The preliminary design criteria of the MP1-200 wind turbine are given along with a brief description of the wind turbine generator. Performance and operational experience and cost factors are included. Recommendations for additional research are listed

Spaulding, A. P., Jr.

English

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WTG ENERGY SYSTEMS' MPI-200 -
200 KILOWATT WIND TURBINE GENERATOR
Allen P. Spaulding, Jr.
WTG Energy Systems, Inc.
Buffalo, New York 14203
INTRODUCTION
The areas to be discussed in this presentation are related to
the preliminary design criteria as utilized on the MPI-200.
The significance of these design criteria are based on the
fact that the MPI-200 is the only wind turbine in operation
today that is producing synchronous alternating current using
a fixed pitch rotor configuration (fig. I).
The MPI-200 is installed on Cuttyhunk Island, Massachusetts
as part of the Island's independent utility grid system. The
municipal utility on Cuttyhunk Island is diesel engine powered
with an installed capacity of 465 kW. The annual demand
curve, Figure 2, is plotted against the wind turbine's
production rate. It is evident from this graph that the wind
turbine will have a profound effect on the rate of fuel
consumption with the exception of the demand peaks expe-
rienced during the summer months. Cuttyhunk Island was chosen
as the site for the prototype because it was felt that this
type of application was typical of the ideal installation
for this type of generating system. As Figure 2 indicates,
the wind turbine operates as the dominant power source much
of the time. For a wind generator to operate effectively in
this type of network it must be capable of maintaining its
frequency while operating in parallel with any size conventional
power plant.
The MPI-200 became operational as a test unit in June, 1977.
Since that time it has been subjected to numeurous operational
and environmental tests. The machine has been run for extended
periods at 70% over rated speed (80rpm) without damage to any
components. It withstood wind velocities in excess of I00 mph
on four separate occasions. This machine has proven the
concept that a fixed pitch rotor configuration can be utilized
effectively at a competitive cost to produce synchronous
power under all operating conditions normally associated with
conventional generating plants.
PRELIMINARY DESIGN CONSIDERATIONS
The first step taken in the preliminary design process was to
define the potential market for a 200 kilowatt wind generating
system. The methods used were simple, direct canvassing of
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potential end users; utility companies and large industry,
located in areas with high wind regimes. The results of this
survey indicated that potential customers would consider a
system such as the MPI-200 at an installed cost of approximately
$I,000 per kilowatt. In addition the survey indicated that
potential buyers wanted a design life for the major components
of at least 20 years, synchronous power production directly
from the system's generator, minimum service and maintenance,
and completely unattended operation over the full operating
range of the system.
The second step in the preliminary design process was to
conduct an historical survey of large wind turbines. Of
particular interest were the fatigue life of large systems
and the method(s) used to control rotor speed. Of equal
interest was the cost breakdown of these systems. The results
of this survey are suLnunarized below.
I. The Gedser Mill as constructed in Denmark in the mid
1950's appeared to be the most fatigue resistent large wind
turbine built to date (1974). In addition the costs involved
in the construction of this machine were within the guide
lines that we had originally set.
2. We found no control systems in the large wind turbines of
the past that could meet present day control requirements for
synchronous generating systems. All wind turbine control
systems up to that time utilized a variable pitch rotor as
the primary speed control. The only way that these systems
can produce constant voltage and frequency to meet present
day standards of accuracy is by parallel operation with a
much larger capacity grid system.
3. A third major problem that has plagued large wind turbines
is rotor fatigue caused, primarily, by the in plane gravitational
loads during operation. A second major contributor to rotor
fatigue results from the location of the rotor down wind from
the tower causing the blade to 'unload' once per revolution.
In addition, this phenomenon has been found to cause erratic
behavior in the generator's frequency control system due to
momentary loss of torque at the rotor.
MPI-200 DESIGN CRITERIA
- All steel construction
- 30 year design life for all major hardware components
- Fixed pitch rotor configuration
- Rotor operation up wind of the tower
- Solid state control and speed governing
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- Automatic, unattended operation
- Remote monitoring and control capability
- Operational range: 60deg. N to 50deg. S. latitude
- AC synchronous power produced directly from the wind
turbine's generator, through out the systems' operating
range, in either parallel or independent operation
- +/- 1% control accuracy of frequency and voltage in
either parallel or independent generator operation
- $i,000 per installed kW (1975 dollars)
MPI-200 WIND TURBINE DESCRIPTION
The MPI-200 wind turbine installed on Cuttyhunk Island,
Massachusetts, utilizes a three bladed, 80 feet in diameter
rotor operating upwind of the tower. The machine is constructed
entirely of steel. The tower height, measured from ground
level to the rotor's center line, is 80 feet. The rotor
operates at a constant 30 rpm driving a 250 KVA synchronous
generator through a 40;1 gear transmission. Blade tips
rotate 60 degrees out of plane to provide aerodynamic braking.
A 24 inch disc brake mounted on the high speed shaft is used
for "parking" the rotor. Yaw position is controlled by dual
hydraulic servo motors working through two speed reducing
transmissions. The entire nacelle assembly rotates on a 59
inch platter bearing. A 72 inch disc brake is provided for
locking the yaw position. The tower used is a pinned-truss
type, constructed of Cor-Ten steel. Wind speed and direction
are sensed on a remote tower and are used to control startuD,
shutdown and yaw sequences. Components are shown in figure 3.
A system for controlling the speed of the wind turbine has
been developed by WTG Energy Systems which utilizes load
modulation with the fixed pitch rotor configuration. An
industrial process controller is used for the control and
monitoring on the MPI-200. This processor represents an
ideal compromise in cost, input/output capabilities, processing
speed and reliable operation in rough environmental conditions.
A versatile software feedback control algorithm is provided
and utilized in the speed control system. The controller is
an "off-the-shelf" item with no required hardware modifications.
PERFORMANCE AND OPERATIONAL EXPERIENCE
The MPI-200 has produced power in excess of 300 kilowatts in
winds of 35 miles per hour. Operation begins in wind speeds
above 8 miles per hour and rated output is achieved at 28
miles per hour. The machine is shut down when the average
wind exceeds 40 miles per hour. Power varies directly with
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the rotor response to variations in wind velocity about the
mean. Power regulation or stabilization of the output is not
used in this design. Fluctuations in power approach 30
percent of nominal output in high gusty winds. As a result
of the relatively low frequency response characteristics of
the high inertia rotor, deviations of this magnitude should
not present a problem to most utility networks.
The pitch of the rotor is adjusted initially to reach its
peak power coeffecient in winds of 18 miles per hour. In
winds above this level the rotor goes into a stalling condition.
This condition was found to be gentle and predictable; Dower
continues to increase up to the peak and levels gradually.
This phenomenon inherently limits the maximum level of power
produced.
Figure 4 shows a strip chart of the wind generator regulating
independently of any other source. Regulation of the generator's
speed is very good in winds up to 25 miles per hour and tends
to degrade slightly above this speed as a result of the high
frequency gust components common with higher wind velocities.
Worst case accuracy of plus or minus 0.75 hertz (generator
output frequency) is specified for isochronous operation.
This accuracy is, of course, improved when operating in
synchronism with a stable source of equal or greater capacity.
Figure 5 depicts an actual strip chart of the wind generator's
performance under synchronous operating conditions. After the
speed is adjusted the main contactor is energized. As is
standard practice, speed droop is provided on the diesel
plant and is adjusted at 2 percent. The load will be divided
proportionally to the generator's speed setting. When the
wind generator is capable of carrying the entire town load it
will do so at a nominal frequency of 60 hertz. The diesel
plant will at this point be idling because of its droop
setting. As the wind generator's capacity drops ( because of
a decrease in wind velocity ) its speed will begin to fall
and the diesel set will pick up the proportion of load
dropped by the wind generator thus allowing the generators to
maintain nominal frequency while dividing the load proportional
to the input torque of the wind generator. System frequency
could fall as low as 59.5 hertz when the diesel is fully
loaded and the wind generator is idling. This condition
would occur when the wind velocity is varying around 8 miles
per hour, and the wind turbine would be taken "off line" to
prevent excessive reverse power flow. When the output of the
wind generator is greater than the Town's demand the remainder
of its output is dissipated in the load bank.
Numerous tests and refinements have been made to achieve a
high level of performance. Modifications on the basic design
have been directed in the following areas:
i. Yaw system drive torque and bedplate-to-tower coupling
The orginal hydraulic motors used to yaw the machine proved
82
to be insufficient in terms of torque capabilities. They were
replaced with motor/transmission units. A slight decrease in
the yaw rate occurred, but the torque was increased to a
level sufficient to drive the machine under any condition.
The bedplate to tower coupling was provided with a 72 inch
disc brake with three hydraulic calipers. This brake maintains
a very stiff coupling at this critical union.
2. Control system bandwidth
The original signal conditioning and output actuating equipment
was found to be insufficient in response, to accurately
control the frequency of the wind turbine in wind velocities
above 25 miles per hour. The wind generator was always
stable in operation when "locked" in synchronism with a
stable source of approximately 4 times its nominal capacity.
Used in "Infinite Bus" applications, interface should present
no difficulty with the system as presently configured. Work
is being done to increase the effective range of operation
for remote applications such as Cuttyhunk. The faster control
system should be operational by May, 1979.
COST
We are continually working to increase the performance and
lower the cost of this system, without sacrificing reliability.
At present production costs, Figure 6, are of prime interest.
Our goal, as stated earlier is $i,000 per installed kW. At
this time WTGEnergy Systems is quoting a price of $226,000
FOB the plant, or approximately $1,130.00 per kW. We have
calculated that with a production run of 5 units the per unit
cost could be reduced by 30%. This would equal an FOB cost of
$158,000 or $791.00 per kilowatt.
FUTURE R & D REQUIREMENTS AND SUGGESTIONS
The areas in the design and operation of the MPI-200 system
in particular, and, wind turbine generator systems in general
requiring additional research and development are listed
below.
I. Increased field testing of large wind turbines interfaced
with small hydro electric installations should be given high
priority. This application has the potential of allocating
greater capacity credits for both systems.
2. Increased emphasis on field testing wind turbine/diesel
packaged systems. Emphasis should be placed on the design of
diesel engine combustion requirements operating with reduced
loads and the retrofitting of existing units for similar
operational parameters.
3. Field testing of multiunit wind generating systems interfaced
83
with conventional grid systems. Of particular interest are
combination systems each with equal installed capacities.
CONCLUSION
To date the system has met or exceeded the original design
criteria. We feel that this system demonstrates that synchronous
power can be produced directly from a wind driven generating
system at a cost that is competitive, in many areas, with
conventionally powered generating systems.
We are continuing to work on improvements in the control
system, on production techniques and methods of installation
to futher reduce the system's cost and increase its reliability.
DISCUSSION
Q. Can you discuss the blade construction?
A. That will be covered in a later paper by Bob Barrows, the chief engineer
of this project. I will let him answer that question.
Q. What is the rotor diameter and rated power?
A. The rotor diameter is 80 feet, and the rating is 200 kilowatts in a 26 to
28 mph wind.
Q. What is your assessment of the market potential, in dollars per year over
the next five years, for intermediate size machines?
A. Since we had our press conference, we have written about ten proposals to
utility companies all over the world--in Australia, Africa and some in the
United States. There are about 500 small diesel utilities in the United
States that are in high wind areas. That's the best I can tell you right
now. We are in the process of doing a lot of work in this area. As a
matter of fact, we are spending most of our money and time on this aspect
of the business.
Qo
A.
How much energy is being discarded during the winter and summer months?
No energy is thrown away in the summer, as this is the island's peak demand
period. At night during the winter, the demand for the island often drops
to as low as 20 kilowatts while the wind turbine is operating at maximum
output. During this period quite a bit of power is discarded.
The island's power plant is a municipal plat. Presently no heat, hot water
and cooking requirements are part of the utility's demand. If more of the
island's energy requirements were served by the utility, less would of
course, be burned off. Ultimately, it will be up to the utility and the
residents to decide how much of their total demand should be electrical and
the economic value of the conversion.
84
Figure  1. - MP1 - 200 wind t u r b i n e  g e n e r a t o r .  (Photo cour t e sy  
of Eagle  S i g n a l  D iv i s ion ,  Gulf and Western Manufactu.ring 
Company. ) 
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Figure  2 .  
MI JUN JUL AUG SEP Kl NOY OEC 
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- Energy comparison. 
85 
Figure  3 .  - Wind t u r b i n e  gener- 
a t o r  components. 
86 
_N[UTOR
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Figure 4. - Wind generator regulation.
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Figure 5. - Performance under synchronous operatingconditions.
87
COMPONENT PER CENT OF TOTAL COST COST
RIBS 18.4% $ 7,560.00
SPARS 12.3% 5,040.00
HUB 18.4% 7,560.00
TIP FLAPS 13.8% 5,670.00
BLADE SKIN 5.4% 2,250.00
MISC. HARDWARE 4.9% 2,030.00
LABOR 26.8% 10,810.00
100Z $ 40r920-00TOTAL
Figure 6.- Cost breakdown MP-I 200 rotor sys-
tem _y major components (sale price for limited
production).
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WTG Energy Systems' MP1-200 200 kilowatt wind turbine generator

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