Electromechanical design of locally manufactured small
wind turbines

Latoufis, Kostas

dc.contributor.author	Latoufis, Kostas
dc.date.accessioned	2025-03-07T07:43:53Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/61250
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.28946
dc.rights	Αναφορά Δημιουργού - Μη Εμπορική Χρήση - Παρόμοια Διανομή 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc-sa/3.0/gr/	*
dc.subject	Small wind turbines	en
dc.subject	Desing global manufactrure local	el
dc.subject	Blade desing	el
dc.subject	Axial flux permanent magnet generator desing	el
dc.subject	Rural electrification	el
dc.title	Electromechanical design of locally manufactured small wind turbines	en
heal.type	doctoralThesis
heal.classification	Electrical and Mechanical Engineering	en
heal.dateAvailable	2026-03-06T22:00:00Z
heal.language	en
heal.access	embargo
heal.recordProvider	ntua	el
heal.publicationDate	2024-06-01
heal.abstract	Open source renewable energy technologies for small scale electricity production, can create an enabling environment for energy access of rural and remote communities, where electrical grid expansion may be limited or unreliable. A widespread technology with such potential is locally manufactured small wind turbines (LMSWTs). This thesis explores LMSWTs using an interdisciplinary approach, through both technical and sociological lenses, and also adopts Participatory Action Research, in order to engage with global LMSWT communities and networks. This methodology aims at grasping the dynamics and needs of practitioners within these communities, and drives one of the main goals of the thesis, to develop useful tools for open-source renewable energy technologies at the grassroots level. In exploring the craft of LMSWTs, the thesis initially examines how users shape technology through "Makeshift Engineering" - a term coined to describe the innovative and craft-based approach to building wind turbines using locally available materials. The historical evolution of makeshift engineering is traced from the 1970s’ alternative technology movement in the UK to recent global networks that design and manufacture small wind turbines (SWTs) locally. It emphasizes on the blend of craft and engineering that enables local manufacturers to adapt technology to specific local conditions and needs. The technical aspects of LMSWTs are investigated in detail, starting with the design and performance of airfoils in SWT applications. Wind tunnel measurements are conducted for airfoils at low Reynolds numbers, and are utilized for the calibration of various simulation tools developed for the prediction of airfoil lift and drag coefficients, such as XFOIL and MapFlow, a computational fluid dynamics Navier-Stokes solver. A boundary layer tripping technique is proposed for enhancing their performance, while their results are compared with a library of airfoils designed particularity for SWT applications which have been extensively wind tunnel tested. Airfoil design requirements are developed for small-scale wind energy conversion systems in direct battery coupling using LMSWTs, while a novel optimized airfoil geometry is proposed specifically tailored for LMSWTs. Aspects of rotor design and performance for LMSWTs are investigated next, with dedicated wind tunnel experimental setups developed for measuring rotor efficiency and SWT power curves. Various simulation methodologies, such as blade element momentum and computational fluid dynamics, are developed and are rigorously compared and calibrated with experimental results. The impact of hand-carved wooden blades on rotor efficiency is investigated experimentally while the influence of various airfoils used in local manufacturing on the efficiency of hand-carved wooden rotors is studied for the first time. 3D printed rotors are investigated experimentally for aerodynamic performance and are compared with hand-carved wooden rotors, providing new insights in alternative techniques for local manufacturing. The performance of a popular commercially manufactured rotor is compared in the wind tunnel with that of a LMSWT, providing new insight into the effectiveness of hand-carved wooden rotors. The effects of yaw misalignment due to the furling mechanism used in LMSWTs are investigated providing insights on their influence on rotor efficiency and power performance. Innovative design optimizations for SWT rotors are performed, based on a collection of low Reynolds number airfoils specifically designed for SWT applications. Specific airfoils and optimal rotor geometries are proposed for various rotor sizes, while airfoils used in LMSWTs are ranked among the best performing airfoils. The study of generator design in SWT applications, and specifically for LMSWTs, is investigated, focusing on the use of axial flux permanent magnet generators (AFPMGs), due to their viability for local manufacturing. The experimental setups and simulation tools employed are presented, including an AFPMG test bench setup and a novel simulation methodology, namely OpenAFPM, based on magnetostatic finite element analysis. A comprehensive comparison between simulation and experimental results is conducted in order to verify and calibrate the simulation tools. Specific aspects of generator design relevant to LMSWTs are studied, based on key AFPMG design parameters, with the aim of developing design guidelines for such applications. The thermal and structural design of AFPMGs is explored, for enhancing heat dissipation and reducing generator mass, with novel back iron disk designs being developed. Acoustic noise mitigation for AFPMGs used in LMSWTs is investigated experimentally, linking acoustic noise to current harmonics introduced by the diode bridge rectifier. The acoustic noise emissions of LMSWTs are measured in the field for the first time, while novel passive filter configurations are proposed for acoustic noise mitigation and their performance is evaluated in field tests. Innovative design optimizations for AFPMGs in LMSWTs are developed, focusing on the use of various magnetic materials, such as Neodymium and Ferrite, and on the design of high-power AFPMGs, which are not typically covered in LMSWT manufacturing manuals. Optimal magnet dimensions are identified and 'universal' magnet designs are proposed. The thesis concludes with a comprehensive analysis of small-scale wind energy conversion systems (WECS) in low wind speed regions, typically associated with LMSWTs. The experimental setups and simulation tools employed are presented, specifically the installation of a SWT test site for measuring LMSWT power performance according to the IEC 61400-12-1 standard, and simulation methodologies such as combinations of FAST/Simulink models for furling SWTs in WECS. A detailed comparison between simulation and experimental results is conducted, for validation and calibration, resulting in a novel power curve modelling tool for LMSWTs. Additionally, an innovative open data application is developed, namely OpenWindLab, which consist of an online data base of all field tests conducted during this thesis on LMSWTs. The power curves of 14 commercially and LMSWTs are compared, as they have been measured by various testing bodies, and with a specific emphasis on low wind speed performance. Best performing SWTs are compared as parts of small-scale PV/Wind hybrid systems, using the HOMER microgrid simulation tool, in order to verify each SWT’s performance from a system perspective, and to develop innovative design criteria for small-scale WECS. Passive rotor power matching techniques for direct battery coupling are investigated, namely the regulation of the power transmission line resistance and the regulation of the AFPMG air gap, with the aim of developing design guidelines for low cost rotor power matching. WECS maintenance aspects are also investigated, namely the effects of leading edge erosion on power performance and acoustic noise, resulting in the proposition of maintenance procedures for LMSWTs. Innovative design optimizations are implemented, resulting in component lookup tables for optimal passive rotor power matching in WECS using LMSWTs, while such an optimized configuration is field tested and compared for the first time with one using a maximum power point tracking (MPPT) converter. Lastly, techno-economic optimisations are conducted for determining the optimal rotor diameter and tower height for various rated power sizes of LMSWTs in direct battery charging WECS, resulting in new design guidelines regarding the choice of rated of wind speed.	en
heal.advisorName	Voutsinas, Spyros
heal.advisorName	Hatziargyriou, Nikos
heal.advisorName	Tympas, Aristotle
heal.committeeMemberName	Dimeas, Aris
heal.committeeMemberName	Manolesos, Marinos
heal.committeeMemberName	Riziotis, Vasilis
heal.committeeMemberName	Lavado Villa, Luiz
heal.academicPublisher	Σχολή Μηχανολόγων Μηχανικών	el
heal.academicPublisherID	ntua
heal.fullTextAvailability	false