POWER April 2011 - 44

FUTURE POWER
15. MARS. Magenn Power's MARS helium-filled
wind turbine can be deflated and
redeployed. It is capable of operating in wind
speeds from 4 mph to more than 50 mph.
Courtesy: Magenn Power
In Germany, Festo (maker of pneumatic
and electrical automation technology) is exploring
the Aerois Enerkite system, which is
an autonomously controlled kite wing of up
to 24 square meters.
In the Netherlands, a system prototype of
16. Tower of London. The Strata Tower
in London's Elephant and Castle neighborhood
is a 43-story, 147-meter-high building that features
three five-bladed built-in wind turbines.
Courtesy: Brookfield Asset Management
the Ampyx Power Plane, a glider plane that
unwinds a winch during flight to propel a
generator on the ground, has actually met its
rating of 10 kW. The system is a spinoff of
the TU Delft University's Laddermill project.
Peak power reached during a test of the Laddermill
system in April 2010 was 20 kW.
In Switzerland, a coalition of academic
researchers (including the University of Applied
Sciences Northwestern Switzerland,
the Swiss Federal Institute of Technology
Zurich, and the Swiss Federal Laboratories
for Materials Testing and Research) is evaluating
high-altitude wind power.
Even China is stepping in, establishing
a high-altitude wind energy research center
in Guangdong Province, where plans are in
place to build a 1-MW airborne wind power
system in Foshan City.
Designs aren't limited to kites and airplanes,
however. A California company, Magenn
Power, has developed an airborne wind
energy system, MARS (Figure 15), consisting
of a helium-filled tethered wind turbine
that rotates on a horizontal axis at altitudes of
600 to 1,000 feet. MARS rotation also generates
the " Magnus effect, " which provides additional
lift, keeping the MARS stabilized.
17. Turbine skin. The NanoVent Skin concept
from designer Agustin Otegui features
miniscule bio-turbines that could clad buildings
to generate power. Courtesy: Agustin Otegui
Other Turbines
An assortment of other turbines, typically a
hybrid of HAWT and VAWT systems, exist-
and are thriving. On the market, for example,
is the Loopwind Wind Turbine, a high-torque,
six-bladed turbine that captures wind with
both front and rear blades. Japanese developers
say that the design allows the Loopwing
to be free of torque-imbalance suffered by
VAWTs while being less affected by centrifugal
force as compared with the propeller type.
They also claim not only that the turbine rotates
at wind speeds as low as 1.6 m/s but that
it has a power coefficient of more than 40% in
wind tunnel tests (with wind speeds of 8 m/s).
Among the " wackier " concepts are the
larger, more ambitious architectural wind
turbines. Several proposals have been made
to integrate wind turbines into skyscrapers.
The 600-meter-tall Anara tower in Dubai, for
example, was designed to look like a massive
wind turbine. Those plans were cancelled in
2009, but others are becoming reality. Last
year, London saw completion of the £113.5
million Strata Tower (Figure 16), which generates
a tenth of the power used by the building
(a total of 50 MWh annually) via three
five-bladed built-in turbines.
44
www.powermag.com
More Info and Images
on the Web
For more on the debate over horizontal-axis
and vertical-axis wind turbines-and
more images of turbine
designs-see the web supplement to
this story, " Horizontal or Vertical? The
Question for Wind Turbine Axis Orientation, "
at www.powermag.com. You'll
find it on our home page in April and
with the archived April issue thereafter.
Other concepts involve " biological " exteriors
for buildings. Agustin Otegui, inventor
of the " NanoVentSkin, " would incorporate
tiny, biological self-repairing wind turbines
into the outer layer of a building (Figure
17). " The outer skin of the structure absorbs
sunlight through an organic photovoltaic
skin and transfers it to the nano-fibers inside
the nano-wires which then is sent to storage
units at the end of each panel, " he says.
" Each turbine on the panel generates energy
by chemical reactions on each end where it
makes contact with the structure. Polarized
organisms are responsible for this process on
every turbine's turn. "
Paradigm Shift or Yard Art?
Unconventional wind turbine designs have
several things in common, small wind expert
Mick Sagrillo told attendees at a small wind
conference in 2009. Among these are roofmounted
or short towers, unconventional rotor
configuration, " eye candy " photos, and a
multitude of claims-which could range from
" small and lightweight " and " only $0.25/
watt " to " maintenance free " and they " generate
even in low speeds. " What's missing,
he said, is that few developers want to talk
about at which speeds the device can generate
power, how it deals with turbulence, what
its annual energy output or performance is,
and if there is any field data that could point
to how much power the device could produce
per hour.
The hoards of claims made by self-styled
inventors- " bozos and shysters, " as Sagrillo
calls them-can be tested by considering
simple parameters, he said. For example,
swept area is inherently limited on rooftops,
and rooftops and short towers experience increased
ground drag and turbulence. Another
factor to consider is that when the wind is
down, cost is up. " What are we demonstrating? "
he asked, " A 'paradigm shift' or yard
art? " One way to resolve this is simple: eliminate
what he calls " wet finger monitoring, "
and get designs certified. ■
-Sonal Patel is POWER's senior writer.
POWER | April 2011
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POWER April 2011

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