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 Bergey
Windpower is currently developing the BWC XL.50, an advanced technology 50 kW
turbine, as part of the US-DOE Advanced Small Wind Turbine Program. With a
rotor diameter of 14 meters (46 ft.) and a peak output of approximately 70 kW,
the XL.50 combines the simplicity and reliability of the BWC 10 kW Excel with
advanced technical features designed to improve performance and reduce the costs
of wind-generated electricity. A computer rendering of the XL.50 is shown
at the right.
The
BWC XL.50 is rated at 50 kW at a wind speed of 11 meters/second (25 mph).
It will be available for three-phase utility interconnected applications with
outputs of 480 VAC, 60 Hz, for domestic customers, and 380 VAC, 50 Hz, for
overseas markets. A UPS (Uninterruptible Power Supply) option will also be
available for customers with grid reliability problems. For off-grid
applications, such as village electrification, a stand-alone version will be
available with an integral 70 kW inverter. As
with all Bergey wind turbines, the XL.50 is mechanically simple, has only three
moving parts, and is designed to require only a minimal level of
maintenance. As a variable speed machine with a direct-drive alternator,
it does not require a gearbox. The tail provides orientation into the wind
and the passive AutoFurl™ system provides storm protection in winds up to 54
m/s (120 mph). The blades are fabricated from fiberglass pultrusions which
feature high strength and outstanding fatigue resistance. The new BWC
SH-3032 airfoil has been optimized using the latest computational fluid dynamics
programs, and verified with extensive wind tunnel tests.  The
XL.50 will be the first variable speed wind turbine to adapt an essentially
off-the-shelf AC variable speed drive for conversion to utility grade
power. Working with engineers from ABB, BWC has developed a 70 kW
electrical subsystem based on their established line of power conversion
systems. It provides exceptional low wind speed performance, optimal rotor
loading throughout the operating range, and a conversion efficiency that peaks
in the neighborhood of 97%. The ABB drive is capable of either connecting
to the power grid or operating in a stand-alone mode using an integrated battery
bank.
 The
photo to the right shows the prototype Bergey XL.50 permanent magnet alternator
undergoing tests at the BWC factory. As with all Bergey wind turbines, the
XL.50 features an inverted configuration in which the outer magnet can turns and
the stator windings and central shaft are stationary. This allows the
stator output to transfer to transfer power without the need for slip rings or
brushes. The blades attach directly to the magnet can, thereby simplifying
the mechanical design of the rotor system. The alternator design is based
on state-of-the-art neodymium "super magnets". It has
demonstrated electrical efficiencies of up to 93%.
Overspeed
protection is provided by a version the well-proved BWC AutoFurl™ passive
furling system. A manual furling and dynamic braking system is included for
inspection and service. The
BWC XL.50 has been specifically designed to perform well in low wind speed areas
traditionally thought of as being unsuitable for wind power. Low wind speed
performance is greatly enhanced by ABB circuitry that optimally loads the wind
turbine down to wind speeds as low as 2 m/s (4.5 mph). Combined with the
new blade system, this circuitry allows the XL.50 to produce useful power more
than 6,500 hours a year at a typical site. For reference, a typical solar
system produces power 3,500 hours a year at a typical site. The
pre-prototype XL.50 is now undergoing developmental testing at the BWC factory
in Norman, Oklahoma, where winter winds and summer thunder storms provide a
challenging test environment. A prototype will be delivered to the
US-DOE's National Wind Technology Center (NREL) in Boulder, Colorado in 2003 for
further performance testing under the extreme wind and icing conditions that
prevail at the test site. NREL has performed structural tests on the BWC
XL.50 pultruded blades, verifying their exceptional strength. BWC
is maintaining a list of individuals and organizations who have expressed
interest in the XL.50 wind turbine. They will receive specific information
on performance and pricing when a delivery schedule has been established.
To receive further information on the BWC XL.50 as it becomes available, please
get in touch with Steve Wilke at his e-mail link at swilke@bergey.com.
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