Linear alternator
Topic: Engineering
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File:Animation TDC 01 jeff.gif A linear alternator is an electromechanical type of alternator that is essentially a linear motor used as an electrical generator.
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
- ↑ Fitzgerald, A. E. (2003). Electrical Machines. McGraw-Hill. ISBN 978-0-07-366009-7.
- ↑ Abdelwahed, Ay; Ibrahim, Ah (2024-10-17). "24th International Conference on Sound and Vibration 2017, London Calling". Institute of Acoustics. doi:10.25144/23803.
- ↑ "Double-Fed Induction Linear Alternator | T2 Portal". https://technology.nasa.gov/patent/LEW-TOPS-114.
- ↑ Commission, California Energy (May 6, 2024). "High-efficiency and Ultra-low Emissions Linear Generator Demonstration Project in Southern California" (in en). https://www.energy.ca.gov/publications/2024/high-efficiency-and-ultra-low-emissions-linear-generator-demonstration-project.
- ↑ 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" (in en). Machines 13 (8): 651. doi:10.3390/machines13080651. ISSN 2075-1702.
- ↑ Nasar, S. A. (1998). Linear Electric Machines. Wiley. ISBN 978-0-47-118209-2.
- ↑ "Double-Fed Induction Linear Alternator". NASA. https://technology.nasa.gov/patent/LEW-TOPS-114.
External links
- (in English) Linear Alternators in Free Piston Engines
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