Optimized design of a novel yokeless mover permanent magnet linear generator for free‐piston stirling engines applied to solar cogeneration systems

Abstract

Considering the growing environmental issues, the use of renewable energy converters such as solar cogeneration systems has received more attention during recent years. Solar cogeneration systems convert the thermal energy of solar radiation into mechanical energy (by means of a free-piston Stirling engine) and then into electrical energy (by means of a linear generator). This paper introduces the novel yokeless mover permanent magnet linear generator (YMPMLG) to reduce mover mass, increase power density, increase thrust and decrease the normal force on the mover, which can make this generator a more suitable structure for operating in solar cogeneration systems. This paper is initiated with a comparative study of a YMPMLG with two reported prototypes in this field. Three generators with similar characteristics are simulated by the finite element method (FEM). The magnetic field flux density, power density, thrust coefficient, normal force, and efficiency parameters are analysed and compared in three generators. Following that, some dimensional parameters of the YMPMLG, including generator diameter and length and permanent magnet dimensions are optimized to achieve the highest possible power density and thrust coefficient using the 'hybrid genetic and pattern search' algorithm. The highest power density and efficiency are 0.58 kW/kg and 90.3%, respectively. In the end, the YMPMLG prototype has been tested to validate the results of the FEM method.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Linear generator design for concentrating solar power technologies: Optimization and prototype development

“…Different magnet array structures have been investigated for single‐phase permanent magnet tube‐type generators [40‐44]. Power density has been increased by using the response surface method [44]. Similar to our study in terms of size and objective function [45], the Halbach array permanent magnet tube‐type generator was studied with power, detent force, and efficiency as objective function [46].…”

“…(a) Crank and connecting rod, rotating generator, (b) free piston, (c) free piston linear generator; pressure–volume convergence [10–12, 43–53]. …”

“…The operation of the Stirling engine may be understood by considering its fixed volume and fixed heat states. The Stirling engine has four states (Figure 2): the process between states 3 and 4 occurs at fixed temperature when heat is drawn from the operating gas; the process between states 4 and 1 when giving heat to the operating gas from an external source; the process between states 1 and 2 occurs when the operating gas expands and moves the piston at fixed temperature; the process between states 2 and 3 process ends in conversion and the heat in fixed volumes should be removed from the operating gas [10–12, 22, 43–53].…”

“…Single-phase generator designs have mostly been considered for small power Stirling engine systems [14,15,39,40]. Different magnet array structures have been investigated for single-phase permanent magnet tube-type generators [40][41][42][43][44]. Power density has been increased by using the response surface method [44].…”

Thermal/fluid characteristics of the inline stacked plain‐weave screen as solar‐powered Stirling engine heat regenerators

“…Considering the growing environmental issues, renewable energy converters such as solar cogeneration systems have received more attention during recent years. Solar cogeneration systems convert the thermal energy of solar radiation into mechanical energy (utilizing a Stirling engine) and then into electrical power (using a linear generator) [5]. Tong and London [6] reported friction factor and heat transfer coefficient measurements for air flowing through inline plain‐weave screen laminates and staggered cross‐rod matrices.…”