Ion Plasma Generator Reduces Wind Turbine Lightning Strikes
Aug 28 - Power Engineering
Inside 20 years, the U.S., Europe and Japan have the potential for generating up to 40% of their electrical needs from wind energy. With the trend toward larger wind turbines, the cost/kWh for generating electricity continues to drop. As a result, many countries are developing and constructing wind farms. Even older wind turbine projects are being re-furbished and upgraded with larger turbines. Wind energy advocates say wind could provide 10% of the world's electricity requirements by 2017.
Unfortunately, today's larger high-tech wind turbines are more vulnerable to
lightning strikes, particularly in storm-prone areas. Therefore, for wind power
to continue to grow it is imperative that they be protected from lightning. Wind
turbines currently being installed have blade lengths exceeding 100 ft and the
cost to replace a single blade is more than $100,000. Without adequate lightning
protection, wind turbines are vulnerable to catastrophic and disastrous
failures.
Data collected from one winter season in Japan revealed losses of
unacceptable proportions. In one season, at least 55 machines at a wind farm in
Honshu had blades destroyed by lightning. The estimated one-year loss for those
machines exceeded $5.5 million and this did not include the cost of lost
production or cleanup.
Regardless of the growth in wind energy, the cost of not adequately
protecting wind turbines from lightning can become a significant drawback to the
benefits of the technology. In at least one recorded case, a turbine blade was
completely destroyed by lightning. Because the two remaining blades continued to
rotate, the resulting unbalance twisted the tower, causing it to collapse. The
total loss of the wind turbine system cost the owner more than $1 million.
Another lightning strike on a wind turbine caused a fire and completely
destroyed the turbine. The subsequent investigation determined that the probable
cause of the fire was from a strong electromagnetic pulse (EMP) from the
lightning strike.
LIGHTNING PROBLEMS
Wind turbines are one of the world's most challenging machines to protect
from lightning. Since wind turbine blades are not electrical conductors,
manufacturers install conductive wires to dissipate stray electrical energy.
Nonetheless, blade failure of can occur if the wire is unable dissipate the
energy from a lightning strike.
Trying to build a better "lightning trap," lightning rod
manufacturers developed a family of strike collectors called "early
streamer emitters" (ESEs). The design of the ESEs is based on the premise
that the faster a streamer is generated the greater the chance of collecting the
incoming lightning leader. Unfortunately, ESEs fail to compete with the
streamers emitted by turbine blades.
According to a study by the USA NFPA Lightning Committee, the use of ESEs is
no better than lightning rods. Further tests, conducted by the New Mexico
Institute of Technology in their mountain top lightning . laboratory, also
showed that ESEs are no more effective than a common lightning rod.
AN ALTERNATIVE PROTECTION SYSTEM
For more than 30 years, Lightning Eliminators & Consultants, Inc. (LEG),
Boulder CoIo., has been involved in developing lightning protection systems.
Over the last ten years the focus of the company has been on researching the
science of strike collection. From this research the company developed a
collection system process: the ion plasma generator (IPG).
In a typical electrical storm, clouds emit a negatively charged downward
leader that is continually searching for an attractive, positively charged,
upward streamer or "counter leader" from the ground. When this occurs
it triggers a lightning strike, which in turn balances the electrical charge.
Analytical tests and operating data has shown that the IPG can successfully
compete with any form of streamer generated.
In contrast to the narrow and weak upward streamers generated from
single-point lightning rods and ESEs, the IPG collector creates a corona plasma
or dense massive flow of attractive ions. During operation, the IPG directs the
corona plasma upward to capture any direct lightning strikes. All are captured
in the last few milliseconds of the lightning's trip to earth. The dense plasma
presents a far more attractive force than the wind turbine blades or any other
form of streamer. The IPG strike collector is effective up to 320 ft. Compared
to a single lightning rod of the same height, the IPG provides a collection zone
several times larger.
Catastrophic wind turbine fa ilure from lightning. Photo courtesy of
Lightning Eliminators & Consultants, Inc.
One of the most vulnerable lightning areas of Japan, with 15 wind turbines in
operation, experienced continual problems with damage from lightning striking
the turbines. The owners decided to evaluate IPG lightning protection systems on
two of the turbines. Since installation, no lightning related losses have been
reported on either of the machines. However, during the same time period, all 13
of the unprotected wind turbines have been struck by lightning, and in one
instance a turbine blade was completely destroyed.
With the successful application of IPG lightning protection, the Japanese are
planning to add lightning protection to all of their wind turbines.
Circle 202
Copyright PennWell Publishing Company Aug 2004