Small Wind Turbines

Abstract

This chapter describes and reviews small wind turbines in terms of their components, costs, applications, opportunities for technology innovation, and future directions for research and development. Most emphasis is given on blades’ design and airfoils choice for turbines of power output less than approximately 10kW. Airfoil development for small turbines has languished this century and there is a need for high performance airfoils that facilitate the accurate manufacture of small blades. Significant development has occurred recently in multidimensional optimization of blade design to maximize power, and minimize blade mass, starting time and noise, while maintaining constraints on size and tip deflection. Further progress to include higher fidelity structural models that reduce the fatigue loads is likely to occur soon. Progress in generators and control has been modest, with the small market share of the smaller wind turbines causing a lack of competitively priced generators with high efficiency and low cogging torque. The use of electrodynamic braking—the shorting of the generator output—has emerged this century as a much cheaper alternative to the use of a mechanical brake. Small wind turbine towers are either monopole, lattice, or guyed. The last are the cheapest but have the largest footprint and are not suitable for many locations. There does not exist sufficient information to assist on the choice between lattice and monopole towers. Our knowledge of the field performance of small wind turbines has increased enormously but many of the fundamental issues have not been resolved. Technical diversity in terms of diffuser augmentation and vertical axis turbines is highlighted and the advantage of small size for the development of reusable blade materials is noted. Several other typical applications of small wind turbines are considered, such as remote power systems and microgrids, and wind power-based small desalination units.