Liquefied natural gas arrives at import terminals at extremely low temperatures, carrying a large reserve of cold energy that is usually released into seawater or the surrounding air during regasification. A new study shows that carefully designed power cycles could convert more of this overlooked resource into useful electricity.
Researchers systematically evaluated working fluids and advanced cycle configurations for recovering cold energy from liquefied natural gas, or LNG. Their results identify a two-stage Rankine cycle with reheating as the most effective design, producing a net power output of 9.2 megawatts at an LNG processing capacity of 216 tonnes per hour.
"LNG regasification terminals handle an enormous temperature difference, but much of that thermodynamic potential is currently lost," said corresponding author Shing-hon Wong. "Our study shows that selecting the right working fluids is important, but choosing the right cycle architecture can deliver an even greater improvement in power generation."
LNG is stored and transported at temperatures near minus 162 degrees Celsius. Although liquefaction requires substantial energy, approximately 830 kilojoules of cold energy can remain stored in each kilogram of LNG. When LNG is warmed and converted back into gas, this energy is commonly discharged with little or no recovery.
To identify better recovery strategies, the researchers developed and optimized two-stage power systems operating between cryogenic LNG temperatures and ambient conditions. The analysis screened 30 combinations of single working fluids and 49 combinations involving binary mixtures. It also compared four advanced configurations incorporating reheating, regeneration and Kalina cycle integration.
The systems were modeled using Aspen HYSYS, while a genetic algorithm implemented in Python searched a broad range of pressures, temperatures and fluid compositions to maximize net power production.
Among single-fluid combinations, hexafluoroethane, known as R116, performed best in the upper cycle, while ethane, or R170, was the strongest partner in the lower cycle. Together, they generated 7.5 megawatts of net power with a thermal efficiency of 24.1 percent.
Binary mixtures provided slightly higher output and more consistent performance across different fluid pairings. The best conventional two-stage system combined R116 in the upper cycle with an optimized R1150 and R23 mixture in the lower cycle, generating 7.7 megawatts, about 2.6 percent more than the best single-fluid system.
The largest improvement, however, came from reheating. In the optimal design, R116 operated in the upper cycle and an R1150 and R170 mixture operated in the lower cycle. The working fluid underwent expansion in two turbine stages, with additional heating between them. This arrangement enabled higher operating pressure, increased the average temperature of heat addition and preserved sufficient heat for the lower cycle.
The resulting 9.2-megawatt output represented improvements of approximately 22 percent over the best single-fluid case and 19 percent over the best mixed-fluid baseline.
By contrast, regeneration and Kalina cycle integration offered little or no improvement. In the two-stage system, regeneration reduced the heat transferred from the upper cycle to the lower cycle, offsetting the benefit of internal heat recovery.
"The findings highlight the importance of optimizing the complete system rather than improving one component in isolation," Wong said. "For practical LNG terminals, reheating appears to offer the clearest pathway toward higher cold energy recovery and additional low-carbon electricity generation."
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Journal reference: Wong SH, Xiao G, Zhang D. 2026. Enhancements and optimization of LNG cold energy recovery via advanced binary working fluid power cycle systems. Energy & Environment Nexus 2: e014 doi: 10.48130/een-0026-0007
https://www.maxapress.com/article/doi/10.48130/een-0026-0007
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About Energy & Environment Nexus :
Energy & Environment Nexus (e-ISSN 3070-0582) is an open-access journal publishing high-quality research on the interplay between energy systems and environmental sustainability, including renewable energy, carbon mitigation, and green technologies.
