A reheated two-stage Rankine cycle configuration can significantly boost power generation from LNG cold energy recovery, according to a study published in Energy & Environment Nexus on 11 May 2026 by researchers at The University of Western Australia.
Methodology
The researchers developed a process simulation and optimization framework to evaluate LNG cold energy recovery under representative terminal conditions. The study used an LNG receiving capacity of 216 tonnes per hour.
A baseline two-stage Rankine cycle was constructed, consisting of an upper cycle heated by seawater and a lower cycle cooled by LNG. The two cycles were linked by an intermediate heat exchanger.
The team screened 30 single-fluid combinations and 49 binary-mixture combinations. Genetic algorithms coupled with Aspen HYSYS simulations were used to optimize cycle parameters for each configuration.
Findings
For single fluids, the combination of R116 (hexafluoroethane) in the upper cycle and R170 (ethane) in the lower cycle generated 7.5 megawatts (MW) of net power with 24.1% thermal efficiency.
The best binary-mixture baseline configuration produced 7.7 MW, marginally higher than the single-fluid result.
Among four advanced configurations tested—Rankine-regeneration, Rankine-reheating, Kalina-regeneration, and Kalina-reheating—only the reheating configuration provided a significant performance improvement. The optimal Rankine-reheating configuration yielded 9.2 MW of net power, a 22% improvement over the optimal single-fluid design. This configuration used R116 in the upper cycle and a binary mixture of R1150 and R170 in the lower cycle.
Regeneration and Kalina-based configurations offered little or no performance benefit.
Conclusions
The study indicates that the efficiency of LNG cold energy recovery depends on both working fluid selection and cycle architecture. The greatest performance gain was achieved through reheating, which enhanced power production in both cycles.
The findings suggest that reheated two-stage Rankine systems may represent a technically feasible strategy for LNG terminals to recover cold energy that is otherwise lost during regasification.
Funding
The first author (Shing-hon Wong) received a PhD stipend scholarship from the Future Energy Exports CRC. Partial support was provided by the Australian Research Council under Discovery Projects DP210103766 and DP220100116.