Heating and Cooling Energy - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 221

than 10-MW, is above 30%, with overall efficiencies reaching 80% when
the cogenerated heat is used.
They generate relatively small amounts of nitrogen oxides other pol-
lutants. Several companies have developed very low NO x units. Their
high temperature exhaust may be used to make process steam and oper-
ate steam-driven chillers. A 1-MW unit can cost $1,800/kW installed while
a 5-MW unit may cost $1,000/kW installed.
In these systems, the turbine generator is about 1/3 of the total cost
with the other costs including the heat recovery steam generator, electri-
cal equipment, interconnection to the grid, labor, project management and
financing.
Reciprocating engines are another mature product used for CHP.
These stationary engines may be spark ignition gasoline engines or com-
pression ignition diesel engines. Capacities range from a few kilowatts to
over 5-MW.
Natural gas or alcohol fuels may also be used in the spark ignition
engines. Electrical efficiency ranges from 30% for the smaller units to more
than 40% for the larger ones. Reuse of the waste heat can provide over-
all efficiencies to 80%. The high-temperature exhaust of 700°F-1,000°F can
be used for industrial processes or an absorption chiller. About 800-MW
of stationary reciprocating engine generation is installed in the United
States.
Development has been closely tied to automobiles and in the last
few decades increases in electric efficiency and power density have been
dramatic as well as emission reduction. Some units can even meet Cali-
fornia air quality standards when running on natural gas. A 100-kW re-
ciprocating engine generating system may cost $1,500-kW installed, while
an 800-kW unit can cost $1,000-kW. The engine is about one fourth of the
total price with the rest going to the heat recovery system, interconnect/
electrical system, labor, materials, project management, construction and
engineering.
Steam turbines are an even older technology, providing power for
over 100 years. Most utility power is produced by steam turbines. The
steam turbine generator depends on a separate heat source for steam, of-
ten some type of boiler, which may run on a variety of fuels, such as coal,
natural gas, petroleum, uranium, wood and waste products including
wood chips or agricultural by-products.
Steam turbine generators range from 50-kW to hundreds of mega-
watts. By 2000, almost 20,000-MW of boiler and steam turbines were used