Recently, the TLC (trilateral power cycle) has attracted significant interest as it provides better matching
between the temperature profiles in the evaporator compared to conventional power cycles. This article
investigates the performance of this cycle and compares it with those for the ORC (organic Rankine cycle)
and the Kalina cycle, from the viewpoints of thermodynamics and thermoeconomics. A low-grade heat
source with a temperature of 120 C is considered for all the three systems. Parametric studies are
performed for the systems for several working fluids in the ORC and TLC. The systems are then optimized
for either maximum net output power or minimum product cost, using the EES (engineering equation
solver) software. The results for the TLC indicate that an increase in the expander inlet temperature leads
to an increase in net output power and a decrease in product cost for this power plant, whereas this is
not the case for the ORC system. It is found that, although the TLC can achieve a higher net output power
compared with the ORC and Kalina (KCS11 (Kalina cycle system 11)) systems, its product cost is greatly
affected by the expander isentropic efficiency. It is also revealed that using n-butane as the working fluid
can result in the lowest product cost in the ORC and the TLC. In addition, it is observed that, for both the
ORC and Kalina systems, the optimum operating condition for maximum net output power differs from
that for minimum product cost.