines are started with the help of compressed air. Diesel engines are started with the help of compressed air following the procedure adopted:
1. First up all open the compressed air valve, then starting lever operated.
2. First up all air should be cut off in the first combustion. Then open the ventilating valve. Start the engine after two or three revolutions
Maintenance of Diesel Electric Power Plant
At the time of diesel engine or diesel-electric power plant, the following points are considered during the maintenance period.
- To maintain the operating condition of diesel engine at every half hour.
- To maintain the correct record of the instrument reading in log sheet.
- To maintain the record of instrument temperature, pressure, electrical load, flow etc.
- To check the level of fuel oil periodically.
- Filtered the fuel and remove unwanted impurities.
- Clean the fuel tank at regular interval.
Advantages of Diesel Power Plant
- This is simple in design point of view.
- Required very small space.
- It can also be designed for portable use.
- It has quick starting facility; the small diesel generator set can be started within few seconds.
- It can also be stopped as when required stopping small size diesel power station, even easier than it’s starting
- As these machines can easily be started and stopped as when required, there may not be any standby loss in the system.
- Cooling is easy and required smaller quantity of water in this type power station.
- Initial cost is less than other types of power station.
- Thermal efficiency of diesel is quite higher than of coal.
- Small involvement is less than steam power station.
- It requires less operating staff.
- The overall cost is much less than that of steam power station of same capacity.
Disadvantages of Diesel Power Plant
- As we have already mentioned, the cost of diesel is very high compared to coal. This is the main reason for which a diesel power plant is not getting popularity over other means of generating power. In other words, the running cost of this plant is higher compared to steam and hydro power plants.
- The plant generally used to produce small power requirement.
- Cost of lubricants is high.
- Maintenance is quite complex and costs high.
- The plant doesn’t work satisfactorily under overload conditions for a longer period.
- The cost of lubrication is generally high.
- The maintenances charges are generally high
Applications of Diesel Power plant
- The diesel oil is used as a fuel in power generation.
- It produces AC as well as DC Voltages.
- It is used where small power is generation is requirement.
- In case of any emergency diesel engines are used.
- It is also used for peal load during small period of time.
- It is used to restart the boilers.
- It is used in remote places.
- It can be used in areas having low load factor.
Uses of Diesel Electric power plant
- Central Station
- Standby Plant
- Peak Load Plant
- Emergency Plant
- Mobile Plant
- Nursery Plant
- Supply Units for Cinemas, Hospitals etc