DEVELOPMENT OF A DIRECT-DRIVE ELECTRICAL TRANSMISSION SYSTEM FOR A KENYAN MANUFACTURED VERTICAL AXIS WIND TURBINE

Abstract

The major reason for the continued low penetration of Small Wind Turbines (SWTs) in Kenya is the high cost of the technology  particularly  the  drive  train  (gearbox  and/or  generator).  Subsequently,  the  main  objective  of  this research was to design and develop a direct-drive generator that eliminates the need of gearbox, is affordable/low cost  and  easy  to  manufacture  and  assemble.  Secondly  the  research  also  sought  to  determine  the  optimal economic cost of production of the  generator. In  achieving this,  the  methodology  used involved: computational electro-mechanical design using FEMM 4.2 software, followed by prototype development and testing. In addition, stratified  random  sampling,  questionnaires  and  face  to  face  interviews  of  SWT  manufacturers  was  also  done. Materials used included permanent magnets, coil windings, steel rotor discs, used vehicle hub bearing, generator mounting frame, polyester resin, epoxy hardener and talcum powder. The results of the research are in form of 1 kW direct drive Axial Flux Permanent Magnet (AFPM) generator, which costs between 5 – 20% cheaper than the existing  SWT  transmission  systems  in  the  market.  Its  performance  ranges  above  average  as  compared  to  the current  ones  and  its  manufacturing  process  technology  is  simpler  and  faster  than  the  existing  approaches.   In conclusion the use of AFPM direct drive generator reduces transmission system costs of SWTs which can greatly accelerate the adoption of vertical axis SWTs in rural off-grid regions of Kenya. The generator is also quite easy to construct,  operate  and  maintain  by  people  with  basic  technical  skills. Its  adoption  will  also  create  employment opportunities in the manufacturing and service delivery sectors.

Key words: Renewable energy, small wind turbines, vertical axis wind turbines, direct drive axial flux permanent magnet generator, Finite Element Magnetic Method (FEMM)