Overtopping Breakwater for Wave Energy Conversion at the Port of Naples: Status and Perspectives

Diego Vicinanza, Pasquale Contestabile, Enrico Di Lauro

1. INTRODUCTION

Nowadays over 1500

Wave Energy Converter (WECs)

are patented worldwide!!

Focusing on the Wave devices,

very few WECs are developed in full

scale but…

none of the patented devices are

ready

for the commercial phase.

Two main problems for the

future commercialization of

these innovative devices:

Very high

cost

Reliability of technologies

1. INTRODUCTION

Move from standalone device to hybrid systems embedded in other costal or offshore structures

DISSIPATE

WAVE ENERGY

The primary function of the “hybrid system”

remains the harbour/coastal protection…

with the adding values of the energy production.

CAPTURE THE

WAVE ENERGY

Cost reduction: breakwater would be built regardless

of the inclusion of a WEC

(sharing cost due to integration)

High reliability: performances and global stability

as traditional breakwaters

Provide useful energy

[electricity]

2. THE OBREC DEVICE

The principal function of this Innovative breakwater remains the harbour/coastal protection, with the adding values of the energy production.

Overtopping Wave Energy Converter (OTD) embedded into coastal defense structure

Vicinanza, D., Contestabile, P., Nørgaard, J., Lykke Andersen, T. (2014). "Innovative rubble mound breakwaters for overtopping wave energy conversion", Coastal Engineering, ISSN 0378-3839, vol. 88, pp. 154-170.

2. THE OBREC DEVICE

Traditional breakwater vs

OBREC

The integration of the OBREC

in the traditional breakwater

improves the hydraulic

performances:

• overtopping at the rear side of the

structures is reduced due the

presence of a triangular parapet at

the top of the wall;

• reflection coefficients are similar

(or in some conditions lower) than

those measured for the traditional

breakwaters due the wave energy

absorption into the reservoir.

2012: First physical model test campaign (Aalborg University,

Denmark)

Traditional

Breakwater

Innovative

Breakwater

Contestabile, P., Iuppa, C., Di Lauro, E., Cavallaro, L., Lykke Andersen, T., Vicinanza, D., (2017). Wave loadings acting on innovative rubble mound breakwater for overtopping wave energy conversion, Coastal Engineering, 60-74.

Flat Configurat

ion

Curved Configurat

ion

2. THE OBREC DEVICE

2014: Second physical model test campaign (Aalborg University, Denmark)

These formulas have been used to

design the first OBREC prototype

breakwater at Naples Harbour (Italy).

A specific set of design formulas are

provided with the intent to be of direct

use by engineers in preliminary

design of full scale devices.

• Different shape of the frontal ramp;

• Influence of the ramp extension under

the SWL;

• Different dimension of the reservoir

width.

3. FULL-SCALE PROTOTYPE AT THE NAPLES HARBOUR

World’s first Overtopping WEC prototype completely embedded into a breakwater has been installed in 2015 at the Port of Naples

3. FULL-SCALE PROTOTYPE AT THE NAPLES

HARBOUR

Average annual wave power: P ≈ 2.5 kW/m

[long periods of calm sea states]

3.1 SITE SELECTION

Ideal site to test the OBREC

prototype

for this stage of development

[Low occurrences of extreme storms]

- Reduction of the construction costs - Safer and less expensive maintenance operations

• Challenge = demonstrate the structural reliability

and evaluate the overall performances during the

storms

• Aim = acquire data during the storm events,

using the pilot plant as a large natural laboratory

in which the field data are collected and analyzed

for future applications in the more energetic and

exposed coastal areas.

Contestabile, P., Ferrante, V., Di Lauro, E., Vicinanza, D., (2016), Full-scale prototype of an overtopping breakwater for wave energy conversion, Proceedings of the 35 International Conference on Coastal Engineering, Antalya, Turkey.

3. FULL-SCALE PROTOTYPE AT THE NAPLES

HARBOUR

Contestabile, P., Ferrante, V., Di Lauro, E., Vicinanza, D., (2016), Full-scale prototype of an overtopping breakwater for wave energy conversion, Proceedings of the 35 International Conference on Coastal Engineering, Antalya, Turkey.

3. FULL-SCALE PROTOTYPE AT THE NAPLES

HARBOUR

(Real Scale laboratory) Ramp crest freeboard = 1.7 m

(Natural Waves Laboratory) Ramp crest freeboard = 1.00 m

Machine room (Internal area: 11.4m2)

Machine room (Internal area: 11.4m2)

Triangular parapet on the top of the vertical

wall

Two frontal reservoirs

6.0 m

3.2 GEOMETRY

3. FULL-SCALE PROTOTYPE AT THE NAPLES

HARBOUR

The waverider buoy, Directional Wave Spectra

Drifting Buoy (DWSDB), uses Global Positioning

System (GPS) technology developed by the

Lagrangian Drifter Laboratory (LDL) of the Scripps

Institution of Oceanography (SIO) in San Diego.

Cheaper than the traditional wave buoy…

..only 12 Kg!

OBREC

waverider buoy

3. FULL-SCALE PROTOTYPE AT THE NAPLES

HARBOUR

The wave data are transmitted via the Iridium satellite system

and they are accessible in real time on dedicated website.

Centurioni, L., Braasch L., Di Lauro, E., Contestabile, P., De Leo, F., Casotti, R., Franco, L., Vicinanza, D. (2016). A new strategic wave measurement station off Naples port main breakwater, Proceedings of the 35 International Conference on Coastal Engineering, Antalya, Turkey.

0 0.2 0.4 0.6 0.8 1 1.20

0.2

0.4

0.6

0.8

1

1.2

Hm0

[m] ADCP

Hm

0 [

m]

SV

P b

uoy

Significant wave height

Bias = 0.0383 m

RMSE = 0.0703 m

0 5 10 150

5

10

15

Tp [s] ADCP

Tp [

s]

SV

P b

uoy

Peak period

Bias = -0.117 s

RMSE = 1.14 s

0 50 100 150 200 250 300 3500

50

100

150

200

250

300

350

Dp [°] ADCP

Dp [

°]

SV

P b

uoy

Peak Direction

Bias = -3.6 °

RMSE = 17 °

Comparison between wave parameters measured from the

GPS-buoy and an ADCP

3. FULL-SCALE PROTOTYPE AT THE NAPLES

HARBOUR

Wave pressure will be measured by pressure transducers located on the different parts of

the structure The aim is to collect and analyze pressure data during storm events in order to: • compare it with the theoretical prediction; • validate the pressure data analyzed in small

scale model.

Wave loading

pressure transduce

r Pressure transducers will be placed on small boxes in the machine room in order to measure the variation of the water depth d(t) inside the frontal reservoirs.

Overtopping in the reservoirs

d(t) H(t) q(t)

Water depth in the reservoirs

Instantaneous flow rate

Hydraulic head

3. FULL-SCALE PROTOTYPE AT THE NAPLES

HARBOUR

3 semi-Kaplan low head turbines have been placed

with a total power of 2.5 Kw

The purpose is to test different low head turbines in order to find the optimal technology

for overtopping hydro-marine turbines, via a cost-benefit analysis.

1

2 3

A. Generator

B. Turbine

C. Inlet flume

D. Draft tube

E. Hydraulic

Head

F. Outlet flume

NUMERICAL ANALYSIS

• Extend the range of application of the design formulas also for 3D conditions

• Provide useful indications for the stability analysis and the geometrical optimization of the OBREC integrated into both rubble mound breakwater and vertical caisson.

Di Lauro, E., Maza, M., Lara, J.L., Contestabile, P., Losada, I.J., Vicinanza, D., (2017), Numerical analysis of a non-conventional breakwater for wave energy conversion, Proc. 8th SCACR – International Short Conference on Applied Coastal Research, Santander, Spain.

Mizar Formentin, S., Contestabile, P., Palma, G., Vicinanza, D., Zanuttigh, B. (2017). "2DV RANS-VOF numerical modeling of a multi-functional harbour structure", Proceedings of the 35 International Conference on Coastal Engineering

Acknowledgments

BRIGAID is a 4-year project (2016-2020) under EU Horizon2020 aimed to effectively bridge the gap between innovators and end-users in resilience to floods, droughts and extreme weather.