Understanding Diesel Power Plants: Components and Operation
In a previous discussion on energy sources for electricity generation, various types were introduced. This column focuses specifically on the diesel power plant, a facility where a diesel internal combustion engine drives an electric generator. Known colloquially as "makina de krudo," an example is the 70-megawatt diesel power plant located in Ermita, Carbon, Cebu City, which uses bunker oil to operate.
The Two Main Components: Generator and Diesel Engine
A diesel power plant consists of two primary parts: the generator and the diesel engine. The generator is an electrical machine that converts mechanical energy into electrical energy based on Faraday's law of electromagnetic induction. It includes a rotor (the moving part) and a stator winding (the stationary part). Depending on the design, either the rotor provides electromagnetism while the stator produces electric current for loads like air conditioners and washing machines, or vice versa.
The diesel engine is an internal combustion engine that burns diesel fossil fuel inside cylinders. Fuel is injected in atomized form for efficient combustion under high temperatures. The resulting high pressure pushes pistons down, connected via connecting rods to the crankshaft, converting reciprocal motion into rotary motion to run the engine—similar to a 10-wheeler truck engine.
Systems Supporting Large Diesel Power Plants
In large setups, the diesel engine connects to the electric generator, rotating it to produce electricity. Several systems are involved on the engine side:
- Fuel System: This includes a large fuel tank, filters, and pumps. Fuel is drawn from the tank, filtered, stored in a "day tank," and then injected into the engine's fuel rail via injectors for atomized burning.
- Lubricating System: An oil pump circulates oil through filters and coolers to lubricate moving parts like crankshaft and camshaft bearings, ensuring smooth operation and preventing overheating.
- Cooling System: This maintains the engine at operating temperature by circulating cold water through an oil cooler and engine block to absorb heat. Hot water moves to a surge tank, then to a heat exchanger cooled by water from a cooling tower.
- Air System: Provides air for fuel combustion. In normally aspirated engines, air is drawn by atmospheric pressure; in turbo-charged engines, it's compressed. Air is compressed in cylinders, raising temperature to ignite injected diesel fuel, with exhaust gases expelled through valves and a catalytic converter.
Limitations and Practical Use
Diesel power plants are fundamental for driving electric generators but are typically used in small-scale applications. For instance, the Ermita plant in Cebu City produces only 70 megawatts, insufficient for a large city like Cebu. Thus, they serve best as backup sources during electricity shortages, rather than primary supply.
