Page 58 - Sustainable On-Site CHP Systems Design, Construction, and Operations

Power Equipment and Systems 37

Typical fuel-to-power equipment includes

• Internal combustion (IC) reciprocating engine generators
• Spark ignition
• Diesel cycle
• Combustion turbine generators (CTGs)
• Aircraft derived (aero-derivative) turbines
• Stationary/industrial turbines
• Microturbines
• Fuel cells

Thermal-to-power prime mover equipment includes processes where heat is deve-
loped by a source outside the prime mover. This includes both, boiler-produced steam
and waste heat derived from another process. It also includes processes where waste
heat is generated by one of the primary prime movers discussed above. When the steam
is derived from one of the prime mover processes listed above and is used to generate
additional power, the process, as mentioned, is called a combined cycle.
Typical thermal-to-power equipment includes

• Steam turbines
• Steam-driven reciprocating engines
• Stirling engines (external combustion engines)
• Organic Rankine cycles

Steam-driven reciprocating engines and Stirling engines are not commonly used
today, although steam reciprocating engines were quite common in the past, and Stir-
ling engines have recently been coupled with solar mirrors to provide the highest solar-
to-electric conversion efficiency yet achieved. Sterling engines are classified as external
combustion engines, where heat on the outside of a cylinder drives a piston and the gas
in the cylinder is expanded and then contracted as the cylinder is cooled. Fuel burned
on the outside or waste heat from some process heats the gases inside the cylinder to
drive the piston. Cooling the cylinder drives the piston back to its original position.
Organic Rankine cycles are typical Rankine cycles, except that they use an organic
working fluid instead of the standard steam/condensate and can operate with rela-
tively low temperature heat sources. Both types of thermal-to-power prime mover sys-
tems are relatively small in their number of CHP installations, and their power output
capacity, typically, is also small, therefore, Stirling engines, steam-driven reciprocating
engines, and organic Rankine cycles are not discussed further in this chapter.
In addition to the prime movers, a CHP plant typically requires many other compo-
nents/systems to make a complete CHP plant. The actual requirements depend on the
CHP plant itself, but the following are common to many CHP applications:

• Fuel supply system(s)
• Gas compressors
• Combustion air