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

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 Two main problems for the future commercialization of these innovative devices: none of the patented devices are ready for the commercial phase. Very high cost Reliability of technologies

1. INTRODUCTION Move from standalone device to hybrid systems embedded in other costal or offshore structures The primary function of the hybrid system remains the harbour/coastal protection with the adding values of the energy production. DISSIPA TE WAVE ENERGY CAPTURE THE WAVE ENERGY Provide useful energy [electricity] 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

2. THE OBREC DEVICE Overtopping Wave Energy Converter (OTD) embedded into coastal defense structure The principal function of this Innovative breakwater remains the harbour/coastal protection, with the adding values of the energy production.

2. THE OBREC DEVICE 2012: First physical model test campaign (Aalborg University, Tradition al Breakwat er Innovativ e Breakwat er Denmark) 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. 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 2014: Second physical model test campaign (Aalborg University, Denmar Flat Configurat ion Curved Configurat ion Different shape of the frontal ramp; Influence of the ramp extension under the SWL; Different dimension of the reservoir width. 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. These formulas have been used to design the first OBREC prototype breakwater at Naples Harbour (Italy). 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.

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 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. 3.1 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. Average annual wave power: P 2.5 kw/m [long periods of calm sea states]

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 3.2 GEOMETRY (Real Scale laboratory) Ramp crest freeboard = 1.7 m (Natural Waves Laboratory) Ramp crest freeboard = 1.00 m Triangular Two Machine frontal parapet room on the (Internal top reservoirs of the area: vertical 11.4m wall 2 ) 2 ) 6.0 m

3. FULL-SCALE PROTOTYPE AT THE NAPLES HARBOUR OBREC 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. waverider buoy..only 12 Kg! Cheaper than the traditional wave 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. Comparison between wave parameters measured from the GPS-buoy and an ADCP Significant wave height 1.2 1 Bias = 0.0383 m RMSE = 0.0703 m H m0 [m] SVP buoy 0.8 0.6 0.4 0.2 350 Bias = -3.6 Peak Direction 0 0 0.2 0.4 0.6 0.8 1 1.2 H m0 Peak [m] period ADCP 15 Bias = -0.117 s 300 RMSE = 17 RMSE = 1.14 s D p [ ] SVP buoy 250 200 150 100 T p [s] SVP buoy 10 5 50 0 0 50 100 150 200 250 300 350 D p [ ] ADCP 0 0 5 10 15 T p [s] ADCP 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.

3. FULL-SCALE PROTOTYPE AT THE NAPLES HARBOUR Wave loading 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. Overtopping in the reservoirs 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. d(t) H(t) q(t) Water depth in the reservoirs Hydraulic head Instantaneous flow rate

3. FULL-SCALE PROTOTYPE AT THE NAPLES HARBOUR 2 1 3 3 semi-kaplan low head turbines have been placed with a total power of 2.5 Kw A. Generator B. Turbine C. Inlet flume D. Draft tube E. Hydraulic Head 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. 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. 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 Di Lauro, E., Maza, M., Lara, J.L., Contestabile, P., Losada, I.J., Vicinanza, D., (2017), Numerical analysis of a nonconventional breakwater for wave energy conversion, Proc. 8th SCACR International Short Conference on Applied Coastal Research, Santander, Spain.

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.