Exergetic Performance of a Cogeneration Plant at Part Load operations

A cogeneration plant can run at off-design due to change of load demand or ambient conditions. The cogeneration
considered for this study is gas turbine based engine consists of variable stator vanes (VSVs) compressor that are re-staggered for loads
greater than 50% to maintain the gas turbine exhaust gas temperature at the set value. In order to evaluate the exergetic performance of
the cogeneration, exergy model of each cogeneration component is formulated. A 4.2 MW gas turbine based cogeneration plant is
analysed for a wide range of part load operations including the effect of VSVs modulation. For loads less than 50%, the major exergy
destruction contributors are the combustor and the loss with the stack gas. At full load, the exergy destructions in the combustor, turbine, heat recovery, compressor and the exergy loss with stack gas are 63.7, 14.1, 11.5, 5.7, and 4.9%, respectively. The corresponding firstand second law cogeneration efficiencies are 78.5 and 45%, respectively. For comparison purpose both the first and second law efficiencies of each component are represented together. This analysis would help to identify the equipment where the potential for performance improvement is high, and trends which may aid in the design of future plants