Thermoacoustic Stirling power generation from LNG cold energy and low-temperature waste heat

Recovering cold energy generated in the regasification process of liquefied natural gas (LNG) can help to improve the energy efficiency of LNG power generation systems, meanwhile, abundant low-grade waste heat can also be exploited from the exhaust gas of gas turbines. This study proposes to apply the thermoacoustic Stirling electric generator to recover LNG cold energy and waste heat simultaneously. A pair of linear alternators is directly coupled with the thermoacoustic loop by replacing the long and bulky resonator completely. Numerical simulation is conducted on the basis of the thermoacoustic theory to characterize and optimize the operations of the system. The effects of the back volumes of linear alternators, feedback tube length and regenerator length on the output performances are investigated. The distributions of key parameters, including pressure, volume flow rate, phase difference, acoustic power and exergy flow, are further studied. One design of the thermoacoustic Stirling electric generator operated with 4 MPa helium gas is capable of generating 2.3 kW electric power with the highest exergy efficiency of 0.253 when the cold and hot ends are maintained at 110 K and 500 K. Performances can be further improved if the conversion efficiency of the linear alternators is further increased. - Highlights: • Thermoacoustic Stirling generator for LNG cold energy and waste heat is proposed. • Linear alternators are directly coupled with the thermoacoustic loop. • Back volume of linear alternators and feedback tube length are critical. • Electric power of 2.3 kW with a highest exergy efficiency of 0.253 is achieved. • Exergy efficiency of acoustic power is around 0.4.