MIL-HDBK-1003/7
Table 34
Typical Performance of Cogeneration Systems Power to Heat Ratio
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*
*
Backpressure
Gas
1Combined
Diesel
*
*
Turb. Gen.
Turbine
Cycle
Gen.
*
*
* kWh/million Btu steam
400 to 1 *
50 to 1
200 to 1
250 to 1
*
* Btu power/Btu steam
0.171
0.683
0.853
1.365
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Gas turbine, heat recovery steam generator, and backpressure turbine generator.
1
21.6.4
Economic Variables. The application of cogeneration to a facility is site
specific insofar as economic evaluation is concerned. The evaluation will require
complete information for the facility concerning electricity and steam (or heat) usage
and load demand on an hourly basis throughout a typical year. The annual costs of fuel
and purchased electricity must be determined for each alternate system to be considered,
including an alternate without cogeneration. Also, for each alternate system
considered, a determination must be made of total capital investment cost, annual
operating costs, and annual maintenance labor, parts, and material costs. Depending on
the type of evaluation used, periodic replacement costs and salvage value may need to be
determined.
Economic Evaluation. The economic evaluation of the various alternate systems
21.6.5
is best done on a life cycle cost basis and by a present worth type analysis. For a
complete description of life cycle costing, modes of analysis, methods and procedures
for analysis, and choice of most economical alternate, refer to NAVFAC P-442 or National
Bureau of Standards Handbook 135, Life-Cycle Cost Manual for the Federal Energy
Management Programs.
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