Abstract
This paper is concerned with the study of low-cost, low-power thermoacoustic electricity generators. Based on target electrical output power values of 50 and 100 W, three standing wave prototypes (of both one-stage and two-stage prototypes) integrating a commercial loudspeaker with different coupling arrangements are conceived. Each stage consists of a square-pore stack sandwiched between hot and ambient heat exchangers. The working gas is air at atmospheric pressure. The prototypes’ efficiency in converting heat to electrical power is simulated by the specialized Design Environment for Low-Amplitude ThermoAcoustic Engines (DeltaEC) design tool based on the linear theory of thermoacoustics. At a given operation frequency, the optimal impedance matching between the loudspeaker and the engine is realized by adjusting both the engine parameters (stack location, stack length, heat exchangers length, loudspeaker location) and loudspeaker parameters (load resistance and box volume). Computations reveal that the one-stage engine and two-stage engine with loudspeakers coupled in side-branch mode are able to meet the target output power values with comparable thermal-to-electric efficiency (4.6%). The two-stage engine with the loudspeaker coupled in push–pull mode is unable to reach the desired power output and is characterized by low conversion efficiencies (2%) due to the poor loudspeaker–engine acoustic impedance matching.
Highlights
Thermoacoustic (TA) engines are energy conversion devices whose operation relies on the interaction between heat and sound near solid surfaces, a phenomenon identified as the “thermoacoustic effect” [1]
All the devices are standing wave-type engines operated with air at atmospheric pressure. This choice meets the goal of the present study of developing low-cost thermoacoustic electricity generator (TAEG)
The use of near atmospheric air, avoids the use of costly pressure vessels, eliminates the problems associated to the availability and cost of noble gases, and reduces the engines’ size due to the relatively low sound velocity
Summary
Thermoacoustic (TA) engines are energy conversion devices (prime movers, refrigerators and heat pumps) whose operation relies on the interaction between heat and sound near solid surfaces, a phenomenon identified as the “thermoacoustic effect” [1]. There is the complete absence of moving mechanical parts, which leads to engineering simplicity, reliability, longevity, and low maintenance costs They are intrinsically low cost, being constituted basically by a small number of standard components made of inexpensive and common materials, namely pressure vessels (acoustic networks/resonators), solid porous materials (stack/regenerators), heat exchangers (generally of the finned-tube or shell-and-tube type), and electroacoustic transducers. In any case, when a particular application requires low power levels, low cost for generated kWe , and not very high transduction efficiencies (~50%) the use of LSs could be justified Relevant examples of this new class of electricity generators integrating LSs in TA engines are the prototypes developed by. The prototypes’ behavior is simulated by standard codes based on the linear theory of thermoacoustics and their performance is compared
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