Comparison of combined heat and power systems using an organic Rankine cycle and a low-temperature heat source

Abstract

Two combined heat and power (CHP) systems using an organic Rankine cycle with R134a and a source at 100°C are modeled. The vapor generator pressure which maximizes the specific (i.e. per unit mass flowrate of the heat source) net power output is determined for different values of the specific heat load and a characteristic temperature difference DT related to the temperature pinch of the heat exchangers. The optimal trade-offs between power and heat outputs are defined and explained for two CHP systems. The results show that both systems generate less mechanical power than the heat delivered to the heating load and that a higher fraction of the heat source is used as the heating load increases. The effects of the specific heat load and of DT on the total thermal conductance, the total exergy destruction and other variables are presented.