Green Collar Careers - Wind
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
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
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
- Highest efficiency - Horizontal Axis
- Lowest cost per kWh - Horizontal Axis
- Lowest wind speed required to operate - Vertical Axis
- Most reliable - Vertical Axis