A ddaskalakis aquaculture-engineeringtechnology-oct 19-17+10-p-pdf

AQUACULTURE EUROPE 2011
OPEN SEA FISH FARMS BASED ON INTEGRATED
INTENSE FLOATATION AND WAVE ABSORBING
TECHNOLOGIES
OFFSHORE ENERGY SYSTEMS SA
Address: 48 Karaoli & Dimitriou str., GR-152 32 Halandri, Greece
Tel. +30 210 6775 003, Fax +30 210 6812 770, www.martech.gr, email: tech
Presented by : Dr Antonis Daskalakis
Offshore Energy Systems SA
OPEN SEA FISH FARMS BASED ON INTEGRATED
INTENSE FLOATATION AND WAVE ABSORBING
TECHNOLOGIES
tech@martech.gr
Offshore Energy Systems SA

WHY DEEP WATERS
Moving to deep waters and far from the coasts is inevitable due
Increased pressures from local communities
Contradiction with other social and economical activities
Increased concerns on health and environmental issues
However it is for the benefits of the industry itself to seek ways of doing so.
The limited space for development, leading to small size units and a disperse
activity.
The confined self cleaning capability of protected waters.
Fish health problems and decease spreading, affect productivity and
quality.
Fish growing speed and fish taste which improve considerably in deep waters
WHY DEEP WATERS
Moving to deep waters and far from the coasts is inevitable due to:
Increased pressures from local communities
Contradiction with other social and economical activities
Increased concerns on health and environmental issues
However it is for the benefits of the industry itself to seek ways of doing so.
tech@martech.gr Presented by : Dr Antonis Daskalakis
The limited space for development, leading to small size units and a disperse
The confined self cleaning capability of protected waters.
Fish health problems and decease spreading, affect productivity and product
Fish growing speed and fish taste which improve considerably in deep waters

WHY DEEP WATERS
Costs involved in going into deep waters will be compensated by:
Concentrating production into a small but of considerable size units
increasing capacity, reducing production and logistic costs.
Improving the quality of the product and widening the market horizons.
Cultivating new fish species, increasing product variability and market
penetration.
INTEGRATED TECHNOLOGIES HAVE TO BE DEVELOPED
WHY DEEP WATERS
Costs involved in going into deep waters will be compensated by:
Concentrating production into a small but of considerable size units
increasing capacity, reducing production and logistic costs.
Improving the quality of the product and widening the market horizons.
tech@martech.gr
Cultivating new fish species, increasing product variability and market
INTEGRATED TECHNOLOGIES HAVE TO BE DEVELOPED

THE MOVE TO DEEP WATERS IS ALREADY A REALITY
Extensive research and investment efforts are undertaken worldwide. More than
$100 million have been spent in USA over a decade.
USA, China, Chile, Israel are reported to lead the efforts.
Main focus is put on sank cages in order to avoid the effects of the sea waves.
The blue revolution in Hawaii, the subflex in Israel, the “ i
The blue revolution in Hawaii, the subflex in Israel, the “ i
installations.
However ,
A new production process is necessary and special skills have to be
developed in order to realize this type of production.
We believe that staying at surface presents a challenge which has to
be answered, for many reasons.
THE MOVE TO DEEP WATERS IS ALREADY A REALITY
Extensive research and investment efforts are undertaken worldwide. More than
$100 million have been spent in USA over a decade.
USA, China, Chile, Israel are reported to lead the efforts.
Main focus is put on sank cages in order to avoid the effects of the sea waves.
The blue revolution in Hawaii, the subflex in Israel, the “ i 0cagesi+ ” , are such
The blue revolution in Hawaii, the subflex in Israel, the “ i cagesi+ ” , are such
A new production process is necessary and special skills have to be
developed in order to realize this type of production.
We believe that staying at surface presents a challenge which has to

WHAT IS INTENSE FLOATATION TECHNOLOGY
BODY UNDER INTENSE FLOATATION: BASIC
MORPHOLOGY
• The main buoyant unit (MBU) that produces
buoyancy in excess of the body total weight.
• The columns that support and connect the deck
with the MBU providing variable buoyancy.
• The deck structure that provides space and
undertakes the live loads.
• The anchor lines that connect the body with the
sea bed being always under tension.
• The anchor blocks which can undertake the
tension from the lines and providing horizontal
holding power.
BODY UNDER INTENSE FLOATATION: BASIC
(MBU) that produces
buoyancy in excess of the body total weight.
that support and connect the deck
tech@martech.gr
structure that provides space and
that connect the body with the
which can undertake the
tension from the lines and providing horizontal

A BODY UNDER IF IS SUBJECTED TO WEATHER FORCES
,LIKE ANY OTHER BODY AT SEA
However the following make it to present a peculiar
behavior:
1. The MBU is below the water to reduce wave forces
and for a safe operation.
and for a safe operation.
2. The body presents a small water plane area reducing
wave forces.
3. The fairleads are forced to move on circular
trajectories.
4. Only planar motions are present with only a small
heave movement. In fact the body moves on the
plane parallel to itself with its deck always horizontal
5. The line lengths are kept short compared to
mooring lines.
A BODY UNDER IF IS SUBJECTED TO WEATHER FORCES
However the following make it to present a peculiar
The MBU is below the water to reduce wave forces
tech@martech.gr
The body presents a small water plane area reducing
The fairleads are forced to move on circular
Only planar motions are present with only a small
heave movement. In fact the body moves on the
deck always horizontal.
The line lengths are kept short compared to catenary

MATHEMATICAL MODELLING OF AN INTENSE FLOATATION BODY
The mathematical formulation follows the same lines as for
a free floating body based on Newton’s second law:
(M + A11)(u'−rv')+ B11u = Fx∑
(M + A22 )(v'+ru)+ B22u = Fy∑
(I + A )r'+ B r = FM∑
surge
sway
yaw
THE PECULIARITIES OF AN IFB PROVIDE USEFUL CHARACTERISTICS. HOWEVER
INTENSE STUDY BEFORE BUILDING AN INTENSE FLOATATION TECHNOLOGY
The total forces exerted on the body (in the three
directions) are:
Fm : Forces from the mooring lines
Fw : Weather forces (wind, waves, currents) and F
Fl (high and low frequency excitations)
Fo : Live or operational forces (loads)
(I66 + A66 )r'+ B66r = FM∑ yaw
ioiwimi
FFFF ++=
The mathematical formulation follows the same lines as for
s second law:
THE PECULIARITIES OF AN IFB PROVIDE USEFUL CHARACTERISTICS. HOWEVER
INTENSE FLOATATION TECHNOLOGY.
tech@martech.gr
The total forces exerted on the body (in the three
: Weather forces (wind, waves, currents) and Fw = Fh +

IMPORTANT NOTES
• The importance of separating the mathematical model
into low and high frequency.
This is because natural frequencies of an IFB can be
within the band of low frequency excitations like swells.
• The body as it is described here operates like an
• The body as it is described here operates like an
inverted pendulum and its natural frequency is given
by:
Under certain circumstances it is possible
natural frequency to avoid excitations. This can be done
during design but also during operation.
ωn =
Pa
MaL
Pa : excess buoyancy
Ma: body mass + added mass
L : line length
The importance of separating the mathematical model
This is because natural frequencies of an IFB can be
within the band of low frequency excitations like swells.
The body as it is described here operates like an
tech@martech.gr
The body as it is described here operates like an
inverted pendulum and its natural frequency is given
Under certain circumstances it is possible to tune the
This can be done
: excess buoyancy
: body mass + added mass
L : line length

RESULTS FROM THE
SIMULATION PROGRAM IN
HARMONIC WAVES OF AN
INTENSE FLOTATION WIND
MEASUREMENT PLATFORM
Total wave force in KN
Input Values
Total wave force in KN
The variation of line
tension and total Excess
buoyancy
Input Values
Wave Height (m) 8
Wave Period (sec) 6
Mean wind speed (m/sec) 36
Current speed (Knots) 1.5
Total wave force in KN Excursions of the platform (m)
tech@martech.gr
Total wave force in KN Excursions of the platform (m)
The variation of line
tension and total Excess
An IF Wind Measurement Platform

CALCULATING PROCEDURES OF AN INTENSE FLOATATION BODY
BASED ON THE GENERAL MATHEMATICAL MODELING EACH COMPONENT
NEEDS AN INDIVIDUAL STUDY ACCORDING TO ITS ROLE.
The body itself: Two main areas of interest:
The body motions,
Its strength for the design loads (environmental and
operating).
Extreme conditions and special low frequency phenomena
can be studied.
Wave forces are calculated based on Morison's equation.
For the strength calculations a finite element model
developed in SAP-2000. is developed.
Mooring lines: Tensions under all circumstances are
calculated from time domain simulation.
Anchors: Calculated minimum weight (for gravity
anchors) and required holding capacity.
CALCULATING PROCEDURES OF AN INTENSE FLOATATION BODY
BASED ON THE GENERAL MATHEMATICAL MODELING EACH COMPONENT
NEEDS AN INDIVIDUAL STUDY ACCORDING TO ITS ROLE.
Two main areas of interest:
Its strength for the design loads (environmental and
tech@martech.gr
Wave forces are calculated based on Morison's equation.
For the strength calculations a finite element model
Tensions under all circumstances are
minimum weight (for gravity

TECHNOLOGIES TO EXPLOIT INTENSE FLOATATION BODIES
BODY DESIGN AND REALISATION
• Simple structures are developed for minimum forces, easy
installation and minimum maintenance.
• To lower costs and increase flexibility, the main
buoyancy module is split into two major parts :
1. Permanent buoyant volume
2. Water tanks for ballasting and de-ballasting
• Modular structures are developed which can be connected
together to form the required area and capacity.
• Vertical floaters can be either the strength members of the
body or just buoyant units.
• Special connectors are developed (screw, wedge type
connectors, elasto-dynamic bearing type connector
Simple structures are developed for minimum forces, easy
installation and minimum maintenance.
To lower costs and increase flexibility, the main
buoyancy module is split into two major parts :
ballasting
tech@martech.gr
are developed which can be connected
together to form the required area and capacity.
Vertical floaters can be either the strength members of the
are developed (screw, wedge type
dynamic bearing type connector

MOORING LINE DESIGN AND REALISATION
• The mooring lines can be of wire rope (or even synthetic
rope of high strength).
• Each line is composed by a number of individual lines
(block of lines) so that :
the required loads can be undertaken, under all
conditions,
conditions,
redundancy can be provided,
while a line can be replaced in situ.
• Special universal connectors are developed that
provide :
Movements in all directions
Easy fitting of a number of individual lines to form
a complete block of an anchor line.
Easy handling and securing
MOORING LINE DESIGN AND REALISATION
The mooring lines can be of wire rope (or even synthetic
Each line is composed by a number of individual lines
the required loads can be undertaken, under all
tech@martech.gr
Special universal connectors are developed that
Easy fitting of a number of individual lines to form
a complete block of an anchor line.

ANCHORS DESIGN AND REALISATION
• The anchors are a major component of the system.
Undertake the excess buoyancy and provide holding capacity.
We introduce here the concept of the split anchor
• Knowledge comes the oil industry in designing and
constructing effective anchors.
We introduce here the concept of the split anchor
The first part, a block is preinstalled at the sea bottom .
The body itself carries the second part, anchors which
during transportation and installation function as ballast
weights.
During installation the anchors are lowered to specially
designed sockets on the preinstalled block.
The preinstalled block provides precision and ease of
installation.
The anchors are a major component of the system.
Undertake the excess buoyancy and provide holding capacity.
split anchor .
Knowledge comes the oil industry in designing and
tech@martech.gr
split anchor .
The first part, a block is preinstalled at the sea bottom .
The body itself carries the second part, anchors which
during transportation and installation function as ballast
During installation the anchors are lowered to specially
designed sockets on the preinstalled block.
The preinstalled block provides precision and ease of

APPLICATIONS OF THE IN INTENSE FLOATATION TECHNOLOGIES
FISHING CAGES
Fishing cages for deep and very deep waters are designed as
intense floatation bodies.:
In several shapes and sizes depending on the requirements.
In heights according to prevailing wave climate.
With deck height depending on the platform envisaged use.
It can be workable at any conditions or it can be allowed to be
washable above certain conditions.
washable above certain conditions.
Net design is of particular importance.
Instead of the freely moving net following the current forces we
propose the double net arrangement.
The first is external and more or less permanently attached to
the mooring lines or to additional auxiliary vertical lines. It is
open at the top and at the bottom as well extends as deeply
as it is required.
The second is the fish net, which is kept inside the
external net. It can be a normal or a sinkable one.
Fishing cages for deep and very deep waters are designed as
In several shapes and sizes depending on the requirements.
In heights according to prevailing wave climate.
With deck height depending on the platform envisaged use.
It can be workable at any conditions or it can be allowed to be
tech@martech.gr
Instead of the freely moving net following the current forces we
The first is external and more or less permanently attached to
the mooring lines or to additional auxiliary vertical lines. It is
open at the top and at the bottom as well extends as deeply
The second is the fish net, which is kept inside the the
external net. It can be a normal or a sinkable one.

FISHING CAGES
• Fishing cages are of modular structure and they can be
connected with several ways to form a complete unit:
• The hexagon shape provided here is only one of the possible
formulations>
• The cages can be organized in subunits according to the
production needs.
production needs.
• Supporting structures, like working platforms, can also be
arranged accordingly.
Fishing cages are of modular structure and they can be
connected with several ways to form a complete unit:
The hexagon shape provided here is only one of the possible
The cages can be organized in subunits according to the
tech@martech.gr
Supporting structures, like working platforms, can also be

WORKING PLATFORMS
• Working platforms can be designed and constructed as
IFB to serve all the needs of a complete installation.
• Working platforms are of modular construction and they
can be connected together to form the shape, the required
load area, the necessary payload.
Working platforms can carry :
Silos and feeding apparatus
Silos and feeding apparatus
Offices and working spaces
Warehouses and machinery
spaces
Accommodation facilities
Crew recreational installations
A two storey accommodation facility
Working platforms can be designed and constructed as
to serve all the needs of a complete installation.
Working platforms are of modular construction and they
can be connected together to form the shape, the required
A two storey accommodation facility An open door
personnel
recreational
platform

LIGHTING AND SURVEILANCE TOWERS
• Lighting towers are IFB designed to carry a lattice
type tower of adequate height.
• Photovoltaic panels can gather enough energy to
feed the lights installed at the top of the tower, while
a battery set can store energy for the night hours .
• A small generator which automatically turns on when
the battery charge goes down can secure complete
energy autonomy.
• A small enclosed area can be provided for a night
guard with substantial facilities.
• Wireless Cameras (also thermal) can provide an all
day and night surveillance.
• A megaphone system can be used for direct
communication of the office with the plant.
• The tower can be installed from 30 m and up to deep
and very deep waters.
Lighting towers are IFB designed to carry a lattice
Photovoltaic panels can gather enough energy to
feed the lights installed at the top of the tower, while
a battery set can store energy for the night hours .
A small generator which automatically turns on when
tech@martech.gr
A small enclosed area can be provided for a night
Wireless Cameras (also thermal) can provide an all
A megaphone system can be used for direct
communication of the office with the plant.
The tower can be installed from 30 m and up to deep

WAVE ABSORBING TECHNOLOGIES
The idea comes from the fact that wave energyis
concentrated at and near the sea surface.
In contrast gravity structures are build on a reverse order
of mass distribution.
We need something to interact with waves in the actual
area of energy concentration.
WHY WAVE ABSORBERS
The first idea leads to floating structures. But free floating
structures move with the waves and produce waves.
Existing breakwaters have a limited capacity up to 3
sec of wave periods.
We replace the free floating body with an IFB. Howver,
Wave breakers act as an obstacle to the waves, creating
huge forces.
Instead of a perpendicular wall to waves we fill the
empty space with wave absorbing cells.
The idea comes from the fact that wave energyis
concentrated at and near the sea surface.
In contrast gravity structures are build on a reverse order
We need something to interact with waves in the actual
Κατανοµή ενέργειας κύµατος
0
25
50
75
100
0 10 20 30 40 50 60 70 80 90 100
Απόσταση από την επιφάνεια ως ποσοστό (%) του βάθους
Κατανοµή(%)ενέργειαςκύµατος
Τ = 2 sec
Τ = 5 sec
tech@martech.gr
structures move with the waves and produce waves.
Existing breakwaters have a limited capacity up to 3-3.5
We replace the free floating body with an IFB. Howver,
Wave breakers act as an obstacle to the waves, creating
Instead of a perpendicular wall to waves we fill the
wave absorbing cells.

There are several proposals for absorbing apparatus like the
perforated plates. With the aim:
To increase absorbing capacity, to minimize forces, to design
something that can be produced under factory conditions,
WAVE ABSORBING CELLS
We have developed the cell type wave absorbers shown here
• The cells are of variable inclination in order to break the
wave field into a number of counteracting wave fields.
• The cells are standardized in sizes and they can be installed
to fill the complete space between floaters and deck.
Wave absorbers can be used to create ports, to protect
coasts from erosion, to protect open water installations like
aquaculture.
The IFB, carrying the absorbing cells, consists a
absorber module.
Modules are connected together to form the complete wave
absorber.
There are several proposals for absorbing apparatus like the
To increase absorbing capacity, to minimize forces, to design
something that can be produced under factory conditions,
wave absorbers shown here
The cells are of variable inclination in order to break the
tech@martech.gr
The cells are standardized in sizes and they can be installed
to fill the complete space between floaters and deck.
Wave absorbers can be used to create ports, to protect
coasts from erosion, to protect open water installations like
The IFB, carrying the absorbing cells, consists a wave
Modules are connected together to form the complete wave

The wave field of an incoming wave can be expressed as
follows:
In the absorbing cells the field is “broken” to a number of
fields Φi , and diffracted waves Φd.
THEORETICAL ASPECTS OF WAVE ABSORBING CELLS
d
dz
tx
g
tzx
I κ
κ
ωκι
ω
ι
cosh
)](cosh[
)]([),,(
+
−−=Φ
∑∑ Φ+Φ=Φ
The outgoing wave field ΦD with less energy content.
The forces exerted on the cell surface are of reduced order.
Field tests of wave absorbers, and of a WAVE ENERGY
EXPLOITATION (WECO) apparatus have been contacted in the
area of Laurion.
The results have led to a complete range of products.
A first application is already working in the port of Laurion.
∑∑ Φ+Φ=Φ dD ι
The wave field of an incoming wave can be expressed as
to a number of
THEORETICAL ASPECTS OF WAVE ABSORBING CELLS
tech@martech.gr
D with less energy content.
The forces exerted on the cell surface are of reduced order.
Field tests of wave absorbers, and of a WAVE ENERGY
EXPLOITATION (WECO) apparatus have been contacted in the
The results have led to a complete range of products.
A first application is already working in the port of Laurion.

Floating wave absorbers of intense floatation
for deep and very deep waters
Bottom supported wave absorbers of a piled
structure for shallow waters
PRODUCT RANGE
A complete range of wave absorbing products has
been developed including:
structure for shallow waters
Absorbing docks for internal port dock
constructions
Floating wave absorbers of intense floatation
Bottom supported wave absorbers of a piled
A complete range of wave absorbing products has
tech@martech.gr
Absorbing docks for internal port dock

OUR VISION FOR THE NEW ERA IN AQUACULTURE
OUR VISION FOR THE NEW ERA IN AQUACULTURE

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