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The following topics contain news items from Wind Energy Weekly,
Vol. 11, #518, 10.12.92, published by the American Wind Energy
Association.  For more information on the Association, contact
AWEA, 777 North Capitol, NE, Suite 805, Washington, DC 20002, USA,
phone (202) 408-8988, fax (202) 408-8536, telex 6503304640 MCI UW.


DUTCH SCORE SUCCESSES
WITH VARIABLE SPEED

While attention in the United States has been focused on U.S.
Windpower's $20 million development of its 33m VS variable-speed
wind turbine, Dutch development of the variable-speed technology
has been largely overlooked here.

Although the variable-speed idea is not new (Bergey Windpower Co.
of Norman, Okla., has been building grid-connected small wind
turbines operating at variable speeds for more than a decade), it
was the Dutch who first employed the concept on utility-scale
machines.

Several years ago, Stork-FDO Wind Energy, a consortium of two Dutch
aerospace companies designed a series of variable speed wind
turbines for the Dutch government's energy research program.  Four
turbines were eventually installed, and two are still in service,
one in the Netherlands, the other on the Caribbean island of
Curacao.

Building on this experience, Lagerweij, a small Dutch manufacturer,
has installed nearly 250 smaller variable-speed machines during the
past six years (see accompanying item).

Variable speed is attractive because it enables designers to gain
greater rotor efficiencies by allowing the rotor speed to vary in
response to changes in wind speed.  There may be additional
benefits as well: slower rotor speeds in light winds may lower
noise emissions just when aerodynamic noise of the blades is most
noticeable, and variable speeds may reduce dynamic loads on the
turbine's drive train, thus extending the turbine's life.

Not all manufacturers are convinced that it is sufficiently
attractive to justify variable speed's greater cost. Nevertheless,
the concept has long attracted the interest of designers.

Stork-FDO began development of variable-speed turbines in the early
1980s, using the technology then available. The Dutch consortium
first built a 26.5-meter (87-foot), 300-kW turbine called the
NEWECS-25.

Three of the two-bladed upwind machines were built, two in the
Netherlands and one on Curacao, an island in the Netherlands
Antilles. Only the turbine on Curacao is still operating.

The NEWECS-25 was a forerunner of a 1-MW turbine, the NEWECS-45,
now operating at Medemblik on the shore of the Ijsselmeer, the
large Dutch inland sea formed by closure of the Zuider Zee.  Both
designs incorporate a variable-pitch rotor driving a variable-speed
generator through a planetary transmission.  The turbines generate
utility-compatible electricity by conditioning the generator's
output with power electronics.

The NEWECS-25 on Curacao has logged more than 43,000 hours of
grid-connected operation since its installation in September, 1985.
The extremely well maintained turbine has been in near-continuous
service since a control failure destroyed the turbine's brake in
1988, and the power electronics manufactured by Brown Boveri
Nederlands have continued to perform to the local utility's
satisfaction.

The turbine, located at Boca San Pedro on Curacao's northeast
shoreline, is the only intermediate-size wind machine still
operating in the Caribbean, according to Margo Guda of Curacao's
Fundashon Antiyano Pa Energia.  Guda characterizes the Stork-FDO
turbine as the unsung success story of Dutch wind turbine
development.

Neither Stork nor FDO currently manufacture wind turbines.  The
chief designer of the NEWECS turbines for Stork-FDO, Paul Hensing,
later engineered the corporate takeover of Belgian turbine maker
Windmaster by the Dutch Begemann conglomerate.

Lagerweij has essentially commercialized the variable-speed concept
in the Dutch domestic market and has begun to export turbines to
nearby Germany.

LAGERWEIJ SEES GROWING
TURBINE SALES

The northern Dutch provinces of Friesland and Groningen are now
dotted with a gaunt two-bladed wind turbine that has come to
symbolize the Dutch private sector's development of wind energy.

As the Dutch utility program "Wind Plan" falters, sales of the
variable-speed machine built by Lagerweij Windturbine BV have
boomed, according to Jos Beurskens of Energie Centrum Nederlands
(ECN), the country's energy research center.

The unusual wind turbine is the brainchild of Henk Lagerweij, who
builds the machines at his shop in the small Dutch farm town of
Kootwijkerbroek in the southern province of Gelderland.  In a part
of the world where nearly all wind turbines use three-bladed rotors
upwind of their towers to drive conventional induction generators,
Lagerweij's design stands apart.

During the mid-1980s, Lagerweij began his quest by building a more
or less conventional three-blade machine 10 meters (33 feet) in
diameter.  A few of the turbines with their distinctive pitch-
regulating mechanism can still be seen on the Dutch landscape. But
Lagerweij found his stride with a 15-meter (49-foot), two-bladed
design that uses power electronics to deliver utility-compatible
electricity. By 1991, when the 75-kW design was superseded by a
larger machine, he had built 150 of the turbines.

Beginning in late 1991, Lagerweij began shipping an 18-meter (59-
foot) version of the machine rated at 80 kW. According to
Lagerweij, the LW 18/80 delivers 40% more energy on the Dutch coast
and up to 50% more energy inland than its predecessor, in large
part due to the turbine's greater swept area.

Unlike other Dutch manufacturers such as NedWind and Windmaster,
Lagerweij has opted for a relatively low generator capacity rating
relative to his turbines' swept area.  Typical Dutch designs such
as NedWind's 35-meter (115-foot), 500-kW turbine and Windmaster's
33-meter (108-foot), 500-kW design load the rotor heavily with
0.52-0.58 kW of generator capacity per square meter of rotor swept
area.  In contrast, variable-pitch Danish machines usually load the
rotor with no more than 0.42 kW/m2.  According to Lagerweij, he
tries to optimize the price-to-performance ratio of the generator
by loading the rotor on his new machine to only 0.31 kW/m2.  No
modern wind turbine has used such a small generator relative to the
turbine's rotor diameter since the advent of a 10-meter (33-foot),
25-kW model from the U.S. firm Carter Wind Systems in the late
1970s.

Lagerweij also uses passive pitch control to regulate the speed of
the flexible two-bladed rotor, a design feature that both Carter
and Windtech attempted to master during the early 1980s.  Lagerweij
carries the design one step further and marries this flexible rotor
system to a variable speed generator, a feat not yet attempted in
the U.S.

Although few details are available, Lagerweij has announced that he
is developing a 250-kW design.

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