The Design of Physical Model and Preparation of Experimental

Study on Articulated Tower – Ocean Wave Energy Converter

(AT-OWEC)

Eko B. Djatmiko

, Heri Supomo

, Setyo Nugroho

and Dwi P. Hendradhata

Department of Ocean Engineering, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS – Sukolilo, Surabaya 60111,

Indonesia

Department of Naval Architecture and Shipbuilding Engineering, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS

– Sukolilo, Surabaya 60111, Indonesia

Department of Sea Transportation Engineering, Institut Teknologi Sepuluh Nopember (ITS), Kampus ITS – Sukolilo,

Surabaya 60111, Indonesia

Keywords: Wave Energy, AT-OWEC, Physical Model, Experimental Study

Abstract: A new concept has been proposed to contribute in the development of national ocean renewable energy

program by the adoption of articulated tower structure for harvesting the ocean wave energy. Therefore the

new concept is designated as the articulated tower for ocean wave energy converter, abbreviated as AT-

OWEC. In the meantime, the establishment of AT-OWEC has come to the stage of the initial physical

modelling and preparation of experimental study. This is commenced by the design of AT-OWEC main

structure physical model by referring to the full scale structure, involving the rules of geometrical, kinematical

and dynamical similarities. Next is the design of instrumentation for motion data measurement and

acquisition, including necessary calibrations. This is followed by the plan of experimental work at the

hydrodynamics laboratory and the expected data to be gathered. Discussion will then be concluded by putting

forward results of numerical modelling on AT-OWEC dynamic behaviours prepared for comparison with

future experimental data.

1 INTRODUCTION

The Director of Various New Energy and Renewable

Energy (VNERE), Ministry of Energy and Mineral

Resources (MoEMR), Republic of Indonesia

describes the current condition of national energy

fulfillment in Indonesia eventually is still dominated

by the fossil energy (Direktur AEBET, 2013). This

comprises of oil 46.77%, coal 23.91% and natural gas

24.29%, therefore in total the proportion is as much

as 94.97%. The rest is supplied by new and renewable

energy (NRE), which contribute only in the order of

5.03%. This condition is recognized by various

parties as a matter of great concern, especially given

the declining national oil reserves. Although

Budiman et al. (Budiman, et al., 2014) is still advising

to increase the utilization of national natural gas and

coal potentials, efforts should be directed towards the

development of NRE.

The Director of VNERE (Direktur AEBET, 2013)

underlines that according to the Presidential

Regulation No. 5 of 2006 on National Energy Policy

the NRE development program has become a national

priority. In the presidential decree, it has been

declared that by 2025 the energy composition should

bring down the contribution of petroleum to 20%,

increasing natural gas to 30%, increasing coal to 33%,

and increasing NRE 17%. The current NRE

variability in Indonesia already includes globally

developed types, including geothermal, microhydro,

and biomass. By 2025 the national NRE variability

will be pushed further, namely geothermal 5%,

biomass 5%, liquid coal 2%, and other NRE up to 5%.

Other NRE types here include nuclear, solar, wind,

and others. Included in other components of NRE is

of course ocean energy.

Ocean energy is not quite developed and operated

globally, especially in Indonesia. The main obstacle

to the limited development of ocean energy,

according to Srikanth (Srikanth, 2014), is that

technology is not yet mature and stable, the cost is

Djatmiko, E., Supomo, H., Nugroho, S. and Hendradhata, D.

The Design of Physical Model and Preparation of Experimental Study on Articulated Tower – Ocean Wave Energy Converter (AT-OWEC).

DOI: 10.5220/0008544300120019

In Proceedings of the 3rd International Conference on Marine Technology (SENTA 2018), pages 12-19

ISBN: 978-989-758-436-7

still relatively high and far from economies of scale,

only in certain locations and often non-mobile, etc.

Considering this, efforts are being made at various

universities and research institutions to develop a

relatively low cost ocean energy conversion

technology.

To meet the aforementioned challenges, early in

2017 a fundamental research on ocean energy

conversion has been initiated at the Laboratory of

Ocean Structure Hydrodynamics (Lab. OSH),

Department of Ocean Engineering (DOE), Faculty of

Marine Technology (FMT), Surabaya Institute of

Technology (ITS), Surabaya, Indonesia. As described

by Djatmiko et al. (Djatmiko, et al., 2017) the rese-

arch was established by the adoption of the well

known articulated tower (AT) platform technology to

be implemented as an ocean wave energy converter

(OWEC) system. Therefore the new concept is

designated as the articulated tower for ocean wave

energy converter, or shortly referred to as AT-

OWEC.

2 THE CONCEPT OF AT-OWEC

SYSTEM

Detail description on the concept development of AT-

OWEC system has been put forward by Djatmiko et

al. (2017). In principle the system adopts the AT

platform technology widely used in offshore oil and

gas industry since early 1970s as the primary dynamic

structure. The common AT design is preserved with

high stability to assure the safety and effective

operation of offshore oil and gas activities

(Chakrabarti & Cotter, 1980; Halvacioglu & Incecik,

1988; Bar-Avi & Benaroya, 1996; Chakrabarti, 2001;

Murtejo, et. al., 2005; Atkins, 2017). However for the

current AT-OWEC design, AT as the main

component is designed to be unstable by configuring

the buoyancy chamber in such a way the center of

gravity is located well above the structure. Like so it

could be expected AT to endure relatively larger

motion when excited by the wave action. Further, the

motion of the AT-OWEC main structure is restrained

in 1-DOF rotational pitch mode by connecting the

base of the supporting pole to a roller joint in the base

template at seabed.

Figure 1: Schematic illustration of AT-OWEC system.

The large rotational pitch motion is then

transformed into translational motion via an axis arm

hinges connected to a double action piston pump

(DAPP) with single pivot, following the idea from

Choy (Choy, 2012). The DAPP is designed with a

single outlet, positioned in the water with an inlet on

each tube, in the plane of pitch motion. The design of

the axis arm hinges in such a way will be able to

transform the rotational motion into translational

motion of the shaft arm, and further the piston move-

ment. Positive or negative rotational motion will

induce the translational motion of each piston in a

double tube in the opposite direction. That way the

AT-OWEC rotational motion is positive and negative

will still produce the water jets out of the pump. The

water jet generated by the DAPP is directed drive a

water turbine and further generate electrical power, as

shown in Figure 1.

3 THE DESIGN OF AT-OWEC

PHYSICAL MODEL

The design of full scale AT-OWEC has been

established as explained in the research report

(Djtamiko, et al., 2017). In this respect parametric

study were carried out on circular and elliptical AT

buoyancy chamber, each with 9 combinations of

diameter Dh and height Hh. Hence overall there are

18 variations of AT-OWEC. For the purposes of

discussions in this paper only one variation is

selected, namely with Dh = 4.0 m and Hh = 5.5 m,

fabricated with steel material of 15.0 mm in

thickness. This structure is hypothetically to be

operated at the sea water depth variations of 10.0 m,

15.0 m, and 20.0 m.

The design of the physical model should meet

three similarity laws, namely: i) geometric similarity,

ii) kinematic similarity, and iii) (hydro)-dynamic

similarity (Djatmiko, 1987; Chakrabarti, 1998;

Grinius, 2006; Chanson, 2008; Munson, et. al., 2013).

The Design of Physical Model and Preparation of Experimental Study on Articulated Tower – Ocean Wave Energy Converter (AT-OWEC)

Further, the design also covers the material selection,

as well as structural components or scantlings.

Specifially the design of AT-OWEC main structure is

depicted in Figure 2.

Figure 2: Basic configuration and components of AT-

OWEC main structures.

In the design of AT-OWEC one primary

consideration to be accounted for is the size of towing

tank at Lab. OSH, which has a water depth d

of 2.0

m. This water depth is then correlated to the case in

the numerical study, where the system is to be

operated at maximum water depth of 20.0 m. In this

relation the scale factor of the model is then found to

be 1 : 10 for the geometrical similarity, or

= 10.

Therefore, the model geometri will be made to have

the size of 1/

to the full scale. Furthermore, the

extent of model’s mass, mass moment of inertia for

pitch motion, and the stiffness should comply with the

dynamic similarity, and are governed by the scale of

, 1/

, and 1/

in relation the full scale.

For the kinematic similarity, the model should

have a natural frequency comparable to the full scale.

This is to be determined by the equivalency in the

non-dimensional frequency

' as given in the

following equation:

𝜔

&/(

(1)

The variables in eq. (1) are, respectively,

is the

wave frequency, g is acceleration due to gravity, and

L is length of the object. In the case of AT-OWEC L

is equivalent to Dh.

Further the design taking also the stage of material

selection to assure the model will meet the similarity

lawas as described above. After some exploration it is

then decided to select aluminum as the primary

material for the buoyancy chamber. At this point the

design of AT-OWEC physical model is concluded, as

shown in Table 1, and ready for the construction.

Table 1: Data of AT-OWEC model main structure as

function of water depth variations.

(a)

(b)

(c)

Figure 3: Physical model of AT-OWEC main structure.

The physical model has been constrcuted and its

photos are displayed in Figure 3. In here, Figure 3a

presents the AT-OWEC model in straight up and

inclined positions, making use of the roller joint at the

pole base. Model comprises three main components,

i.e. cylindrical buoyancy chamber, supporting pole,

and base template. Between the pole and cylinder, as

revealed in Figure 3b, is furnished with bolted

connector which could be released to take off the

cylinder from the pole, and other cyinders of different

sizes and configuration whenever available could

then be fitted. Figure 3b also depicts the base template

so designed to ease the installation of the structure on

SENTA 2018 - The 3rd International Conference on Marine Technology

the towing tank base. At the center of the base tem-

plate is located a roller joint as the rotational axis of

the AT-OWEC. Figure 3c shows the internal space of

the cylinder which is equipped with some vertical

square tube which can be filled with solid

counterweight to adjust the dynamical properties of

the model. The upper part of the model equipped with

the cover to assure the watertightness during the test

is performed.

4 DESIGN AND ASSEMBLY OF

TEST INSTRUMENTS

Experiments or test models are to be carried out

primarily to measure the motion of the AT-OWEC

structure when subjected to the excitation of regular

wave loads in the towing tank. In this case the motion

measuring instrumentation will be designed

consisting of two types. First is the 3-axis accelero-

gyro instrument or gyroscope, which functions to

measure the model motion based on the acceleration

of translational and rotational motions. The

gyroscope instrument to be used is MPU 6050 GY87,

capable of producing angle output formed by MPU

6050. In MPU 6050 there is an axis of orientation x,

y and z, which will produce the respective angle of

deviations. The magnitude of the angular deviation

will be amplified and received by the Arduino UNO

microcontroller and then be transferred to a laptop

computer in digital quantities. The gyroscope sensor

instrument, as in Figure 4 is placed at the top of the

AT-OWEC cylinder cover.

Figure 4: Gyroscope to measure the model pitch motion.

Secondly, as a checking instrument, visual tracer

movements will be used in the form of target objects,

namely two red plastic balls mounted with a support,

and placed in two parallel upright positions at the top

side of AT-OWEC floating cylinder, as can be seen

in Figure 5. The target movement will be recorded by

a video camera. Video recording can be downloaded

by the appropriate software on a data processing

computer, through digital image processing (DIP).

Figure 5: Positioning red balls as visual tracing target.

DIP is the processing of two-dimensional images

by a computer device, which is the process of taking

image attributes with input and output in the form of

images. In this study DIP is used for the detection of

objects in the video which is used to analyze the

translational motion in x-direction or surge that

occurs in the AT-OWEC model when afloats in the

towing tank and is exposed to waves with a number

of period variations. In the process of representation

and modeling of an image, the quantity and character

of the picture element (pixel) describe an object.

Pixels are small units of dots that make up an image.

Each pixel in the image stores the color information

represented by the pixel. The number of pixels that

make up an image depends on the resolution or

density of the desired color. The DIP process here is

done using a Logitech c270 webcam camera, as

shown in Figure 6 which records video. Where from

the video consists of many frames which are then

processed using the help of visual basic c ++

software.

Figure 6: Digital camera and red ball visual tracing

targets.

In addition to instrumentation for measuring the

model structural motions, load cells are also made

available in the test, as shown in Figure 7. These are

The Design of Physical Model and Preparation of Experimental Study on Articulated Tower – Ocean Wave Energy Converter (AT-OWEC)

utilized to measure the load acting on the pole of the

structure.

Figure 7: Load cell instrument to measure the load on AT-

OWEC supporting pole.

The next instrument to be used in the test model

are wave probes, which are devices to measure wave

elevation. The wave probes used are three units over

all, one is placed at a distance of about 3.0 m from the

wave maker or wave generator, and the other two are

positioned in the vicinity of the model. Thus, from the

three wave probes, it can be checked if there is a

significant change in the wave profile during one set

of test is executed.

Figure 8: Calibration of gyroscope on swivel board with

ruler arc.

Calibration on all measuring instruments were

conducted to generate reference data to be inputted in

the data acquisition system (DAS). Anytime the test

is run and instruments measure the related variables

to be transferred in the DAS, it will then be adjusted

into the actual values of output data. An example of

calibration is demonstarted for the case of gyroscope.

As shown in Figure 8 it is performed with the aid of a

swivel board equipped a ruler arc. The gyroscope is

placed on the swivel board and then turned gradually

from 0

up to 60

, at interval of 10

. The digital output

of gyroscope is then correlated with the turning angle,

as presented in Table 2. This is further used to plot a

graphical correlation to derive the calibration

equation as contained in Figure 9.

Table 2: Calibation data for gyroscope:

Anti-Clockwise

Clockwise

Angle

(deg)

Gyro

Output

(unit)

Angle

(deg)

Gyro

Output

(unit)

-0º

-0.37

0º

0.60

-10º

-10.38

10º

10.20

-20º

-20.14

20º

20.42

-30º

-30.05

30º

30.75

-40º

-40.18

40º

40.44

-50º

-50.61

50º

50.05

-60º

-60.20

60º

60.30

Figure 9: Calibration chart and equation for gyroscope.

5 DESIGN AND PREPARATION FA

DATA ACQUISITION SYSTEM

Data acquisition system (DAS) is a series of

measurement instruments, supporting instruments

and collecting software and data recorders in a

computer. In this study the DAS is arranged as shown

in Figure 10. The first element is in the form of

measurement instrumentation described in section 4,

namely a gyroscope, a load cell and three wave

probes.

The second element is a multi-channel amplifier,

which functions to increase the voltage generated by

the measuring instrument, which in this case is the

load cell and wave probes. Voltage fluctuations that

occur are derived from the help of resistors or

capacitors that work on the instrument. For the

purpose of transforming from voltage fluctuations

into digital data, it is necessary to first calibrate

related instruments. While the gyroscope does not

require an amplifier. The third component is the

micro-controller, which regulates signal fluctuations

from direct measuring instruments and amplifiers.

From the micro-controller the electronic signal is

transmitted to the micro-processor, as the fourth

component. This equipment consists of digital

circuits, registers, arithmetic logic processors, and

SENTA 2018 - The 3rd International Conference on Marine Technology

sequential circuits. The role of microprocessors in the

system is as a unit that controls the entire system

work. Take instructions and data from memory, move

data to and from memory, and send signals. Signal

delivery from the microcomputer is done wirelessly

through the help of Wi-Fi, as the fifth component.

Finally the digital signal will be received by the

computer as the sixth component.

Figure 10: The general diagram of data acquisition system.

Inside the computer there is software that will pro-

cess digital data coming from signal wave probes,

gyro-scope, and visual tracer camera recordings. The

raw digi-tal data from each of these equipment will be

processed into real motion elevation data at any

elapsed time, taking into account relevant calibration

data.

6 PREPARATION OF

HYDRODYNAMIC MODEL

TESTING

Figure 11: Towing tank and the positioning of AT-OWEC

model.

Experimental study or hydrodynamic tests on the

physical model of AT-OWEC will be carried out at

the Lab. HBL, DOE - ITS, in a towing tank sized 50

m x 3 m x 2 m (LxBxd). This test tank is equipped

with a wave generator of a flap type, which is driven

by a hydraulic machine. Generated waves can be

either regular or random. But in the present study

regular waves only will be used.

Diagramatically the towing tank can be explained

by referring to Figure 11. At the right end there is a

small pool or pit, as a place to prepare the model

before the test. Right on the lip of the small tank, a

wave absorber is installed. At the left end of the pool

is a hydraulic machine positioned to drive the wave

generator. In this study the AT-OWEC model was

installed at a position of about 25.0 m from the wave

generator. Regular waves will propagate from the

generator towards the wave absorber. With the

absorber, there is a possibility to restraint the

emergence of a reflected wave from the right side,

which is likely to disrupt the generated wave profile.

Figure 12: AT-OWEC model installed in the towing tank.

The AT-OWEC model installed in the towing

tank is as shown in Figure 12. Wave elevations will

be detected by the first wave measuring instrument or

wave probe (WP # 1) positioned in the center axis of

the pull pool at a distance of 15.0 m from the plant.

The Design of Physical Model and Preparation of Experimental Study on Articulated Tower – Ocean Wave Energy Converter (AT-OWEC)

With this position allows the measured waveform to

show a profile that is not disturbed by the presence of

objects in the water. Two other wave probes, namely

WP # 2 and WP # 3 are placed on the transverse sides

of the model at a distance of about 0.75 m. Both WPs

will record wave patterns that may be deformed by

the presence of the model.

The test will be carried out by generating waves,

measuring 5.0 cm high or 2.5 cm amplitude. The

wave period is varied from 1.0 sec to 8.0 sec, where

between 1.0 and 5.0 sec the increase interval is 0.5

sec, while between 5.0 sec and 8.0 sec the increase

interval is set to 1.0 sec. Data test recording will be

carried out with a sample density or sampling rate of

10 Hz, or 10 samples per second. Thus it is believed

that it will be able to provide a fairly smooth elevation

curve.

7 NUMERICAL PREDICTION OF

AT-OWEC MOTIONS

The beginning of this study has begun with numerical

modeling of the main structural variants of AT-

OWEC measuring the diameter and height of the

buoyancy chamber, respectively, Dh = 4.0 m and Hh

= 5.5 m, notionally to be operated in three variations

of sea depth d of 10.0 m, 15.0 m and 20.0 m. At this

stage the structure is assumed to be fabricated with

steel material. The choice of this variant is done with

consideration to get a system that has a larger

movement. The main data of the variants reviewed,

including mass, moment of inertia, mass of pitch

movement, stiffness of pitch movement and natural

frequency of pitch movement as a function of water

depth d are as shown in Table 3. It is obvious when

comparing the data in Table 3 and those in Table 1,

although the units are different but the values of mass,

mass moment of inertia, as well as stiffness are quite

similar, i.e. in the order multiplication of

= 10. The

differences are also notable for the case of pitch

natural frequencies and periods, due to the scaling as

described in eq. (1).

Table 3: Data of full scale AT-OWEC main structure as

function of water depth variations.

Figure 13: Results of numerical prediction on Pitch RAO of

AT-OWEC sized Dh = 4.0 m and Hh = 5.5 m at three water

depth variations.

Numerical modelling of AT-OWC pitch motion

has been carried out using the software based on 3-D

diffraction theory. Mathematical formulation of

dynamic behaviour was developed with the

implementation of pulsating-source theory

distributed on the panels enclosing the buoyancy

chamber, as described in the references (Murtejo, et.

al., 2005; Atkins, 2017; Choy, 2012; Djatmiko et. at.,

2017). With the input data of the structure in Table 3

the modelling is executed for variations in the regular

wave frequency between 0.2 up to 2.0 rad / sec.

Output data from running the software in the form

of AT-OWEC RAO pitch motion are as presented in

Figure 13. It is interesting to observe this graph,

where the largest response occurs when AT-OWEC

is operated at a depth of d = 10.0 m, with the peak

reaching around 38.0 deg/m. The area under the curve

for this case is also quite large, thus indicating the

capacity to absorb relatively large wave energy.

When the operating depth rose to 15.0 m and 20.0 m

apparently the motion intensity decreased,

respectively, only reaching around 25.0 deg/m and

20.0 deg/m. As a consequence the area under the

curve also decreases. This means that there will not

be enough wave energy that will be absorbed.

Especially if considering the occurrence of waves

with large periods, above 12.0 seconds, the number of

occurrences is relatively rare.

The numerical modelling results so presented are

prepared for a comparative study with the results of

the AT-OWEC model test, which will be

implemented in the near future. In due course the

results of the comparative study will be published in

the appropriate dissemination forum or scientific

journal.

SENTA 2018 - The 3rd International Conference on Marine Technology

8 CONCLUSIONS

This paper presents a stage in the development of AT-

OWEC research, which involves the preparation of

physical test models at the Laboratory of Ocean

Structure Hydrodynamics, DOE - ITS. A number of

important aspects that have been explained can

further be summarized as follows:

• The AT-OWEC physical model measures 1 : 10

to the full scale, sized Dh = 400 mm and Hh =

550 mm, made of aluminum material, and has

been designed to meet geometric, kinematic and

dynamic similarities;

• The pitch motion measurement will be carried

out utilizing the gyroscope as primary

instrument, assisted by checking the target

visual tracing recorded through a digital

camera;

• Data acquisition system has been prepared with

appropriate tools to produce outputs that take

into account the appropriate calibration factors;

The results of numerical modelling of pitch moti-

ons have been prepared as data for comparative

studies with the results of the test model, which will

be implemented in the near future.

ACKNOWLEDGEMENTS

The authors are deeply grateful to the Ministry of

Research Technology and Higher Education,

Republic of Indonesia, for providing the research

grant to AT-OWEC establishment through the

Higher Education Primary Basic Research (PDUPT)

scheme in the fiscal year of 2018.

REFERENCES

Atkins, 2017. Chrysaor Solan Development, North Sea

(West of Shetland), WS Atkins Plc.. [Online]

Available at: http://www.atkinsglobal.com/zh-

cn/projects/solan-offshore-development

[Accessed 22 2 2017].

Bar-Avi, P. & Benaroya, H., 1996. Planar motion of an

articulated tower. J. of Sound and Vibration, 198(1), pp.

27-50.

Bar-Avi, P. & Benaroya, H., 1996. Response of a two

degrees of freedom articulated tower to different

environmental conditions. Int. J. of Non-Linear

Mechanics, 31(5), pp. 717-741.

Budiman, A. et al., 2014. Sepuluh Gagasan untuk

Menguatkan Kembali Sektor Energi Terbarukan.

s.l.:Global Energy & Materials, McKInsey &

Company.

Chakrabarti, S., 2001. Stability analysis of interaction of an

articulated tower with waves. WIT Trans. on the Built

Env., Volume 56, pp. 1-10.

Chakrabarti, S. K., 1998. Physical model testing of floating

offshore structures. Huston, Texas, USA, Dynamic

Positioning Conf., Marine Technology Society.

Chakrabarti, S. K. & Cotter, D. C., 1980. Transverse motion

of articulated tower. J. of Waterways, Port, Coastal and

Ocean Division, ASCE, p. 107.

Chanson, H., 2008. Physical modelling, scale effects and

self¬similarity of stepped spillway flows. Honolulu,

Hawai, USA, World Environmental and Water

Resources Congress 2008, ASCE.

Choy, L. T., 2012. Blue Energy - Ocean Power (Piston

Pump & Racks). s.l. Patent No. International Patent

Application No. PCT/SG2011/000232.

Direktur AEBET, 2013. Kebijakan pengembangan dan

peman¬faatan sumber energi terbarukan. Yogyakarta:

Lokakarya Nasional VI: Manajemen Penelitian dan

Pengabdian Kepada Masyarakat di Perguruan Tinggi.

Djatmiko, E. B., 1987. Experimental investigation into

SWATH ship motions and loadings. M.Sc. Thesis ed.

Dept. NAOE, Univ. of Glasgow, UK.

Djatmiko, E. B. et al., 2017. Concept Development of

Articulated Tower – Ocean Energy Converter (AT-

OWEC). Int. Conf. on Marine Tech. SENTA 2017,

Surabaya.

Djtamiko, E. B., Syahroni, N. & Sujantoko, 2017.

Perancangan dan analisis sistem konversi energi

gelombang laut berkonfigurasi articulated tower.

Laporan Akhir Program Penelitian Laboratorium, Dana

Lokal ITS, Surabaya.

Grinius, V. G., 2006. Physical model testing of floating

struc¬tures innovations and challenges. US/EU Baltic

Int. Sympo, Klaipeda, Lithuania.

Helvacioglu, I. H. & Incecik, A., 1988. Dynamic analysis

of coup¬led articulated tower and floating production

sys¬tems. Huston, Proc. of the 7th Int. Conf. on

Offshore Mechanics and Arctic Engineering, ASME.

Munson, B. R., 2013. Fundamentals of Fluid Mechanics.

7th ed. New York: WileyPLus.

Murtedjo, M., Djatmiko, E. B. & Sudjianto, H., 2005. The

influence of buoyancy parameters on the dynamic

behavior of articulated tower. J. Mekanikal, UTM,

Volume 19, pp. 32-47.

Srikanth, N., 2014. Barriers to ocean energy technology

adop¬tion and role of policies & institutional system to

promote in Asia, Presentation Energy Research

Institute, Nanyang Technological University,

Singapore.

The Design of Physical Model and Preparation of Experimental Study on Articulated Tower – Ocean Wave Energy Converter (AT-OWEC)