Thermodynamic Performance Analysis of Different Organic Rankine Cycles to Generate Power from Renewable Energy Resources

Organic Rankine cycles (ORCs), are promising technologies for generating power from low and medium grade heat resources such as geothermal fluids or synthetic gas from biomass gasification that have been received lots of attention during past twenty years. In this study we used thermodynamic evaluations to compare different organic fluids and different configuration of Rankine cycles. This article represents the first and second law analysis for organic Rankine cycles. Energy and exergy analysis of different configurations of ORCs including basic ORC, basic ORC with Internal Heat Exchanger (IHE), Regenerative ORC and Regenerative ORC with IHE for four dry organic fluids including R113, RC318, iso-pentane and n-hexane, were done by simulation of the systems using engineering equation solver (EES). Results indicated that cycles with internal heat exchangers show better performance by their thermal efficiencies. Moreover, Regenerative ORC with IHE shows the best performance compare with others. In addition, Exergy analysis showed that Regeneration and IHE decrease their exergy destruction rate. It was also specified that reduction in ambient temperature causes increment in both thermal and second law efficiencies. N-hexane was the best and RC138 was the worst working fluid by their thermal efficiencies among others.

Keywords:

Organic Rankine cycle , Exergy destruction , Regeneration , Renewable energy