Reheated two-stage Rankine cycles can increase power output from liquefied natural gas (LNG) regasification terminals by 22% compared to standard single-fluid designs. A study published May 11, 2026, in Energy & Environment Nexus by researchers at The University of Western Australia identified this configuration as the most efficient method for capturing cryogenic energy that is typically vented as waste during the regasification process.
How does LNG cold energy recovery work?
LNG is transported at approximately −162 °C, a temperature that contains significant thermal energy. According to the research team led by Shing-hon Wong, traditional terminals regasify this fuel by releasing that cold energy into ambient air or seawater, effectively losing it. By using a two-stage Rankine cycle, terminals can capture this exergy. The system uses an upper cycle heated by seawater and a lower cycle cooled by the cryogenic LNG, linked by an intermediate heat exchanger to minimize temperature mismatches across the system.
LNG must be warmed to reach pipeline specifications before it can be distributed. Most current facilities treat this cooling capacity as a byproduct rather than a power source, missing a major opportunity for onsite electricity generation.
What is the most efficient configuration for power generation?
The study found that a reheated two-stage Rankine cycle generates 9.2 MW of net power, outperforming other configurations. Researchers tested four advanced setups: Rankine-regeneration, Rankine-reheating, Kalina-regeneration, and Kalina-reheating. While binary mixtures of working fluids improved thermal matching, the integration of reheating provided the largest performance boost. This configuration allows for higher pressure expansion in the upper cycle while maintaining ideal exhaust temperatures for the lower cycle.
Which working fluids yield the highest output?
Matching the right working fluids to the cycle architecture is critical for maximizing output. The researchers screened 30 single-fluid and 49 binary-mixture combinations. For the upper cycle, hexafluoroethane (R116) consistently outperformed others due to its dry-fluid properties. For the lower cycle, ethane (R170) and ethylene (R1150) proved most effective. When combined in a reheated system, the R116 and R1150–R170 mixture delivered the study’s peak output of 9.2 MW.
| Configuration | Net Power Output |
|---|---|
| Optimal Single-Fluid | 7.5 MW |
| Best Mixed-Fluid Baseline | 7.7 MW |
| Reheated Two-Stage Rankine | 9.2 MW |
Why do these findings matter for LNG infrastructure?
This research provides a technically feasible pathway for existing LNG terminals to reduce operational energy losses. According to the study, the systematic optimization framework used by the team—which coupled genetic algorithms with Aspen HYSYS simulations—can be applied to various terminal conditions. By adopting these architectures, operators can convert wasted cold energy into cleaner, onsite power, potentially lowering the carbon footprint of the regasification process.
When upgrading terminal infrastructure, focus on cycle architecture over simple fluid substitution. The data shows that while mixed fluids help, structural changes like reheating offer nearly triple the performance gain of shifting to binary mixtures alone.
Frequently Asked Questions
What is the primary benefit of a two-stage Rankine cycle?
It reduces temperature mismatch between the extremely cold LNG and ambient heat sources, allowing for more efficient energy extraction compared to single-stage systems.
Does using binary mixtures always improve efficiency?
Not necessarily. While binary mixtures help match the non-isothermal warming curve of LNG, the study found the performance gain over optimized single-fluid systems was modest, at approximately 0.2 MW.
How was this research funded?
The study was supported by the Australian Research Council under the Discovery Projects Scheme and the Future Energy Exports CRC, according to the published paper.
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