Current Status and Future Challenges for Small Horizontal Axis Wind Turbines

This paper examines the category of small wind turbines. Numerous definitions are found in the literature. However, this paper's focus is on fixed pitch, small horizontal axis wind turbines, with a direct drive DC generator in the 1-10 kW class. Small wind turbine growth world-wide is analyzed for trends and predicted development. It is necessary to discuss design tools available for design, including computational fluid dynamic models and experimentally testing both open rotors and wind tunnel models. Wind turbines must be optimized for peak performance to include startup/cut-in speeds and other modifications. These wind turbines will rely on new and purposely designed airfoils; however, for low-Reynolds number conditions, computational tools do not accurately predict separation. An analysis of noise generation as well as design techniques for reducing noise is necessary for future designs. Discussions on the technologies particular to small wind turbines should include the topics of aerodynamics and structures/materials. Small wind turbines are contributing to the concept of distributed generation. Urban applications are leading to studies of flow fields in and around buildings. Interest in hybrid systems, which combine wind with other energy generation systems such as solar, internal combustion engines, and diesel engines, is growing. These systems are advantageous for the homeowner, small business, cell phone towers, remote locations, and backup emergency power systems (to include lighting). Finally, the concept of energy storage must be addressed in the context of small wind turbines, especially those turbines used in an isolated application.