Lastly, simplifying wind turbine components/systems also adds to the attractiveness of wind turbine application and reduces maintenance costs. This can be achieved by using low-noise blade designs, vibration isolators to reduce sound and sound absorbing materials around the gearbox and generator. Another objective is to reduce/eliminate noise associated with blade rotation and gearbox/generator noise. To be more attractive for integrating into buildings, micro wind turbines are also being designed to be more visually attractive, without compromising their performance.
In this way, electricity can be generated with wind speeds as low as a few metres per second. Furthermore, the use of permanent magnet generators, based on rare earth permanent magnets, results in lightweight and compact systems that allow low cut-in wind speeds. Wind turbine blades are now designed with lightweight materials and aerodynamic principles, so that they are sensitive to small air movements. Recent developments in building integrated wind turbine technologies involve improving reliability, improving efficiency at low wind speeds and lowering capital cost. As technologies improve, modern wind turbines can also directly generate AC power. Conventionally, grid-connected systems require power converters to convert the generated DC electricity to AC electricity to be compatible with power grid and AC-electricity-based appliances. Their application is most suitable for rural and remote areas, such as remote villages and small isolated islands, where grid power is not available. Off-grid systems require battery storage to store surplus electricity, thereby providing a more stable electricity supply. Wind turbines can be grid-connected or off-grid. Figure 1: Horizontal axis wind turbine (HAWT)