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Green Collar Careers - Wind Turbines

In regions with steady wind conditions wind turbines can be very cost effective for electricity production.  Commercially wind has been by far the largest investment in renewable energy generation.  From 2007 to 2008 the volume of commercial wind generated power in America nearly doubles to 1.3%, and is expected to reach 10% before 2015.  Spain currently generates over 1/3 of their electricity from the wind with Germany in excess of 10%.

Cost effective wind energy is an economy of scale; airflow close to the surface of the earth, around 100 feet is often obscured by objects including trees and natural land formations.  While it may feel windy on the ground, above 100 feet there is almost always a stronger more steady wind current.  Therefore the more efficient systems rely on a taller tower for the wind turbine, and that comes at a higher cost.

Windmills are mechanical devices that are more susceptible to failure then solar PV based systems.  Commercial generation companies can plan on having a staff in place to service and repair systems, however home owners are generally on their own when a failure occurs, and they generally don't have access to wholesale service/repair component pricing.

Windmills consist of at least 3 component groups; Turbine, Generator, Pedestal (or tower).

Turbines are the "sails" that catch the wind and convert that energy to rotating energy.  Most conventional designs are the 3-bladed propellers however there are several other designs.  On large scale commercial wind turbines the angle of the blades to the wind (pitch) may be altered to maintain some level of rotating speed control over varying wind speeds.

Generators are coupled to the rotating turbine shaft usually via a gearbox and generate either direct current or alternating current.  On large scale commercial wind turbines the generator/gearboxes are also known as "nacelles".  As high wind conditions prevail these systems may require a mechanical braking systems.

Pedestals provide the mounting for the wind turbine and generator system.  Most conventional designs (horizontal shaft) require the blades be pointed into the wind (Yaw direction) and the pedestal is equipped with a system to steer the blade facing to the desired direction.  Simple smaller systems may just rely on a tail fin where larger commercial systems are motor driven Yaw control.  Commercial systems and most horizontal shaft systems are mounted high so the Tower is included as a Pedestal component.

There are two classes of wind turbine designs;  Horizontal Axis and Vertical Axis.

 

Horizontal Axis are those with the turbines mounted on a horizontal shaft.  Horizontal Axis wind systems typically provides the most cost effective design particularly for large scale commercial applications.

 

Vertical Axis have turbines mounted on a vertical shaft.  Two key designs of vertical shaft turbines include the Darrieus and Savonius styles.  Small scale vertical axis turbines (under 25kWh) have been making some great progress with cost, reliability and low speed wind operation.  One of the newer technologies has been the use of magnetic levitation (maglev) eliminating bearing wear and friction.

• Highest efficiency - Horizontal Axis
• Lowest cost per kWh - Horizontal Axis
• Lowest wind speed required to operate - Vertical Axis
• Most reliable - Vertical Axis