Thermoacoustic engines

Thermoacoustic engines are a promising technology for the conversion of thermal energy into acoustic power, or vice versa, by relying on the so-called thermoacoustic effect. The interaction of acoustic waves with a stack of spaced plates with a temperature gradient along it leads to acoustic power production, or conversely a temperature gradient along the stack can be generated by imposing acoustic waves. This technology has attracted considerable attention in recent years owing to its noteworthy advantages including a lack of moving components, environmental friendliness due to the use of noble gases as a working fluid, and its low cost and high reliability. Although it is difficult to provide a technoeconomic comparison between this technology and alternatives, due to the lack of economic data the manufacturing costs of thermoacoustic devices can be lower than their counterparts. The onset temperature difference for such devices to start producing acoustic power can be as low as 30 K. The most efficient thermoacoustic devices have efficiencies approaching 40% of the Carnot limit, with the record currently standing at 49% of the Carnot efficiency at the available heat source temperature. These devices can be designed and produced over a wide range of sizes, for example, from small thermoacoustic coolers/heat pumps with lengths of a few cm for thermal management in microcircuits to large engines with lengths up to about 10 m for gas liquefaction and driving refrigerators. In this section, a history of thermoacoustic engines is provided, along with an explanation of the relevant fundamentals, theoretical and practical performance expectations, and the most recent developments, and practical proposed models by investigators are discussed.