What are the advantages and disadvantages of a diesel power plant?

The diesel engine is also known as a compression ignition engine to distinguish it from gasoline or spark ignition. Thermodynamically the diesel engine cycle is more efficient than gasoline (Otto cycle) because efficiency increases with compression ratio. Gasoline would ignite at compression ratios over 10 because of the heat generated during compression of the air and gasoline vapor. Diesel fuel is injected into the cylinder at much higher pressures than allowable in gasoline engines.
Diesel power plants are efficient but the fuel is to expensive. Coal and natural gas are much cheaper fuels.
Diesel fuel is more stable than gasoline (does not form a sludge easily like gasoline does) and therefore the engine and fuel can be left on standby for long periods. This makes diesel a good choice for emergency back up such as in fire protection systems and standby generators.

Small scale diesel generators have lower capital cost than a boiler and steam turbine, which would be orders of magnitude larger in size. Also, steam power plants need a staff of operators.