report for installation of lidar based offshore structure for wind

1

Report for Installation of LiDar based Offshore Structure for wind

measurement

Submitted

to

Ministry of Environment and Forest

Government of India

Delhi – 110003

By

SAMIRAN UDAIPUR WINDFARMS LIMITED

Ahmedabad

Technical Consultant

National Institute of Ocean Technology

Ministry of Earth Sciences, Govt. of India

Chennai -600 100 February 2016

2

Table of Contents Table of Figures ......................................................................................................................... 4

List of Tables ............................................................................................................................. 4

1. Form 1 ................................................................................................................................ 5

2. Executive summary .......................................................................................................... 21

3. Introduction ...................................................................................................................... 21

3.1. Need for Renewable Energy & World Scenario ....................................................... 21

3.2. Offshore Wind Potential in India and wind energy Policy ....................................... 22

3.3. SUWL, SEL and NIOT involvement ........................................................................ 24

4. Project Description........................................................................................................... 24

4.1. Site Details ................................................................................................................ 24

4.2. Bathymetry & Physical Processes ............................................................................. 25

4.2.1. Bathymetry ......................................................................................................... 25

4.2.2. Tide .................................................................................................................... 25

4.2.3. Currents .............................................................................................................. 26

4.2.4. Wave .................................................................................................................. 26

4.2.5. Rainfall ............................................................................................................... 26

5. Proposed Data collection Mast ........................................................................................ 26

5.1. Description with layout ............................................................................................. 26

5.2. Structural Design ....................................................................................................... 27

4.2.1. Basic Load ................................................................................................................. 27

5.2.1.1. Dead load........................................................................................................ 27

5.2.1.2. Live Load ....................................................................................................... 28

5.2.1.3. Wind loads...................................................................................................... 28

5.2.1.4. Hydrodynamic loads ...................................................................................... 28

5.2.1.5. Seismic loads .................................................................................................. 30

5.2.2. Load Combinations................................................................................................ 32

5.2.3. Monopile ................................................................................................................ 32

5.2.4. Cyclones ................................................................................................................ 33

5.2.4.1. Axial Compression: ............................................................................................ 34

5.2.4.2. Elastic Local Buckling Stress ............................................................................. 34

3

5.2.4.3. Inelastic local buckling Stress. ............................................................................ 34

5.2.4.4. Allowable Bending Stress: .................................................................................. 36

5.2.5. Earth Quake ............................................................................................................... 36

5.2.5.1. Member Capacity for Earthquake Load Combination: ....................................... 37

5.2.6. Boat Impact ................................................................................................................ 37

5.2.6.1. Member Capacity for Boat Impact Combination: .............................................. 37

5.2.7. Platform...................................................................................................................... 38

5.2.7.1. Material Properties .............................................................................................. 38

5.2.7.2. Loads & Load combinations ............................................................................... 39

5.2.7.3. Staad Results ....................................................................................................... 40

5.2.7.4. Sectional Classification ....................................................................................... 41

5.2.7.5. Shear Capacity .................................................................................................... 41

5.2.7.6. Moment Capacity ................................................................................................ 42

5.2.7.7. Check for deflections .......................................................................................... 42

5.2.7.8. Check for web buckling ...................................................................................... 42

5.2.7.9. Check for web bearing ........................................................................................ 43

5.2.7.10. Check for stiffeners ........................................................................................... 43

5.2.7.11. Check for compression flange buckling ........................................................... 43

5.2.7.12. Secondary beams .............................................................................................. 44

5.2.7.13. Sectional Classification ..................................................................................... 44

5.2.7.14. Shear Capacity .................................................................................................. 44

5.2.7.15. Moment Capacity .............................................................................................. 45

5.2.7.16. Check for deflections ........................................................................................ 45

5.2.8.17. Check for web buckling .................................................................................... 46

5.2.7.18. Check for web bearing ...................................................................................... 46

5.2.7.19. Check for stiffeners ........................................................................................... 46

5.2.7.20. Check for compression flange buckling ........................................................... 47

5.2.7.21. Welded Connection design ............................................................................... 47

4

6. Installation procedure....................................................................................................... 48

6.1. Decommissioning procedure ..................................................................................... 49

6.2. Construction and operational impact assessment ...................................................... 50

6.2.1. Noise level ......................................................................................................... 50

6.2.2. Air Environment ................................................................................................ 50

6.2.3. Water Environment ............................................................................................ 50

6.2.4. Fishery................................................................................................................ 50

7. Project Schedule and cost estimates ................................................................................ 51

7.1 Project Schedule......................................................................................................... 51

7.2 Cost estimate .............................................................................................................. 51

Table of Figures

s

Fig. 1 Installed Cumulative Capacity in European countries (Source: EWEA, (2013)) ......... 22

Fig. 2 Wind Speed Distribution at 80m Elevation ................................................................... 23

Fig. 3 Power Production for 3 MW Offshore Wind Turbine. .................................................. 23

Fig. 4 Google earth map –Jakhau ............................................................................................ 23

Fig. 5 Topography map(20km buffer)-Jakhau ......................................................................... 23

Fig. 6 Regional Connectivity map-Jakhau .............................................................................. 23

Fig. 7 Topography map-Jakhau ............................................................................................... 23

Fig. 8 Hydrographic map-Jakhau ............................................................................................. 23

Fig. 9 Bathymetry profile for the prosed site ........................................................................... 25

Fig. 10 Layout of Supporting Platform for LiDar.................................................................... 27

Fig. 11 Current profile for operational and critical condition .................................................. 28

Fig. 12 Regions of Applicability of Various Wave Theories .................................................. 30

Fig. 13 Seismic zone of India .................................................................................................. 31

Fig. 14 Acceleration Spectrum ............................................................................................... 32

Fig. 15 Deflected Profiles for Various Sea States .................................................................... 33

Fig. 16 Installation methodology for wind mast ...................................................................... 49

List of Tables

Table 1 Instruments for collecting various Parameters............................................................ 26

Table 2 Waves Parameters ....................................................................................................... 29

Table 3 Soil Parameters for Different Layers .......................................................................... 33

5

1. Form 1

(For seeking clearance for project attracting CRZ notification)

Name of the project: Installation of Lidar based Offshore structure for wind

measurement

CRZ classification of the

area:

CRZ-IV

Expected cost of the

project:

4 crore

(I) Basic Information

Sr

No. Item Details

1. Name of the project/s

Installation of Lidar based Offshore

structure for wind measurement in

Jakhau

2. S. No. in the schedule

3.

Proposed capacity/area/length/tonnage to

be handled/command area/lease

area/number of wells to be drilled

1.2m diameter monopile to support

5m diameter platform which is

located at 7.5m clearance above

water level

4. New/Expansion/Modernization New

5. Existing Capacity/Area etc. Not Applicable

6. Category of Project i.e. ‘A’ or ‘B’ B1

7. Does it attract the general condition? If

yes, please specify.

No

8. Does it attract the specific condition? If

yes, please specify.

No

9. Location:

N23o 07’ 24.42” E 68o 27’ 48.24”

Plot/Survey/Khasra No. NA

Village Jakhau

Tehsil Abdasa

6

Sr

No. Item Details

District Kutch

State Gujarat

10. Nearest railway station/airport along with

distance in km

Naliya (28km from Jakhau).

Bhuj (120km from Jakhau)

11. Nearest Town, city, District Headquarters

along with distance in km.

Naliya is the district headquarters

located 28km away from this

location

12.

Village Panchayats, Zilla Parishad,

Municipal Corporation, Local body

(complete postal addresses with

telephone nos. to be given)

Offshore facility near Jakhau port.

13. Name of the applicant Samiran Udaipur Windfarms Limited

14. Registered Address

C/o Suzlon Energy Limited

Suzlon House,

5,Shrimali Society,

Near Sri Krishna Complex

Navrangpura,Ahmedabad-380009

Gujarat

India

15. Address for correspondence :

Name Mr. Ranjit Singh Parmar

Designation (Owner/Partner/CEO) Sr. President-India Business

Address

C/o Suzlon Energy Limited

Suzlon House,

5,Shrimali Society,

Near Sri Krishna Complex

Navrangpura,Ahmedabad-380009

7

Sr

No. Item Details

Gujarat

India

Pin Code 380009

E-mail [email protected]

Telephone No. 079-66045201, 66045000

Fax No. 079-26565540, 26442844

16.

Details of Alternative Sites examined, if

any. Location of these sites should be

shown on a topo sheet

NA

17. Interlinked Projects None

18. Whether separate application of

interlinked project has been submitted?

NA

19. If yes, date of submission -

20. If no, reason -

21.

Whether the proposal involves

approval/clearance under: if yes, details

of the same and their status to be given.

( c )

(a) The Forest (Conservation) Act, 1980?

(b) The Wildlife (Protection) Act, 1972?

(c) The C.R.Z Notification, 1991?

22. Whether there is any Government

Order/Policy relevant/relating to the site?

Offshore wind energy policy of

Ministry New and Renewable Energy

23. Forest land involved (hectares) None

24.

Whether there is any litigation pending

against the project and/or land in which

the project is propose to be set up?

None

(a) Name of the Court

(b) Case No.

(c) Orders/directions of the Court, if any None

8

Sr

No. Item Details

and its relevance with the proposed

project.

(II) Activity

1. Construction, operation or decommissioning of the project involving

actions which will cause physical changes in the locality (topography,

land use, changes in water bodies and the like)

S.No Information/Check list

confirmation

Yes/

No

1.1 Permanent or temporary

change in land use, land cover

or topography including

increase in intensity of land use

(with respect to local land use

plan)

No The proposed site is 18km from the shore

and hence there is no change in the land

use

1.2 Details of CRZ classification as

per the approved Coastal Zone

Management Plan?

CRZ IV as per CRZ notification 2011

1.3 Whether located in CRZ -1

area?

No Not Applicable.

1.4 The distance from the CRZ – I

areas?

- 16.3km

1.5 Whether located within the

hazard zone as mapped by

Ministry of Environment &

Forests/National Disaster

Management Authority?

No Not Applicable.

1.6 Whether the area is prone to

cyclone, tsunami, tidal surge,

subduction, earth quake etc.?

Yes Extreme conditions such as cyclone and

earthquake are being considered in

structural design of the Wind Mast.

9


confirmation

Yes/

No

1.7 Whether the area is prone for

salt water ingress?

No Not Applicable.

1.8 Clearance of existing land,

vegetation & buildings?

No Not Applicable.

1.9 Creation of new land uses? No Not Applicable

1.10 Pre-construction investigations

e.g., borehole, soil testing?

No Not Applicable

1.11

Construction works Yes Pile driving and erection of structure.

1.12 Demolition works? No Not Applicable

1.13 Temporary site used for

construction works or housing

of construction workers?

No Not Applicable

1.14 Above ground buildings,

structures or earth works

including linear structures, cut

and fill or excavations

No Not Applicable

1.15 Underground works including

mining or tunneling?

No Not Applicable

1.16 Reclamation works? No Not Applicable

1.17 Dredging/ reclamation/land

filling/disposal of dredged

material etc?

No Not Applicable

1.18 Off shore structures? Yes Offshore wind mast (1.2m diameter pile to

support 5m diameter platform which is

located at 10m above MSL.

1.19 Production and manufacturing

processes?

No Not Applicable

10


confirmation

Yes/

No

1.20 Facilities for storage of goods

or materials?

No Not Applicable

1.21 Facilities for treatment or

disposal of solid waste or liquid

effluent?

No Not Applicable

1.22 Facilities for long term housing

of operational workers?

No Not Applicable

1.23 New road, rail or sea traffic

during construction or

operation?

No

Not Applicable

1.24 New road, rail, air water borne

or other transport infrastructure

including new or altered routes

and stations, ports, airports

etc?

No The route is away from the navigation and

hence no alteration for routes required.

1.25 Closure or diversion of existing

transport routes or

infrastructure leading to

changes in traffic movements?

No Not Applicable

1.26 New or diverted transmission

lines or pipelines?

No Not Applicable

1.27 Impoundment damming,

culverting, realignment or other

changes to the hydrology of

water courses or aquifers?

No Not Applicable

1.28 Stream and river crossings? No Not Applicable

1.29 Abstraction or transfers of

water from ground or surface

waters?

No Not Applicable

1.30 Changes in water bodies or the No Not Applicable

11


confirmation

Yes/

No

land surface affecting drainage

or run-off?

1.31 Transport of personnel or

materials for construction,

operation or decommissioning?

Yes Transport of personnel or materials for

construction, operation or decommissioning

through vessel (boat / Jackup / barge).

1.32 Long-term dismantling or

decommissioning or restoration

works?

No No dismantling or decommissioning is

proposed.

1.33 Ongoing activity during

decommissioning which could

have an impact on the

environment?

No Not envisaged

1.34 Influx of people to an area in

either temporarily or

permanently?

Yes Temporary construction workers during

construction phase.

Operational / maintenance staff will do

monthly visit to the platform.

1.35 Introduction of alien species? No Not Applicable

1.36 Loss of native species or

genetic diversity?

No Not Applicable

1.37 Any other actions? No Not Applicable

2. Use of natural resources for construction or operation of the project

(such as land, water, materials or energy, especially any resources

which are non-renewable or in short supply):


confirmation

Yes/

No

Details thereof (with approximate

quantities/rates, wherever possible)

with source of information data

2.1 Land especially undeveloped No Not Applicable

12


confirmation

Yes/

No




or agricultural land (ha)

2.2 Water (expected source &

competing users) unit: KLD

No Not Applicable

2.3 Minerals (MT) No Not Applicable

2.4 Construction material – stone,

aggregates, sand/soil

(expected source – MT)

No Only prefabricated steel will be used..

2.5 Forest and timber (source –

MT)

No Not Applicable

2.6 Energy including electricity

and fuels (source, competing

users) Unit: fuel (MT), energy

(MW)

No Self-propelled boats are being used.

2.7 Any other natural resources

(use appropriate standard

units)

No Not Applicable

3. Use, storage, transport, handling or production of substances or

materials, which could be harmful to human health or the environment

or raise concerns about actual or perceived risks to human health

S.N

o

Information/Check list

confirmation

Yes/

No




3.1 Use of substances or materials,

which are hazardous (as per

MSIHC rules) to human health or

the environment (flora,fauna and

water supplies)

No Not Applicable

3.2 Changes in occurrence of No Not Applicable

13

S.N

o

Information/Check list

confirmation

Yes/

No




disease or affect disease vectors

(e.g., insect or water borne

diseases)

3.3 Affect the welfare of people e.g.,

by changing living conditions?

No Not Applicable

3.4 Vulnerable groups of people who

could be affected by the project

e.g., hospital patients, children,

the elderly etc.,

No Not Applicable

3.5 Any other causes, that would

affect local communities,

fisherfolk, their livelihood,

dwelling units of traditional local

communities etc

None Not Applicable

4. Production of solid wastes during construction or operation or

decommissioning (MT/month)


confirmation

Yes /

No


quantities/rates, wherever possible) with

source of information data

4.1 Spoil, over burden or mine

wastes

No Not Applicable

4.2 Municipal waste (domestic

and or commercial wastes)

No Not Applicable

4.3 Hazardous wastes (as per

hazardous waste

management rules)

No Not applicable

4.4 Other industrial process

wastes

No Not Applicable

14


confirmation

Yes /

No




4.5 Surplus product No Not Applicable

4.6 Sewage sludge or other

sludge from effluent

treatment

No Not Applicable

4.7 Construction or demolition

wastes

No Not Applicable

4.8 Redundant machinery or

equipment

No Not Applicable

4.9 Contaminated soils or other

materials

No Not Applicable

4.10 Agricultural wastes No Not Applicable

4.11 Other solid wastes No Not Applicable

5. Release of pollutants or any hazardous, toxic or noxious substances to

air (Kg/hr)


confirmation

Yes/

No




5.1 Emissions from combustion

of fossil fuels from stationary

or mobile sources

No

Not Applicable

5.2 Emissions from production

processes

No Not Applicable

5.3 Emissions from materials

handling including storage or

transport

No Not Applicable

5.4 Emissions from construction No Not Applicable

15


confirmation

Yes/

No




activities including plant and

equipment

5.5 Dust or odours from

handling of materials

including construction

materials, sewage and

waste

No Not Applicable

5.6 Emissions from incineration

of waste

No Not Applicable

5.7 Emissions from burning of

waste in open air (e.g., slash

materials, construction

debris)

No Not Applicable

5.8 Emissions from any other

sources

No Not Applicable

6. Generation of noise and vibration and emissions of light and Heat:


confirmation

Yes/No Details thereof (with approximate



6.1 From operation of

equipment e.g., engines,

ventilation plant, crushers

Yes Negligible noise is expected during

operation. The machinery to be used will

be properly maintained to avoid noise

pollution.

6.2 From industrial or similar

processes

No Not Applicable

6.3 From construction or Yes During construction there will be noise

16


confirmation




demolition arising out of loading/unloading,

transportation of construction materials,

crane operation, piling work, etc which will

not be significant.

Noise levels will be monitored to ensure

compliance to norms.

6.4 From blasting or piling Yes Negligible noise is expected during

construction work which is in the sea.

6.5 From construction or

operational traffic

No Not applicable

6.6 From lighting or cooling

systems

No Not Applicable

6.7 From any other sources None -

7. Risks of contamination of land or water from releases of pollutants into

the ground or into sewers. Surface waters, ground water , coastal waters

or the sea


confirmation




7.1 From handling, storage, use

or spillage of hazardous

materials

No Not applicable

17


confirmation




7.2 From discharge of sewage

or other effluents to water or

the land (expected mode

and place of discharge)

No Not applicable

7.3 By deposition of pollutants

emitted to air into the land or

into water

No Not Applicable

7.4 From any other sources No Not Applicable

7.5 Is there a risk of long term

build up of pollutants in the

environment from these

sources?

None Not Applicable

8. Risk of accidents during construction or operation of the project, which

could affect human health or the environment


confirmation




8.1 From explosions, spillages,

fires etc from storage,

handling, use or production

of hazardous substances

No Not Applicable

8.2 From any other causes No Not Applicable

8.3 Could the project be

affected by natural disasters

causing environmental

damage (e.g., floods,

earthquakes, landslides,

No Not Applicable

18

cloudburst etc)

9. Factors which should be considered (such as consequential

development) which could lead to environmental effects or the potential

for cumulative impacts with other existing or planned activities in the

locality


confirmation




9.1 Lead to development of

supporting facilities,

ancillary development or

development stimulated by

the project which could have

impact on the environment

e.g.,

Supporting infrastructure

(roads, power supply, waste

or waste water treatment

etc.,)

Housing development,

extractive industries, supply

industries, other

NO Not Applicable

9.2 Lead to after use of the site,

which could have an impact

on the environment

No Not Applicable

9.3 Set a precedent for later

developments

No Not Applicable

9.4 Have cumulative effects due

to proximity to other existing

No Not Applicable

19


confirmation




or planned projects with

similar effects

III. Environmental Sensitivity:

S.N

o

Areas Name/

Identity

Aerial distance (within 15

km ) proposed project

location boundary)

1 Areas protected under

international conventions,

national or local legislation for

their ecological, landscape,

cultural or other related value

None Not Applicable

2 Areas which are important or

sensitive species for ecological

reasons – wetlands,

watercourses or other water

bodies, coastal zone, biospheres,

mountains, forests

None

3 Areas used by protected,

important or sensitive species of

flora or fauna for breeding,

nesting, foraging, resting, over

wintering, migration

None

4 Inland, coastal, marine or

underground waters

Coastal Marine

waters

5 State, national boundaries No Not Applicable

20

6 Routes or facilities used by the

public for access to recreation or

other tourist, pilgrim areas

No Not Applicable

7 Defense installations No Not Applicable

8 Densely populated or built up

area

No Not Applicable

S.N

o

Areas Name/

Identity

9

Areas occupied by sensitive

man-made land uses (hospitals,

schools, places of worship,

community facilities)

No Not Applicable

10 Areas containing important, high

quality or scarce resources

(ground water resources, surface

resources, forestry, agriculture,

fisheries, tourism , minerals)

No - Not Applicable

11 Areas already subjected to

pollution or environmental

damage (those where existing

legal environmental standards

are exceeded)

No - Not Applicable

12 Areas susceptible to natural

hazard which could cause the

project to present environmental

problems

(earthquakes, subsidence,

landslides, erosion, flooding or

extreme or adverse climatic

conditions)

Yes

Seismic Zone ( V)

21

2. Executive summary

As the onshore wind energy demands more space, higher wind speed and visual intrusion the

focus has been shifted towards Offshore Wind Energy in India. The preliminary studies

indicated two wind potential sites in Gujarat and in Tamilnadu. Hence the Government has

announced National Offshore Wind Energy Policy as an initial step towards the development

of offshore wind in the country. This policy allows various government and interested private

agencies to get involved in preliminary data assessments in the potential sites.

Hence Samiran Udaipur Windfarms Limited (SUWL) have entrusted Suzlon Energy Ltd

(SEL) to arrange for the Survey and Investigations off the coast of Jakhau. M/s Suzlon

Energy Limited approached ESSO-NIOT in order to set up a data collecting platform at off

coast Jakhau, Gujarat for a period of two years. M/s SEL along with NIOT has done

preliminary wind assessment, Environmental Impact Assessments and various other

feasibility studies. This report presents the summary of these studies, seeking for CRZ

Clearance from Ministry of Environment, Forest and Climate Change.

3. Introduction

3.1. Need for Renewable Energy & World Scenario

Worldwide, wind energy is accepted as one of the most developed, cost-effective and proven

renewable energy technologies to meet increasing electricity demands in a sustainable

manner. While onshore wind energy technologies have reached a stage of large scale

deployment and have become competitive with fossil fuel based electricity generation with

supportive policy regimes across the world, exploitation of offshore wind energy is yet to

reach a comparable scale. The promising factors for offshore wind development are i) Strong

/ Consistent winds compared to land, ii) Less sound pollution and visual intrusion, iii) Best

benefit to coastal areas due to less transmission cost and iv) Exploitation of available onshore

wind sites.

The first offshore wind power test facility was setup in Sweden, in 1990; however the first

commercial offshore wind farm was commissioned in1991in Denmark [Nikolaou, (2004)].

As of January, 2013 the installed capacities of wind farms in Europe, China and Japan are 5

GW, 0.51 GW and 0.033 GW respectively [EWEA, (2013)]. Proposals exist to expand the

respective capacities to 40 GW (Europe) [EWEA, (2009)], 30 GW (China) [Da et al., 2011]

22

and 1 GW (Japan) [www.ewea.org] by 2020. Actually, more than 90% of the global offshore

wind farms were located in European waters and the contribution from various counties is

shown in Fig. 1. Recently, World’s largest wind farm ‘London Array’ with a capacity of 630

MW is commissioned in United Kingdom [London Array, (2013)]. A project with 0.468 GW

capacity is under construction in USA with proposals for expanding the capacity to 10 GW

by 2020 [U.S. Department of Energy, (2011)].

Fig. 1 Installed Cumulative Capacity in European countries (Source: EWEA, (2013))

3.2. Offshore Wind Potential in India and wind energy Policy

India has achieved significant success in the onshore wind power development with about 24

GW of wind energy capacity already installed and generating power.

The share of the renewable energy sources under operation in India is around 12% [CEA,

(2013)], of its total production, whereas the developed countries already achieved over 20-

30%. Preliminary studies indicated many potential sites in India for wind farms and still this

huge potential remains untapped.

Initial preliminary wind potential studies have been carried out along the Indian coast based

on the available satellite and buoy data. It is observed that the offshore wind of magnitude

6m/s or more persist for more than 300 days along the coast of Tamilnadu and Gujarat. A

suitability analysis for three potential sites of Rameshwaram, Kanyakumari and Jakhau along

the Indian coast was carried out in this study based on the long term wind data (1999 to 2009)

obtained from ESSO - INCOIS. The data obtained at 10m elevation for 10 years were scaled

to 80 m elevation (i.e hub height of wind turbine) using power law. The percentage

59%18%

8%

6%

5%3% 1%

UK

Denmark

Belgium

Germany

Netherland

Sweden

Others

http://en.wikipedia.org/wiki/United_Kingdom

23

distribution of these derived wind speeds for the sites Jakhau, Rameshwaram and

Kanyakumari are shown in Fig. 2. The mean wind speeds at Rameshwaram, Kanyakumari

and Jakhau for derived winds at 80m elevation are 8.5 m/s, 9.1 m/s and 7.3 m/s respectively.

Fig. 2 Wind Speed Distribution at 80m Elevation

Offshore winds were used to estimate the power production from the power curves provided

by the manufacturer. The Plant Load Factor (Ratio of average power produced to the

Capacity of turbine) was estimated for various wind turbines with capacities varying from 1.5

to 5 MW. It was observed that 3.0 MW turbine operates at high Plant Load Factor at all the 3

locations along Indian coast. Fig. 3 shows the power produced along with plant load factors

for the 3 MW turbines, which is optimum for Indian wind conditions, however, which needs

confirmation from the measured data.

Fig. 3 Power Production for 3 MW Offshore Wind Turbine. Fig. 4 Google earth map –Jakhau

Fig. 5 Topography map(20km buffer)-Jakhau

Fig. 6 Regional Connectivity map-Jakhau Fig. 7 Topography map-Jahau

Fig. 8 Hydrographic map-Jahau

Based on these studies Ministry of New and Renewable Energy(MNRE) has formulated

National Offshore Wind Energy Policy in September 2015(Refer Annexure II) attempting to

Per

cen

tag

e o

f D

ay

s

Jakhau Rameshwaram Kanyakumari

24

replicate the success of onshore wind power development in the offshore wind power

development.

Electricity generation from renewable sources of energy is an important element in the

Government’s National Action Plan on Climate Change (NAPCC) announced in the year

2008. With introduction of this policy, the Government of India is committed to provide a

conducive environment for harnessing offshore wind energy in India.

3.3. SUWL, SEL and NIOT involvement

National Wind energy Policy of India provides permission for Carrying out preliminary wind

resource assessment, oceanography & bathymetric surveys etc. by any government agencies

or by interested private players who have proven expertise in offshore studies. While SUEL

is given permission for survey and Investigation offshe coast of Jakhau by the Gujarat

Maritime Board (GMB), (Ref Annexure I) M/s Suzlon Energy Limited on behalf of SUWL

approached ESSO-NIOT for the activities of offshore structures for the wind farms in India. M/s

SEL has requested NIOT to take up the activity of design and installation of LIDAR based

offshore wind mast at offshore location near Jakhau in Gujarat for offshore wind assessment.

M/s SEL with the support of NIOT is setting up a data collecting platform at Jakhau in order

to validate the wind potential sites. This data collection platform will be functioning over a

period of 2-3 years.).

4. Project Description

4.1. Site Details

The project site location is located off coast in kutch district of Gujarat. The project is 18km

from the shore, 30km from Jakhau and 42km from Naliya port. The geographical coordinates

of the site is N23o 07’ 24.42” E68o 27’ 48.24”.The project site location is shown in

Annexure III and Annexure IV. The project site lies within the Indian Territorial waters

which is 12 Nautical miles from baseline. The other major towns near project site are Bhuj,

Kandla and Mundra. Regional connectivity map of the project site is shown in the Annexure

V. Initially three locations have been considered and this location has been finalized based

on suitable soil strata, Hydrodynamic condition and also as it is away from navigation

channel. Other details such as Topographic and Hydrographic are found in Annexure VI and

Annexure VII.

25

4.2. Bathymetry & Physical Processes

4.2.1. Bathymetry

The bathymetry of the project site is relatively flat with minimum undulations. The

bathymetry reveals that from -1 m to -5m contours are almost parallel to the shore. The -5m

contour is at 5.4km from the shore, -10m contour varies from 5.4km to 14.8km away from

the shore. The bathymetry details are shown in Fig.6.The proposed project site is about 10m

from MSL which is shown in Fig.9

Fig. 9 Bathymetry profile for the prosed site

4.2.2. Tide

Mean High higher water level (MHHW): 2.9m

Mean Low higher water level (MLHW): 2.65m

Mean High lower water level (MHLW): 1.43m

Mean Low lower water level (MLLW): 0.63m

26

4.2.3. Currents

The currents in the Gulf and associated Creeks are largely tide induced. Maximum speed of

current is 2m/s.

4.2.4. Wave

Significant wave height, Hs =5.5m

Wave Period, Tp=12s

4.2.5. Rainfall

Average annual rainfall is of 250mm.Generally rainfall occurs in the period of July to

September and the number of wet days per year is 30.

5. Proposed Data collection Mast

5.1. Description with layout

The LIDAR based offshore met mast is to be located at a water depth of 10m with a tidal

variation of 5m. The platform housing LiDAR is at about 7.5m from the MSL. The data

collection platform consists of instruments for collecting various parameters required for

wind potential studies and design of substructure for wind turbine. This data collection

platform is of 5m diameter. The setup of platform is shown in Fig.2 and details of the

instruments are given are given in Table 1. To supply power for operation of these

instruments solar panel and small wind turbines along with battery supply for back are

provided.

S.No Parameters Instrument

1 Wind Velocity, Direction and Profiles LiDar

2 Wave Direction, Height and Periods Wave Rider Buoy

3 Current Velocity, Direction and Profiles ADCP, RCM

4 Tide RTG, ATG

5 PH, Salinity & TSS Water Quality buoy

6 Temperature, Pressure, Humidity Automatic weather Station

Table 1 Instruments for collecting various Parameters

The platform is provided for supporting all the equipment’s required to measure. Platform

consists of central rigid circular beam and main beams radiating from the central beam. Main

27

beams are connected with secondary beams. Trapezoidal plates are resting over the main

beams, over which all equipment loads such as wind turbine, LiDar, solar panels, wind

measurement instruments and batteries are resting.

Fig. 10 Layout of Supporting Platform for LiDar

The Monopole supporting the data collection platform is of 1.2m diameter which is of 25mm

thick. The detailed structural design of the wind mast and platform is as below

5.2. Structural Design

The platform is located at water depth of 10 m with a tidal range 5m. The soil is

predominantly silty sand with an angle of friction as 34o. The maximum current speed at the

location is considered as 1.5m/s.

4.2.1. Basic Load

The various loads considered in the design of support structure include dead load, live load,

wind loads, Hydrodynamic loads and seismic loads.

5.2.1.1. Dead load

Self-weight of the structure, nonstructural members like hand rails, ladder and various

instruments mounted on the platform are considered.

28

5.2.1.2. Live Load

A live load of 5kN/m2 is considered in accordance with IS 875: part-2 to accommodate for

people’s moment during operations and installation of instruments on platform

5.2.1.3. Wind loads

The extreme wind loads were considered in accordance to IS 875 part-3. The critical

(extreme) and operational basic wind speeds at reference height of 10m above SWL were 50

m/s and 12 m/s respectively.

The design wind speed, V = k1 x k2 x k3 x Vb = 53 m/s

Where Vb is Basic wind Speed, k1 is probability factor (risk coefficient), k2 = terrain, height

and structure size factor and k3 = topography factor.

The forces on monopole due to this wind profile were calculated in accordance with API RP

2A WSD.

F= Cs (ρ/2) A V2 = 1.03KN

Where F is wind force, ρ is mass density of air (1.225 kg/m3), V is wind speed, Cs is shape

coefficient (0.5 for cylinder shape) and A is projected area.

5.2.1.4. Hydrodynamic loads

In this study two sea states as shown in Table 2 were considered, critical condition (extreme

environment) and operational condition. In critical condition the maximum wave height was

3m with a period of 12s and for operational condition the maximum wave height was 1.5m

with a period was 7s.The current profiles considered for both sea states are shown in Fig. 2.

Wave and current were considered to act in the same direction.

Fig. 11 Current profile for operational and critical condition

-15

-13

-11

-9

-7

-5

-3

-1

0 0.5 1 1.5 2

Heig

ht

(m)

Velocity (m/s)

Current Profile

Operational

Extreme

29

Sea

State

Wave Height

(H, m)

Wave Period

(T, s)

Water

Depth

(d, m)

Wave Length

(L, m)

H

g T2

d

g T2

Severe 3 12 15 137 0.0021 0.011

Normal 1.5 7 15 68 0.0031 0.031

Table 2 Waves Parameters

Wave kinematics is estimated using suitable wave theory. Fig.6 (API RP 2A WSD, 2007)

shows suitability of various wave theories for a region. Selection of wave theory depends on

wave height, Period and water depth. The required parameters for selecting suitable wave

theory were given in column 6 and 7 of Table 4. Based on these parameters and Fig.6, Stokes

5th order wave theory was considered for calculating wave kinematics.

Wave and Current forces were calculated using Morison’s equation. This was a semi-

empirical formula which assumes the total force as a sum of inertia component due to the

fluid acceleration and a drag component due to fluid velocity. Applicability of Morison’s

equation depends on the ratio of the wavelength to the member diameter. If this ratio was

greater than 5 then the structure will not cause incident wave to diffract and Morison’s

equation can be used. If ratio was less than 5 then Diffraction theory, which computes the

pressure acting on the structure due to both the incident wave and the scattered wave, should

be used, instead of the Morison equation, to determine the wave forces. In this study, this

ratio is more than 5 for waves considered in all stated. So, Morison equation is used for

calculating forces which was of the following form.

F = CD (ρ/2) D V2 + (π/4) D2 ρ Cm U2

Where F is Force per unit length, ρ is mass density of water (1025 kg/m3), CD is Drag

Coefficient for Tubular Section (1.05 – Rough surface), Cm is Inertia Coefficient for Tubular

Section (1.2 – Rough surface), U =Acceleration of water particle, V =Velocity of water

particle.

30

Fig. 12 Regions of Applicability of Various Wave Theories

For each sea state the phase of the wave was varied from 0° to 360° with a step of 10°. It was

observed that maximum base shear and base moment for Monopile occurs at a phase shift of

350°. The wave load at this phase angle was considered for analysis.

5.2.1.5. Seismic loads

Response Spectral method was used for calculating Earthquake forces for both the

substructure concepts. In this method response of a structure was obtained by combining the

responses of different Mode Shapes. Initially, free vibration analysis was carried out to obtain

the modal frequencies and mode shapes. For each mode, a response was obtained from the

design spectrum based on the modal frequency and they were combined using suitable modal

combination rule to provide an estimate of the total response of the structure. Complete

Quadratic Combination (CQC) modal combination rule was used here, as it gives more

reliable values when compared with square root of the sum of the squares (SRSS) and sum of

absolute peaks methods. In this study for earthquake load cases the Pile-Soil iteration was

assumed to be linear.

31

Fig. 13 Seismic zone of India

Earthquake spectrum was considered as per IS 1893 Part–4.The considered site comes in

zone II (Rameswaram).Reduction factor “R” is 2. Importance factor “I” is 1.5 (same as steel

chimney). Soil type is taken as Type II (medium soil). ‘Sa/g’ is the spectral acceleration

coefficient corresponding to site specific spectra. The seismic coefficient was calculated as.

𝐴ℎ =[

𝑍

2]×[

𝑆𝑎𝑔

]

(𝑅

𝐼)

Where Ah is Horizontal acceleration coefficient, Sa/g is the spectral acceleration, Z is Zone

factor (0.36), R is Response Reduction factor (2) and I is Importance Factor (1.5).

The acceleration spectrum shown in Fig.7 was obtained by multiplying Ah with acceleration

due to gravity ‘g’ and Scale Factor. The Scale Factor for spectrum along both horizontal

directions was 1.0 and for vertical direction was 0.5.

32

Fig. 14 Acceleration Spectrum

5.2.2. Load Combinations

Load combinations for offshore wind turbine are considered as per API RP 2A WSD. Three

critical cases were considered in design of support structure. Extreme sea state during critical

like cyclone, LC1. As a design rule occurrence of two critical events should not be

considered at same time in design of any structure. So, while considering earthquake loads all

other environmental loads should be normal condition (i.e. operational condition), LC2.

Impact of boat on structure at controlled condition, LC3 Combinations. As the Monopile was

axi-symmetric, application of load along any direction will have same influence. So, wave

heading is not varied with in each load combination.

5.2.3. Monopile

The support structure is designed for three load combinations. Pile-soil interaction was

modelled using 3 nonlinear springs for each soil layer (Two horizontal and one vertical

spring). The nonlinear properties for all horizontal springs are governed by p-y curve (i.e.

Lateral Load Vs. deflection of the pile), vertical springs for all layers except bottom most

layer by t-z curves (i.e. Skin Frictional resistance vs. deflection along pile) and vertical spring

for bottom most layer by Q-z curve (i.e. Tip resistance Vs. Pile Tip Deflection). These curves

are generated using API RP 2A-WSD. For Earthquake analysis these curves were linearized

(i.e. soil was assumed to behave linearly). The estimated skin friction and end bearing are

shown in Table 5.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 1 2 3 4

Acc

lera

tio

n (

m/s

2 )

Period (s)

Accleration Spectrum

33

DEPTH (m) SKIN FRICTION

(Pa) Tip Resistance

(Pa)

1.5 1957.5 -

3 5872.5 -

4.5 9787.5 -

6 13702.5 -

7.5 17617.5 -

9 21532.5 -

10.5 25447.5 -

12 29362.5 -

13.5 33277.5 -

15 37192.5 1620000

Table 3 Soil Parameters for Different Layers

5.2.4. Cyclones

The appropriate loads as explained in earlier were considered and the obtained deflection

profiles were shown in Fig.15. The deflections at the platform level are within the allowable

limit of l/150. The capacity of the members is checked using API RP 2A WSD. The

utilization of monopole is 0.41 and monopile is 0.42. The details calculations are explained

below.

Max Deflection - 0.015 m

Max Rotation - 0.042o

Max Deflection - 0.106 m

Max Rotation - 0.29o

Normal Sea State Severe Sea State

Fig. 15 Deflected Profiles for Various Sea States

34

5.2.4.1. Axial Compression:

Allowable Axial Compression Fa is determined from the AISC formulas for cylindrical

members based on the diameter to thickness ratio. When the ratio is less than 60 then local

buckling stress are not checked and if the ratio is greater than 60 Fy is substituted with critical

local bucking stresses (Fxe or Fxc whichever is less).

Fa =

[1 −(Kl/r)2

2Cc2 ] Fy

53 +

3(Kl/r)8Cc

+1(Kl/r)3

8Cc3

for (Kl/r) < Cc

Fa =12π2E

23(Kl/r)2 for (Kl/r) ≥ Cc

Where,

Cc=(12π2E

Fy)

1

2

E = young′smodulus of elasticity, Mpa

K = effective length factor

l = unbraced length, m

r = radius of gyration, m

The members having D/t ratio more than 60 local buckling due to axial compression should

be investigated.

5.2.4.2. Elastic Local Buckling Stress

Elastic buckling stress can be determined from:

Fxe = 2CEt/D

Where,

C = critical elastic buckiling coefficient,

D = outside diameter , m,

t = wall thickness, m.

5.2.4.3. Inelastic local buckling Stress.

Inelastic local buckling stress can be determined from:

Fxc = Fy [1.64 − 0.23 (D

t)

1/4

] 2CEt/D.

35

In our case allowable Fa for Beam element is determined as follows:

Diameter, D(m) = 1.2

Wall Thickness, t (m) = 0.025

Young's modulus, E(Mpa) = 2.10E+05

Yield Strength, Fy(Mpa) = 250

Unbraced Length, l (m) = 27.5

Effective length factor K = 2

Radius of gyration, r(m) = 0.346554469

Moment (KNm) = 850

Vertical load (KN) = 250

Area of the section A(m2) = 0.061575216

Moment of inertia I(m) = 0.007395183

Sectional Modulus Z(m3) = 0.012325306

Radius of Gyration R(m) = 0.346554469

Slenderness ratio λ = 158.7052106

D/t ratio = 50

Cc = 315.4133991

Kl/r ratio = 158.7052106

As D/t ratio is greater than 60 we have to check for local buckling and substitute critical local

buckling stress stresses (Fxe or Fxc whichever is less) for Fy. In the calculation of local

buckling stress the value of critical elastic coefficient “C” has been taken as 0.3 as per API.

The allowable compression and calculated axial stress are as below.

Local Elastic Buckling Fxe (Mpa) = 2520

36

Local Inelastic Buckling Fxc (Mpa) = 257.7872

Allowable Axial

Compression Fa(Mpa) = 118.5

Calculated Axial Stress fa cal(Mpa) = 4.06

5.2.4.4. Allowable Bending Stress:

The allowable bending stress can be determined as following:

Fb = 0.75 Fy for D

t≤

10340

Fy

Fb = [0.84 − 1.74 FyD

Et] Fy for

10340

Fy<

D

t≤

20680

Fy

Fb = [0.72 − 0.58 FyD

Et] Fy for

20680

Fy<

D

t≤ 300

Here in our case the D/t ratio satisfies the second condition and as per API the stresses are as

follow

Allowable Bending Stress Fb(Mpa) = 184.107

Calculated Bending Stress Fb cal(Mpa) = 68.96

Interaction Ratio

fa cal/Fa + fb cal/Fb = 0.408

Similarly in case of Static analysis for Pile element the interaction ratio is 0.41.

5.2.5. Earth Quake

The occurrence earthquake during normal sea state is considered in this case. The deflections

at the top of substructure are 0.142 m and less than allowable limit of l/150. From the

deflections it can be observed that the design of structure is mainly governed by earthquake.

The capacity of the members is checked using API RP 2A WSD. The utilization of monopole

is 0.35 and monopile is 0.37. The detailed calculations are given below

37

5.2.5.1. Member Capacity for Earthquake Load Combination:

For Beam Element

Allowable Axial





Interaction Ratio fa cal/Fa + fb cal/Fb = 0.348

For Pile Element

Allowable Axial






5.2.6. Boat Impact

Boat landing is considered for small boats with a weight less than 25 tons which will be used

to transporting people for inspection and maintenance of equipment. Controlled boat velocity

of 0.5 m/s is considered for analysis. The kinetic energy due to boat impact is equated to the

work done by the structure to find an equivalent point load at water level. This load is applied

on the structure along with operational sea state condition. The deflection during boat impact

is 0.12 m and less than allowable limit of l/150. The capacity of the members is checked

using API RP 2A WSD. The utilization of monopole is 0.42 and monopile is 0.44.

5.2.6.1. Member Capacity for Boat Impact Combination:

For Beam Element

38

5.2.7. Platform

The platform is provided for supporting all the equipment’s required to measure. Platform

consists of central rigid circular beam and main beams radiating from the central beam. Main

beams are connected with secondary beams. Trapezoidal plates are resting over the main

beams, over which all equipment loads such as wind turbine, LiDar , solar panels, wind

measurement instruments and batteries are resting. The platform is analyzed for the ultimate

and service conditions as per of IS 800:2007. The detail design of structural members is given

below.

5.2.7.1. Material Properties

Central rigid beams

= ISMC 150

Length of rigid beam

= 620 mm

Main beams

= ISMC 150

Length of main beams

= 1300 mm

Allowable Axial Compression Fa(Mpa) = 143.885





For Pile Element

Allowable Axial Compression Fa(Mpa) = 143.885





39

Secondary beams

= ISMC 75

Length of secondary beams = 1290 mm

Plate thickness

= 16 mm

(Increased 4mm for marine consideration)

Steel for plates /Beams

= E250 (As per IS 2062:2011)

Field welds

= E410

Unit weight of steel

= 78.5kN/m3

5.2.7.2. Loads & Load combinations

Loadcase 1

Self weight of the

beam

Loadcase 2

Self weight of the

plates

Loadcase 3

LiDar weight = 0.765 kN

radius of central rigid = 0.6 m

circumference of

central rigid portion

= 3.768 m

U.d.l. of LiDar = 0.20 kN/m

Loadcase 4

Windturbine

2nos

= 0.981 kN

one turbine weight = 0.4905 kN

Loadcase 5

Solar panels +

mounting accessories = 0.491+ 0.343

= 0.834 kN

u.d.l for solar panels = 0.2836735 kN/m

Loadcase 6

Batteries & enclosures = 2.4525+0.981

= 3.433 kN

radius of central rigid = 0.6 m

circumference of

central rigid portion

= 3.768 m

40

U.d.l. of battery = 0.91 kN/m

Loadcase 7

Wind measurement

instruments = 0.491 kN

Loadcase 8

Central plate

area of central plate = 1.1304 m2

volume of central plate = 0.0180864 m3

weight of central plate = 1.4197824 KN

u.d.l of central plate = 0.3768 kN/m

Loadcase 9

People movement = 5kN/m2 (From IS875)

Loadcase 10

For ultimate condition = 1.5(L.C1+L.C2+L.C3+L.C4+L.C5+L.C6+L.C7+L.C8+L.C9)

Loadcase 11

For servicability

condition = 1.0(L.C1+L.C2+L.C3+L.C4+L.C5+L.C6+L.C7+L.C8+L.C9)

5.2.7.3. Staad Results

S.No Members B.M(kNm) S.F(kN) Deflections(mm)

1

Main

beams 10 10.5 3.86

2 Rigids 21 12.166 0.279

3 Sec beams 0.691 1.687 0.736

Main beams & Central Rigid beam

ISMC150 (2Sections faced front to front)

From SP -6

A = 4176 mm2

H = 150 mm

B = 150 mm

D = 132 mm

tf = 9 mm

41

tw = 5.4 mm

Ixx = 15588000 mm4

Iyy = 2046000 mm4

Zxx = 204800 mm3

Zyy = 38800 mm3

Zp = 272384 mm4

r1 = 10 mm

5.2.7.4. Sectional Classification

ε =

= 1

From Table 2 IS 800:2007

d/tw = 132/5.4 = 24.4444 < 84ε

84

Hence the section is

plastic

5.2.7.5. Shear Capacity

According to Cl 8.2.1.2 IS 800:2007

V < 0.6Vd

Vd = Vn

γmo

Vn = Av x fyw

Av = Ah

(b+h)

= 2088 mm2

42

Vn = 301385.7

Vd = 273.987 kN

0.6Vd = 164.3922 kN

V < 0.6Vd

Hence the section is safe in shear condition

5.2.7.6. Moment Capacity

M < Md

Md = βb Zpfy

γmo

Since the section is plastic

βb = 1

Md = 62.26977 kNm

M < Md

Hence the section is safe

5.2.7.7. Check for deflections

Allowable deflection

From table 6 IS 800-2007

For Main beams = L/180 = 7.22222 mm

For rigid beams = L/300 = 2.06667 mm

Deflection of main beam = 3.86 mm safe in deflection

Deflection of rigid beam = 0.279 mm safe in deflection

5.2.7.8. Check for web buckling

Assume bearing length = 0 mm

Ab = (b+n1) tw

43

n1 = 75

Ab = 405 mm2

Slenderness ratio,λ = 2.5d/t

= 61.11111

From Table 9c of IS 800-2007

fcr = 167 N/mm2

Capacity of the section

= 67.635 kN

Hence the section is safe against web buckling

5.2.7.9. Check for web bearing

Fw = (b+n2) twfy

γmo

n2 = 2.5(R+tf)

= 47.5 mm

Fw = 58.29545 kN

Hence the section is safe against web bearing

5.2.7.10. Check for stiffeners

According to Cl 8.6.1.1 IS 800-2007

d/tw <200ε Not required for stiffeners

d/tw = 24.44444 < 200

Hence transverse and longitudinal stiffeners not required.

5.2.7.11. Check for compression flange buckling


d/tw < 345 ε 2

24.444444 < 345

44

Hence no buckling of compression flange into web occurs.

5.2.7.12. Secondary beams

ISMC75

(2Sections faced front to front)

From SP -6

A = 867 mm2

h = 75 mm

b = 40 mm

d = 67.7 mm

tf = 7.3 mm

tw = 4.4 mm

Ixx = 760000 mm4

Iyy = 126000 mm4

Zxx = 20300 mm3

Zyy = 4700 mm3

Zp = 24766 mm4

r1 = 8.5 mm

5.2.7.13. Sectional Classification

ε =

= 1

From Table 2 IS 800:2007

d/tw = 17.04545 < 84ε

Hence the section is

plastic

5.2.7.14. Shear Capacity

According to Cl 8.2.1.2 IS 800:2007

V < 0.6Vd

45

Vd = Vn

γmo

Vn = Av x fyw

Av = Ah

(b+h)

= 565.4348 mm2

Vn = 81615.88

Vd = 74.19625 kN

0.6Vd = 44.51775 kN

V < 0.6Vd

Hence the section is safe in shear condition

5.2.7.15. Moment Capacity

M < Md

Md = βb Zpfy

γmo

Since the section is plastic

βb = 1

Md = 5.628636 kNm

M < Md

Hence the section is safe

5.2.7.16. Check for deflections

Allowable deflection

From table 6 IS 800-2007

For secondary beams = L/300 = 4.3 mm

46

Deflection of secndary beam = 0.736 mm safe in deflection

5.2.8.17. Check for web buckling

Assume bearing length = 0 mm

Ab = (b+n1) tw

n1 = 37.5

Ab = 165 mm2

Slenderness ratio,λ = 2.5d/t

= 38.46591

From Table 9c of IS 800-2007

fcr = 197 N/mm2

Capacity of the section

= 32.505 kN

Hence the section is safe against web buckling

5.2.7.18. Check for web bearing

Fw = (b+n2) twfy

γmo

n2 = 2.5(R+tf)

= 39.5 mm

Fw = 39.5 kN

Hence the section is safe against web bearing

5.2.7.19. Check for stiffeners


d/tw <200ε Not required for stiffeners

d/tw = 17.04545 < 200

Hence transverse and longittudinal stiffeners not required.

47

5.2.7.20. Check for compression flange buckling


d/tw < 345 ε 2

17.045455 < 345

Hence no buckling of compression flange into web occurs.

5.2.7.21. Welded Connection design

Connection between the rigid beams and main beams

S.F = 10.5 kN

B.M = 10 kNm

Factor of safety = 1.5 (from table 6 of IS 800-2007)

Web connection

Maximum size of weld = 3.9 mm (table 21 of IS 800-2007)

Minimum size of weld = 3 mm

Assume weld size of = 3.5 mm

Throat thickness,t = 2.45 mm

Strength per 1mm length of weld

= 386.6436 N/mm

Length of the weld = 27.15679 mm

Hence provide weld of 3.5 mm for a length of 30

mm along the

web

Flange connection

V = 66.7 kN



Assume weld size of = 6 mm



= 662.8176 N/mm


Hence provide weld of 6 mm for a length of 104

mm along the

flange

48

Connection between the secondary beams and main beams

S.F = 1.687 kN

Factor of safety = 1.5 (from table 6 of IS 800-2007)

Web connection



Assume weld size of = 3 mm



= 331.4088 N/mm


Hence provide weld of 3 mm for a length of 8

mm along the

web

6. Installation procedure

The steel Monopiles will be fabricated and transported to the site from shore with the help of

barges. Approximate weight of the pile is around 50tonnes. These piles are constructed from

welded steel tubular sections which are driven vertically into the sea bed. The piles support

the weight of the platform and the instruments primarily using the friction between the pile

walls and the sea bed. The monopile will be fabricated at a suitable fabrication yard and

transported to site. A brief typical installation sequence is as follows:

Transportation of monopile to offshore site via vessel, barge or float-out

Up-ending the pile by Jack-up crane vessel with buoyancy assistance if required

Monopile is lowered to seabed location, while pile weight provides initial sea bed

penetration.

Hammering the pile till the desired depth. (Soil plugging if any will removed till

desired depth is achieved).

Installation of platform at the top which is followed by the installation of LiDar

equipments.

49

Transporting to location Lifting with crane

Launching Positioning

Driving by hammer Completion of Driving Monopile

Removing of Hammer after driving

Fig. 16 Installation methodology for wind mast

6.1. Decommissioning procedure

For the wind mast it is envisaged that the foundation pile would be cut to below the natural

level of the seabed to such a depth to ensure that the remains are unlikely to become

uncovered. Complete removal of the pile below the seabed is considered neither practical nor

environmentally desirable. The appropriate depth of removal will depend on the sea-bed

conditions and site characteristics at the time of decommissioning which is in line with IMO

standards as complete removal of the foundations would involve an unacceptable risk to the

marine environment and are likely to involve extreme cost. If an obstruction exists above

seabed following the decommissioning which is attributable to the Met Mast, it will be

marked so as not to present hazard to other sea users.

Decommissioning of pile structure:

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Divers are deployed to inspect pile footing and reinstate lifting attachments if

necessary

Jack-up barge or heavy lift vessel is mobilized to the site

Any scour protection that has been placed around the support structures should be

removed

Crane hooks are deployed from decommissioning vessel and attached to the lift points

The pile is cut below the natural seabed, following the pile removal the seabed is

inspected for debris and any found is subsequently removed.

6.2. Construction and operational impact assessment

6.2.1. Noise level

The noise and the disturbances created during construction phase is very minimal. Noise level

generated by pile driving for such a small diameter is <50dB. Hence the noise generated

during the construction phase will not affect the aquatic environment nearby. Transport of

construction material to the site will restricted in daytime.Use of personal protective devices such

as ear-muff, ear-pugs etc. will be enforced wherever necessary.Periodic maintenance of

Construction machinery and transportation vessels will be undertaken to reduce the noise impact.

Since the construction phase is for very short term it will have negligible effect.

6.2.2. Air Environment

There will not be any dust emission during a pile driving in sea water. There will be no on-

site burning of any waste arising from any construction activities. However Nose masks will

be provided to construction workers, while carrying out operations.

6.2.3. Water Environment

As the construction phase is for short period and also the number of workers involved is of

less quantity impact on water quality is negligible. Sanitation facilities will be made available

for disposal of sewage generated by the workers as per SPCB norms. Since, the construction

activity happens with the help of vessels proper sanitation facilities will be provided in order

to maintain hygienic condition of labourers.

6.2.4. Fishery

There are not much commercial fish trawling operations off Jakhau port. However drifts and

other local nets are commonly used by local fishermen community. These operations are not

hampered much during construction as well as operational activities.

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7. Project Schedule and cost estimates

7.1 Project Schedule

The period of completion for the project is about 60days. Preparation of drawing, design will

constitute about 20 days .Fabrication of the structure and mobilization to the site is will take

about 40days. Installation will take about another 30days.

7.2 Cost estimate

The total cost of the project including Wind Profiler, mobilization, demobilization and

installation is Rs 493 lakhs.

report for installation of lidar based offshore structure for wind

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