engines are the most common and most technically mature of all DG technologies.
They are available from small sizes up to 7 MW.
engines use commonly available fuels such as gasoline, natural gas, and diesel
or internal combustion (IC), engine converts the energy contained in a fuel into
mechanical power. This mechanical power is used to turn a shaft in the engine.
A generator is attached to the IC engine to convert the rotational motion into
There are two
methods for igniting the fuel in an IC engine. In spark ignition (SI), a spark
is introduced into the cylinder (from a spark plug) at the end of the compression
stroke. Fast-burning fuels, like gasoline and natural gas, are commonly used in
SI engines. In compression ignition (CI), the fuel-air mixture spontaneously ignites
when the compression raises it to a high-enough temperature. CI works best with
slow-burning fuels, like diesel.
Engines are also classified as high-speed, medium-speed, or low-speed:
units are derived from automotive or truck engines and operate at 1200-3600 rpm.
These engines generate the most output per unit of displacement and have the lowest
capital costs but also have the poorest efficiency.
engines are derived from locomotive and small marine engines and operate at 275-1000
rpm, have higher capitalcosts, but also have greater efficiency.
units are derived from large ship propulsion engines and operate at 58-275 rpm.
Low-speed engines are designed to burn low-quality residual fuels and are practical
only if there is a large price differential between heavy oil and natural gas
and there are no environmental restrictions (not in U.S.)