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“Potential of floating wind
turbines in Aegean Sea”
Prof. Nikitas Nikitakos, Dr. Theodoros Lilas
University of the Aegean
Chios- Greece
Outlines
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Introduction
State of the art review
Technical issues
Case Study: Floating desalination
Legal/ Political issues
Conclusions
Air Space
Rights
Development
Rights
Navigation
Rights
Access
Rights
Fishin
g
Rights
Water Column
Rights
Seabed Use
Rights
Mineral
Rights
Disposal
Rights
Nichols, S., It's Our Ocean: How Well Will We Govern It? Presented at the Offshore
Issues Consultation Workshop. Viewed at
http://gge.unb.ca/Research/OceanGov/documents/LUNCH.PPT (July 28, 2003).
Windpower at sea
Why at sea
In some distance from the land the wind
velocity is increased by 20%. The wind
energy is analogous to the third power of
wind speed. As result the available wind
energy at sea is much more than in the
land.
More stable resulting to the increase of produced
energy by 40% related with land .
Smaller height.
Much smaller disturbances related with land =
greater life time for the wind power .
Offshore wind projects
SEVERAL APPROACHES
AND STUDIES
VERY IMPORTANT
ANCHORING
ANCHORING TECHNOLOGY
TRANSFER FROM OTHER
APPLICATIONS
ANCHORING MODES
RETENTION – COST
LAB
PROTOTYPES
ITALIAN AND DANISH
COOPERATION
GERMANY
The German wind industry is looking for affordable foundations for offshore
turbines
Six types of foundations are considered potential candidates for offshore use:
• Steel monopile foundations are driven deep into the seabed.
• Gravity foundations made of steel and concrete are placed on the seabed.
• Bucket foundations are pressed into the ground and suction themselves
into place in a vacuum.
• Tripod foundations consist of three steel piles anchored in the seabed.
• Four-legged steel jackets form a stable latticed construction.
• Floating foundations are carried by buoys and float under the
water surface. Chains anchored in the seabed keep them fixed in position.
NORWAY
Hydro
The future goal is to have large-scale
offshore wind parks with up to 200
turbines capable of producing up to 4
terawatt hours (TWh) per year and
delivering renewable electricity to both
offshore and onshore activities. This
goal is far in the future, but if we’re to
succeed in 10-15 years, we have to start
the work today. —Alexandra Bech Gjørv,
Hydro’s director of new energy forms
UK
The Beatrice Wind Farm is the flagship project for
offshore wind energy development in Scotland, the UK
and Europe. The project aims to install two demonstrator
wind turbines adjacent to the Beatrice oil field, 25 km off
the east coast
Technical issues
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Water depth
Wave load conditions
Wind speed conditions
Current velocity
Surge depth
Soil type and strength
Turbine size
Turbine operating conditions
Structure type
Structural response to wind, waves and currents in
shallow waters.
FLOATING ECOLOGICAL
DESALINATION
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LAUNCHING 2006
INITIAL SEA TRIALS 6 months
IN AEGEAN SEA from 6/2007
27 MONTHS IN THE WAVES
27 MONTHS IN THE SEA
WIND SPEEDS UP TO 120 km/hour
INOVATION - PATENTS
LLOYD’S Innovation Award, REGIO STARS
2008
• Design for 1.000 m3/day
Selection of main dimensions
Platform parameters:
• Height
• Diameter of floaters
• Diameter of floating structure
Evaluation with respect to:
• Stability
• Wave response
Floating Structure Response Simulation
Structural members of the platform
The floating platform is comprised from 4 peripheral floating cylinders with total
height of 8 m and diameter 2 m each.
And a central floating cylinder the diameter of which is 4 m and height 8 m
Description of the structural members of
the platform
The connection of all cylinders takes
place with a tubular mesh with pipe
diameter of 273 mm and wall thickness
of 8,8 mm.
There are peripheral and central mesh
connections .
Inside the peripheral cylinders there are
vertical structural pipe elements which are
connected on the tubular mesh, thus
preventing the cylinder shell to bear the axial
compressive or tensile developed forces during
normal operation at sea.
Stress Analysis Calculations
The developed stresses are calculated with the use of finite element analysis.
The scope of the analysis is to:
1.Derive the maximum operating
axial loads exerted on the mesh
piping and compare them with
those theoretically calculated
with Euler and
2.Calculate the Misses yield
stress and compare it with the
material yield stress.
Stress Analysis Calculations
Four different loading cases are examined
1. Static loading under sagging condition.
1.1 The 4 peripheral cylinders
are supported
1.2 The 2 diagonal
cylinders are supported
Stress Analysis Calculations
2. Static loading under hogging condition.
The central cylinder is simply supported and the peripherals are free.
Stress Analysis Calculations
3. Dynamic motion with respect to external excitation
In this case the Platform is
supported from springs.
The spring coefficient is calculated
from the buoyancy characteristics
of the cylinders with respect to
their draft.
Maximum buoyancy is achieved
when the draft of the platform
equals to the height of cylinders.
Spring elements
Operation
Conclusions
•Operational
•Autonomous
•Ecological
•Scalable
•Transferable
Political Landscape
• Targets
– 20% renewables by 2020
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Energy is a reserved issue
Environmental issues devolved
Planning Bill
Grid connection
Marine Bill
EC Directives
– Birds
– Habitat
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Seabed lease initiative
Public policy questions
Whose resource is being used?
Whose actual use is being affected?
Who bears the direct and indirect burdens of
the use?
Who acquires the direct and indirect benefits?
Does the use foreclose other near-term or
future uses?
Ocean Governance
Puzzle
Planning/Siting (science-based)
– Where should you put/allow an activity?
Zoning (law-based)
– Where can you put/allow an activity?
Permitting (stakeholder process)
– Where will you put /allow an activity?
Regulating
(management/enforcement)
– How will the site/activity be regulated?
Conclusions
• Wind power at sea a new potential for
renewable energies
• Technical issues
• Legal and regulatory issues
• The floating desalination platform shows
its potential for use of in Aegean sea
Thank you for
your attention
[email protected]
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