Exergy analysis in combined heat and power systems: A review.

• Exergy analysis in combined heat and power systems is reviewed and discussed. • The focus is on exergetic and thermodynamic indices in combined heat and power. • CHP of gas turbine, reciprocating engine, Rankine, fuel cell and ORC is considered. • The highest exergy destruction occurs in boilers and combustion chambers. • CHP fed by gas turbine, fuel cell and combustion engine has high exergy efficiency. The increasing demand for energy around the world makes it vital to use more suitable and efficient power generation systems. Combined heat and power (CHP) systems can produce power and heating with high possible efficiency. Also, in recent years, there has been a particular emphasis on exergy analysis for enhancing the efficiency of CHPs. In this work, the exergy analyses for different CHP systems with varying sources of power are reviewed. This paper includes six sections as gas turbines, reciprocating engines, Rankine cycles, fuel cells, organic Rankine cycles (ORC), and hybrid energy systems. Also, it has been tried to cover the modeling, experimental, analytical, and simulation studies. The results show that the exergy analysis of high-performance small-scale CHPs, for residential areas, are not adequate still. More research works are also recommended on hybrid CHPs with renewable power sources like fuel cells, solar energy, ground-source heat pumps, and biomass fuels. Besides, conducting economic studies is recommended, along with exergy analyses. Based on the survey, the gaps have been identified. Some recommendations for future developments are proposed based on the application of renewable sources in CHPs and improving their exergy efficiency. [ABSTRACT FROM AUTHOR]