In this paper the design and manufacturing processes for coreless axial flux permanent magnet generators are described for low cost rural electrification applications, where local production of small wind turbines is considered. The process is based on already existing open source design and construction manuals, while a systematic approach to designing generators of varying nominal power and for grid connection or direct battery charging schemes is described. The manufacturing process of a 3 kW small wind turbine generator for grid connection is used as a case study. Emphasis is given to the use of simple tools and techniques to achieve a lower cost, while intricate steps in the manufacturing process are described in more detail. The generator design is simulated and the constructed machine is tested in the laboratory.

The local manufacturing of small wind turbines has become increasingly popular over the last decade, among international networks of renewable energy practitioners, for the implementation of rural electrification applications. Locally manufactured small wind turbines (LMSWTs), used most frequently in off-grid battery based renewable energy systems, typically utilize wooden blades and coreless axial flux permanent magnet generators due to their simple manufacturing process and local availability of materials. In this paper the effects of leading edge erosion on locally manufactured small wind turbine blades are researched experimentally, both in terms of power performance and acoustic noise emissions. From the research it is concluded that a yearly maintenance of the wooden blades of a LMSWT can lead to less acoustic noise emissions and better power performance, with the latter becoming more significant as the mean wind speed of the installation site increases. For practitioners, installers and manufacturers of LMSWTs, these findings can significantly guide manufacturing processes and techniques in terms of preventing leading edge erosion, while also advising preventative maintenance procedures on the field, in order to keep small wind electric systems quiet and productive.

In this article, we explore the sustainability potential of an alternative commons-based mode of production called cosmolocalism. Cosmolocal production combines global knowledge production with local physical production. Such a production mode has been applied across the globe for locally manufacturing small wind turbines (SWTs) for rural electrification. We assess the sustainability of such cosmolocal SWTs in a case study of electrifying a rural community in Ethiopia. In this context, the life cycles of five SWT alternatives have been compared, ranging from conventional industrially produced turbines to open-source locally manufactured and maintained ones. Our case study indicates that the local manufacturing and maintenance of SWTs offer significant advantages and may redeem small wind turbines as a sustainable component for rural electrification. Specifically, the fully cosmolocal alternative (A1) performs better than any other alternative in technical, environmental, and social criteria, while it is close to the best-performing alternative with regard to economic objectives. For this solution to be implemented, the institutional burden cannot be neglected, but can rather be considered a sine qua non condition for locally manufactured and maintained SWTs. A set of generic institutional interventions to create favourable conditions for cosmolocal production is proposed, which needs to be elaborated in a context-specific manner.

During the last decade, the local manufacturing of small wind turbines has become a common approach in rural electrification applications, especially among international networks of renewable energy practitioners. Locally manufactured small wind turbines (LMSWTs) used in off‐grid battery based renewable energy systems, typically utilize coreless axial flux permanent magnet generators (AFPMGs) due to their simple manufacturing. Typically, low cost three phase uncontrolled diode bridge rectifiers are used for the direct coupling of the AFPMG to the battery bank, which increases significantly the total harmonic distortion (THD) content in the stator current. LMSWT users have occasionally reported AFPMG noise as contributing to the overall acoustic noise emissions of the small wind turbine, especially during low wind speeds. In this paper the relation between current harmonics and acoustic noise emissions in AFPMGs is investigated and verified experimentally, while appropriate passive filtering techniques are utilized in order to reduce their effect. Furthermore, the overall acoustic noise emissions of a LMSWT are measured experimentally in the field and are compared to noise standards for residential areas. Finally, electromagnetic and aerodynamic sources of acoustic noise are investigated experimentally in the field, while design recommendations are developed for LMSWTs towards the reduction of acoustic noise emissions.

Acoustic noise emissions from locally manufactured small wind turbines, caused by current harmonics during low wind speeds, have been mitigated with the use of passive filters, thus increasing user community acceptance. In this paper various topologies of passive filters are investigated, while their optimal design is developed through a novel whole-system electro-mechanical approach. Specifically, the L-RLC passive filter topology is optimized for minimum line current total harmonic distortion, minimum change in the terminal voltage of the axial flux permanent magnet generator, and for reduced power losses. The optimal filter design is manufactured and field tested for acoustic noise emissions and power performance, while also being compared to other passive filter topologies.