Wind Power Tower and Foundation by Bhagat

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Project Report (Template)

Wind Power Basics

Title: Wind Power Tower Types and

their foundations

*Name of Participant: Govind V. Bhagat

Goa, India

*May 2011

NITTTR BHOPAL GOA EXTENSION CENTRE



Project ReportWind Power Tower Types and their

Foundations

Title

*

Participant

Govind V. Bhagat, Goa, India

*

SupervisorsAlan S. Rocha ,

J oshua Earnest

*

May, 2011

*



Introduction

Describe the background, context, problem/questions, aim for the project assignment, and the

delimitations that are made (what aspects you will include and what you have excluded).

Turbine Sizes:Wind generation equipment is categorized into three general classifications:

Utility-Scale – Corresponds to large turbines (900 kW to 2 MW per Utility-Scale –

Corresponds to large turbines (900 kW to 2 MW per turbine)

intended to generate bulk energy for sale in power markets. They are typically

installed in large arrays or ‘wind energy projects,’ but can also be installed in small

quantities on distribution lines, otherwise known as distributed generation.

Industrial-Scale – Corresponds to medium sized turbines (50 kW to 250 kW)

intended for remote grid production, often in conjunction with diesel generation or

load-side generation to reduce consumption of higher cost grid power and possibly to even

reduce peak loads.

Residential-Scale – Corresponds to micro- and small-scale turbines (400 watts to 50

kW) intended for remote power, battery charging, or net metering type generation.

The small turbines can be used in conjunction with solar photovoltaics, batteries,

and inverters to provide constant power at remote locations where installation of a

distribution line is not possible or is more expensive.)

The power production from a wind turbine is a function of wind speed.

The relationship between wind speed and power is defined by a power curve, which is

unique to each turbine model and, in some cases, unique to site-specific settings. In general,

most wind turbines begin to produce power at wind speeds of about 4 m/s (9 mph), achieverated power at approximately 13 m/s (29 mph), and stop power production at 25 m/s (56

mph). Variability in the wind resource results in the turbine operating at continually

changing power levels. At good wind energy sites, this variability results in the turbine

operating at approximately 35% of its total possible capacity when averaged over a year. The

rotor diameters and rated capacities of wind turbines have continually increased in the

past 10 years, driven by technology improvements, refined design tools, and the need to

improve energy capture and reduce the cost of energy. Optimum turbine size is heavily

dependent on site-specific conditions. In general, turbine

hub heights are approximately 1 to 1.4 times the rotor diameter.

Small wind turbines can be grid-connected for residential generation or they can be used in

off-grid applications such as water pumping or battery charging. Small turbines are typicallyinstalled as a single unit or in small numbers. The smallest turbines (with power ratings less

than 1 kW) are normally used to charge batteries for sailboats, cabins, and small homes.

Turbines with power ratings between 1 kW to 20 kW are normally used for water pumping,

small businesses, residential power, farm applications, remote communication stations, and

government facilities. They are often found as part of a hybrid system that can include

photovoltaic cells, grid power connections, storage batteries, and possibly back-up diesel

generator sets. Small turbines with power ratings between 1 kW and 20 kW can be

connected to single-phase electrical service that is typical in almost every home.

Turbines less than 1 kW are usually customer installed on short pole-type masts which can

be located on roofs or boats. For turbines over 1 kW, tower heights can range from 12 m

(40 ft) to 36 m (120 ft). Rotor diameters range from 1.1 m (3.5 ft) for a 400 W turbine to15 m (49 ft) for a 50 kW turbine. For towers that use guy wires, the guy anchors are



TABLE OF CONTENTS

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choose Index and Tables. Click on the Table of Contents tab. Be sure to use the Custom Style

format.

Table of Contents (Say)

Executive Summary 3

Preface 4

Introduction 5

List of Tables 7

List of Fig. 8

Ch.No. Title Page No.

1. Wind Turbins: A necessity 9

Learning Outccome1.1 Introduction 91.2 …………………………….

2. Types of Wind Turbines 13Learning Outccome

2.1 Introduction 132.2 ……………………….

3. 1 MW Wind Turbine 20Learning Outccome

3.1 Introduction of Suzlon 203.2 ………………………..

3.3 Conclusion 25

References 26Appendices 27



TABLE OF FIGURES

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choose Description. Insert the correct label in the window and make sure the cursor is

positioned at the place of the label.

Fig. No. Name of Fig Page No.

1 Parts of a Wind Power Plant 3

2 4

3 6

4 15

5 16



LIST OF TABLES

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choose Description. Insert the correct label in the window and make sure the cursor is

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Table. No. Name of Table Page No.

6 Classification of Wind Turbines 3

7 4

8 6

9 15

10 16

Table 1 Approved XXX, Source BWEA April 2003 . Error! Bookmark not defined.



Chapter 1: Wind Turbines: A necessity

Title

Learning Outcome: At the end of this chapter you will be able to understand the use of small wind turbine

1.1 INTRODUCTION

Wind.energy.offers.both.environmental.and.economic.benefits:.it.is.

installation..Key.site.evaluation.factors.include: emissions-

free.and.renewable,.and.the.fuel.itself.is.free,.local,.and.will.

Wind speed: . – .Most.small.turbines.require.a. minimum .wind.

never.fluctuate.in.cost..But.wind.systems.are.a.long-term.investment,.speed.of.15.km/hr.(4.m/s).or.higher.just.to.operate..In.general,.

and.wind.energy.is.a.very.site-specific.resource..



IS WIND ENERGY COST EFFECTIVE?

the primary wind turbine customers have a choice of power generation options. The industries are investing in wind as one of the options to meet a portion of rising domestic electricitynd. Wind is an abundant, clean energy source, with wind turbine installations closely tied to government mandates for renewable energy, the ability to finance wind projects, and the

competitiveness of wind energy. The ability to finance projects and the cost-competitiveness of wind energy are closelyo federal tax policies. These factors affect wind turbine installations and, therefore,

emand for wind turbines.



Chapter 2

Title:Wind Turbine Towers types: A brief

rning Outcome: At the end of this chapter you will be ableto learn types of wind turbine towers and their foundations.

INTRODUCTION

er are of various types, viz.eel shell tower designed in a conventional way with flanges and both longitudinal and transverse welds.eel shell tower with bolted friction joints only.

oncrete tower with pretensioned steel tendons.

ybrid tower with a lower concrete part and an upper part built as a conventional steel shell.

ttice tower.ooden tower.

TYPES OF WIND TURBINE TOWERS

DED STEEL TOWER:y the welded steel shell tower dominates the wind turbine market. Largernes and higher hub heights result in larger optimal tower base diameters.he road transportation there are limitations due to bridges and otheracles. In Sweden the limit for transports with special permits in generalmizes the diameter to 4,5 metres. In other areas the restrictions may be

e severe. To some extent it is still technically possible to build towers withs than optimal diameter, but due to the high mass and the large wall

ness they tend to be uneconomical in comparison with other alternativese a hub height of roughly 100 metres. In this report welded steel shellrs were outlined for 3 MW turbines up to a hub height of 150 metresreas the limit for the 5 MW towers was 100 metres.n diameter restrictions tend to make welded towers uneconomical, thelogical choice is steel shell towers with bolted friction joints bothtudinally and laterally. Such a tower is transported as the separate cut,, drilled and painted steel plates, which are assembled at the turbine site.

technology was in use already during the 1980s for the much smallernes of that time. Today it is just starting to reappear.

TENSIONED CONCRETE TOWERS:pretensioned concrete towers have a long history in wind power, startingin-situ built slip formed towers. Today most concrete towers are

mbled from prefabricated elements, cast in sizes allowing roadsportation.

CRETE TOWERS:advantages of the concrete towers are concentrated to the lower parts,h are capable of absorbing large moments in an economical way.efore hybrid towers are appearing on the market, with a concrete part forower section and a conventional steel shell tower for the upper. Thision also provides the designer with some freedom regarding both the

gn of the concrete tower and the placement of the eigenfrequencies of ther. From this study one can draw a quite firm conclusion that hybridrs generally are more economical than pure concrete ones.

ICE TOWERS:

to the very large base width, lattice towers reveal the lowest weights andstments of all towers. The so far tallest wind turbines have been furnishedlattice towers. The advantages are counteracted by disadvantages that

be equally strong. The number of bolts is very high and they needdic checking. The dynamic properties are hard to control. During icing

itions large accumulation of ice in extreme cases may endanger thene. An acceptable level of safety for the maintenance personnel may beto maintain. And finally the visual qualities are controversial.

ODEN TOWERS:d has been used as a construction material for wind turbine blades fordes, but only recently considered for wind turbine towers. This may seemge, since towers should be a less demanding application than blades.

d is also in general known to be an economical construction material

tant to fatigue and buckling. The so far only large wind turbine tower of d is designed by a German company for a 1,5 MW wind turbine. In thisrt the wooden towers were studied less extensively than the others, duee less developed and known technology especially regarding joints.

ILE CRANE TOWERS:y mobile cranes are the dominating way of lifting tower segments andnes. With the cranes available today and current weights there is a limit

5 - 150 metres in hub height for this technology. Still higher hub heightsbe served with lifting towers, which however today are quite expensiven this report the immediate reason why hub heights above 150 metres

uneconomical. Thus there is a need for more economical ways of liftingturbines to the highest hub heights. the study one can draw a general conclusion that it is economical totaller towers than the hitherto conventional one turbine diameter. This

ency is more pronounced in a forest than in the open farmland, which isto the higher wind shear above a forest. However, larger turbines, ins of turbine diameter and power level, are not more economical, at least

with the turbines specified for this study.ing at e.g. a hub height of 125 metres, it is possible to save up to 30 %



Chapter 3

Title: Wind Turbine Towers: Detailed Study

Learning Outcome: At the end of this chapter you will be able in a detailed manner the types of towers for a wind turbine.

neswind turbine assembly operations are performed with mobile cranes,

h may be either of crawler type or truck-mounted. Crawleres are often the preferred choice, however, they have the drawback of ing quite wide tracks for travel between the turbine sites within a wind

Of the cranes mentioned below, the LR 1400 needs a 9 m wide trackthe LR 1800 needs 12,5 m. In order to avoid excessive costs for roadsthe crane may be dismantled between use at the successive turbine siteswind farm, although such dismantling also involves a cost.es in general have benefits of a short installation time per turbine and avely small crew. Disadvantages are the areas needed for the liftingation, need for wide roads inside parks, rigging between turbine sites,restrictions (maximum 5 – 8 m/s during lifting) and the cost forlization and hire, especially of the largest units.oximate costs for mobilization and hire are depicted in Table 6. In thelations of the report, the cost of 300 km of land transportation from Swedish port has been added.

ng towersg towers have traditionally been used in industry for installation of heavypment. Reasons to select this technology were in this case heavy li fts, uneven terrain and high wind conditions, making it hard to find calm periods for liftingcranes. With lifting towers it is possible to perform lifts up to 15 – 18 m/s wind speed.e is ongoing development work aiming at creating less costly alternativesfting wind turbines to high heights.

ded steel shell towerwelded steel shell tower today dominates the wind turbine market. Itsts of cylinders made of steel plate bent to a circular shape and welded

tudinally, Transversal welds connect several such cylinders toa tower section. Each section ends with a steel flange in each end. The

ons are bolted to each other. The bottom flange is connected to thedation and the top one to the nacelle.wer is primarily dimensioned against tension and buckling in the extremecases. Ideally the margin should be the same for both criteria, sinceasing the diameter, with a corresponding reduction of plate thickness,

ases the tension strength but reduces the buckling margin. Finally ther has to be checked against fatigue. According to BSK and Eurocode

ecting welds (transversal and longitudinal) and dimension changesges) affects the strength in a negative way. Thus it is the welds and the

metry that primarily determine the fatigue strength rather than the quality

e steel. Therefore wind turbine towers mostly use ordinary qualities of steel. In this report use of S355J2G3 (earlier known as SS2134, tensile yield limit 355 MPa)

sumed for both the welded and friction joint towers. In the dimensioning load case, the tower is affected by the thrust from the rotor. This thrust will create a bending

ent, which increases with thedistance from the turbine shaft, i.e. inversely proportional to the height abovethe ground. To cope with this increasing bending moment it

vourable to make the tower conical in shape, to the limit of buckling. However, land transportation even with a special permit is not possible for diameters exceeding 4,5Sweden. Other countries and certain roads may create even more severe restrictions, e.g. 3,5 m. To a certain degree these restrictions may be counteracted by an

ase of plate thickness, however, the tower will then become less economical.

el shell tower with friction jointsprevious section clearly demonstrates that a restriction on the baseeter of a wind turbine tower has a detrimental effect on the weight andcost when reaching hub heights of 100 m and above. One way to get

of that restriction is to do away with the workshop welding and insteadthe tower plates with screws and nuts, forming friction joints, performede field. This is also a way to reduce how the weldings detoriate theue resistance of the steel. An example of a screw joint is revealed inbvious problem of bolted connections is how to get access to the outerof the tower. One solution is to put the screws with nuts in advance in

outer, upper section of the tower and prepare the next section with long,ed holes. Another solution is depicted in Fig. 8 and 9.20 Here the screws may bented from the inside, provided that the outside nut is held in place withe provisional arrangement. Note that the double friction plates provide ale lap joint, which is an ideal load path, although the number of nuts and

ws gets high. Each tower section is assembled on the ground from nearanels, which are easy to transport irrespective of tower diameter. Theections, with a diameter allowing for transportation, are shipped assembled.main advantage of the friction joint towers is that they can be built

out any restriction regarding the diameter. On the other hand, assemblye may be expensive as well as regular checks of the pretension of the

number of bolts. The holes in the large steel panels need to beioned with a high degree of accuracy, creating a need for specialized andy equipment.is chapter it is anticipated that all joints are performed as friction joints.real design the sections with a diameter of less than 4,5 meters may be designed partly with welded joints, if this provides any advantages.

tensioned concrete towerconcrete tower the concrete proper only withstandssure. The ability to absorb tension is provided primarily by pretensionedons, located in ducts in the concrete or internal/external of the concrete

Putting them internal or external enables easy inspection There are



pared to steel towers, concrete towers are much heavier and takes longerto erect. On the other hand, the concrete or the concrete elements, if

e small enough, are not subject to transportation restrictions, as for the case with welded steel towers with large base diameters.

rdless if the tower is slip formed or assembled from precast elements, itvantageous to install the post-stressing tendons from below, thus noting to lift the heavy rolls of tendons to the tower top. Then it is howeverssary to furnish the foundation with a cellar.21

formed towere basic case the tower shell is fabricated by slip forming, which is anuous process running 24 hours a day until the tower is finished. Theons are mounted and tensioned after the concrete has cured.cost distribution for a 3 MW slip formed tower in Fig. 15 reveals primarilythe tower cost, in relation to the production, is increasing with increasing

height, although the specific investment cost was decreasing (up to aht of 150 m), see Fig. 14.g. 15 it is also clear that a quite large proportion of the cost is due to thetressed reinforcement tendons, and that the relative amount evenases with increasing height. This is due to the fairly large amount of

erial, and especially to the high cost of this high-quality steel (7 €/kg), bly at least partly due to a market lacking competition. Although theunt of concrete is large, the cost is low (0,06 €/kg). Also the cost of the ary, un-tensioned reinforcement is low (1 €/kg).

concrete is either produced in an existing concrete factory or in a mobilet erected for the purpose. The latter case presumes that the volume is large enough. In the calculation a 150 km transport of the concrete isded.

cation the slip formed towers in cold weather is not possible withoutming.22 Slip forming implies a high degree of quality control regarding workmanship and climatological factors, e.g. precipitation and temperature.

er assembled from precast elementsssembling a concrete tower from precast elements fabricated in a factory,

ould be possible to achieve more stable conditions and thus a more eventy level, and also to reduce the excess costs associated with productione.basic method for production of conical towers creates a need for a largeber of moulds, see Fig. 16. Due to transportation reasons, wide elements

to the base are divided in two or three sections.NC milling it may be possible to produce concrete elements featuring highances, making assembly easier.24

other method25, the tower is assembled from identical corner elements

flat segments of varying width in between. In this way the number of ds and elements is reduced, which should reduce the cost, especially

n producing towers in low numbers.tory for the production of 60 000 m3 of ring-shaped concrete tower elements a year, enough for 200 towers, is reported to cost 33 M€.26

crete/steel hybrid towerdea behind building a hybrid concrete/steel tower is to use concrete in

wide lower part and steel in the upper part, where a conventional weldedshell tower section may be designed without any risk of conflict with the

sportation limitations. In reality it also makes it easier to design therete part and to get the eigenfrequencies right.

is report the length of the steel section was to determined to be 50ers for the 3 MW turbines and 40 meters in the 5 MW cases. In this way itpossible to stay within the 4,5 meter limit set. There may exist antional cost for joining the concrete and the steel sections, which howevert included in the reported calculations.y hybrid towers are widely used by Enercon and also introduced by

tice towerce towers have been used in large numbers for smaller wind turbines,cially in non-European countries. For larger turbines they have mainlya choice when a stiff (under-critical) tower was needed.

clear that they often are considerably lighter than towers based on othernologies. The physical background to this phenomenon is the large widthse lower sections. The need for material to take strain or pressure isrsely proportional to the width. With a tubular section a thin-walled

truction will finally meet with buckling, which restrains the maximumeter. A lattice design does not buckle like a shell. The risk of buckling of ndividual members is controlled by inserting numerous struts that giveattice tower its characteristic look.Finnish company Ruukki is introducing a further developed design of e towers based on use of hexagonal steel profiles and high strength, enabling lower weights and better economy.29

German wind turbine manufacturer Fuhrländer use lattice towers forning very high hub heights. An open design, like a lattice tower, is moree to icing than a tubularr. The possible impact on the dynamic properties may be the most

re consequence, which may endanger the wind turbine in an extreme It may also be a problem for maintenance personnel, even if their

ator runs on heated rails. Another danger is the increased risk of falling ice.stated advantage of lattice towers is that they should have less

dynamic drag and hence create less tower shadow and noise. This isever questionable. The probably noisiest wind turbine ever built was the 2GE Mod-1 from the early 1980s. Its down-wind turbine was erected on a sturdy lattice tower.They need small areas

he assembly. On the other hand, the normal procedure seems to be tomble the tower lying on the ground before raising, which implies need of rea at least as long and wide as the tower itself. A width at the base of 30 m is quite considerable.

oden towerd has been used as a construction material for wind turbine blades for



owers that use guy wires, the guy anchors are typically spaced one half to three quarters of the tower height from the base. A steel base plate or concrete foundation is

ssary to adequately support the tower, depending on the turbine and tower size. Monolith-type concrete foundations are approximately 3 to 6 ft square. Free-standingrs can require construction of more elaborate concrete piles for each tower leg. Tilt-down towers are also available to facilitate easier access for maintenance.

dations – In general, the foundation design is based on the weight andguration of the proposed turbine, the expected maximum wind speeds, and the

characteristics at the site. Typical foundation approaches include an inverted

lab design and the patented concrete cylinder design (Figure 7 and Figure 8,

ectively).

rted “T” Slab Foundation



So depending upon the tower type the foundation is prescribed.



17

Chapter 4

Discussion

Learning Outcome: At the end of this chapter you will be able……………………...



18

Conclusion



19

6. REFERENCES

(For the references, write in alphabetical order in the format as given below, with surnameoccurring first when writing author’s name)

1. Wizelius, Tore – Windpower Planning; Windpower Distance Education Module;

Gotland University, Visby, Sweden, 2006 (say)

2. www.suzlon.com 24th Feb 2007 (say)

3. http://library.wustl.edu/~listmgr/devel-l/Jun1995/0154.html 12th Nov 2006 (say)

***************

http://www.suzlon.com/





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7. APPENDICES

If any

Wind Power Tower and Foundation by Bhagat

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