An Overview of Small Wind Turbines
The wind turbines that are used by the windmills today typically have three-bladed rotors. There are also wind turbines with two, or four, or even multiple micro-blades. While most wind turbines come in rotor diameter below 10m, today we have small wind turbines, or SWTs. coming in diameter ranges of up to 20m. The turbines are typically mounted on wind towers of heights ranging from 12 to 24m.
Wind turbine rotors
Today, alternative manufacturing methods are used to make the giant rotors of wind turbines. Processes such as injection molding, compression molding, and reaction injection molding are used to manufacture blades at a cheaper and faster rate. Such alternate manufacturing processes have also lead to lower costs of parts and easier replicability of the process. However, in spite of such cost saving and better technological processes, the tooling costs associated with rotor manufacturing remain significantly high.
Trends in wind generators
Traditionally, most wind turbine generators used ferrite magnets for their electromagnetic converters. The modern developments in generators have replaced ferrite magnets for rare-earth permanent magnets. There are two key advantages of rare-earth permanent magnets.
- They have better magnetic properties and their prices have been declining in the market.
- They make for more efficient, compact and lightweight generators.
Induction generators have started to make a comeback in the wind energy sector due to their low cost of operations and maintenance along with better reliability. In spite of their rising popularity, not many manufacturers make induction generators of capacities less than 50 kW.
Inverters and grid connectivity
One of the most cost-intensive components for connecting wind turbines to the grid is the inverter, also known as AC/DC inverter. The inverters that are used today are usually sourced from the solar market, which are used with PV panels. They are modified accordingly to work with wind turbines along with voltage control equipment. Recently wind turbine compliant inverters have been engineered which can come in both single or three phase settings.
As of today, small wind turbines are typically designed for low wind speeds which call for bigger rotors and towers, and accurate power control devices for handling occasions of strong gusts. The yawing or "furling"characteristic protects the rotors of small wind turbines. Yawing is a method of aerodynamically breaking the strong wind that hit the blades of the turbine. Some popular modern alternatives to aerodynamic yawing are stall control, dynamic braking systems, hydraulic and mechanical brakes, and centrifugal and active pitch control.
Further technological developments are taking place which aim to reduce noise production. For this, reduced rotor speed during peak hours is to be achieved.