Effect of variable mechanical resistance on electrodynamic alternator efficiency

• Quantitative analysis on how the main parameters affect ηEA has been performed.
• The significant role of frictional losses on ηEA was demonstrated.
• The simulation confirms the analytical model and clarifies the gap impact on Zc.
• A new evaluation method of Rm, based on direct measurement of Zc has been proposed.
• The new method allows finding the system natural frequency before field operation.

The rapidly growing energy market constantly discovers new alternatives for generating environmentally-friendly electricity from sustainable energy sources. An externally-heated traveling wave thermo acoustic Stirling heat engine is a leading candidate, operating using a variety of viable heat sources. Although this engine holds great promise for a low-cost and maintenance-free solution, its current reported efficiency still inhibits its market penetration, probably owing to the friction introduced by the single moving element – the linear alternator.This research quantifies the main parameters affecting the complex thermal–acoustical–electrical system, clarifying the critical role of frictional losses. An analytical model has been developed, enabling examination of the influence of the critical physical parameters on the electro-acoustic conversion efficiency. A measurement method for precise determination of the mechanical friction constant has been developed, which enables measuring the friction at the engine’s working frequency. A direct measurement of an engine’s transfer impedance at room temperature enables to find the exact natural frequency before field operation, and calibrate external hardware accordingly. A detailed simulation using DeltaEC™ indicates that the tight seal gap between the moving piston and its cylinder has a significant impact on the system’s overall efficiency.