Linear alternator

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A linear alternator is an electromechanical type of alternator that is essentially a linear motor used as an electrical generator.

Contents

An alternator generates alternating current (AC) electricity. It converts mechanical energy into electrical energy, unlike a motor, which converts electrical energy into mechanical energy. Although similar to other electric generators, an alternator typically uses rotary motion, while a linear alternator uses motion in a straight line, operating via electromagnetic induction. [1] Moving-magnet linear alternators power thermoacoustic converters. [2]

History

In 2016 NASA introduced a double-fed induction linear alternator, which operates at 950°C for extreme environments such as aircraft systems and downhole drilling, achieving 25% greater efficiency than conventional models. [3] The California Energy Commission funded a high-efficiency, ultra-low-emissions linear generator demonstration project in 2024 to support renewables with fuel-flexible dispatchable power. [4] In 2025, researchers developed and validated a tubular permanent magnet linear alternator (PMLA) for free-piston engine applications. [5] As of 2025, Hyliion's KARNO system integrates a sealed, 3D-printed linear heat engine with an alternator for modular prime power in data centers, defense, and microgrids.

Theory

A linear alternator converts back-and-forth motion directly into electricity, eliminating the need for a crank or linkage to transform reciprocating motion into rotary motion for a generator. [6]

Applications

A shake flashlight uses a simple linear alternator. Shaking the device moves a permanent magnet through a coil, inducing an electric current via electromagnetic induction. This current charges a capacitor, storing energy to power a light-emitting diode until discharged. Further shaking recharges the capacitor. Other devices employing linear alternators include the free-piston linear generator, an internal combustion engine, and the free-piston Stirling engine, an external combustion engine. NASA’s Glenn Research Center developed a lightweight, double-fed induction linear alternator. [7]

A linear heat engine integrated with an alternator can provide modular prime power in data centers, defense, and microgrids.

Other devices that use linear alternators to generate electricity include the free-piston linear generator, an internal combustion engine, and the free-piston Stirling engine, an external combustion engine.[ citation needed ]

References

  1. ↑ Fitzgerald, A. E. (2003). Electrical Machines. McGraw-Hill. ISBN   978-0-07-366009-7.
  2. ↑ Abdelwahed, Ay; Ibrahim, Ah (2024-10-17). "PERFORMANCE INDICATORS OF LINEAR ALTERNATORS AT DIFFERENT ELECTRICAL LOADS UNDER THERMO-ACOUSTIC-POWER-CONVERSION CONDITIONS" . 24th International Conference on Sound and Vibration 2017, London Calling. Institute of Acoustics. doi:10.25144/23803 . Retrieved 2025-06-01.
  3. ↑ "Double-Fed Induction Linear Alternator | T2 Portal". technology.nasa.gov. Retrieved 2025-10-02.
  4. ↑ Commission, California Energy (May 6, 2024). "High-efficiency and Ultra-low Emissions Linear Generator Demonstration Project in Southern California". www.energy.ca.gov. Retrieved 2025-10-02.
  5. ↑ Famouri, Parviz; Subramanian, Jayaram; Mahmudzadeh-Ghomi, Fereshteh; Bade, Mehar; Musho, Terence; Clark, Nigel (2025-07-25). "Development and Experimental Validation of a Tubular Permanent Magnet Linear Alternator for Free-Piston Engine Applications". Machines. 13 (8): 651. doi: 10.3390/machines13080651 . ISSN   2075-1702.
  6. ↑ Nasar, S. A. (1998). Linear Electric Machines. Wiley. ISBN   978-0-47-118209-2.
  7. ↑ "Double-Fed Induction Linear Alternator". T2 Portal. NASA. Retrieved 2025-06-01.
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