International Journal of
Physical Sciences

  • Abbreviation: Int. J. Phys. Sci.
  • Language: English
  • ISSN: 1992-1950
  • DOI: 10.5897/IJPS
  • Start Year: 2006
  • Published Articles: 2569

Full Length Research Paper

Efficiency assessment of a cogeneration system

Mustafa Bayrak* and Afsin Gungor
Department of Mechanical Engineering, Faculty of Engineering, Nigde University, 51245 Nigde, Turkey.
Email: [email protected]

  •  Accepted: 25 July 2011
  •  Published: 09 November 2011



For the sustainable usage of fossil fuels; thermodynamic analysis allows for improvements not necessarily attainable via energy methods, like increased efficiency, reduced fuel use and reduced environmental emissions. The first law is widely used in engineering practice and is the basis of the heat-balance method of analysis that is commonly used in energy systems performance analysis. However, the second law involves the reversibility or irreversibility of processes and is a very important aspect in the exergy method of energy systems analysis. From this point of view, in this study, thermodynamic analysis of an actual diesel engine based cogeneration plant with a total capacity of 11.52 MW electrical powers, 9 t/h of steam and 140 t/h of hot water is carried out by analyzing the components of the system separately. Both the performance characteristics of the internal combustion engine unit and the supporting components in the plant are evaluated. The present study provides important information regarding exergetic performance of the entire plant and its components through exergy destructions and exergy efficiencies. Identifying the main sites of exergy destruction shows the direction for potential improvements. The exergetic performance results show that the diesel engine is the major component contributing most to the plant’s total inefficiency, due to its inherent nature. The results show that 39.86% of the exergy entering the plant is converted to electrical power. The net steam production of the plant constitutes 8% of the total exergy input and the hot water production of the plant constitutes only 1.26% of the total exergy input. The remaining 50.88% of the exergy input is lost.


Key words: Thermodynamic analysis, exergy, optimization, cogeneration, sustainable.