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FLOREM project FLOw REctifying Methods

Infrastructure: Wave and Current Basin

Aalborg University - Denmark

Department of Civil Engineering

Marinet2 – FLOREM, FLOw REctifying Methods

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AALBORG UNIVERSITY ACCESS REPORT OF:

FLOREM - FLOw REctifying Methods - project

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under

grant agreement number 731084.


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Document Details

Grant Agreement Number 731084

Project Acronym MaRINET2

Title FLOREM project - FLOw REctifying Methods

Distribution Public

Document Reference FLOREM_731084

User Group Leader, Lead Author

Giacomo Vissio EPF Elettrotecnica Srl Via Langhe, 24 - 12061 Carrù (Cn) Italia

User Group Members, Contributing Authors

Alberto Dalmasso EPF Elettrotecnica Srl

Infrastructure Accessed Aalborg - Wave Basin

Infrastructure Manager or Main Contact

Amelie Tetu

Document Approval Record

Name Date

Prepared by

Checked by Amélie Tetu 15/12/2017

Checked by Amélie Tetu 05/01/2018

Approved by Amélie Tetu 08/01/2018

Document Changes Record

Revision Number

Date Sections Changed Reason for Change

Disclaimer The content of this publication reflects the views of the Authors and not necessarily those of the European Union. No warranty of any kind is made in regard to this material.


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Table of Contents Table of Contents ............................................................................................................... 3

1. Introduction and Motivations ........................................................................................ 4

1.1 EPF Company ....................................................................................................... 4

1.2 The FLOREM Project ............................................................................................. 4

1.3 The infrastructure ................................................................................................. 5

1.4 Objectives ............................................................................................................ 7

2. Wave Energy Conversion Concept ................................................................................. 8

3. Testing Schedule ......................................................................................................... 8

4. Main Outcomes ......................................................................................................... 12

4.1 Synthetic Results presentation ............................................................................. 12

4.2 Comments.......................................................................................................... 13

5. Conclusions ............................................................................................................... 14

6. Further Activities ....................................................................................................... 14

7. The Team ................................................................................................................. 15


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1. Introduction and Motivations

1.1 EPF Company EPF was founded as EPF Elettrotecnica in 1961 and since then it has been working on a National

and International level in the automation and industrial plant design sectors. Managed by the same

family for two generations, EPF has maintained its Headquarters in Carrù, just outside the Langhe

(Piedmont) in Italy. EPF Automation designs and manufactures robotic applications, integrated in

industrial automation plants. EPF Automation is a system integrator, able to completely manage

the installation of Industrial robots, starting from initial feasibility studies and assisting the

customer in the design of the application, in the development of the control software and in the

installation and commissioning phases.

EPF acts as EPC contractor for turn-key plants of energy from renewable sources, working mainly

on photovoltaic and hydroelectric power plants. EPF is strongly interested in the field of very small

head turbines, understanding the fundamental topics of off-design operations, maintenance and

environmental impact.

Regarding wave power field, EPF collaborates with the Italian Institute for Research on Energy

System (RSE S.p.A). For RSE WaveSax, EPF developed the electric Power Take Off and the control

system, being actively involved in the project. The characterization of the performance of its

electro-mechanical conversion system required the realization of an in-house dry test bench.

Coherently with its company mission, EPF is also involved in the design of control systems for

Wave Energy Converters with its “WEQUAD FRAME” project, financed by Wave Energy Scotland.

The company is working to prove the feasibility of its technology applied to different Wave Energy

Converter technologies.

1.2 The FLOREM Project Starting from the company previous experience in very low head hydro power plants, the company

is focused on finding solutions for the application of water turbines to the wave energy field.

Analyzing the application of this technology to wave power, the main obstacle for using turbines

is the oscillatory nature of the water resource. Some WEC technology developers have already

tried to find methods for making the water flow uni-directional in order to apply these rotary

machines in the first stage hydro-mechanical power conversion: Wave Dragon overtopping

principle and the Hann-Ocean Energy twin-chamber oscillating water column are just some

examples. A key advantage of turbines is their high efficiency in the conversion between the

hydraulic and mechanical power for almost steady state water flows. This last consideration

highlights the importance of these tests: the experimental measurement of main physical

quantities involved in the oscillating to continuous flow conversion, the identification of unmodeled

dynamics components and the final validation of the hydraulic modelling approach.

Prior to the infrastructure access, EPF developed a lumped-parameters time domain numerical

model utilized in the design of the structure devoted to the transformation of the water flow

oscillatory motion into a continuous one. Using this numerical model, a first concept working

principle verification was carried out with time domain simulations but a complete extended

validation with experimental data was required. This is coherent with the development and

evaluation protocol standard (OES-IA Document nº T02-0.0).


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In fact, this passage must be accomplished before the design and construction of higher scale

prototypes, to establish better basis in the working principle knowledge and de-risk future company

private investments. It is in fact widely known that the first phase in a project is the most important

and that small early errors can have a technical and economic dramatic impact at following phases.

Also, system key components (the uni-directional valves) have been validated through numerical

simulations, but require to be tested with the realistic boundary conditions in lab tank tests, to

enhance the reliability of the concept and to validate the design procedure.

Starting from the results of these tests, different WEC concepts (floating, onshore, platforms) could

be developed, depending on the effects and dynamic performances observed. These can be very

diverse but all characterised by a simple and relatively cheap architectures.

The validation of the in-house lumped parameters numerical model is fundamental for the specification procurement of a modern model based design approach.

Dealing with real hydrodynamics and problems has been a valuable experience; it has been useful for a deeper comprehension of the WEC conversion principles. The lessons learned are fundamental for moving forward in the development of the program.

1.3 The infrastructure The infrastructure accessed for the tank tests was the Wave & Current Basin at the Aalborg

University Civil Department. It is a new infrastructure, highly flexible and automatized.

The wave basin (Figure 1) is 14.6m x 19.3m, with an active test area of 13 x 10m. It was filled

with 1.1 m of water. The basin can accommodate testing on deep and shallow water. The basin

is equipped with a long-stroke segmented piston wavemaker for accurate short-crested (3-

dimensional) random wave generation with active absorption. The wavemakers are powered by

electric motors which allow for less acoustic noise, no oil pollution in the basin and more accurate

waves. A maximum significant wave height of 15cm at 3s of peak period was tested during the

access period. Also, the possibility of having an accurate generation of 3D waves due to narrow

vertically hinged paddles (0.43m segment width) was explored.

The tank provided a reliable data log system, with its own hardware and software, and 14

resistance wave gauges (with electronics and auto-tuning capabilities), as requested by the

experimental campaign specifications.


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Figure 1 - Aalborg University - Waves and Currents Basin

Figure 2 – Tank AAU Wave Probes setup


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1.4 Objectives The objectives realized during the project can be categorized among the first stage activities of

the development and evaluation protocol standard. In the following Table 1 the previous status

and the activities carried out in the project are highlighted.

Previously completed:

Realised through FLOREM project: ♣

Table 1 - Objectives of the FLOREM project

STAGE OBJECTIVES Status

Stage 1 – Concept Validation

Numerical validation through a simplified lumped-parameters model

First concept physical validation of a simple prototype in un-calibrated tank

Linear monochromatic waves to validate or calibrate numerical models of the system (25 – 100 waves)

♣

Linear panchromatic waves to validate or calibrate numerical models of the system (25 – 100 waves)

♣

Restricted degrees of freedom (DoF) as required by the early mathematical models ♣

Provide the empirical hydrodynamic co-efficient associated with the device (for mathematical modelling tuning)

♣

Initially 2-D (tank) test programme ♣

Initially 3-D (tank) test programme (first assessment) ♣

Initial indication of the full system load regimes ♣

Investigate physical process governing device response. May not be well defined theoretically or numerically solvable.

♣

The FLOREM project has as main objective to study a wave energy conversion concept already

validated through a Matlab/Simulink time domain numerical model and proved via a simple physical

concept validation at the company headquarter.

During the project several analyses using both regular and irregular waves have been carried out,

testing 7 different configurations of the machine, to make a first assessment of the differences

among several solutions. For simplifying the approach, several simplifications have been carried

out for the tests; the major hypothesis was to constrain all the degree of freedoms of the wave

energy converter main body, making it fixed. In this way the conversion principle has been isolated

and the comparison with numerical simulations was made simpler.

Thanks to the analysis and comparison between experimental and simulated data, it is possible to

identify empirical coefficients for enhancing the model reliability and improving the accuracy of the

simulated results. For reaching this result, both 2D and 3D waves have been performed. An

important outcome was the low influence of a full three-dimensional spectrum for some

configurations.


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Thanks to the tests it has also been possible to get a first assessment of the full system load

regimes and conversion capabilities, as more deeply illustrated in the following sections.

2. Wave Energy Conversion Concept Following the analysis of the data gathered during tank tests, the wave energy concept patent has

been filed. Since it is currently patent pending, at this stage it is not possible to share any detail

about the power conversion concept.

The innovative EPF concept will nonetheless be a type of Oscillating Water Column device,

introducing some elements for rectifying the water motion into a subsystem of the device.

The idea of making the flux uni-directional and using a first passive, hydraulic, power conversion

step, rises from considering the CAPEX and OPEX costs associated to the rectification of the motion

in more conventional WECs. The challenge is to build a low-performance WEC with a very low

price, trying to obtain a competitive final LCOE.

In particular, in this way the PTO will be designed with a very satisfactory maximum over average

power ratio, also reducing at minimum the losses due to the PTO cooling system.

Finally, always looking at the overall efficiency, reducing the elements in the conversion chain

facilitates the possibility of having a final higher conversion efficiency.

As principal draw back, the system will not be able to resonate with the incoming sea state, thus

reducing the converted power.

This project represented the first step in the analysis of this challenging wave energy project.

3. Testing Schedule The testing schedule has been built considering both the waves running time and the time required

for setting-up the prototype and changing between three configurations for both the two main

setups. Almost a day of setup was expected. This includes the installation of the structure linked

to the bridge, the installation of the valves for the desired configuration and the positioning of the

floater in water at the specified draft (the first week, at the arrival, the system was already setup

with the correct valves pack). The last part of the first day has been left to some qualitative testing

and observations. These were useful for deciding to reinforce the chamber wood structure with

some flexible elements (cable ties) provided by the access provider. Starting from the second day,

the tests were performed, following the order already designed and discussed prior to the tank

access with the infrastructure manager, Amelie Tetu. In Figure 3 it is possible to see the 10 days,

two weeks, work programme. During the whole project, 2 main setups were tested in 3 different

configurations, plus a 3rd type of concept was introduced in the final day. These last tests were

left in order to have a buffer time that could be exploited in case of problems and delays during

tank testing.


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WEEK 1

WEEK 2

For each prototype configuration regular, irregular and 3D irregular waves were performed.

Regular waves were used for obtaining the system Response Amplitude Operator between the

waves and the unidirectional water flow, meanwhile the irregular waves were analysed in order to

assess the power harvesting capabilities of the concept and have a first idea of a full scale

installation through the scaling up of its performances.

In the following tables the tests performed for each configuration are shown. It must be mentioned

that the tests with irregular waves have not been performed completely for each configuration and

have only a qualitative comparison motivation.

DAY 1 DAY2 DAY3 DAY4 DAY5

08:00 - 10:15Config. 1-B RUN 3

10:15 - 12:30

13:30 - 15:45

15:45 - 18:00First Waves Config. 1-B

2nd SETUP

Config 2-A

1st SETUP

Config. 1-ARUN 1

RUN 3

RUN 2

Config. 1-C

DAY 1 DAY2 DAY3 DAY4 DAY5

08:00 - 10:15Config. 2-B RUN 6

10:15 - 12:30 Config. 3

13:30 - 15:45

15:45 - 18:00 Config. 2-B

RUN 4

RUN 5

Config. 2-C

RUN 6 RUN 7

DISMANTLING

Prototype SETUP

Testing

Figure 3 – FLOREM project Tests Schedule


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Regular Waves

Period (s)

0.65 0.80 0.95 1.10 1.25 1.40 1.55 1.70 1.85 2.00 2.15 2.30 2.45 2.60 2.75 2.90 3.00

Height (m)

0.05 X X X X X X X X X X X X X

0.1 X X X X X X X X X X

0.15 X X X X X X X X X X

Number of tests: 33

Test duration: 90 s

Wait Time: 120 s

Overall Time: 2 hr

Irregular Waves

Peak Period (s)

0.65 0.80 0.95 1.10 1.25 1.40 1.55 1.70 1.85 2.00 2.15 2.30 2.45 2.60 2.75 2.90 3.00

Hs (m)

0.05 X X X X X X X X

0.1 X X X X X X X

0.15 X X X X X X X

Number of tests: 21

Test duration: 300 s

Wait Time: 45 s

Overall Time: 2 hr

Irregular 3D Waves

Peak Period (s)

0.65 0.80 0.95 1.10 1.25 1.40 1.55 1.70 1.85 2.00 2.15 2.30 2.45 2.60 2.75 2.90 3.00

Hs (m)

0.05 X X X X

0.1 X X X

0.15

Number of tests: 7

Test duration: 300 s

Wait Time: 45 s

Overall Time: 1 hr

The overall number of tests performed is 352. This is less than expected for some minor delays,

but still very good, considering that all the more sensitive tests important for the development of

the WEC development programme have been performed and the data correctly logged and

elaborated.


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The choice of water depth and wave periods and heights was made for testing the WEC concept

in conditions that can fit the scaling up to a sea-like WEC prototype both in 1:10 and 1:20 scale.

Also, the choice of a wide range of wave periods reflects this intent: in 1:10 scale the period range

covers values between 3s up to 9.5s and for the 1:20 scale between 4.25s up to 13.5s. These

values are identified looking at wave conditions characteristic of the Mediterranean resource, that

is where the company would preferably focus its current plans and future actions.

Figure 4 - The prototype installed in the basin


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4. Main Outcomes In this section the dimensionless synthetic results of the tests are shown. Looking at the irregular

waves, the mean unidirectional power resource is computed for each sea state and system

configuration. The main outcomes of this analysis are maps showing the hydraulic conversion

capabilities of the different configurations of this machine in converting the oscillating water motion

of waves into a continuous unidirectional flow. The maps are shown in the following and some

conclusions are drawn and presented.

4.1 Synthetic Results presentation In the following maps the ratio between the average power over the maximum power obtained

during the whole test campaign is presented. The maximum average power has been obtained

with the prototype being in “Configuration 1”, thus in this table the maximum relative value is “1”.

The available power is computed using the standard equation for the hydro resource exploitable

by a water turbine.

Configuration 1

Power (P/P max) Peak Period Tp (s)

0.95 1.25 1.55 1.85 2.15 2.45 2.75 3

Hs (m)

0.05 0.053 0.066 0.076 0.070 0.063 0.069 0.040 0.036

0.1 0.401 0.347 0.365 0.321 0.321 0.262 0.337

0.15 0.791 0.821 0.765 1.000 0.632 0.780

Configuration 2


0.95 1.25 1.55 1.85 2.15 2.45 2.75 3

Hs (m)

0.05 0.001 0.011 0.027 0.033 0.035 0.049 0.031 0.025

0.1 0.085 0.121 0.175 0.183 0.208 0.187 0.232

0.15 0.327 0.435 0.464 0.614 0.424 0.584

Configuration 3


0.95 1.25 1.55 1.85 2.15 2.45 2.75 3

Hs (m)

0.05 0.020 0.049 0.065 0.058 0.064 0.074 0.047 0.041

0.1 0.369 0.297 0.304 0.273 0.267 0.227 0.262

0.15 0.667 0.648 0.563 0.677 0.453 0.533


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Configuration 4


0.95 1.25 1.55 1.85 2.15 2.45 2.75 3

Hs (m)

0.05 0.001 0.003 0.003 0.003 0.002 0.002 0.002 0.001

0.1 0.011 0.010 0.010 0.009 0.007 0.006 0.006

0.15 0.026 0.023 0.019 0.021 0.013 0.014

Configuration 5


0.95 1.25 1.55 1.85 2.15 2.45 2.75 3

Hs (m)

0.05 0.001 0.001 0.002 0.002 0.002 0.002 0.002 0.001

0.1 0.002 0.003 0.003 0.003 0.004 0.003 0.004

0.15 0.005 0.005 0.005 0.006 0.005 0.005

Configuration 6


0.95 1.25 1.55 1.85 2.15 2.45 2.75 3

Hs (m)

0.05 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.1 0.008 0.003 0.003 0.001 0.001 0.001 0.001

0.15 0.015 0.014 0.013 0.012 0.009 0.009

4.2 Comments Looking at the synthetic uni-directional flow power resource results, it is possible to identify the

1st configuration as the one with the best conversion performances. Another conclusion that can

be drawn is the high robustness with regard to the variation of the sea state peak period. This is

something that will be further analysed and that validates a trend that was already apparent in

numerical simulations. The system is on the other hand highly sensitive with respect to the wave

height. This was also an expected trend given the fact that the resource is proportional to the

square of the wave height.


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Looking at configurations 4, 5 and 6, the productivity values are much lower with respect to the

ones of the first three configurations. This was expected and is matching the results obtained with

numerical simulations. The positive outcome of this second part of tests is the good match that

this solution has with respect to numerical simulations.

5. Conclusions In general, the working principle of the concept has been validated and a relevant amount of

experimental data is now available for making comparisons with the numerical model and for

identifying previously unmodeled dynamic effects. The design procedure of the prototype has been

validated and some of the hypothesis revealed very accurate. On the other hand, some phenomena

were not foreseen and have been now identified. Several upgrades of the model have already

been planned and some of which have already been introduced. Next steps will be to introduce a

more detailed modelling approach, like a flow potential theory analysis and a time domain CFD

characterisation/optimization of some of the fundamental elements in the conversion chain.

The analysis of the data gathered during this first wave tank access reported interesting results

that proved to be of strategic interest for the company and the final decision of concluding the

patent pending procedure has been drawn.

6. Further Activities Given the interesting results of this experimental campaign, the following step in the WEC

development programme is to design a seaworthy shape and structure. Several optimizations are

then possible, starting from the hydraulic geometry optimization up to the turbine design, the

structural optimization, the design of a control system capable of reducing the final LCOE of the

power plant.

The access to wave tank will be fundamental for prosecuting the scientific analysis of the working

principle and the setup of an accurate lumped parameters model capable of representing the real

physical phenomena involved in the conversion. This instrument will be fundamental in the design

of a sea prototype and full-scale device. For reaching this scope, the company is working to design

a project for applying to a next Marinet2 access call. The access to a bigger infrastructure could in

fact possibly permit to test a full functional prototype, with a small turbine.


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7. The Team Giacomo Vissio, M.Sc. in Mechanical Engineering and Ph.D. in Wave Power field at Polytechnic of

Turin (Italy). Giacomo completed his PhD at Polytechnic of Turin and during the same period

worked as consultant for Wave For Energy Srl, the company devoted to the commercialisation of

the ISWEC device. He is now working in EPF Elettrotecnica Srl as R&D Wave Power engineer. He

is now responsible of the modelling and design of the EPF wave energy converter.

Alberto Dalmasso, M.Sc. in Electrical Engineering at Polytechnic of Turin. Alberto is a 10 years

experienced control engineer with a strong background in electrical applications and long-term

experience in research and development applications. Among his work experiences, he coordinated

a mixed university and industries group devoted to software development activities for the subway

in Rome. In recent years he was involved in both high and low-level software architecture design

and implementation. He is now working as specialist in EPF Engineering/R&D department.

Figure 5 - Alberto and Giacomo in the AAU tank during the setup

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