| dc.description.abstract | Cogeneration is a highly efficient approach to generating electricity and process heat
from the same fuel source. It is an approach of utilizing waste energy products for a
useful purpose that significantly improves the optimal provision of the different grades
of energy from high-quality, high-grade electricity or power to low quality and low-grade
heat. As a result, combined heat and power can be applied to various situations using
various technologies.
In the present work, performance of two gas turbine cogeneration systems is analyzed
using the first and second laws of thermodynamics. A basic gas turbine cogeneration
system and a steam injection gas turbine cogeneration system are investigated. In the
analysis the system components, compressor, combustion chamber, turbine and heat
recovery steam generator are modeled. The CO2 emissions of both systems are also
evaluated. In this investigation the decrease in CO2 emissions was found in the steam
injected gas turbine cogeneration system as compared to the basic gas turbine
cogeneration system.
In the parametric study the influence of pressure ratio and turbine inlet temperature on
the performance characteristics of the systems such as specific work, energy and exergy
efficiencies are investigated. In the efficiency calculations all the three forms of outputs:
power, heat and cogeneration are considered. Thus power generation, heat generation
and cogeneration efficiencies are estimated. The carbon dioxide emissions are
estimated for both systems. In addition, the effect of pressure ratio and turbine inlet
temperature on the CO2 emissions is studied. The results show that pressure ratio and
turbine inlet temperature are the key operating variables to optimize the performance
of the cogeneration systems.
The second law analysis revealed that the maximum exergy destruction occurs in the
combustion chamber. In this analysis, the chemical and physical component of the
exergy is considered.
The role of specific heat as the function of temperature in estimating the performance
of cogeneration is also investigated and the performance results are compared with the
results assuming constant specific heat. The results with specific heat as the function of
temperature are more realistic and accurate compared to the actual performance of the
cogeneration systems.
The analysis and the results are useful for optimizing the operating parameters of the
gas turbine cogeneration systems and thereby enhancing the system performance. The
study is also useful for choosing appropriate cogeneration system for a specific
application. | en |
