The work presents a design methodology for a Surface Mounted Permanent Magnet Linear Alternator (SMPMLA) for use with an External Combustion-Free Piston Engine (EC-FPE). This topic has attracted research interest in the past (2-3) decades as an alternative to the conventional rotary engine in special applications, such as range extender for hybrid vehicles, combined heat power generation into the grid, generation on board spacecraft or use as a standalone power supply.

The work is focused on investigating the performance of a linear alternator for use with external combustionfree piston engine. This family of engine can be powered either from renewable sources, scavenging waste energy from other sources of heat, or bespoke combined heat and power plants. Finite element analysis optimisation techniques followed by development of a Matlab/Simulink model were used to investigate the effects of electrical machine inductance and the combined electromagnetic loading of the machine on the resulting force. Cogging force is showed to have the most effect on the resultant force fluctuation, whereas machine inductance has showed its effect at loads exceeding (76 %) of machine rating besides reshaping the resulting force profile. The model also accounts for machine loading and total efficiency variation over mechanical cycle. This enables the system designer to investigate the effect of actual machine model thrust force on the engine performance rather than assuming the electrical machine behaves as a simple damper.

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This paper describes the effect of alternative power conversion techniques on the performance of a Linear Alternator driven by a Joule Cycle-Free Piston Engine for electrical power generation. The design of a tubular Longitudinal Flux machine with axial magnets is performed using 2-D axisymmetric FEA modelling with transient solver to extract the rated power for three power conversion scenarios: Resistive Loading, Grid Interface, and Unity Power Factor Controlled Converter. The design study is carried out for a specific engine operating force and velocity, taking into consideration geometrical constraints for a compact system. Results are presented and discussed emphasizing the effect of the power conversion method on the idealized resultant machine physical and performance parameters.