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LoREPRESEA 0 •EXIR S OR
LEG L NOnCE
u e f or or d mages resuh-
rmallon appa tu.pr •or composition
Thl r pori was pr pared b 8al elle as an account of spon ored
resear h aCflvill .either ponsor nor 8anell nor any p rson acting
on beh If of either:
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Wind Energy Alternative for the
Railbelt Region of Alaska
Volume XVI
Ebasco Services Incorporated
Bellevue,Washington 98004
August 1982
Prepared for the Office of the Governor
State of Alaska
Division of Policy Development and Planning
and the Governor I s Policy Revi ew Committee
under Contract 2311204417
Battelle
Pacific Northwest Laboratories
Richland,Washington 99352
ARLIS
Alaska Resources Library &Information Services
librarY BuildiTHl,Suite 111
32ri Providence Drive
Anchorage,AK 995084614
1"K
1425
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ACKNOWLEDGMENTS
The major portion of this report was preparecr by the Bellevue,Washington,
and Newport Beach,California.offices of Ebasco Services Incorporated.Their
work includes the Introduction.Technical Description,Environmental and Engi-
neering Siting Constraints,Environmental and Socioeconomic Considerations and
Institutional Considerations.Capital cost estimates were prepared by
S.J.Groves and Sons of Redmond,Washington,and reviewed by the Ebasco cost
estimating department in New York City.Cost of energy calculations were pre-
pared by Battelle,Pacific Northwest Laboratories of Richland,Washington.
iii
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PREFACE
The state of Alaska,Office of the Governor,commissioned Battelle,
Pacific Northwest Laboratories (Battelle-Northwest)to perform a Railbelt
Electric Power Alternatives Study.The primary objective of this study was to
develop and analyze long-range plans for electrical energy development for the
Railbelt Region (see Volume I).These plans will be used as the basts for
recommendations to the Governor and Legislature for Railbelt electric power
development,including whether Alaska should concentrate its efforts on
development of the hydroelectric potential of the Susitna River or pursue
other electric power alternatives.
Large wind energy conversion systems were selected for consideration in
Railbelt electric energy plans for several reasons.Several areas of excel-
lent wind resource have been identified in the Railbelt,notably in the Isabel
Pass area of the Alaska Range,and in coastal locations.The winds of these
areas are strongest during fall,winter and spring months,coinciding with the
winter-peaking electric load of the Railbelt.Furthermore,proposed hydro-
electric projects in the Railbelt would prove complementary to wind energy
systems.Surplus wind-generated electricity could be readily Ustored ll by
reducing hydro generation.Hydro operation could be used to rapidly pick up
load during periods of wind insufficiency.Wind machines could provide addi-
tional energy,whereas excess installed hydro capacity could provide capacity
credit.Finally,with the exception of their visual presence,wind systems
have few adverse environmental effects and appear to have widespread public
support.
A prototypical large wind energy conversion system was selected for study.
The prototype consi sted of a wi nd farm located in the Isabel Pass area and was
comprised of ten 2.5-MW-rated capacity,Boeing MOD-2,horizontal axis wind tur-
bines.This report,Volume XVI of a series of seventeen reports,documents
the findings of this study.
Other power-generating alternatives selected for in-depth study included
pulverized coal-fired power plants,natural gas-fired combined-cycle power
v
plants,the Chakachamna hydroelectric project,the Browne hydroelectric proj-
ect and coal-gasification combined-cycle power plants.These alternatives
are examined in the following reports:
Ebasco Services,Inc.1982.Coal-Fired Steam-Electric Power Plant
Alternatives for the Railbelt Region of Alaska.Prepared by Ebasco
Services Incorporated and Battelle,Pacific Northwest Laboratories
for the Office of the Governor,State of Alaska,Juneau,Alaska.
Ebasco Services,Inc.1982.Natural Gas-Fired Combined-Cycle Power
Plant Alternative for the Railbelt Region of Alaska.Prepared by
Ebasco Services Incorporated and Battelle,Pacific Northwest Labora-
tories for the Office of the Governor,State of Alaska,Juneau,
Alaska.
Ebasco Services,Inc.1982.Chakachamna Hydroelectric Alternative
for the Railbelt Region of Alaska.Prepared by Ebasco Services
Incorporated and Battelle,Pacific Northwest Laboratories for the
Office of the Governor,State of Alaska,Juneau,Alaska.
Ebasco Services,Inc.1982.Browne Hydroelectric Alternative for
the Railbelt Region of Alaska.Prepared by Ebasco Services Incor-
porated and Battelle,Pacific Northwest Laboratories for the Office
of the Governor,State of Alaska,Juneau,Alaska.
Ebasco Services,Inc.1982.Coal-Gasification Combined-Cycle Power
PlantAlternative for the Railbelt Region of Alaska.Prepared by
Ebasco Services Incorporated and Battelle,Pacific Northwest Labora-
tories for the Office of the Governor,State of Alaska,Juneau,
Alaska.
vi
SUMt-'iARY
'.'Several sites showing substantial potential for -the development of wind-
powered electricity generation have been identified in the Railbelt Region of
Alaska.These include sites along the Gulf of Alaska and the Isabel Pass
Region in the Alaska Range,south of Big Delta.The seasonality and magnitude
of the Isabel Pass wind resource was thought to be sufficiently favorable to .
warrant an in-depth investigation of the costs and performance characteristics
of wind turbine generators in this area.
Accordingly,a suitable site,wind turbine design and cluster configura-
tion were chosen for further study.The site for the proposed project is
north of Isabel Pass in the valley of the Delta River,near the Black Rapids
Glacier.The wind farm would consist of 10 Boeing MOD-2 (BWT-2560)units
rated at a full load capacity of 2.5 MW each,for a total installed capacity
of 25 MW.The machines would be installed in two clusters of five machines
each,on the west side of the Richardson Highway.Power from the project
would be transmitted at 138 kV,approximately 50 miles to intertie with the
Golden Valley Electric Association (GVEA)system at Big Delta.The proposed
138-kV line would be of sufficient capacity to transmit up to 80 MW of power,
providing additional capacity for future wind turbine clusters.The estimated
annual average energy production from the project is 73.3 GWh.
Cost estimates for the proposed project indicate an overnight capital
cost of 2490 S/kW,fixed operation and maintenance costs of 3.68 $/kW/yr and
variable operation and maintenance costs of 3.3 mills/kWh.AssUming a 1990
in-service date,(a)levelized busbar energy costs were estimated to be
103 mills/kWh.This busbar energy cost should not,however,be used for
direct comparison with other generating options,since wind machines operate
intermittently and should be evaluated as fuel savers.The cost of energy
produced by the machines should be compared to the energy cost of production
potentially displaced by wind turbine operation.Given the current suite of
generating plants in the Fairbanks Municipal and GVEA systems,it appears
(a)Used for comparative purposes in this series of power plant analyses.
vii
that the winter peaking wind resource would largely displace oil-fired com-
bustion turbine production.Thus,even given the somewhat high forecasted
cost of energy from the proposed wind turbine farm,the installation could
conceivably be economically competitive.However,if the Anchorage-Fairbanks
electrical intertie is completed,the availability of lower-cost natural gas-
fired capacity to the Fairbanks-GVEA region may substantially alter the feasi-
bility of the proposed wind system.
A minimum of 3 years would be required for project development,including
a minimum of 1 year for wind resource studies and 2 years for construction.
The BWT-2560 machines described in this analysis are currently available for
order;however,further testing of the prototype machines currently installed
at Goodnoe Hills,Washington,and assessment of potential machine performance
in cold climate conditions appear to be desirable prior to order.
Environmental effects of the proposed wind turbine farm appear to be
minor.Hydrologic and atmospheric effects would be minimal;the principal
impact would be aesthetic.No significant engineering constraints appear to
be present other than the fairly lengthy transmission link required to inter-
tie with the existing GVEA system.The costs of the transmission link could
be shared with several additional wind turbine clusters.
viii
CONTENTS
ACKNOWLEDGMENTS
PREFACE
SUMMARY
1.0 INTRODUCTION
1.1 WIND ENERGY HISTORY.
1.2 U.S.WIND ENERGY PROGRAM
1.3 CURRENTLY AVAILABLE AND ADVANCED TECHNOLOGIES
1.4 ADVANTAGES AND DISADVANTAGES OF WINO
ENERGY SYSTEMS .
2.0 TECHNICAL DESCRIPTION
2.1 SITE DESCRIPTION
2.2 PLANT DESCRIPTION
2.2.1 Overview
2.2.2 Wind Machines
2.2.3 Operation and Performance
2.2.4 Auxiliary Facilities
2.3 TRANSMISSION SYSTEM .
2.4 SITE SERVICES .
2.5 CONSTRUCTION
2.5.1 General Construction Methods
2.5.2 Construction Schedule .
2.5.3 Construction Work Force
2.6 OPERATION AND MAINTENANCE
2.6.1 General Operating Procedures
ix
iii
v
vii
1.1
1.1
1.2
1.3
1.4
2.1
2.1
2.11
2.11
2.16
2.25
2.29
2.31
2.32
2.34
2.34
2.37
2.39
2.40
2.40
2.6.2 Operating Parameters
2.6.3 Plant Life
2.6.4 Operating Work Force
2.6.5 General Maintenance Requirements .
3.0 COST ESTIMATES.
3.1 CAPITAL COSTS .
3.1.1 Construction Costs
3.1.2 Payout Schedule
3.1.3 Capital Cost Escalation
3.1.4 Economics of Scale
3.2 OPERATION AND MAINTENANCE COSTS
3.2.1 Operation and Maintenance Costs
3.2.2 Operation and Maintenance Cost Escalation
3.2.3 Economies of Scale
3.3 COST OF ENERGY.
4.0 ENVIRONMENTAL AND ENGINEERING SITING CONSTRAINTS
4.1 ENVIRONMENTAL SITING CONSTRAINTS
4.1.1 Water Resources
4.1.2 Air Resources
4.1.3 Aquatic Ecology
4.1.4 Terrestrial Ecology
4.1.5 Socioeconomic Constraints
4.2 ENGINEERING SITING CONSTRAINTS
4.2.1 Meteorological Aspects.
4.2.2 Site Topography and Geotechnical
Characteristics
x
2.41
2.44
2.44
2.44
3.1
3.1
3.1
3.1
3.1
3.3
3.4
3.4
3.4
3.4
3.4
4.1
4.1
4.1
4.1
4.2
4.2
4.2
4.3
4.3
4.4
4.2.3 Access Road and Transmission Line
Considerations
5.0 ENVIRONMENTAL AND SOCIOECONOMIC CONSIDERATIONS
5.1 SUMMARY OF FIRST ORDER ENVIRONMENTAL IMPACTS.
5.2 ENVIRONMENTAL AND SOCIOECONOMIC EFFECTS.
5.2.1 Water Resource Effects .
5.2.2 Air Resource Effects
5.2.3 Aquatic Ecosystem Effects
5.2.4 Terrestrial Ecosystem Effects
5.2.5 Socioeconomic Effects .
6.0 INSTITUTIONAL CONSIDERATIONS
6.1 FEDERAL REQUIREMENTS
6.2 STATE REQUIREMENTS •
6.3 LOCAL REQUIREMENTS .
7.0 REFERENCES
xi
4.4
5.1
5.1
5.1
5.1
5.2
5.2
5.2
5.3
6.1
6.1
6.2
6.4
7.1
I
FIGURES
2.1 Area Location Map
2.2 NCC Station Locations in Southcentral Alaska
2.3 Seasonal Average Wind Power in Southcentral Alaska
Winter
2.4 Seasonal Average Wind Power in Southcentral Alaska -
Spring
2.5 Seasonal Average Wind Power in Southcentral Alaska
Summer
2.6 Seasonal Average Wind Power in Southcentral Alaska
Autumn
2.7 Annual Average Wind Power in Southcentral Alaska
2.8 Histogram of Seasonal Wind Power Density at
Delta River Canyon.
2.9 Wind Variations at Big Delta.
2.10 Examples of Variation of Wind Velocity with
Height for Various Wind Speeds
2.11 large Wind Energy Conversion System Plot Plan
2.12 BWT-2560 Features and Characteristics
2.13 Rotor Blade Configuration
2.14 Rotor Hub Arrangement
2.15 Drive Train Arrangement .
2.16 Nacelle Arrangement
2.17 Wind Turbine System Conceptual Site Plan
2.18 Control System Interface Diagram .
2.19 BWT-2560 System Power Output Profile
2.20 One-Line Diagram
2.21 Project Schedule
xii
2.2
2.3
2.5
2.5
2.6
2.6
2.7
2.8
2.9
2.14
2.17
2.18
2.20
2.21
2.21
2.23
2.25
2.27
2.28
2.30
2.38
2
3
5
5
6
6
7
8
9
14
17
18
20
21
21
23
25
27
28
30
38
2.22 Construction Work Force Requirements
2.23 Estimate of Expected Average Power Output for Wind
Turbines as a Function of Cutout,Rated and Mean
Wind Speeds and Rated Power Output
3.1 Cost of Energy Versus Capacity Factor
3.2 Cost of Energy Versus Year of First Commercial
Operation
xiii
2.40
2.42
3.5
3.6
TABLES
2.1 Classes of Wind Power Density.
2.2 Computation of Average Annual Energy Production
2.3 Preliminary Preventative Maintenance List for MOD-6-
Sized Wind Turbine
3.1 Bid Line Item Costs for Wind Energy Conversion System
3.2 Payout Schedule for Wind Energy Conversion System
5.1 Environment-Related Power Plant Characteristics
6.1 Federal Regulatory Requirements
6.2 State Regulatory Requirements.
2.4
2.43
2.45
3.2
3.3
5.1
6.3
6.4
1.0 INTRODUCTION
3
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The intent of this study is to describe the characteristics and costs of
a typical wind farm that can be treated as a modular unit in the development
of Railbelt electric energy plans.The typical wind farm consists of 10 hori-
zontal-axis,2.5-MW MOD-2 wind turbines,with a 25 MW total rated capacity.
Because the Railbelt electric energy plans may include several typical wind
farms,this study presents an understanding of possible economies of scale
resulting from use of joint facilities (e.g.,maintenance and control facil-
ities)by adjacent wind farms.
Machine design is based upon technology that is now available and appli-
cable to cold climate regions.The wind farm can be constructed to come on
line in the 1985-1986 time frame.
The typical wind farm is assumed to be located in the Isabel Pass wind
resource area south of Big Delta.Estimates of the wind resource in this
vicinity were obtained from the Alaska Wind Resource Atlas (Arctic Environ-
mental Information and Data Center (AEIDC)1981).It is assumed that access
to the potential wind farm sites will be from the Richardson Highway and that
a 138-kV transmission line would have sufficient capacity to deliver the
output to the Fairbanks area.
1.1 WIND ENERGY HISTORY
The history of large wind energy conversion systems stretches back to
Persia,to as early as 200 B.C.During this period the use of windmills of
various types spread throughout the Islamic world.By the 11th century A.D.
windmills were in extensive use in the Middle East and were introduced into
Europe in the 13th century by returning Crusaders.Windmills were extensively
developed and deployed in Holland for draining and reclaiming low lands.
Later they were applied to commercial tasks such as grinding grain and oper-
ating sawmills.By the middle of the 19th century some 9,000 windmills were
in use in the Netherlands for a variety of purposes.With the introduction of
1.1
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the steam engine during the Industrial Revolution,the use of wind power
started to decline.However,there are still many windmills operating in
Holland today.
In the United States the use of windmills has been widespread.Since the
mi d-19th century,more than 6 mi 11 i on sma 11 wi ndmi 11 s of 1es s than 1 horsepower
each have been built and operated to pump water,generate electricity,and per-
form other functions.Over 150,000 windmills are still in operation.Wind
energy supplied a significant amount of energy to rural areas of the U.S.until
the Rural Electrification Administration (REA)introduced electrical coopera-
tives in the mid-1930s.With widespread electrical energy availability,there
was diminishing use of and interest in wind power,and almost all alternative
forms of energy production,until the early 1970s when a sharp increase in the
price of imported oil occurred in the U.S.
1.2 U.S.WIND ENERGY PROGRAM
As a result of the increase in energy costs~the U.S.Federal Government
undertook an accelerated Wind Energy Conversion System (WECS)program with the
objective of stimulating the development of WECS capable of producing a sig-
nificant amount of the U.S.energy needs by the year 2000.This program
originated in the National Science Foundation and was moved to the Energy
Research and Development Administration (ERDA)when it was formed.In October
1977 ERDA became part of the Department of Energy (DOE).Major parts of the
Federal Wind Energy Program were administered by the Lewis Research Center of
the National Aeronautics and Space Administration (NASA)under DOE funding.
The DOE has spent about ~200 million on wind turbine research and devel-
opment.The purpose of the program is to develop small-~intermediate-,and
large-scale wind turbines to harness the wind in a cost-effective way.This
wind turbine development effort includes construction of several intermediate-
and large-scale wind turbines at utility sites and experimental testing of
these machines on utility networks.
1.3 CURRENTLY AVAILABLE AND ADVANCED TECHNOLOGIES
~r-
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The MOD-2 wind turbine,a second-generation machine rated at 2.5 MW in a
wind of 27.5 mph,is the latest development in the U.S.wind program.MOD-2,
designed,built,and installed by the Boeing Engineering and Construction
Company,is the culmination of an effort to design a machine with a high
potential for commercial production.It is projected that the MOD-2,when
produced in quantities of 100 or more,can generate electrical energy at a
cost very close to the current costs of fossil-fuel generated electricity
(Linscott et al.1981).The first cluster of three MOD-2 demonstration wind
turbines,located near Goodnoe Hills,Washington,has been producing power for
the Bonneville Power Administration.
The Bureau of Reclamation of the Department of the Interior is examlnlng
the integration of large clusters of wind-turbine generators with existing
hydroelectric power systems.The technical and economic feasibility of this
concept will be evaluated by the installation and operation of two different
wind turbines.Each wind turbine,called a Systems Verification Unit (SVU),
will be installed at the site of a potential cluster of wind turbines.One
such site is located approximately 5 miles southwest of Medicine Bow,Wyoming.
The SVU wind turbines will be placed about 3000 feet apart and are scheduled
to start checkout operations in late-1981.The Bureau of Reclamation awarded
a contract to Hamilton Standard to design,fabricate,install,and test a wind
turbine called the WTS-4 SVU machine.The WT5-4 has a 265-foot-diameter rotor,
supported on a tubular steel tower with a hub height of 262 feet.~ith a wind
speed of 36 mph at hub height,the WTS-4 is designed to produce 4 MW of power.
In addition,NASA awarded a contract to the Boeing Engineering and Construc-
tion Company to install a MOD-2 SVU machine near Medicine Bow.The MOD-2
machine is described in detail in later sections of this report.
NASA has awarded contracts to General Electric Company and Boeing Engi-
neering and Construction Company to design a MOD-5 wind turbine generator,with
7 MW output.The MOD-5 is to reduce the cost of electricity by 25 percent
under that predicted for the MOD-2 machines.Typically,it has taken about
3 years from the start of a program to first rotation,with about another year
1.3
i___helilill!!~======~_
for testing and commercial acceptance by the purchaser.However,no money has
been authorized for construction of a demonstration MOD-5.Thus,the avail-
ability of this machine is highly uncertain.
1.4 ADVANTAGES AND DISADVANTAGES OF WIND ENERGY SYSTEMS
As with most of the solar energy alternatives,the advantage of the wind
energy conversion system is that the energy,or IIfuel,1I is free and operating
costs are low.The major revenue requirements are for repayment of the capital
costs associated with the initial construction of the facility.Hence,the
revenue requirements are practically lIinflation prooL II
The disadvantages are that the capital cost is somewhat high relative to
other generation capacity in terms of cost per kilowatt,and that power is
available only on an intermittent basis,thus depriving wind turbines of sig-
nificant capacity credit.A third disadvantage is that the power density is
low so that the cost of switchgear,tie lines,transmission lines,and other
required components needed to consolidate power will add to the already high
cost per kilowatt.
Even the largest wind generator now envisioned,the 7.2-MW,MOD-5B,is
still very small by contemporary util ity standards.New coal-fired power
plants have power ratings of 500 to 700 MW.The simplicity of the wind genera-
tor compared to such a plant is counterbalanced by the need for two hundred
twenty-five 7-MW units operating at a capacity factor of 0.35 over the year to
match the annual energy production of one 70Q-MW coal-fired plant (DeRenzo
1979).
Because of the finite probability that a low wind condition would result
in no energy production from the wind farm,the cost of backup capacity must
be considered.Backup capacity can be provided by hydroelectric projects with
storage capacity,energy storage facilities (i.e.,pumped hydro)or thermal
units with load-following capability.When operated in parallel with hydro-
electric or thermal facilities,wind systems are operated as intermittent
baseload capacity,displacing plants of higher variable operating cost.This
is so-called IIfuel saver ll operation.The fuel saved may be coal,gas or oil
for disp'laced thermal capacity,or water (retained in storage)for displaced
1.4
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....
hydroelectric capacity.Two factors,the amount of high variable cost capac-
ity available for displacement and possible system control difficulties with a
high percentage of intermittent generation,may limit the amount of wind
energy capacity that should be installed to around 20 percent of total system
capacity.
Whether wind energy systems can be economically justified depends upon
both the capital costs and the availability of the wind energy compared to the
energy value of the power displaced.Evaluation of the economic feasibility
of wind energy systems is accomplished by computing the levelized busbar cost
of energy over the period of study with and without wind energy systems.
Rather than prejudge whether large-scale wind energy conversion systems
can be competitive in Alaska,a conceptual design for a 25-MW wind farm on the
Delta River is presented in this report.The potential amount of wind energy
available through this system is evaluated,and estimates are prepared for
capital and operating costs for this system,which would deliver its energy to
Fairbanks.Since energy storage is not available,the economics of wind power
must be evaluated in terms of its energy savings in the existing power system.
The basic procedure to be followed is to evaluate the proposed site on
the Delta River,north of Isabel Pass,using the site-selection criteria of
Hiester and Pennell (1979),considering available wind resource data (AEIDC
1981,Hiester 1980).A conceptual design is prepared using the Boeing MOD-2
system description for wind turbines.A tentative site and configuration are
selected.The required supporting facilities and transmission systems are
examined in the context of the severe environment.It is concluded that once
the support facilities are in place,the resource is of sufficient magnitude
that the power output of the site could be increased by an order of magnitude
without requiring a substantial increase in the support facilities.The con-
templated transmission facilities would be capable of supporting up to 55 MW
of additional capacity.
A tentative project schedule is developed.The lead time of the wind tur-
bine equipment is reasonably short.One of the pacing items in the construc-
tion schedule is having a wind-free period during the summer months for the
1.5
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L ;
I
installation of the nacelles and rotors on the 20D-foot towers.It is expected
that these conditions would occur for about 6 to 8 weeks each summer.The
entire construction schedule,equipment,and labor force must be keyed around
this "window."
In summary,two clusters of five MOD-2,2.5-MW wind turbines will comprise
the proposed 25-MW large wind energy conversion system.A tentative site has
been selected on the west side of the Delta River at the foot of Black Rapids
Glacier.It is estimated that this installation will produce an annual aver-
age of 7773 MWh of electrical energy per year (35.5 percent equivalent capacity
factor).The energy will be transmitted by means of a 138-kV line to Fairbanks
where it will be incorporated in the local utility grid.The project could be
on line in a period of about 36 months from authorization to proceed,provid-
ing that the decision-to-proceed date was synchronized with the summer con-
struction cycle.
1.6
ted
:l
ise
ity
lks
2.0 TECHNICAL DESCRIPTION
2.1 SITE DESCRIPTION
The site for the proposed project is north of Isabel Pass,in the vicin-
ity of the Black Rapids Glacier on the Delta River in southcentral Alaska
(refer to Figure 2.1).While most of the interior of Alaska is characterized
by rather calm winds for most of the year,the Isabel Pass Region appears to
have an excellent wind energy resource (AEIDC 1981).
The region is characterized by rugged mountainous terrain that is domi-
nated by the Alaskan mountain range.Mount Deborah,12,540 feet,Mount Hess,
12,030 feet,and Mount Hayes,13,832 feet are to the west of the Delta River,
and numerous peaks such as Mt.Gakona,9,460 feet,and White Princess,
9,860 feet,are east of the Delta River,which is at about 2,400 feet in
elevation in this area.The Alaskan Range presents a high barrier to the flow
of air between the Copper River Plateau and the Tanana River Valley.With
differences in atmospheric pressure between the two regions,the Delta River
Valley forms a natural IIfunnel ll for the air to flow between the two basins.
The Wind Energy Resource Atlas (AEIDC 1981)discusses the wind resources
in the region in some detail.The data are based primarily on observations
made at Big Delta (64.0 o N,161.8°W),Paxson (63.0 o N,145.5°W),and Rapids
(63.5°N,145.5°W)(refer to Figure 2.2).Paxson is just south of Isabel Pass,
on the Richardson Highway.Rapids is in the Delta River Canyon,and Big Delta
is about 10 miles southeast of the junction of the Delta and the Tanana Rivers,
about 50 miles north of the proposed windfarm site.
The Wind Energy Resource Atlas presents wind resource potential by classes
of wind power density at 10 m (33 ft)and at 50 m (164 ft)above ground level.
Classes of wind power density are given in Table 2.1.
Isabel Pass is cited as having an annual wind power of class 4 to 7 com-
pared to the annual wind power of class 1 that prevails in the interior
regions,such as along the Tanana River (AEIDC 1981).
2.1
~----------_......._------......---------------------~
SCALf I-Z50000
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DATUJ.1IS MEAN SEA lEVEL •
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FIGURE 2.1.
....
Area Location Map
2.2
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o DIGITIZW UAIA
_DIGITIZED AND
SUMMARIZm UAJA
fJ.SUMMARIZLD DATA
...UNSUMMARIZfD IJATA
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TANAIIANPOINI kI\SIIOI,"'""=0 i=--"";L ...'IN.'/~~SEWARiJ it,O',r;;f{tE ~INCHINBRO~K~~KATAGA,fP '>V SEWAIl~DO(Kl 0 I~h "° ,~'"I~'n-"I "\4
10 ~e--ttCAPE ST WAS •
HOMIR::f/7 •'Ii>\~I\oHOMERSPITt~1/V ,',110 •MIDDLETON ISLAND
1-,:')
50
NCC Station Locations in Southcentral Alaska
If,(i O
o 50 100 150 KILOMETERS=PI\IL J-195 WfRA 10
o
/t>l'O
L~-·-)::..._.'-.-'·.A...-'::""'".'.U'---'~-'-__,..",'J __"'<1'.c·'f',(S'I'"-"-'-"~'~~--~\~'1~1;\716~
FIGURE 2.2.
[,OPHIR
TATALINA AI?_MCGRA III
Il I'\,FLAT
'\...STUYAHLJKL.HOn (ROSS OIAREWHL
•~~,.,r=----f
OHOGAMLJn,t..-J'K.~~CROOKWCRElK
KAI SKjGL-e I\NI~j '''\./.p STON~RIVIR
I D
BETHEl
l?(}o
~
/1,.1°
-f:-"-
/......·0
~.BEIl 1",0
\SAVOONGANORTHEA~~t.r
l/(Jo__L-__
J.,r ~TMAT::-J
6()0 ~SLAND
">"'0 ~_._~...._..
l?.!o 6{Jo 16-10
CAfE ROMANIOf
JIII!'-'
NUNIVA~LAN~
1<)0 ¥
1111,')
N.
W
TABLE 2.1.Classes of Wind Power Density(a)
10 IT1 (33 ft)50 m (164 ft)
Wind Wind Power Mean Wind Wind Power Mean Wind
Power Dens ity,Speed,(b)Dens ity,Speed,(b)
Class watts/m2 m/s (mph)watts/m 2 m/s (mph)
a a 0 0
1 100 4.4(9.8)200 5.6(12.5)
2 150 5.1(11.5)300 6.4(14.3)
3 200 5.6(12.5)400 7.0(15.7)
4 250 6.0(13.4)500 7.5(16.8)
5 300 6.4(14.3)600 8.0(17.9)
6 400 7.0(15.7}800 8.8(19.7)
7 1000 9.4(21.1}2000 11.9(26.6)
(a)Vertical extrapolation of wind speed based on the 1/7 power law.
(b)Mean wind speed is based on a Rayleigh speed distribution of
equivalent mean wind power density.Wind speed is for standard
I·sea-level conditions.To maintain the same power density,speed
I,increases 5 percent/5000 ft (3 percent/lOOO m)of elevation.
The seasonal wind power for the Isabel Pass Region is shown in a series
of maps for the southcentral region that are reproduced here as Figures 2.3
through 2.8.Generally,winter is the season of maximum wind power in the
mountain passes because of the high barometric pressure differentials.
In winter,the wind corridor in the Isabel Pass Region has class 7 power
for the northern part of its length,as shown in Figure 2.3.In spring the
wind corridors at Isabel Pass have class 3 or 4 wind power,as shown in Fig-
ure 2.4.In summer,class 1 wind power prevails over most of southcentral
Alaska,as shown in Figure 2.5.During autumn the Isabel Pass wind corridor
has class 5 and 4 wind powers,as sh9wn in Figure 2.6.The annual average
wind power for this region is given in Figure 2.7.A histogram of seasonal
wind power classes is shown in Figure 2.8.
2.4
,L
-........-_.LIII.•UU..,_:__t.Ji.aS."..,.,.lJ.JS.:..•s:.;.u.u.a•••••••••••••••••
Tn.nnrX1I'rirT'
•~
;rr "srr7 .,
WINTER
ttl
_..,..~
~
63.&toi~.....••
..,'....~
...........?'.....'"
PNL~S1915 WEfllA-'O
ED RlDQI CA_DTII1A1El1
o SO 100 1SO MIUS
o 50 100 1SO KILOMETERS
..' - ,j····C···········..-=r
&I 7 '!.~
•~
FIGURE 2.3.Seasonal Average Wind Power in Southcentral
Alaska -Winter (Source:AEIDC 1981)
SPRING
I'NL-S'lIlI _....'0
ED---
o 5Il 1(1)1SO M1US
o 5Il 1CIl 1SO KILOMETERS
.~....-~~....
~
......-...
To~
FI GURE 2.4.Season a1 Average Wi nd Power in Southcentra 1
Alaska -Spring (Source:AEIDC 1981)
2.5
..
SUMMER
..60'"
1...",..".~...,.~
~$.
AUTUMN
lsa'oe"\Pass
Region
.....~
"b~l~'
~
2.6
PNL·319S WERA,'Q
c::::J _tcllUTUflMRU
o Sll 100 1Sll MILES
o 5[)100 1SO KILOMETERS
PNL.3191 WEflA-10
EZJ "'DGEC""""_
o so 100 1SO MILES
SO ,00 1SO KILOMETERS
FIGURE 2.6.Seasonal Average Wind Power in Southcentral
Alaska -Autumn (Source:AEIDC 1981)
FIGURE 2.5.Seasonal Average Wind Power in Southcentral
Alaska -Summer (Source:AEIDC 1981)
-"--...,.2C,\;.
.....~.•~~..
<0
~
.
~~~
..~.
80·.
""".<..
.
~
t'"
11
FIGURE 2.7.Annual Average Wind Power in Southcentral Alaska (Source:AEIDC 1981)
600
lsab.e\paSS
Reg\on
t-J"!
w.q
t:J1U0Q1 cRist p"M"'U
o 50 100 150 MilES-=
«L 50 100 150 KILOMETERS
PNL-3195 INERA·'O
'q
l'o
~
o
Q)
~
o
~1640 .,
•
°'It
<0
-59°,
!i
~
t':.-
oIY 0,....
~
&
~
62 0
6/0
63
600
o
!j
600 ,
N.
.......
-
-
I--
--
I--
--
I--
~..
7
6
~
S 5
u
n::
~4
o
0..
~3
~
2
SPRING SUMMER
SEASON
AUTUMN WINTER
W/m 2 m/SEC MPH
2000 11.9 26.6
800 8.8 19.7
600 8.0 17.9
500 7.5 IG.8
400 7.0 15.7
300 6.4 14.3
200 5.6 12.5
0 0
FIGURE 2.8.Histogram of Seasonal Wind Power Density
at Delta River Canyon
Data on interannual variations of wind power and speed are presented for
Big Delta,which is located on the Delta River about 10 miles southeast of its
confluence with the Tanana River.This station is affected by flow through
Isabel Pass.The terrain is gently rolling for about 10 to 15 miles in all
directions from Big Delta,so that under some conditions air moving through
Isabel Pass can have sufficient momentum to produce strong winds at Big
Delta.Therefore,Big Delta shows variations from class 1 to class 7 wind
power from one year to another,as shown in Figure 2.9A.
The data for Big Delta,Figure 2.9B,show a winter maximum and a summer
~.
mi n imum with respect to monthly average wi nd power and speeds.As shown in
2.8
--~-----_:_-~'~~.:,------_._,--_.,.',--
PC '(arm::4
YEAR
MIS
WIND POWER
WINO SPEED
A.Big Delta showing variations from
Class 1 to Class 7 wind power from
one year to another.
BIG DELTA AK 07A8-12/64
26415 Z=8.8 R.v-4.3.p-228
8DO ·····~····,..···:·····,····'..···r····[·..··,·······,····8
600'u..+....+....~L...+....;.....~_...* _of···:8
400 .~1.:.::.~~~~.,".:.:;:.~.~.).'-+.:r..4
~:o 0
J P W A W J J A SON 0
MONTH
MIS
WIND POWER
WIND SPEED
B.Big Delta showing a winter maximum
and a summer minimum .
•----.SPRING
&3---111 AUTUMN
s
MIS
BIG DELTA AK 07A8-12/64
26415 Z=8.8 R.Vz 4.2.pz 215
1:I::::::::::::::::::::;:::::::;:::::::i:::::::r:····r::::::]
6 ~~~!~~····i·······~
:B:~.~~:rr.=t:f.S
o-!--;--i--+--+--+---;---;-......,o 3 8 9~·~~21 U
HOUR
----WINTER
SUMMER
C.Big Delta showing some diurnal variation with
maximum winds between noon and late afternoon
1oca 1..
FIGURE 2.9.Wind Variations at Big Delta
2.9
"
,
,
•
,
Figure 2.9C,there is some diurnal variation,with maximum winds between noon
and late afternoon.This variation is largest at Big Delta during the spring
and summer,and least during the winter when there is very little warming by
the sun.
Strong east-southeast winds exist at Big Delta,with mean wind speeds of
7.9 to 9.2 m/s (17.7 to 20.5 mph).These winds are associated with flow
through Isabel Pass.
It should be noted that,for wind energy purposes,the elevation of the
Delta River in the region where the wind farm will be located is about
2400 feet above sea level,which implies a reduction in energy density of
about 2 percent because of the reduced air density.However,because of the
low temperatures generally prevalent in the region,the effect of altitude is
approximately compensated by the hlgher density of cold air.
Siting of the wind farm can be established after determining the magnitude
of the wind resource.From Figure 2.1,it can be seen that there is roughly a
30-mile section along the Delta River from Rainbow Ridge to Bear Creek where
the river goes through a canyon.The river is relatively flat in this area,
with an average elevation of about 2200 feet above sea level.The bottom of
the canyon varies from 1 to 2 miles wide,then the canyon wall rises steeply,
reaching altitudes of 5000 feet or more about 1 mile from the edge of the
canyon flood plain.The walls of the canyon are defined in several areas by
large glaciers (i.e.the Black Rapids Glacier,the Canwell Glacier,the Fels
Glacier,and the Castner Glacier).From the presence of the glaciers and the
braided nature of the river channel it can be assumed that the bottom of the
canyon is made up of deposits similar to glacial till so that reasonable foun-
dation conditions can be assumed for the wind turbine towers.
The canyon is traversed by the Richardson Highway,Route 4,and the
Alyeska pipeline,which moves crude oil to the Port of Valdez.Aside from
these two features,which include the Aladyn pumping station and the military
Reservation at Black Rapids,it appears possible to locate the wind farm any
place along the canyon,in a roughly 50 square mile area.
2.10
de
a
As a first approximation,the most logical location for the wind farm
will be in the region with the highest wind velocity,which will normally be
the part of the canyon with the smallest cross-sectional area.By construct-
ing the wind farm in a canyon,yawing of the wind turbines to track the wind
is minimized.From the meteorlogical data (Hiester 1980)it is concluded that
the wind in the canyon will be predominantly from the south whenever there is
appreciable wind.The turbines will face up the canyon (assuming an upwind
rotor design)and will rarely change direction when the wind is bloWing with
any strength.This can simplify the design and operating strategy for the
turbines (Andrews et ale 1981).With more detailed wind data available it
will be possible to evaluate whether the wind turbine systems should even
include yawing systems.Elimination of yawing controls would allow appre-
ciable savings in capital costs and simplify operations.The wind farm should
be placed at the upwind end of the canyon to reduce turbulence on the wind
generators,since the turbulent boundary layer thickness increases with dis-
tance along the flow channel.
The Isabel Pass Region is characterized by two factors that are unfavor-
able for the wind-farm project:1)the long distance from the site to the
region where the electricity can be used,and 2)the remoteness of the area
when viewed from a maintenance standpoint.
2.2 PLANT DESCRIPTION
2.2.1 Overview
The objective is to examine a large wind energy conversion system (wind
turbines)configured as a wind farm.For study purposes,the wind farm rated
capacity has been established as 25 MW.Using presently available technology
as represented by the 2.5-MW MOD-2 wind turbines,the wind farm will consist
of 10 of the MOD-2 wind turbine systems.
Several possible arrangements exist for the wind turbine farm.The
general siting relations are specified to avoid aerodynamic interference.
This will require that the units be spaced about 3 blade-diameters apart,
perpendicular to the prevailing wind direction,and about 10 blade-diameters
2.11
apart parallel to the prevailing wind direction.For the MOD-2 machines with
rotor diameters of approximately 300 feet,the minimum spacing perpendicular
to the wind would be 900 feet,while the spacing parallel to the wind would be
3000 feet.
The spacing limitation parallel to the wind arises because as energy is
removed from the moving air the velocity is reduced.The mass flow continuity
condition requires that the air that has slowed must have a larger flow area,
so the streamlines behind the wind turbine disc expand toa larger flow diame-
ter.In the downstream direction,the slowed flow looks like the inverse of a
submerged jet,i.e.,a region of slow flow rather than a region of high flow.
In the submerged jet case,analysis shows that the edges of the jet mix with
the surrounding fluid and that within about 10 diameters the original jet has
all but disappeared.Since the boundary layer mixing mechanisms are similar
between the faster and slower jets,the 10-diameter characteristic length
should be applicable to both cases.One of the parameters being investigated
at the 7.5-MW,MOD-2 wind turbine cluster located at Goodnoe Hills near
Goldendale,Washington,is the interaction between adjacent wind turbines.
The spacings between the three Goodnoe Hills wind turbines are approximately
5,7,and 10 rotor diameters (Axell et al.1980).These spacings enable
evaluation of wake effect of one of the turbines on a downwind turbine.In
the absence of data from these tests,it is assumed that the three diameter
and ten diameter spacings discussed above are reasonable.
One possible configuration,using these spacing criteria for the wind
farm,is to locate the wind turbine generators in a line more or less along
the middle of the valley,3000 feet apart,making the total length 5.1 miles.
This configuration may be the lowest-cost alternative if the Richardson High-
way can be used for close;i.e.,200 feet,access to all sites.However,this
configuration will have the highest costs for consolidating the power at one
location for step-up to transmission line voltages.
A second configuration would be to array the ten wind turbines in two
rows of five each across the valley,the two rows being about 3000 feet
apart.This configu~ation would probably require one or more bridges across
('"
the Delta River to provide access to the units on the western bank if the
2.12
JIIiOU';.'
.2 as £i!..21#i!iJ [:21:3.II [hilS
units were placed in a narrow part of the canyon.In this case the length of
electrical connection lines would be reduced from 5.1 to 1.9 miles.
A third potential configuration that may be posslble at this location,
because the wind is highly undirectional,is to place the wind turbines in a
staggered pattern with the turbines in the back row(s)offset by 1.5 blade
diameters from the front row,and spaced at about 3 diameters behind the front
row.This configuration will provide the shortest interconnecting network,
1.5 miles,and result in the shortest access road.
One important consideration is the question of avoiding wind turbulance
because it increases fatigue loading on the turbine blades.There is a gra-
dient in the velocity profile above the surface of the earth.The velocity is
zero at the ground/air interface and increases to the free stream velocity at
some distance above the earth.This velocity profile is usually characterized
by what is called the 111/7 power law,1I which describes the vertical variation
in velocity in the present case.The thickness of the boundary layer is a
function of the Reynolds number.The higher the velocity and the longer the
distance it has been maintained,the thicker the boundary layer.Figure 2.10
illustrates this effect.
The variation in wind velocity within the boundary layer causes uneven
loading on the rotor blades.The blades experience a higher loading when they
are at the top of the rotation arc than at the bottom of the arc.This peri-
odic variation in stress,once per rotation,requires that the rotor be
designed with stresses below the fatigue limit.
If it were possible to place the wind turbine in a manner such that the
wind velocity were more uniform,then more efficient use of the structural
properties of the materials of construction could be realized by the reduction
in the fatigue factor.This may be possible at the Delta River site if the
canyon is viewed as analogous to a wind tunnel.As the air moves southward,
the Alaska Range topography is relatively open so that the average air move-
ment velocity will be relatively low as it approaches the Isabel Pass Region,
as shown in Figures 2.3 through 2.6.With this low average velocity of
approach,a thin boundary layer appropriate to this low velocity will develop
,
L
2.13
- - - - -Theoretical gradient
45mph30mph20mph
5
15
10
o"'oI\i~"""---""'-------",,---""'--_.loo-_--------'o
20
He ight ,ft.
FIGURE 2.10.Examples of Variation of Wind Velocity with Height
for Various Wind Speeds (Source:Andrews and Baskin
1981)
in the flow.When the air approaches the narrow part of the canyon and is
accelerated to a higher velocity,the boundary layer starts to thicken as the
flow proceeds down the canyon.The thickness of the boundary layer is a func-
tion of the Reynolds number,which is the product of the velocity times a
characteristic distance (in this case the distance down the canyon)divided by
the kinematic viscosity of the air.Therefore,if it were possible to locate
the wind turbine cluster close to the region where the air is accelerated,
then a more uniform velocity profile should be experienced.For the purpose
of boundary layer analysis,we can assume that the canyon can be represented
as a very high wind tunnel test section.
If we consider a wind of 26 ft/s blowing along a box-like structure
1.2 miles wide,with sidewalls 1.2 miles high and 31 miles long,the turbulent
boundary layer will build up to a thickness of about 52 feet (almost to the
bottom Gf the~ind turbine blades)in a distance of 1.9 miles.If this "box"
2.14
was defined as starting with the east sidewall at Darling Creek Ridge and the
west sidewall at the prominence called Mt.Pillsbury of Ann Creek~,the52-foot
thick boundary layer thickness would occur at the foot of Black Rapids Glacier.
At this point the canyon widens out and there is a relatively flat spot
about 2 miles wide on the west side of the Delta River that might make a suit-
able site for the wind farm.Access to this site would require the construc-
tion of a bridge across the Delta River.
For a project of this magnitude,it appears appropriate to construct and
test a physical model of this region in a wind tunnel to evaluate which site
would be the most desirable from an energy conversion standpoint.This
approach would yield data allowing the alternate sites to be weighed against
each other.
It should be noted that there are a variety of sites to choose from along
the Delta River.If we look at the wind energy contained in a channel
10,000 feet wide by 500 feet high moving with a velocity of 38 ftls,and
assume a power coefficient of 0.5,we arrive at an available wind power of
250 MW.The suggested wind turbine cluster could be much larger if there was
a market for the electricity and suitable backup capacity.Assuming momentum
transfer from overlying moving air masses not affected by the wind turbines
over distances of the order of 10 to 20 layer thickness (1.1 to 2.1 miles),it
should be possible to have about 10 wind turbine clusters along a 15.5-mile
length of the Delta River Valley.
y
t
For the sites to be examined,the units are arranged in two clusters of
five machines each.A main control house gathers the outputs from the clusters
(two in this case)and the total site output is elevated to the transmission
voltage.This system of two clusters can be easily expanded to include addi-
tional clusters.However,the main step-up transformer size must be increased
and an additional 13.8-kV air circuit-breaker will be required for each addi-
tional cluster.
The proposed 138-kV transmission line can easily transmit 80 MW of power,
so that four additional clusters (of five units)can be added either in the
Delta River Canyon or enroute to Fairbanks.
2.15
A plot plan of the proposed wind farm arrangement is given in Figure 2.11.
2.2.2 Wind Machines
Three government-funded design studies of large-scale (MOD-2)wind tur-
bines were conducted by General Electric Company,Kaman Aerospace Corporation
and Boeing Engineering and Construction Company.The designs are very similar,
with the major external differences being that the Boeing configuration has
the rotor upwind of the pedestal,primarily to relieve the rotor of cyclic
stresses caused by passing through the wake of the tower.The G.E.and Kaman
designs had the rotor downwind.The Kaman Aerospace design for the control
system was based on conventional electromechanical controls,while the G.E.
and Boeing designs were predicated on a dedicated microprocessor for a major-
ity of the control decisions.Since the three studies were prepared in
response to a NASA specification,the units all have the same output and the
designs were based on the same set of wind condition assumptions.Three units
of the Boeing MOD-2 design were fabricated and installed near Goldendale,
Washington,in 1980,and began producing power for utility customers in May
1981.A fourth unit is being installed at Medicine Bow,Wyoming,while a
fifth unit is being installed in northern California.
Boeing Wind Turbine System Description
The Boeing wind turbine (BWT-2560)is a horizontal-axis wind turbine gen-
erator (WTG)featuring an upwind 30G-foot-diameter teetering rotor with con-
trollable blade tips.The rotor turns at a rated speed of 17.5 rpm.It is
attached to the low-speed end of a drive train that is housed in a nacelle,
which in turn is supported by a 193-foot-tall cylindrical tower.Rated power
output of the machine is 2.5MW.The system is designed for unattended,remote
operation in utility grids.While the main considerations in selecting the
configuration were minimum energy cost and reliable operation,attention was
also given to minimizing visual and environmental impact.Machine specifica-
tions are summarized in Figure 2.12;details of the WTG are described in
subsequent sections.
The machine is designed to be fully automatic.with its operation con-
trolled by a microprocessor unit.Low maintenance requirements and a high
2.16
I
AFF
USING
-N
PLOT PLAN
I"","OOFT
----------~-~---~-------_.--------._------~-~-~---~-~~-
\\-30MVA MAIN TRANSFORMERtMA1NCONTROL
HOUSE
/
2.5 MWeMOD-2
3000'WIND TUR.BINE:__--===::::::.1000'SYS"TEt-1';,-II)Ui'J115-I ~~.
~tit
I 1000'-1-
~
LANDING STRIP
r+-
1
i-
S1+
I~QI-CONTROL HQg~2
I
I Q(h
ONE PERMO
+----w
I
l-
I
- -TRANSMI5S>ION 1 lI)
::l
------ -
o --
SKV OVERHEAD
.J
Sl
~5 KCMIL ~~~NS.WOOD POl-Eo
u
He
I
+gsg~Jii<UCTION~LUSTER NO I O:.T
I I"-m"N ~SUPPORT AREA.__
!15MVA
OJ DELTA ~~~~____~~.
CLUSTER N02 c'KT
RIVER~____~_-:-
15MV~
-------._-'-._~'-~-t~-------~~~----
:II
--
_.,-;=
--------
-
-~
--
-----
..............
N.
FIGURE 2.11.Large Wind Energy Conversion System Plot Plan
.-~,--=·=,-v "-'0.'='~----"-.-~,"-'"~*~~~~'~~~,\'_r~*-.-_",,_-;..,,~~-~-_~~~~i=.:io .:.'--.,g;-:·:":·.-~,·,-~~,)~..,."..,.,;;;:;;::n!";;r;p::;rt::701rrr'T""M..h7'1'::J:!::1~:;d~~~""''''"__~~_..........._
fa
Weight Summary
Item Pounds
Rotor 192~OOO
Drive train 102~OOO
Nacelle 82~000
Tower 256~00O
Total 632~OOO
2.5 MIri
3125 kVA
300 ft
Teetered -tip control
Upwind
NACA 230XX
27.3 mph
14 mph
60 mph
125 mph
275 ft/sec
17.5 rpm
Synchronous ac
1800 rpm
4160V~3-phase
60 Hz
Compact planetary gear
200 ft
Steel-shell type
Hydraulic
Hydraulic
Microprocessor
Field Splices
(4 Places)
20 ft -10 in.o.d..
Top of Fdn.
200 f1
/Field Splices
-N~~
Tower·
10ft o.d.
"-Rock Anchors
Teetered IIII--+-+-37 fRotor1111 t 9 ft -6 in.
50 ft
I
I ~Controllable Tip
45 ft
J__
11i----r--24 ft
Rated power
Capacity
Rotor diameter
Rotor type
Rotor orientation
Rotor airfoil
Rated wind @ hub
Cut-in wind speed @ hub
Cut-out wind speed @ hub
Survivable wind speed @ hub
Rotor ti p speed
Rotor speed
Generator type
Generator speed
Generator Voltage
Generator Frequency
Gearbox
,Hub height
Tower
Pitch control
Yaw control
Electronic control
-Wind
300 ft diameter
~IGURE 2.12.BWT-2560 Features and Characteristics (Source:
Linscott,Dennett and Gordon 1981;BECC 1980)
2.18
....
on-line availability are facilitated by careful attention to design details.
Components are easily accessible,and the system is maintainable by,existing
utility industry skills.Safety criteria followed throughout the design pro-
cess assure the absence,and/or proper control,of safety hazards.
BWT-2560 design features resulted from extensive technical trade-off
studies accomplished during the MOD-2 program.These studies,conducted under
contract with the Department of Energy,had the prime objective of minimizing
the cost of energy over the operational life of the WTS.Design work started
in 1977 and by mid-1981 five wind turbines had either been completed or were
under construction.This development process has resulted in a machine with
the following key features:
1.Rotor design employs consistent,well-understood,and thoroughly
documented materials (steel)and methods of construction.
2.Upwind rotor orientation maximizes available energy,and reduces
rotor fatigue loads and noise.
3.Rotor size and configuration maximize power output during low wind
periods and also provides rated power up to 60 mph.
4.Tip controlled rotor signficantly reduces weight and cost through
simplification of hub structure and pitch control system.
5.Relatively low rotor tip speed of 275 fps (187 mph)minimizes noise.
6.Teetered hub reduces fatigue loads and minimizes system weight and
cost.
7.Pitch control hydraulic system mounted on drive shaft eliminates
hydraulic transfer bearings.
8.Driven yaw system controls the rotor heading to maximize energy
capture.
9.Soft drive system minimizes torsional fatigue loads and maintains
steady electrical power output by isolating the gearbox and genera-
tor from torsional oscillations of the rotor.
2.19
2.20
p
Bolted Splice
Rotation Wind
C.W.Viewed /'
from up Wind
~
i}
I Flying Attitude
~~hWood Attilud.
lUPR B1e rSkin Splice (typ)
Surface \)Trailing
Edge
FIGURE 2.13.Rotor Blade Configuration (Source:
Linscott,Dennett and Gordon 1981)
The mechanical drive system includes a low-speed shaft,a step-up gearbox
and a high-speed shaft,as shown in Figure 2.15.
Rotor.The rotor is comprised of two outboard tip sections,two mid-span
sections and the hub section,as illustrated in Figure 2.13.The tip sections
rotate with hydraulic actuators to control rotor speed or power.The rotor
hub incorporates e1astomeric radial bearings that allow the rotor to teeter.
Mechanical stops are employed to limit teeter excursions to 6 degrees.The
hub arrangement is shown in Figure 2.14.
The rotor is a welded steel structure that is fabricated from high-quality
low-carbon-a11oy steel.Sealed water-tight hatches allow access to the rotor
i nteri or.
10.Small,compact,lightweight,high-efficiency gearbox employs advanced
technology epicyclic gearing.
11.Steel shell tower configured for minimum cost and weight with funda-
mental bending frequency below the rotor exciting frequency.
Power Generation System.The power generation system includes mechanical
drive equipment and electrical equipment required for the generation,condi-
tioning and distribution of electric power.
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Teeter
~Low Speed Shaft
Teeter Shaft --1I-+----f----1it--1
FIGURE 2.14.Rotor Hub Arrangement (Source:
Linscott,Dennett and Gordon 1981)
Rotor Brake
Teeter
Brake
Teeter Stop
Access Hatch
'"
II,
'.'I
Gearbox
Generator
High Speed
1\ShafVCouplinQs
~Flex Mount
Oil Outlet
Removable Coupling
FIGURE 2.15.Drive Train Arrangement (Source:
Linscott,Dennett and Gordon 1981)
2.21
The low-speed shaft,consisting of a welded steel outer structural assem-
bly with an integral quill shaft,supports the rotor and transmits torque to
the gearbox.The alloy steel quill shaft is configured with a torsional stiff-
ness designed to dampen rotor torque fluctuations.Mounted on the outer
assembly are the hydraulic power system for the pitch control actuators,and
electric slip rings to conduct electrical power and control signals across the
rotating interface.The low-speed shaft is supported by both a forward and an
aft bearing.
The gearbox is a three-stage epicyclic planetary-type with a 103:1 step-up
ratio.The gearbox is equipped with a conditioned recirculation lubricating
oil system.The gearbox installation is designed to permit disassembly within
the nacelle for overhaul.
A high-speed shaft connects the gearbox to the generator.Bolted cou-
plings on either end of the high-speed shaft,as well as on the aft end of the
low-speed shaft,allow removal and replacement of drive-line components.A
chain-driven gear on the high-speed shaft facilitates positioning of the rotor
with an auxiliary motor for maintenance.Also located on the high-speed shaft
is the drive system brake.
The electrical system employs a four-pole synchronous generator containing
an integral brushless exciter.It is a three-phase,60-Hz,4160-volt generator
with a 3125-kVA capacity at 0.8 power factor.The generator accessory unit
houses an excitation control,voltage regulator,power factor controls,elec-
trical fault protective relays,current-limiting devices and a backup generator
circuit-breaker.Power from the generator is transmitted via a slip ring from
the nacelle down the tower and then underground to a bus-tie contactor.Near
the bus-tie contactor unit is the main transformer that increases the generator
output voltage to the customer tie line voltage.Electrical interface is at
the utility side of the fused manual disconnect switch on the utility side of
the main transformer.Additional transformers near the bus-tie contactor and
in the nacelle provide auxiliary equipment load voltages of 480,208 and 120.
A battery,floating across a charger,provides an uninterruptible power supply
for operation of protective devices and critical loads.
2.22
".
The bus-tie contactor operation is controlled by automatic synchronization
equipment.Once the WTG and the uti 1ity are electrically connected,"the gen-
erator voltage and frequency will be automatically controlled.
Nacelle.
generator,the
control unit.
width is 11.5
The nacelle,shown in Figure 2.16,
yaw drive mechanism,the hydraulic
Its overall length is 41 feet,its
feet.
houses the drive train,the
power supply systems and the
height is 10 feet,and its
The nacelle has a welded steel structural frame fabricated from rolled
structural shapes.The top and sides are sheathed with trapezoidally corru-
gated steel sheets.The bottom is enclosed with safety plate walkways.Roof
NCU Rack
A_sole Root Panels
Rotcr Acessa
Door
Gear Sox all Coaler
;;:;Generator Cooling Exllaust
Ventilat()(s
Halon 80ttle
(Firs Extinguisher
System)
Naealls To Platform Acessa
FIGURE 2.16.Nacelle Arrangement (Source:Linscott,
Dennett and Gordon 1981)
2.23
p.iiU.J4.
panels are removable for major equipment access.Hinged doors for personnel
and equipment access are located in the aft (downwind)and forward (upwind)
walls and in the floor.
A conceptual site layout is shown in Figure 2.17.The ground area dis-
turbed during construction is about 1-1/2 acres.The permanent installation
occupies less than one-quarter acre.
Auxiliary Systems.Personnel access stairways,ladders,and walkways
suitable for equipment maintenance purposes are provided in the nacelle.A
two-person-capacity lift,including emergency escape provisions,is provided
from the tower floor to the top of the tower.A monorail and hoist for equip-
ment transfer between the nacelle and the ground is also provided.Fixed
exterior maintenance platforms are located at the forward (rotor)end of the
nacelle a~p at the to~of the tower.The nacelle is ventilated with
The nacelle is connected to the tower through the yaw bearing,which
provides full-circle rotation capability.The yaw bearing is of a crossed
roller configuration with an integral ring gear.The nacelle is yawed by
advancing a hydraulic motor-driven pinion gear along the ring gear.
Tower,Foundation and Facility Layout.The nacelle assembly is supported
by a 193-foot-tall,cylindrical,welded steel tower.The tower is 10 feet in
diameter with a base section flaring to 21 feet in diameter.It is bolted to
a reinforced concrete foundation that is designed on the basis of site soil
conditions.The tower contains an internal lift to provide transportation
from the ground to the nacell e.The 1ift ends at a pl atform near the top of
the tower,where final nacelle access is by means of a ladder.A ladder with
safety cable runs the entire height of the tower to allow access or egress in
the event of a lift failure.The electrical power output cable runs from the
slip ring at the top of the tower down the tower side.The tower base interior
contains an enclosure for electrical and control equipment.A hinged key-
locked access hatch is located near the ground level.
to the tower,supports both the bus-tie
The power output cable from the tower
A separate concrete pad,external
contactor and the step-up transformer.
to this pad is buried.
2.24
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FIGURE 2.17.Wind Turbine System Conceptual Site Plan
(Source:BECC 1980)
unconditioned air and convenience electrical outlets are provided for main-
tenance requirements.A polyurethane paint,which provides a nominal 10-year
coating life,is applied to all exterior structural surfaces and equipment.
All interior structural surfaces subject to corrosion are treated with a
protective coating.
Safety systems are provided to shut down the wind turbine during hazardous
conditions.Rotor crack detection is provided by an electro-pneumatic system
which distributes conditioned air into the rotor and measures proportional
flow rates.Detection of a crack will shut down the WIG.Ice accumulation is
detected by rotor-mounted sensors that are included in the control system.
Deicing systems are not standard equipment,but may be required due to the
potential for freezing precipitation conditions at the proposed site.
2.2.3 Operation and Performance
Control Systems
WTG control systems principally include those associated with the posi-
tioning of blade tips,yaw orientation of the nacelle,control of brakes,and
scheduling of electrical functions.Commands originate from either the main
or the emergency backup control unit.
2.25
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Control of the blade tip position (pitch)is provided by an electrohy-
draulic power supply and servo valve-controlled actuators that allow up to
100°angular pitch movement of the tips.The power supply,including the
pump,filter,oil reservoir,and redundant supply accumulators,is installed
on the low-speed shaft.All hydraulic tubing is of stainless steel.The rate
of pitch change is variable up to a maximum capability of lSo/second.The
rates are l°/second and 4°/second for normal pitch operation and emergency
shutdown,respectively.Integrated with the pitch system is an electrohy-
draulic brake system that engages at low rotor speeds.
The nacelle yaw control is provided by an electrohydraulic power supply
and servo valve-controlled drive motor.The turning rate is lSo/minute.Fail-
safe,hydraulically actuated brakes maintain position of the nacelle when not
commanded to yaw.
As shown in Figure 2.18,an electronic control system provides the sens-
ing,computation,and commands necessary for unattended operation of the WIG.
The controller is a microprocessor that is located in the nacelle control unit.
It initiates startup when the wind speed is within prescribed limits.After
start-up,the microprocessor computes blade pitch and nacelle yaw commands to
maximize the power output for varying wind conditions.Continuous monitoring
of wind conditions,rpm,power and equipment status is also prOVided to the
microprocessor,which shuts down the WIG for out-of-tolerance conditions.
A control panel and CRT terminal are located in the tower base to provide
operating and fault data displays as well as manual control for maintenance.
A remote CRT terminal at the utility control center also provides display of
key operating data and fault information as well as shutdown control.
An independent failsafe emergency shutdown system provides sensor redun-
dancy on critical components,and initiates shutdown,when necessary,indepen-
dent of the primary control system.
Performance
The wind turbine system will produce electricity whenever the wind speed
at hub height (200 ft)is between 14 and SO mph.Below the rated wind speed
:',
2.26
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Yaw Drive train Nacelle
WindPitchelectrical
actuator assembly assembly power sensors
system
,
•Drive t I -+I
commands •Status •Status •Brake •Generalor •Field enable
•Pump
•RPM commands power
1 •Commandscommands.!I•Position command
.......Pump commands Nacelle control unit
•Status
•Tip positions r-------------.,•Wind velocity and directionIEmergencyshutdownI
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I system I1._____________..1
•Status •Commands t I •Aulo sync enable
•Bus tie conlactor command
•Data !•Data
•Status I
Ground Ground'RemoteOperationalmanualutility electrical
instructions control •Commands control power
units syslem
FIGURE 2.18.Control System Interface Diagram (Source:
Linscott,Dennett and Gordon 1981)
(27'.3 mph),power output is a function of wind speed.Above rated wind speed,
the control system positions the blade pitch angle to maintain a constant power
output at the rated level of 2.5 MW.This power level can be maintained on
hot-day conditions up to an altitude of 7000 feet.The system can also operate
to a minimum temperature of -4SoF.At wind speeds exceeding 60 mph,the wino
turbine is automatically shut down to avoid excessive loads on rotor blades.
The system power output profile is shown in Figure 2.19 for sea level,
standard-day conditions.
The design specifications for the wind turbine systems will have to be
reviewed in a number of areas.The first is that there is very little likeli-
hood of the wind turbine being exposed to 120-mph storm wind conditions.How-
ever,there is a high probability that the system will experience high seismic
stress.The proposed site on the Delta River appears to be on the border
2.27
.:iAi;
Cut-out
60 mph
'0
Cut-in Rated
14 mph 27.3 mph
'0 0,
V
I1
3
Power 2
Output,
MW
00 10 20 30 40 50 60
Wind Speed,mph lat hub height!
FIGURE 2.19.BWT-2560 System Power Output
Profile (Sea Level,Standard
Day);Source:BECC 1980
between the zone of moderate and major probability of structural damage (events
between 6.0 and 8.8 on the Richter scale)(Hart et ale 1978).
Another factor that must be considered is the possibility of encountering
permafrost.While buildings can be put on piles,and utilities can be placed
above ground in utilidors to mitigate against permafrost,the tower founda-
tions must be in intimate contact with the soil.Data from Hart (1978)shows
that permafrost coverage in the region being considered is generally about
50 percent.Since there is flexibility in the location of the cluster and the
individual towers,movement of the site to an area free of permafrost would be
the preferred alternative.If that is not possible,the foundation methods
outlined by Anderson (1978)will provide acceptable solutions.
It should also be noted that if temperatures in the Isabel Pass area
prove to be consistently lower than the present MOD-2 design minimum,-4SoF,
design modifications can be accomplished to change the fatigue stress of the
steel components.The oil system has heaters and will not be affected by
cold-region operation.
2.28
2.2.4 Auxiliary Facilities
It is contemplated that the WTG would be supplied as complete~nits and
that the supplier would be responsible for all equipment to the main trans-
former that raises the generator output voltage to the tie-line voltage.The
electrical interface is defined as the utility side of a fused manual discon-
nect switch on the utility side of the main transformer.The other interface
is through the control system.A data line is provided for a remote CRT ter-
minal to provide remote display of key operating data,fault information,and
startup and shutdown control.
Auxi 1i ary facil ities are therefore required to consol idate the power out-
put from the individual wind turbine systems,to raise the voltage to transmis-
sion line levels,to consolidate the data channels to a common long-distance
data carrier,and to provide onsite maintenance shops and operating supply
storage.
In describing the auxiliary facilities,it is assumed that there are two
wind turbine clusters of five 2.5-MW MOD-2 wind turbines.Each cluster is
comprised of two rows,with a cross-wind spacing of about 3 blade-diameters
for the three front-row turbines,and a downwind spacing of about 3 blade-
diameters for the back two turbines in the gaps behind the front row,as shown
in Figure 2.11.The entire wind farm is supported by a main control house and
transformer yard where the voltage is stepped-up to transmission line voltage.
Switchyard and Electrical Onsite Arrangement
A one-line electrical diagram of the site is shown in Figure 2.20.Each
machine generator is rated 2.5 MW,0.8 PF,4160 volts (the standard voltage
supplied by Boeing).A transformer supplied as part of each wind turbine
system boosts the output to 13.8 kV.The five generators that comprise one
cluster are paralleled at 13.8 kV on a 13.8-kV,50D-MVA bus located in a
cluster-control house.The power is transmitted at 13.8 kV to the main
control house 13.8-kV,500-MVA bus,where the outputs of each cluster are
gathered.The total site output (two clusters)of 30 MVA is then elevated to
138 kV through a 30-MVA transformer for transmission to the Golden Valley
Electric Association System.
2.29
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FIGURE 2.20.One-Line Diagram
2.30
The basic equipment per cluster will consist of five MOD-2 wind machines
and one control house with 13.8-kV,500-MVA switchgear,including Slx 400-amp
air circuit-breakers (five for generators,one for cluster common power supply,
control,heating,lighting,etc.),and one 48-V dc battery and charger for
control.
The basic equipment for the main control house will consist of 13.8-kV,
500-MVA switchgear,including three 1200-amp air current-breakers (two for
clusters,one for cluster common power supply,control,heating,lighting,
etc.),one 2000-amp air circuit-breaker for site output to the main trans-
former,and one 125-V dc battery and charger for control (13.8-kV switchgear
and 13.8-kV oil circuit-breaker).
A small diesel generator of approximately 300 kW is recommended to provide
power for house loads in the event of a complete breakdown or freezeup of all
generation facilities.This unit,generating at 480 volts can feed into the
"house load"panel.One three-phase,160D-amp,15-kV bus duct to the main
transformers in the switchyard will also be included.
The basic equipment for the switchyard will include one main step-up
transformer,30 MVA,13.8{138 kV;two 3-pole,138-kV,600-amp group-operated
disconnect switches and towers;one 138-kV,20D-amp,50-kiloamperes,symmet-
rical,interrupting-capacity,pneumatically operated,125-V dc close-and-trip
SF 6 circuit-breaker,and one 138-kV transmission tower.
2.3 TRANSMISSION SYSTEM
The transmission voltage recommended is 138 kV,w·:th phase conductors of
300 MCM ACSR.The conductor size and voltage level were chosen based on the
length of the line and on the minimum conductor size required to avoid the
corona effect.Approximately three to four steel towers per mile will be
required.This line can transmit 80 MW from the proposed site to Big Delta and
thence to Fairbanks.The line losses for transmitting 25 MW from Isabel Pass
to Fairbanks would be 1.6 MW,or roughly 1.05 kW per mile.A complete system
analysis (not within the scope of this study)will be required to ascertain if
line compensation is required.
2.31
III
Since the proposed line will pass close to Fort Greeley,a connection to
the existing system at this point may be advantageous.Should this prove fea-
sible,the existing transmission line from Fort Greeley to Big Delta should be
upgraded to the proposed 138-kV level.
2.4 SITE SERVICES
The Boeing MGD-2 wind turbine is designed for unattended operation,with
remote dispatch through a data link.Because of the costs of supporting onsite
personnel in the Alaskan interior,unattended operation will be assumed.The
wind turbines are designed so that most of the maintenance required by the mov-
ing power train components can be performed in the cab or in the nacelle.How-
ever,because of the severe climatic conditions at this location,for a major
part of the year it will probably be necessary to provide a heated maintenance
shop for repair work when needed.Spare parts and operating supplies such as
lubricating oils,bearings,and seals would normally be stored at this facil-
ity,along with the disassembled lOG-ton gin pole and hoisting engines used
for rotor and major component replacement.Special equipment or fixtures
required to transport the rotor and other components will also be stored at
t his 1oc at ion.
Because of the value of the equipment and the remoteness of the area,it
will be prudent to have quarters for at least one full-time resident at the
site.It is contemplated that electronic intrusion detection equipment would
be incorporated in all WTG components and support buildings,so the resident's
role would be primarily supervisory.
The supportf acil ity wi 11 house the onsite data recording i nstrumentati on
system for the WTGs,an automatic meterological recording station,and the base
station equipment for a microwave data link to the dispatch station,assumed
to be in Fairbanks.The only periodic attention required for these activities
is the occasional changing of data recording media.It is anticipated that
the data link will incorporate video channels that could be used with con-
trolled scan cameras for physical surveillance of the site and equipment for
transmi~sion in one "direction,and used in the other direction for maintenance
and repair supervision or instruction.
2.32
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The support facility will also encompass the voltage step-up station,iso-
lation switches,and oil circuit-breaker for the 138-kV transmissiorr.line.The
size of the rnaintenancesupport facilities will be determined by th'e preventa-
tive maintenance and scheduled maintenance required by the 10 WTGs,and the
limited time during the year that outside maintenance can be performed.For
example,the WTG specifications cite a nominal 10-year coating life for all
exterior structural surfaces and equipment.This leads to a requirement to be
able to renew the exterior coatings on at least one of the 10 WTGs each summer
work season.
It is contemplated that complicated,infrequent repairs such as replace-
ment of bearing surfaces and gear-tooth restoration,which would require
specialized shop equipment,would be performed by removing the defective com-
ponent and sending it to specialized shops for repair.The primary shop capa-
bilities implemented in the maintenance support activity would be hydraulic
and electrical system replacement and repair,with the primary emphasis on
replacement.All electronic;system repairs will be on a replacement basis
only.Major maintenance activities would be scheduled during the summer
months when the winds are light and the electrical demand is low.(The sup-
port facility could support many more than the two wind turbine clusters previ-
ously discussed without a significant enlargement in size or a duplication of
facil ities.)
The wind turbine clusters will be served by the Richardson Highway.In
some areas,it may be necessary to build bridges across the Delta River to pro-
vide access to the West bank of the river if some of the WTGs are placed on
that bank.
While there is no operational requirement for an airfield to serve the
wind farm,the novelty of an installation of this magnitude would probably
bring a stream of worldwide visitors.It may be more cost effective to provide
a landing strip adjacent to the area to ferry visitors in and out than it would
be to maintain facilities at the site to handle visitors for extended periods.
2.33
_.......-...._---------------~-------------------------
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The only utilities required at the site would be for the support of the
maintenance shop and the caretakers'living quarters.These would include the
usual amenities for cold-region living such as an all-weather water supply,
sanitary waste disposal system,fuel oil storage,diesel oil storage,gasoline
storage,and an emergency diesel generator to support the living quarters,
data recording,and microwave data link in case of an outage on the 138-kV
line or lack of wind.
It may be more cost effective to provide temporary living quarters and
recreational facilities onsite for the workers doing scheduled maintenance in
the summer than to transport these workers each day the some 50 miles each way
from Big Delta or Delta Junction.These facilities would also be of value dur-
ing the construction stage,but will probably be supplemented with temporary
portable facilities during that stage.
2.5 CONSTRUCTION
2.5.1 General Construction Methods
Since three MOD-2 wind turbine systems have been constructed and installed,
and two are under construction,the procedures to be followed are straight-
forward (Axell and Woody 1981,Axell and Helms 1980).Under the assumption
that the sites have been selected,borings will be made to determine the soil
conditions for the foundations and access roads.
Initial construction tasks cover site preparation activities such as
grubbing,grading access roads,preparation of storage or laydown areas,and
placing of temporary support facilities.The next step covers foundation
excavation,form placement,placement of reinforcing steel or rock anchors,
concrete batch plant erection,and then pouring concrete for the tower,erec-
tion systems,transformer pads,and building foundations.A typical tower
foundation may comprise 400 cubic yards of concrete in an octagonal pad.Care
will have to be taken to preserve the permafrost when making a pour of this
magnitude.Seventy-two anchor bolts set into the foundation are used to bolt
the four tower base sections to the foundation.The four base sections are
then welded together along field splices.The remainder of the tower is then
2.34
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2.35
erected by vertically stacking each of the tower sections and welding to the
lower tower section along field splices.
In parallel with tower erection,site electrical"installation would take
place.The switchgear,transformer and a grounding grid are installed at each
site.Electrical power panels are installed inside the tower bases and power
and signal wiring are connected from the tower base up the tower raceway to
yaw slip rings at the top of the tower in preparation for installation of the
nacelle.
Previous MOD-2 installations had the nacelle assembled onsite.This
included installation of the gearbox,generator,lubrication module,and roof-
mounted equipment.The nacelle units were then subjected to an integrated
test at ground level to verify proper operation of all significant functions
before committing them to installation at a 200-foot elevation.Because of
the remoteness of the proposed site in the interior of Alaska,it is suggested
that the nacelle be completely assembled and tested prior to shipping.These
tests would include:1)continuity testing of all electrical wiring,2)opera-
tional and failure mode control system tests,and 3)operational tests of the
gearbox,lubrication system,pitch system,and yaw system.
Once the nacelle equipment has been functionally tested on the ground,it
would then be installed on its tower by means of a gin pole.Because the gin
pole is used for placing the nacelle and rotor and for removing major compo-
nents for repair,a permanent pod and anchors for the gin pole would be placed
at each wind turbine.A light mobile crane would be provided to assist in
assembling or removing the gin pole and the hoisting engines.The gin pole
used for the MOD-2 cluster i sa 240-foot truss boom with a lOO-ton capacity,
secured and manipulated by steel cables.After the initial construction
phase,only one gin pole would be required onsite to service several clusters
of wind turbines.
Because it is so large,the rotor would be assembled onsite.The hub and
two midspan sections would be bolted together at field splices and the wooden
controllable tips would be assembled on the pitch-control actuators.The
!
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rotor would be integration tested on the ground prior to installation.Tests
would include electrical wiring continuity~operation and setting of the pitch
system blade position potentiometers~tests of the ice detection and blade
crack detector system~operation of the pitch system actuators and hydraulic
system,and verification of all the engineering instrumentation system sensors
and wiring.Once the rotor integration tests are completed~the rotor would
be installed using the gin pole or a heavy-duty high-lift crane.Activities
of this nature are best conducted during calm wind periods~which would
restrict this type of operation to the summer months.The large "sail"area
of the central span would cause very large,fluctuating horizontal loads,
which would be difficult to handle if placement or removal of the rotor were
attempted during windy weather.
Once the rotor is installed,pre-free rotation tests would be conducted
to measure drive-train alignment and rotor strain gauge calibration.Integra-
tion testing of the complete machine would then be accomplished.These tests
would include the same tests that were run on the ground,but with all systems
completed and all operational sensors installed.Upon completion of these
tests,the rotor would be allowed to rotate.
Wind-powered checkout and acceptance tests would follow to demonstrate
that the machine is fully operable and ready for acceptance.These tests
would include wind-powered operation for a specified number of hours,opera-
tion through various operating regimes,specified numbers of start/stop cycles~
demonstration of fail safe system operations,and operabil ity demonstrations of
all systems.
r
2.36
Once all of the turbines in a cluster are operational,they would be
operated in parallel on the cluster 13.8-kV bus,and the integrated control
systems would be tested.When both clusters are operational,the entire sys-
tem would be operationally tested using the 138-kV transmission line tie to
the load,and the various systems would be tested in response to commands over
the microwave data link from central dispatch in Fairbanks.At this time~the
acceptance test on the various units would be completed and the system would
be turned over to the utiJity system.
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2.5.2 Construction Schedule
Figure 2.21 shows the estimated schedule for the wind farm prDject.
There are two key features or assumptions inherent in this schedule.First,
field construction work is scheduled for the five summer months,May through
September.Second,it is assumed that the wind turbine supplier could manu-
facture lO-wind turbine systems at one time within a 16-to 20-month period.
Nominally 16 months are allowed from receipt of order to shipment from the
plant,and present production capacity is about one unit per month.With an
increase in production resources,the potential supplier could meet the sched-
ule shown.If this is not possible,placement of the wind turbine order
earlier in the program would allow the 3-year schedule to be met.
The schedule provides for the first activities to be the compilation of
wind measurements,an analytical analysis,and wind tunnel testing to select
the best site for the wind farm.From available macrodata,the logical area
has been selected,so the microclimatological effects will have to be examined
to select the appropriate site.Once potential sites have been selected,geo-
technical studies would be conducted during the summer months to determine the
foundation conditions at each potential site.The wind farm configuration is
extremely flexible,so the site choice will be based primarily on the best
foundation conditions available.Solid rock,close to the surface,allowing
tower foundation bolts to be anchored firmly in the rock,would provide the
most desirable condition.
Site selection could be made at the end of the first year,at which time
the firm order for the wind turbine systems could be phced.The time require-
ment for obtaining permits and licenses should be rather short,the major
activities being the obtaining of land use and construction permits for the
various facilities.Federal Aviation Administration notification is required
because the towers will be higher than 199 feet above ground level.
As previosly cited,a wind turbine system manufacturer has quoted a time
of 16 months from receipt of order to having the equipment ready for shipment.
The wind turbine equipment would probably be moved by rail from the U.S.and
offloaded from the Alaska Railroad at Delta Junction,then trucked to the
2.37
~I
....
ACTIVITY
I.ON SITE STUDIES
WIND SURVEYS &MODELING
GEOTECHNICAL INVESTIGATION
PRELIMINARY SITE SELECTION
FINAL SITE SELECTION
II.PERMITS &LICENCES
LAND USE PERMITS
FAA NOTIFICATION
YEAR 1 r------~A~I YEAR 3
J I F rM I A I M I J I J IA I S I 0 I N I 0 I J I F 1M I A I M I J I J I A I S I 0 I NI 0 I J I F IM I A I M, J I J I A I s I 0 IN I 0
I I~.----------------------------4
I
~
I
~
YEAR 4
JIF1MIAIM!JIJIAlsloINI0
f
N.
Wco
'til.WINO TURBINE SYSTEMS
PLACE FIRMOROER
OESIGN
MANUFACTURING
SHIPMENT TO SITE
ERECTION
SYSTEM CHECK OUT
ACCEf'fANCE TESTING
IV.TRANSMISSION LINE
OESIGN
CONSTRUCTION
V.SITE DEVELOPMENT
GRADING
ROADS
TOWER FOUNDATIONS
VI.SUPPORT FACILITIES
AIR STRIP
CONSTRUCTION CAMP
SHOPS
RESIDENCES
I
<>
....
....I
.-.-.0
...-.
FIGURE 2.21.Project Schedule
rj
_prirt rrnttnrrsnS'T,'rr -"'"
..
wind farm site.The schedule provides for erecting one turbine system per
week on the foundations that were placed the previous summer.System checkout
and acceptance testing would take place in the fall of·the third year when the
winds increase after the summer lull.
Design of the transmission line can start once a preliminary site has
been selected.The summer of the first year is spent selecting the right-of-
way and collecting the necessary topographic data.Activities in the summer
of the second year cover construction of the transmission line tower and other
foundations,particularly those in permafrost areas.Activities in the third
summer cover placement of the towers,stringing the wiring,and erecting sub-
stations.The transmission line must be in place for the system check out and
acceptance testing of the wind turbine system.
Development of the site and the supporting facilities would follow a nor-
mal schedule,with roads,airstrip,construction camp,and shops built during
the second summer.Maintenance personnel residences could be built the third
summer or sooner,if desired.For the foundation and site development work
during the second summer,it is probable that a portable concrete batch plant
would be set up onsite and then moved at the end of the construction season.
2.5.3 Construction Work Force
Since most of the wind turbine equipment will be preassembled at the fac-
tory,the size of the construction work force at the site will be reasonably
small.During the first summer season the number of people at the site per-
forming wind and geotechnical measurements will be of the order of 20 to 25.
A peak construction force of about 100 people would be employed during
the second construction season,with about 80 personnel developing the site,
permanent structures,and tower foundations for the wind turbines and the
transmission line (refer to Figure 2.22).
During the third construction season there would be a peak of about
140 people on the project installing the wind turbine equipment and the 138-kV
transmission line.The crew assembling the wind turbines would number about
55 people at the peak activity period.
2.39
''''~
.~Il
~'\
•.-nl
'f'iiI
60
50
40
30
III
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0::o...
'"0::
o
~ao
Ot'J~-F~"7.---;-A ---cM::-----;---;J-""7A--=S--=O--:"N:---:O:---J-:---=-F-M-:-----:-A--:M--:J.,...--:--Ac--S-.....:OL.
MONTH
NOTE:Does 170f ""elude V40I7d'or personnel.own40r p4!'r.ro"n~/,
A~E ~Ag;neerS',or f'e:lAJnus-.."ol7 !t:',40 co"sfr~cfto"
personnel/oeeded err s/fe.
f'~ak worklbrce r~9uir~du·"fs IAcleu/inS'iraAS'/1'Jisslon
VAe C'o"str~ctic",ptrrsonl1el wOf,(ld he 100 1/1 'y~ar I
and 140 in J4!'ar 2.
FIGURE 2.22.Construction Work Force Requirements
2.6 OPERATION AND MAINTENANCE
2.6.1 General Operating Procedures
Following system acceptance,it is planned that operational control of
the wind turbine systems would be through a central dispatch in Fairbanks.
The central dispatcher can start the wind turbines individually if the wind
velocity is higher than the "cu t-in n speed (see Figure 2.19).Power level
2.40
fA.'--_.'.£.:.,.J.__4&_,_Ltll.IILII.•:11..,1I,.:a_._2.liUILILIJI.IUIUliLIUil.LIJUI'IJil,Zlli&2I...•...•..o,_d..lCa
.Ii_.srrriTf';7 rmrilnrr17mnnn r r
'"
II .'
control would be maintained by remotely starting or shutting off various wind
turbines in the cluster.Controls would be provided so that personQel at the
site can start or stop the individual turbines in case the data link is lost,
or for maintenance purposes.
It is anticipated that the wind turbine systems would be operated to off-
set base load insofar as is possible.System maintenance would be scheduled
for the summer months when the winds are light and the system load is small.
2.6.2 Operating Parameters
Estimates of forced outage rates for wind turbines are as follows (Elec-
tric Power Research Institute 1979):
Unscheduled Outage Rate 6%
Planned Outage Rate 5%
Equivalent Annual Availability 89%
There will probably be several unscheduled outages as the project is
started up and initial problems are worked out of the system.The unscheduled
outage rate will probably decrease to the level cited above;then in 15 to 20
years start to increase as major system components begin to exceed their nor-
mal tolerances.From a utility standpoint,utilization of the wind energy
will also depend upon the availability of the step-up transformers,the col-
lection system,and the transmission line.All of these units have very high
availabilities and low forced outage rates.
There should not be any variation of forced outage rate with facility
(machine and/or cluster)size.Increasing the facility size will not change
the annual plant factor,since operation of the individual machines is statis-
tically independent and the machines are essentiallY,drawing on the same wind
resource.However,as the number of identical machines is increased,the reli-
ability of the system increases as the square root of the number of machines.
2.41
I~i
:'l~~
I!~I~
lIn
Il~,.,
Capacity factor (annual plant factor)is dependent upon the availability
of the wind resource and machine availability.Wind resource availability for
the proposed site is summarized in the cumulative distribution of Figure 2.8.
Equivalent annual machine availability is estimated to be 89 percent.
Capacity factor was calculated using the method described by Cliff (1977).
Average turbine power output is estimated using a set of curves relating the
ratio of annual mean wind speed to rated wind speed to the ratio of average
power output to rated power,as shown in Figure 2.23.The choice of appro-
priate curve is based on the ratio of cut-out speed to rated speed (1.95 for
the BWT-2560).The Cliff method assumes a Rayleigh wind speed distribution,
corresponding to the wind speed data of the Alaska wind resource atlas (AEIDC
1981)from which the data of Figure 2.2 are taken;and a simplified machine
performance curve having a linear ramp,as in Figure 2.19.
FIGURE 2.23.Estimate of Expected Average Power Output for Wind
Turbines as a Function of Cutout,Rated and Mean
Wind Speeds and Rated Power Output (Heister and
Pennell 1980)
0.9
0.8
5 0.7
Q..
f0-
g e5 0.6
0::3:
;:.~
0 0 0.5
0......
LLJfo-~ ~0.4
0::
~...:0.3
0.2
0.1
0 0 0 I 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
ANNUAL MEAN WINO SPEED
RATEU WIND SPEED
CUT -OUT SPEED
RATED SPEED
2.2
1.7
1.4
1.25
LO
1.1 1.2 1.3 1.4 1.5
2.42
Ii
RI:
iiIi
'I~!'~:II'I'illl!,:1
\ I Iii'
"I~_••i --;.:_;.:_-"••_ttJ.JU•.•,.U.L.l..I._~_.l__.J.L.!.JS.jl.JI::S.jlt••j.lILI,l.tl...IUliIJil_l..1...141211_-...._ai,U,.
·rp,t_mrrrrnornnT';mrs'r OJ :!"P''JI •
'..
I
Ratios of the seasonal average wind speeds (Figure 2.8)to the rated wind
speed of the BWT-2560 (27.3 mph~Figure 2.19)were taken (Table 2.2').These
r.'
ratios were transformed through the curves of Figure 2.23 to obtain ratios of
seasonal average power output to rated power (not shown in Table 2.2).Poten-
tial seasonal energy production was then readily determined (Table 2.2).
Potential spring~winter and autumn energy production was then reduced by
6 percent corresponding to the unscheduled outage rate.Potential summer
production was reduced by a seasonal average availability factor computed as
(I-FOR)(I-S0R),where FOR is the annual forced outage rate of 6 percent,and
SOR is a "summer season u planned outage rate taken as 20 percent (four times
the annual planned outage rate,since maintenance would normally be scheduled
in summer).The resulting energy production for the four seasons was summed
to obtain an annual average energy production of 7328 MWh (Table 2.2).This
is equivalent to a capacity factor of 33.5 percent.
Wind data from the Rapids weather observation station~unavailable for
this study,would help provide a better estimate of average annual energy pro-
duction.Review of the Rapids weather data would be one of the first tasks if
a decision were made for further investigation of the wind energy alternative.
TABLE 2.2.Computation of Average Annual Energy Production
Ratio of Potential Potential Estimated
Mean Seasonal Seasonal Machine Seasona 1
Seasonal Average Wind Speed Average Average Availability Energy
Wind s}eed to Rated Power Energy Factor Production
Season (mph Wind Speed (MW)(MWh)(%)(MWh)
Spring 16.2 0.59 0.85 1862 94 1750
SUlIIIler 12.5 0.46 0.45 986 75 740
Autumn 17.5 0.63 0.90 1971 94 1853.
Winter 26.6 0.97 1.45 3176 94 2985
Annual Average 7328
2.43
2.6.3 Plant Life
The wind turbine systems are designed for a plant life of 30 years.Since
there are no high temperatures,rapidly moving parts or corrosive atmospheres,
the projected units should be capable of achieving these goals.Accelerated
testing of many of the critical components reinforces the original design
assumptions (Andrews and Baskin 1981).
2.6.4 Operating WorkForce
Operati on will
link to Fairbanks.
by three people who
be controlled by remote dispatch over a microwave data
It is anticipated that routine maintenance can be handled
will be in full time residence at the site.
2.6.5 General Maintenance Requirements
Some background on projected wind turbine maintenance requirements have
been presented by A.D.Little,Inc.(1980).NASA Lewis Research Center con-
tractors have carried out a detailed analysis of operating and maintenance
times and costs for intermediate-range WTS in the 100 to 500 kW size range.
Data for the 2.5-MW wind turbine shoul&be similar.These analyses,which
have not as yet been published,were developed from a data base derived over
many years,and are based primarily on experience with utility and aircraft
component operation and maintenance experience.Estimates of component reli-
ability were derived using a computer modeling technique.
For a fully mature,500-kW machine similar to a MOD-2,but without a
teetering rotor,annual maintenance time was estimated to be 205 man-hours
(40 scheduled and 165 unscheduled).Added to this sum are 61 hours per year
for status checking,32 hours per year for recording failure histories and
reordering spare parts,and 26 hours per year for data recording,resulting in
a total of 324 man-hours per year per turbine.For 10 turbines this would
total 3,240 hours per year,or 1.84 people.Because of the lower productivity
due to the cold weather and maintenance required by the support facilities,
three people are provided.
Table 2.3 presents a preventative maintenance list and estimated times
required for a MOD-6-sized wind turbine.The functions and times should be
similar for th~MOO-2.
2.44
~.d £1 .t2J 1551 SiiJ .Jd l j[a:it II au:lUi!JIJillii£J!Ji2JtJlli2C ..it.i ..it ....MLUJaS,_.LiiLtJRU
m...,_nImn·lSrrrrr r F-----'iif~Sin tn·;.;l'
'0:
TABLE 2.3.Preliminary Preventative Maintenance List for
MOO-6-Sized Wind Turbine
&stimated Annual
Time Time
I nterva 1 Required Requ ired
Item Typical Maintenance Action (Months)(Hours)(Hours)
Rotor Inspect for Damage 12 4 4
Rotor,Tower,and Nacelle Pai nt 12D 9D 9
Low Speed Shaft Bearings,Inspect for Damage,Leaks 12 D.5 D.5
Seal s
Nacelle Structure Inspect for Cracks 12 0.5 D.5
Pitch Change Hydraulics Visual Check for Leaks,Accumulator 12 2 2
Pressure,Fluid Level,Fluid Condition,
and Filters
Pitch Change Mechanism Calibrate and Check for Wear 12 1 1
Gear Box Check Dil and Sensor 12 6 6
Generator,Electrical Check Cond iti on 12 2 2
Switches,and Brushes
Slip Rings (for Power Check Condition 12 2 2
and Signals)
Rotor Brake Change Disc 12 1 1
Yaw Brake Check Disc Wear 12 1 1
Wind Sensors Calibrate 12 2 2
Yaw Drive Mechanism Clean,Check Condition 12 4 4
Yaw Drive Hydraulics Visual Check for Leaks,Fluid Level,12 2 2
Fluid Condition,and Change Filters
Aircraft Warning Lights Change Lamps 12 1 1
TDTAL 38
2.45
--rrF 711 PET r
'"
3.0 COST ESTIMATES
3.1 CAPITAL COSTS
3.1.1 Construction Costs
.-J
..
Construction costs have been developed for the major bid line items
comm9n to wind energy conversion systems.These line item costs have been
broken down into the following categories:labor and insurance,construction
supplies,equipment repair labor,equipment rental,and permanent materials.
Results of this analysis are presented in Table 3.1.Total overnight con-
struction costs for the 25-MW wind farm is estimated to be $62.3 million.(a)
The equivalent unit capital cost is $2490 per kilowatt.
3.1.2 Payout Schedule
A payout schedule has been developed for the entire project and is
presented in Table 3.2.The payout schedule for the project was based on an
18-month basis from start of project construction to commercial operation.
3.1.3 Capital Cost Escalation
Estimates of real escalation in capital costs for the plant are presented
below.These estimates were developed from projected total escalation rates
Materi a1sand Construction
Equipment Labor
Year (Percent)(percent}
1981 1.0 0.5
1982 1.2 1.7
1983 1.2 1.7
1984 0.7 1.3
1985 -0--0-
1986 -0.1 -0.1
1987 0.3 0.3
1988 0.8 0.8
1989 1.0 1.0
1990 1.1 1.1
1991 1.6 1.6
1992 -on 2.0 2.0
(a)January 1982 dollars,not including land or land rights,owner's costs
or transmission costs beyond the main wind farm switchyard.
3.1
r llll'"
I Jilli
I III
,IJ~
1 1111)
1 1111>
,«IIi!
TABLE 3.1.Bid Line Item Costs for Wind Energy Conversion System(a)
(January 1982 dollars)
Construction
labor and Construction
Insurance Supplies
Equipment Permanent
Rental Materials
948,400
99,700
315,200
980,000
Total
Direct
Cost
87,600
408,600
2,215,100
4,400,000
8,800,000
62,252,200
112,500 457,000
9,700
595,100 1,281,300
250,000
83,200
1,622,800
75,000
272,500
742,100
10,100,000 10,870,800
82,000 101,000
25,000,000 25,195,600
6,082,200
38,935,200 49,052,2.00
33,300
85,800
2,500
8,000
300
10,600
5,000
99,000
46,800
291,300
19,700
105,100
159,000
4,000
73,700
154,400
515,900
Equipment
Repair
and labor
1,900
600
500
15,000
2,300
81,500
11,500
765,700
5,212,400
6,091,400
3,800
158,100
569,300
22,100
12,400
221,400
182,700
564,800
19,000
195,600
97,700
3,200
497,700
668,600
3,218,400
TOTAL PROJECT COST
SUBTQTAl
Contractors Overhead
and Profit
Contingencies
Bi d Li ne Item
3.Concrete
1.Improvements to Site
2.Earthwork and Piling
4.Structural Steel and
lift Equ i pment
5.Bui ldings
6.Turbine-Generator
7.Other Mechanical
Equipment
8.Instrumentation
12.Substat i on
9.Electrical Equipment
10.Pai nt i ng
11.Off-Site Facilities
13.Construction Camp
Expenses
14.Indirect Construction
Costs and Architectl
Engineering Services(b)
(a)The project cost estimate was developed by S.J.Groves and Sons Company.No allowance has been made
for land and land rights,client charges (owner's administration),taxes,interest during construction,
or transmission costs beyond the substation and switchyard.
(b)Includes $4,400,000 for engineering services and $1,682,200 for other indirect costs including construc-
tion equipment and tools,construction related buildings and services,nonmanual staff salaries,and
craft payroll related costs.
3.2
Ed hlbC:I.a 51 dU.it L iLJ ..Sili...i ..ilL jg 24ij .JiiJUJiiUSUS_tUI I:jjj
""
1ABLE 3.2.Payout Schedule for Wind Energy Conversion System
(January 1982 dollars)
Cost Per Month,Cumulative Cost,
Month Doll ars Doll ars
l.1,528,900 1,528,900
2.1,528,900 3,057,800
3.1,853,000 4,910,800
4.1,853,000 6,763,800
5.1,733,500 8,497,300
6.1,733,500 10,230,800
7.1,104,700 11,335,500
8.1,104,700 12,440,200
9.1,104,700 13,544,900
10.1,104,700 14,649,600
1l.1,104,700 15,754,300
12.1,104,700 16,859,000
13.8,714,700 25,573,700
11191
14.8,714,700 34,288,400
15.8,847,700 43,136,100 'I'~l
11,1
16.8,847,700 51,983,800 lil~
17.8,898,500 60,882,300
18.1,369,900 62,252,200 111~i
Iq~1
"I
(including inflation)and subtracting a Gross National Product deflator series
which is a measure of inflation.Materials and equipment represent about
93.4 percent of capital costs;labor about 6.6 percent.
3.1.4 Economics of Scale
At the present time,wind turbine systems reflect unitized costs for the
major pieces of mechanical equipment and therefore these components would not
reflect any economies of scale.However,with power plant capacities up to
80 MW (the maximum capacity of the recommended 138-kV transmission lines;
3.3
!i
II
I'
II
II
11
I
II
I
1 ---~--~
refer to Section 2.3),transmission line costs would show a substantial
savings on a dollar-per-megawatt basis with increased plant capacity.
Economies of scale could also be expected for many site development costs,
including costs for temporary facilities,construction equipment,and
construction labor.These savings could be brought about through more
efficient scheduling of construction activities for a larger-sized system.
3.2 OPERATION AND MAINTENANCE COSTS
3.2.1 Operation and Maintenance Costs
The operation and maintenance costs for the 25-MW wind energy conversion
system,expressed in January 1982 dollars,are as follows:
Fixed Costs
Staff (3 Persons)
Variable Costs
Operating Supplies and Expenses
Maintenance Supplies and Expenses
3.2.2 Operation and Maintenance Cost Escalation
$92,000 (3.68J/kW/yr)
Nil
3.3 mill s/kWh
Real escalation of fixed and variable operation and maintenance costs
over the planning period is zero.
3.2.3 Economies of Scale
Costs associated with personnel salaries are generally the major economic
item of operation and maintenance costs for energy-generating facilities.In
light of this fact,economies of scale would result from larger-capacity wind
farms because the personnel requirements would not increase in direct
proportion to additional capacity,but rather at a slower rate.
3.3 COST OF ENERGY
Estimated busbar energy cost for the 25-MW wind farm is 103 mills per
kilowatt-hour:This is a levelized lifetime cost,in January 1982 dollars,
3.4
Jikt ..u tJSJLi LEi 32 J jJ .IJJU.2LltblLilLSL [.l££tCSbiJUux.u=a_.;a···Jaw
we _r57"n trTm 7:l prn nrn Fn •
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11II I
assuming a 1990 first year of commercial operation,and full utilization of
the estimated annual power output of the facility.Estimated busbear energy
"costs for lower capacity factors and later startup dates are shown in
Figures 3.1 and 3.2.Because the real escalation rate for O&M costs is zero,
levelized costs will be the same as first (and subsequent)year costs.First
year cost components are as follows:
Cap ita1
O&M
Total
98.5 mills/kWh
~mills/kWh
103.1 mills/k~~h
.!::::.:.::--<II
E
~
I-
Vlou
>-~c::w
Zw
c::
<l::
IJJ
Vl
::J
IJJ
Cl
W
N
..J
W>W
..J
ow
I-
<l::
::;E
I-
Vlw
200
150
100
50
ESTIMATED AVERAGE OPERATING
/CONDITION FOR ISABELL PASS SITE
"
o
o 20 40 60
CAPACITY FACTOR {%]
80 100
..
FIGURE 3.1.Cost of Energy Versus Capacity Factor
(January 1982 dollars)
3.5
150
..c::::.:s:.-<II
E
~
U'l
0
U
>-100
"0::w
Zw
0::«
(I)
U'l
:::l
CC
CI
W
N
-I 50
w>W
...J
CIw
I-«:a;
~~i\I-
U'lw
o
1990 1995 2000
YEAR OF FIRST COMMERCIAL OPERATION
FIGURE 3.2.Cost of Energy Versus Year of First Commercial
Operation (January 1982 dollars)
2005
These costs are based on the following financial parameters:
Debt Financing
Equity Financing
Interest on Debt
Federal Taxes
State Taxes
Bond Life
General Inflation
3.6
100%
0%
3%
None
None
30 years
0%
!!.-.I•-_.-------.._---------
'"
The capital cost escalation factors given in Section 3.1 were employea.
Weighted average capital cost escalation factors were derived usin~a labor!
material ratio of 7 percent!93 percent.
Because wind turbine generators operate intermittently,they normally
cannot receive capacity credit.Thus,the cost of energy estimates presented
above should not be used in comparing this project with other generating
projects considered in this study.The wind turbine generators discussed in
this study should be evaluated as fuel-saver devices.The decision to build
should be predicated on the cost of energy potentially displaced by operation
of the wind machines,compared with the cost of energy produced by the wind
machines.Thus,direct comparison of this project with alternative sources of
generation is not properly done on the basis of busbar cost of energy alone,
but instead should be done in the context of a system analysis.Such a system
analysis has been done in Volume I of the Railbelt Electric Power Alternatives
Study (Jacobsen et al.1982).
3.7
.&
zc PC 7T T 1!Jfi if 7 rn .T~'I
...
...
4.0 ENVIRONMENTAL AND ENGINEERING SITING CONSTRAINTS
',!
This section presents many of the constraints that would be evaluated
during an engineering siting study.Special attention is given to the appli-
cability of these constraints to the Railbelt Region,especially to the loca-
tion considered in this study.The purpose of such an engineering study is to
identify a preferred site and possibly viable alternative sites for the con-
struction and operation of the wind farm.Through this optimization process,
environmental and engineering considerations are minimized,which subsequently
minimizes project costs.It should be realized that there may be a few con-
straints placed upon the development of a wind turbine power plant that are
regulatory in nature and therefore the discussion presented in this section is
complemented by the discussion in Section 6.0.
4.1 ENVIRONMENTAL SITING CONSTRAINTS
4.1.1 Water Resources
Water resource siting constraints generally center about two topics:
water availability and water quality.The wind turbine has no significant
water requirements or discharges.Hence,there are no major water-siting
constraints anticipated.Problems with changes in runoff quality during site
construction can be mitigated using proper engineering techniques.
4.1.2 Air Resources
There are no significant atmospheric discharges associated with a wind
turbine generating facility.However,due to potentiai radio frequency inter-
ference,the plant should not be located in close proximity to important radio,
television,or microwave transmission stations.This should not prove to be a
significant constraint in the Isabel Pass Region.In addition,due to the ver-
tical size of the structures,an attempt should be made to position the facil-
ity in a manner that does not hinder air traffic and is aesthetically pleasing.
4.1
"liI'!
I![.
"1ll..
4.1.3 Aquatic Ecology
The facility has no water intake or discharge requirements.Construction
runoff would be mitigated through proper engineering.Engineering constraints
would prevent location of the facility in a marshy area.Therefore,no aquatic
ecology constraints are anticipated.
4.1.4 Terrestrial Ecology
Since habitat loss is generally considered to represent the most signifi-
cant impact on wildlife,the prime terrestrial ecology siting activity will be
an identification of important wildlife areas,especially critical habitat or
threatened or endangered species.Based upon this inventory,exclusion,avoid-
ance,and preference areas will be delineated and factored into the overall
plant siting process.This identification would include location of any major
flyways or areas frequented by birds,due to the collision potential with the
rotating blades.As a number of important and sensitive species inhabit the
potential site area (including moose,black bear,and perigrine falcons),
appropriate consideration of these species and their habitat will be required
during the plant siting process.
4.1.5 Socioeconomic Constraints
Major socioeconomic constraints center about potential land use conflicts,
and community and regional socioeconomic impacts associated with project activ-
ities.Potential exclusionary land uses will include land set aside for public
purposes,areas protected and preserved by legislation (federal,state,or
local laws),areas related to national defense,areas in which a wind turbine
installation or transmission line might preclude or not be compatible with
local activities (e.g.,urban areas or Indian reservations),or those areas
presenting safety considerations (e.g.,aircraft facilities).Avoidance areas
will generally include areas of proven archaeological or historical importance
not under legislative protection,and prime agricultural areas.
Regarding other socioeconomic concerns,minimization of the boom/bust
cycle will be a prime criterion.Through the application of criteria per-
taining to community housing,population,infrastructure and labor force,
4.2
.·'srrrt:nri q:;e·-'"
this important consideration will be evaluated and preferred locations identi-
fied.Due to the fact that the potential wind farm site is somewhat remote
~
some boom/bust-related impacts on small population communities may occur.
These should be relatively minor,however,as the peak work force requirement
is only 140 and the site location is easily accessible to a number of moderate-
sized communities such as Delta Junction.
4.2 ENGINEERING SITING CONSTRAINTS
The development of engineering criteria for use during the site evaluation
process is necessary to minimize engineering and construction problems and,
thereby,minimizing facility investment and operating costs.The development
of the proposed wind farm could be constrained by a number of factors bearing
upon the engineering aspects of the project.These factors,which are dis-
cussed below,include meteorological aspects,site topography and geotechnical
characteristics,and access road distance.
4.2.1 Meteorological Aspects
Site selection of a wind turbine generating facility on a meteorological
basis is critical to the successful operation of the facility.Clearly,a
suitable site should have steady and strong winds,based on annual,seasonal,
monthly and diurnal wind patterns.Locations with excessive periods of calm
or gusts of wind exceeding the shutdown point must be avoided.The wind power
density,a function of location,should be matched for the maximum efficiency
point of the wind turbine.These considerations should be used to plot the
specific site within a general area,and should be given prime consideration
in the site-selection study.
Very good wind power (400 to 500 w/m 2 )exists along exposed coastal and
offshore areas of th~Railbelt Region of Alaska.The wind power throughout
interior Alaska and sheltered coastal regions (e.g.,bays,inlets,and sounds
in rugged terrain)appears quite low,except for mountains and isolated ridges.
A few interior places show greater than 200 W/m 2;these are primarily canyons
and valleys where the winds are enhanced by topography,such as the Isabel Pass
Region considered in this study.
4.3
'II
1
'I,
'I11"
In general!potential wind power sites shou1d be initially chosen based
on large-scale wind power inventories that have already been performed over
the State (AEIDC 1981).Further examination of potential sites should include
site reconnaissance!qualitative topographic considerations!local inquiry!
examination of aeolian features and selected qualitative observations during
certain weather conditions.Ultimately!a wind monitoring system should be
installed at each of the more favorable sites chosen from the above procedures.
The monitoring program should include at least 1 year1s data and the installa-
tion of wind sensors at a level of 60 feet or more above the surface.Other
equipment!including recording devices!electric power!and the installation
of a tower!may be required.An extensive intercomparison of all data moni-
tored and a comparison with long-term data must be carried out.Selective
relocation of monitoring systems and extended monitoring at some sites may
also be required before a siting decision can be reached.
4.2.2 Site Topography and Geotechnical Characteristics
In general!the WTGs should be sited on relatively flat terrain.Rough
terrain should be avoided.This will minimize the amount of required access
grading and excavation and associated cost.It will also minimize the poten-
tial for adverse environmenta1 impacts due to rainfall runoff transport of sus-
pended solids to nearby waterways.The WTGs should also be sited above the
lOo-year floodplain of any major streams to avoid flooding incidents.
Another criterion is the avoidance of areas with unstable or poor soi1
conditions!as the towers will require a substantial foundation.Seismic
activity can also be an important site-differentiating factor!with sites away
from fault lines or in a region of low seismic activity preferred.The avail-
ability of suitable foundations for the wind turbine towers is a secondary con-
straint!which can usually be overcome by available engineering technology!but
at higher costs than the cost estimates provided.
4.2.3 Access Road and Transmission Line Considerations
Due to the relatively small size (25 MW)of the project!construction of
a long!major access road is not feasible from an economic point of view.
However!the~weight and size of components of the wind turbine precludes a
4.4
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conventional type of air-lift construction.Hence,the site should be con-
structed near the existing highway system so that access roads construction is
minimized.Route selection will also be affected by ~oi1 and meteorological
conditions;as permafrost,potential frost heave problems,and other soil-
related characteristics can significantly add to the cost of road facilities.
In addition,consideration will need to be given to wind temperature and
ice loading in design of the transmission line.This may further reduce fea-
sible transmission distance due to line loss and economic reasons.One of the
advantages of wind applications for Alaska is that very few production people
are required on the site,and the electrical product can be economically deliv-
ered from the remote sites to the consumption points by means of high-voltage
transmission lines or underwater cables.An important consideration in a
feasibility study of a proposed wind farm in the area investigated in this
study is the cost of the transmission link.
4.5
II
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'"
5.0 ENVIRONMENTAL AND SOCIOECONOMIC CONSIDERATIONS
5.1 SUMMARY OF FIRST ORDER ENVIRONMENTAL Hv1PACTS
The construction and operation of a 25-fvlW large wind turbine generating
facility will impact the land,water,air,and socioeconomic environments in
which it is located.These impacts are directly related to various power
plant characteristics.A summary of these characteristics is presented in
Table 5.1.These primary effects are then analyzed and evaluated in light of
existing environmental conditions to determine the significance of the impact
and the need for additional mitigative measures.
TABLE 5.1.Environment-Related Power Plant Characteristics
Air Environment
Noise
RF Interference
Water Environment
Land Environment
Land Requirements
Socioeconomic Environment
Construction WorkForce
Operating Work Force
Estimated less than 10 db above
background at site boundary
Significant within 0.6 miles of the
facility
No first order impacts
Approximately 60-125 acres,depending
on final configuration
140 personnel (peak requirement)
1-3 maintenance personnel
5.2 ENVIRONMENTAL AND SOCIOECONOMIC EFFECTS
5.2.1 Water Resource Effects
Wind-driven turbine generators do not require water for operation,and
therefore no first order water resource impacts are anticipated.Secondary
impacts from rainfall runoff during plant construction can be mitigated by
implementing proper construction practices.
5.1
5.2.2 Air Resource Effects
Wind turbine generators have small impacts on the atmospheric or meteoro-
logical conditions around the site.No effects on air quality are generated.
The impacts relate to small microclimatic changes and interference with elec-
tromagnetic wave transmission through the atmosphere.
Wind turbines extract energy from the atmosphere and therefore have the
potential of causing slight modifications to the surrounding climate.Wind
speeds will be slightly reduced from surface levels up to a distance equiva-
lent to approximately 5 rotor-diameters.Small modifications in precipitation
patterns may be expected,but total rainfall over a wide area will not be
impacted.Nearby temperatures,evaporation,snowfall,and snow drift patterns
will be affected only slightly.The microclimatic impacts will be qualita-
tively similar to those noted around large isolated trees or tall structures.
The rotation of the turbine blades may interfere with television,radio,
and microwave transmission.Interference has been noted within 0.6 miles of
relatively small wind turbines.The nature of the interference depends on
signal frequencies,blade rotation rate,number of blades,and wind turbine
design.Due to the project location,this phenomenon is nat anticipated to
have a significant impact.
5.2.3 Aquatic Ecosystem Effects
Stream siltation effects from site and road construction are the only
potential impacts associated with this technology due to the lack of opera-
tional process water requirements.Silt in streams may adversely affect feed-
ing and spawning of fish.These potential problems can be avoided by proper
construction techniques and should not be significant.
5.2.4 Terrestrial Ecosystem Effects
The greatest impact resulting from wind energy projects on terrestrial
biota would be loss or disturbance of habitat that in the general site area is
probably predominantly moist tundra with limited areas of spruce and hardwood
forests.Wind-generating structures can furthermore impact migratory birds by
5.2
'IJ itttJ La Ui ...i 1 ~---------
III
'"
~~
increasing the risk of collision-related injury or death.One endangered
species,the peregrine falcon,is known to exist in the region.Ho~eVer,it
has been estimated that the chance of a bird being struck by a large two-blade
machine,assuming no evasive action by the bird,is less than 15 percent.
Hence,this collision risk is not very large.
Another potential impact is low-frequency noise emanating from the genera-
tors.However,from reports on existing facilities,this noise is minimal,
barely perceptible at any distance above ambient wind noise.Sound generation
outside the human audible range,however,remains to be investigated,and
impacts are therefore possible.
5.2.5 Socioeconomic Effects
Construction of a 25-MW wind turbine system and associated transmission
lines would require a relatively small work force with a peak requirement of
approximately 140 personnel.This would create some minor impacts on the
small surrounding communities,but would not significantly alter the communi-
ties infrastructures as long as the work force was not concentrated solely in
one community.The wind turbine facility requires a very small operating work
force,and has minimal maintenance requirements.Therefore,once the facility
is operational,impacts to the surrounding communities are not anticipated.
The cost breakdown for a wind turbine investment is based on the assump-
tion that the monitoring field work,site preparation,and installation would
be performed by Alaskan labor and that all components would be imported from
outside manufacturers.Therefore,approximately 80 percent of the capital
expenditures would be spent outside the region,while 20 percent would remain
within Alaska.The allocation of operating and maintenance expenditures would
be 15 percent spent outside the Railbelt Region and 85 percent within the
Railbelt.The high percentage of costs allocated to outside maintenance would
be offset to some extent by the small requirements for supplies.
5.3
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.....
6.0 INSTITUTIONAL CONSIDERATIONS
The technology of a large wind turbine system is still in the develop-
mental stage,with experimentation being performed in both the public and
private sectors.The diverse technologies being developed could be subject to
distinct sets of institutional considerations in the future.Currently,how-
ever,governmental control of wind turbines as sources of energy is limited,
as evidenced in the discussion below.
6.1 FEDERAL REQUIREMENTS
On the federal level,construction of a wind power system would not be
.subject to the requirements of the major environmental regulatory programs
traditionally associated with new energy production facility projects.As the
system would not produce air or water pollutants,it would not require PSD or
NPDES permits issued by the EPA.(Note:an NPDES permit may be required for
construction runoff).Unless excavation during construction would uncover
hazardous wastes in the soil that must then be disposed of,the project will
also fail to produce hazardous wastes that would require compliance with EPA's
hazardous waste management program under RCRA.Since the project would not
require construction in navigable waterways or the discharge of dredged or
fill material,it would be free from compliance with the environmental regu-
latory programs implemented by the Army Corps of Engineers.The system would
also not be covered by any environmental controls imposed upon energy genera-
tors,as no federal agencies license the construction of wind power generating
systems (i.e.,there is no permit equivalent to that issued by FERC for hydro-
electric power operations).
As a result of the fact that none of the major federal regulatory programs
apply to the construction of a wind turbine system,the activity will probably
not be subject to the requirements of NEPA.The requirement in NEPA that an
environmental impact statement be prepared for a project is placed upon federal
agencies to insure that they consider the environmental impacts of any action
they may take.Based upon the information currently available,it does not
6.1
appear that any federal agency will be performing a major action of the sort
that invokes NEPA responsibility with respect to this project.
It should be noted,however,that federal agencies could have some impact
upon project siting.For example,the Federal Aviation Administration (FAA)
controls the locatiDn of structures within navigable airspace.To protect
aircraft,the FAA imposes marking requirements on structures that are either
200 feet or more in height or located in the vicinity of an airport.The
200-foot towers currently proposed for construction at Isabel Pass would be
subject to FAA requirements.
Federal regulatory authorities may also become involved in reviewing a
wind turbine project if it is located on federal land.A large percentage of
Alaska's 375 million acres is owned by the federal government.Permission
will have to be obtained for use of or access to that land.For example,a
special permit is required for persons wishing to gain access to or through
federal lands under the jurisdiction of the Bureau of Land Management (BLM).
In addition,the site could be located on part of the 103,866,899 acres in
Alaska that have been set aside as national parks,monuments,preserves,
forests,or wild and scenic rivers,in which case development of the land may
be restricted depending upon the land use classification.Limited access can
be obtained to those areas from the Department of Interior or the Department
of Agri culture.
As the construction and operation of a wind turbine system are not sub-
ject to any major environmental regulatory programs,owners and operators of
the system may not be involved in a licensing process for the system.The
review and approval of the project by federal agencies and the processing of
state permits can probably be completed in less than 1 year.A summary of
potentially applicable federal regulatory requirements appears in Table 6.1.
6.2 STATE REQUIREMENTS
The primary regulatory requirements that will be imposed upon a wind
turbine system at the state level are those imposed upon the control of use of
state lands such as the 182,800,000 acres the State of Alaska was given the
6.2
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TABLE 6.1.Federal Regulatory Requirements
Ag_~ncy
En vi ronmenta 1
Protection Agency
Forest Service
Bureau of Land
Management
Fish and Wildlife
Service
Advisory Council
on Historic
Preservation
Federal Aviation
Administration
Requirement
Hazardous Waste
Management Permit
Facility Operation
Special Use Permit
Rights-of-Way for
BLM Land s
National Wildlife
Refuge
Threatened or
Endangered Species
Review
Determination that
Site is not Archeo-
logically Significant
Determination that
Site does not Infringe
on Federal Landmarks
Air Navigation
Approva 1
Scope
Hazardous \~aste
National Forests
Access to
Federal Lands
Access to
Federal Lands
Air,Water,Land
Land Use
Land Use
Air Space
Statute
or Authority
42 USC 6901
et seq.;
section 6925
36 CFR 251
43 USC 1701
et seq.;
50 CFR 26
16 USC 1531
~seq.
16 USC 402 aa
et seq.
16 USC 416
et seq.
49 USC 1304,
1348,1345,
1431,1501
opportunity to acquire under the Alaska Statehood Act.Examples include an
access route permit to gain an easement across state lands or waters,or the
special land use permit needed to construct structures on state lands or
waters.
State regulatory authorities may have some impact on the location of the
wind turbine project even if the site is on private lands.These permits are
presented in the list given in Table 6.2.Examples include the permit for
development of areas that are critical habitats of fish and wildlife,and the
solid waste disposal permit issued by the Alaska Department of Environmental
Conservation in the event that hazardous wastes are generated during
construction.
6.3
TABLE 6.2.State Regulatory Requirements
Agency
Alaska Department
of Environmental
Conservation
Alaska Department
of Fish and Game
State Game Refuge
Land Use Permit
Alaska Department
Natural Resources
Requirement
Solid Waste Management
Facility Operation
Critical Habitat
Area Permit
Land Use Permit
Leasing of State-
owned Lands for Other
then Natural Resource
Extraction
Access Route Permit to
State Lands or Waters
Special Land Use
Permit for State
Lands of \~aters
State Park Non-
Compatible Land Use
Scope
Solid Waste
Land Use
Land Use
Land Use
Land Use
Land Use
Land Use
Statute
or Authority
Alaska
Statute
46.03.100
Alaska
Statute
16.20.230
A1ask a
Statute
16.20.010
Al ask a
Statute
38.05.070-107
Alaska
Statute
41.20 .020
and 040
Al aska
Statute
41.20.020
and 040
Alaska
Statute
41.20.020
and 040
6.3 LOCAL REQUIREMENTS
The most intensive controls could be those imposed on the local level
where zoning ordinances may strictly control land use in the community.Some
communities in the United States have even enacted ordinances specifically
controlling the location of wind turbine systems.Discussions with municipal
officials of Delta,Alaska,revealed that apparently no zoning ordinances exist
for the area in the vicinity of Isabel Pass,north of Paxson.In the event
that this technology is selected,further investigation can be conducted to
determine wh~ther controls may be imposed on a borough level from Glennallen.
The likelihood that such controls exist,however,is not great.
6.4
'PSt rrrrnr 1Er:nrrtt Tn Sst .r I -
7.0 REFERENCES
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Technology Status Report,No.2.EPRI AP-1641,Project 1348-1,Interim
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Anderson,O.R.and D.M.Anderson.1978.Geotechnical Engineering for Cold
Regions.McGraw Hill Publishing,New York,New York.
Andrews,J.S.and J.M.Baskin.1981.Development Tests for the 2.5 Mega-
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Arctic Environmental Information and Data Center (AEIOC).1981.Wind Energy
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Axe",R.A.and P.W.Helms.1980.The tvlOO-2 Wind Turbine.AIAA Paper
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Aeronautics and Astronautics,New York,New York.
Axell,R.A.and H.B.Woody.1981.Test Status and Experience with the
7.5 Megawatt MOD-2 Wind Turbine Cluster.Boeing Engineering and Construc-
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Boeing Engineering and Construction Company (BECC).1980.Commercial 2.5 MW
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Cliff,W.C.1977.The Effect of Generalized Wind Characteristics on Annual
Power Estimated from Wind Turbine Generators.PNL-2436,Pacific Northwest
Laboratory,Richland,Washington.
DeRenzo,D.J.1979.Wind Power,Recent Developments.Noyes Data Corpora-
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Ridge,New Jersey.
Electric Power Research Institute.1979.Technical Assessment Guide.
EPRI PS-1201-SR,July 1979,Electric Power Research Institute,Palo Alto,
California.
Hart,C.W.and P.R.Johnson.1978.Environmental Atlas of Alaska.Uni-
versity of Alaska,Anchorage,Alaska.
Hiester,T.R.1980.Preliminary Evaluation of Wind Energy Potential -Cook
Inlet Area,Alaska.Prepared for Alaska Power Administration,contract
DE-AC06-76 RLO 1830,Pacific Northwest Laboratory,Richland,Washington.
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Hiester,T.R.and W.T.Pennell.1979.Siting Technologies for Large Wind
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Hiester,T.R.and W.T.Russell.1980.Ther~eteorological Aspects of Siting
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Jacobsen,J.J.et ale 1982.Railbelt Electric Power.Alternatives Study:
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Linscott,8.5.,J.T.Dennett,and L.H.Gordon.1981.The MOD-2 Wind Tur-
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7.2