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Will TMA Wind Blow Away the Competition?
Vertical axis wind turbine technology with concentrating air foils
enables TMA to compete with the best horizontal turbine costs at lower wind
speeds, while the return on investment is even greater at higher wind speeds,
where the horizontal turbines have to shut down. Other advantages are
many.
Full Disclosure:
The author of this piece is involved in bringing capitalization to
the company, from which he will benefit financially. |
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TMA Wind's most recent prototype at King Ranch
outside Cheyenne, Wyoming, has been grid-connected for around 2.5 months.
Photo by Sterling D. Allan, Jan. 20, 2007 |
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An investor chats inside the generator room
below the turbine, where the service components are easily
accessible. The devices on the shaft, from top to bottom, are: two
braking mechanisms, gear box, and generator -- all off-the-shelf devices.
Photo by Sterling D. Allan, Jan. 20, 2007 |
by Sterling
D. Allan
Pure Energy Systems News, Exclusive
Copyright © 2007
CHEYENNE, WYOMING, USA -- On January 20, I was able to meet the TMA Wind company
executives, Ron Taylor and Duane Rasmussen, and view their test site just
outside Cheyenne, Wyoming. Though it was a seven-hour drive each way, in
the middle of a cold and sometimes snowy passage from the Salt Lake City area, I
thought it was a trip well worth taking.
From my perspective, I am inclined to agree with TMA's assessment that they have
the next big thing in wind technology. Their design will overturn the past
scientific dogma that says that vertical turbines can't produce as well as the
typical propeller-like, horizontal blades.
TMA has done extensive research and development over the past eleven years,
including wind tunnel and on-site testing to come up with an optimal, patented
vertical axis wind turbine design that operates at around a 40% wind conversion
efficiency, doesn't kill birds, can be installed more densely per given real
estate, runs much more quietly, has nearly no vibration, doesn't need to be
installed as high, and can be blended in better with landscape -- all at a price
that is competitive with the best horizontal wind turbine designs presently in
use.
At lower average wind speeds, from between 10 and 35 mph, the TMA turbine design
has a comparable generation cost to the most cost-effective horizontal wind
turbines -- in the range of between 3.5 and 4.0 cents per kilowatt-hour.
But at higher wind speeds, where the horizontal turbines have to be shut off,
the present TMA turbine designs can keep generating all the way up to 65 mph,
where the return on investment comes even faster.
The higher-speed limitations are not in the structure, but in the generator,
which should not be over sped, lest it burn out. A generator could be
selected for high-wind-speed areas. The mechanical structure itself is
engineered to withstand into the category 5 hurricane classification, which
begins at 156 mph.
When they first started the company, they were hoping to find a niche in the
high-wind scenarios (class 6 and 7 winds), where horizontal turbines can't
go. They have been pleased to confirm through wind tunnel testing that
their design is also competitive even at the lower wind speeds.
Eventually, the design could also be applied downward into river and tide
harnessing applications, but the company is postponing those applications in
order stay focused in their launch of the wind applications.
Their most recent prototype outside Cheyenne has been grid-connected for nearly
three months, complete with all the certifications required for that to
happen. TMA expects that within a month they will have sufficient power
curve data from installed capacity that will enable them to definitively prove
the superiority of the design. They have just been awarded their third
U.S. patent, so now all they are waiting for is the newest power curve data to
give them the green light to launch full steam ahead. The company is
presently in various stages of negotiation with a number of international
clients to license construction of the turbines commercially.
Many components in the TMA design are off-the-shelf items, including the
generator, the bearings, the gear box, the braking mechanism, and the
electronics. The turbine and the support structure are the only
specialized component in the design, and those are things that "can be
easily produced by any quality fabrication shop."
Before installing a turbine, TMA will analyze the wind data available for the
target site to see what the average wind speeds are as well as the most frequent
direction. (Such data is already available for many locations
worldwide.) The design is then tailored for those parameters. While
the design is omni-directional, it is engineered to optimize the wind from one
direction, where its efficiency is between 40 and 45%, while wind coming from
the back side might be 30%, which is still better than what horizontal turbines
do.
In addition to a turbine, the TMA design has a wind-capture mechanism via
protruding funnel-like air foil structures that direct the wind into the
rotating turbine. The advantages of this are comparable to the
concentrated solar designs that focus the sun's energy onto photovoltaic cells,
for example, reducing the number of expensive components in the system.
The TMA design thus incorporates a "concentrated wind" aspect.
That particular design feature constitutes an important part of the patented
intellectual property of the company.
During their research and development phase, TMA tried around 300 iterations in
wind tunnels, and built nine turbines for on-site testing. "The the
newest turbine we are testing is out-performed what we saw in the wind
tunnel," said Ron Taylor, Chairman of TMA.
The TMA design is scalable from 1 kW up to 1 MW, though the company does not
plan to build anything larger than 500 kW. "If a one megawatt turbine
goes down with a mechanical problem, that's a lot of generating capability that
goes off line at once." And it is more time-consuming to fix larger
devices than smaller ones. The longest a 500 kW unit might be down would
be one day (assuming availability of personnel and spare parts). The lower
thrust bearing of the turbine is a split-bearing design for easy replacement, if
and when necessary.
Vertical v. Horizontal
The advantages of TMA's vertical axis design over the traditional horizontal
wind turbine design are many. The "concentrated wind" aspect mentioned
above is one.
The air-foil design of the TMA turbine is such that not only does the wind push
the one foil forward, but it pulls the foil coming back toward the direction of
the wind (Bernoulli's Principle).
Because the generator is near the ground where it is easily accessible, the
maintenance costs on a TMA design are considerably less of what they are for a
horizontal design where the equipment is high up in the exposed air.
The TMA design is much more stable due to the tripod arrangement of the air
foils that direct and accelerate the wind into the rotor. Therefore the
footings only need to be about 48 inches deep on a 250 - 500 kilowatt TMA
turbine, compared to 10 to 20 feet on a comparable horizontal axis turbine
footing. (Ref.)
Also, whereas the moving blades on the horizontal design are fixed to one point
at the hub, there are two points of connection (top and bottom) on the TMA
design. This also causes vibration to be nearly non-existent in the TMA
design, whereas the vibrations from horizontal turbines have been documented to
rattle dishes two or three miles away. The TMA design does not produce
communications interference, which has been a problem with horizontal wind
farms.
Wind shear does not effect the vertical axis design, which can handle changes in
wind direction with no problem, being nominally omni-directional, while such
changes create tremendous stresses on the blades of horizontal-design turbines.
Because TMA's turbine spins 1.1 times the speed of wind, it doesn't pose the
hazard to birds or bats that the horizontal turbines do, with their fast-turning
blades, which approach near supersonic speeds at the tips of some of the larger
turbines. The birds and bats don't perceive them coming and get whacked.
The efficient aerodynamics of the turbine are such that it has a low wake
signature (the air turbulence that tumbles out the back side), which allows more
of the turbines to be installed per square foot of real estate, per kilowatt
produced, than what horizontal turbines allow because of their larger
wakes. Taylor says that they can fit two to three times as much power
density on property as horizontal wind turbines.
There are visual advantages as well. The TMA design sits lower to the
ground, and the stationary air foils can be colored or camouflaged to blend into
the surrounding scenery. Alternatively, the air foils could also be lined
with solar panels for secondary power generation -- a feature not available in
the horizontal turbine pillar design.
NREL v INEL
Traditionally, the U.S. National Renewable Energy Lab (NREL) has questioned
the feasibility of vertical-axis wind turbines, and has favored the horizontal
prop design.
However, representatives from the Idaho National Energy Lab (INEL) have visited
TMA's Cheyenne test site, and have become believers in the plausibility of the
vertical axis design.
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ACKNOWLEDGEMENT:
See also
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Page composed by Sterling
D. Allan Jan. 1, 2007
Last updated February 03, 2007
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