Overtopping Breakwater For Energy Conversion Research Articles

A predictive machine learning model for estimating wave energy based on wave conditions relevant to coastal regions

Growth and expansion in construction has increased recently and especially in coastal areas. In Alexandria, Egypt, mega projects such as El-Max Port Project (Middle Port), Port of ABU QIR (EG AKI), hotels, and restaurants were spread along the coastal lines, thus, it will need a high electrical energy. Although, the great economic benefits of such projects, it will have some negative impacts, such as overloading on the present grid. According to recommendations of COP 27, Egypt is one of the countries targeting to increase the dependency on green energy to minimize the production of greenhouse gases. This study is interested in wave energy as a renewable source of energy. Using a machine learning model that predicts wave height and wave period through the year 2030 in three separate places (Alamein, Alexandria, and Mersa-Matruh), this study will try to estimate the future amount of wave energy along Egypt's coast. Hourly measurements of the significant height and the mean wave period for the period 1979–2023 have been utilized for this. An extractor for wave energy can also be built on the Overtopping Breakwater for Energy Conversion (OBREC) in order to use this energy to fill the hole in the electric grid. The machine learning model was developed using hourly wave height and period data from three buoys, and as a result, the results have a root mean square error (RMSE) of 0.52. The amount of energy taken, wave power, and system efficiency at each place were then fully determined using a mathematical model for each of the three locations. The area along the coast of Alamein had the highest energy extraction rates, followed by Alexandria and Mersa-Matruh in that order. The results of the mathematical model indicate that the yearly power generation for Alamein, Alexandria, and Mersa-Matruh is 25287 MWhr, 14713 MWhr, and 4865 MWhr, respectively.

A NEW SEAWATER LOW-HEAD TURBINE FOR THE OBREC

The OBREC (Overtopping Breakwater for wave Energy Conversion) is based on the overtopping phenomenon [1] where incoming waves run over an overtopping ramp and fall into a reservoir located above the sea level inside a conventional rubble mound breakwater, or into a vertical caisson breakwater. The wave energy is transformed into potential energy, with some contribution of kinetic energy. Then, the flow is driven through a turbine addressing the final transformation into electrical energy. The OBREC prototype is located in the middle of the San Vincenzo breakwater, in Naples harbour (Italy). The key target of the whole pilot project was to demonstrate the high capacity factor of the system (expressed as the ratio of the electrical energy produced to the electrical energy that could have been produced at continuous full power operation), even in a low-energy wave climate. At the study site, in fact, the yearly average wave power was found to be 1.8 kW/m over the last 42 years [2]. However, during last 5 years, a maximum wave height of over 5 m has been registered, confirming the high reliability under severe wave conditions.
 Due to the short monitoring period and to the undersize of the previous power take-off (PTO) systems, no definitive power matrix is available for OBREC [3]. The energy conversion efficiency of OBREC has been deeply investigated over the last years through both physical and numerical model tests. Within the ongoing full-scale monitoring activities in real environments, a new set of power take-off was installed. A propeller-type pico-turbine equipment was in 2021, and its final setting was completed in 2022. Performance and reliability of the entire structure were closely monitored under different “stress tests”, i.e. start & stop cycle in marine environment with a high variable combination of flow rate/hydraulic head.
 This paper presents the design stage for the new equipment and preliminary results from these tests numerical and field tests.
 
 
 Contestabile, P., Crispino, G., Di Lauro, E., Ferrante, V., Gisonni, C., & Vicinanza, D. (2020). Overtopping breakwater for wave Energy Conversion: Review of state of art, recent advancements and what lies ahead. Renewable Energy, 147, 705-718.
 Contestabile, P., Russo, S., Azzellino, A., Cascetta, F., Vicinanza, D. (2022). "Combination of local sea winds/land breezes and nearshore wave energy resource: Case study at MaRELab (Naples, Italy)", Energy Conversion and Management, ISSN 0196-8904, 257, 115356, https://doi.org/10.1016/j.enconman.2022.115356 
 Mariani, A., Crispino, G., Contestabile, P., Cascetta, F., Gisonni, C., Vicinanza, D., & Unich, A. (2021). Optimization of Low Head Axial-Flow Turbines for an Overtopping BReakwater for Energy Conversion: A Case Study. Energies, 14(15), 4618.

Optimization of Low Head Axial-Flow Turbines for an Overtopping BReakwater for Energy Conversion: A Case Study

Overtopping-type wave power conversion devices represent one of the most promising technology to combine reliability and competitively priced electricity supplies from waves. While satisfactory hydraulic and structural performance have been achieved, the selection of the hydraulic turbines and their regulation is a complex process due to the very low head and a variable flow rate in the overtopping breakwater set-ups. Based on the experience acquired on the first Overtopping BReakwater for Energy Conversion (OBREC) prototype, operating since 2016, an activity has been carried out to select the most appropriate turbine dimension and control strategy for such applications. An example of this multivariable approach is provided and illustrated through a case study in the San Antonio Port, along the central coast of Chile. In this site the deployment of a breakwater equipped with OBREC modules is specifically investigated. Axial-flow turbines of different runner diameter are compared, proposing the optimal ramp height and turbine control strategy for maximizing system energy production. The energy production ranges from 20.5 MWh/y for the smallest runner diameter to a maximum of 34.8 MWh/y for the largest runner diameter.

Development of an experimental test for evaluating ramp shapes on overtopping breakwater for energy conversion

The utilization of the existing breakwater constructions into wave energy conversion has been often adopted to rendering a revenue of the capital cost of investment. The paper has contributed to viable concept of a new integration design through more effectively capturing wave-overtopping which finally converts into electrical energy. This design is hereafter called Overtopping Breakwater for Energy Conversion (OBREC). The development of an experimental test of the current OBREC has been conducted to obtain a proper ramp shape through evaluating the amounts of the wave-overtopping discharges into the reservoir incorporated with wave-reflection coefficients. To achieve the objective, several geometry ramps such as linear, convex, concave and cubic shapes have been experimentally investigated at the National Research Institute Malaysia (NAHRIM) laboratory. The experimental study showed that the cubic-ramp shape has resulted in more significant amount of the wave-overtopping discharge into the reservoir associated with the low wave-reflection coefficient than the other ramp shapes. In general, it is merely concluded that this investigation provides very promising concept of the new proposed OBREC design to harness the larger wave energy.

The Influence of Ramp Shape Parameters on Performance of Overtopping Breakwater for Energy Conversion

Overtopping breakwater for energy conversion (OBREC) is integration between breakwater and wave energy converter (WEC) that allows incoming waves to be stored in the reservoir. The higher the overtopping amount collected in a reservoir, the greater the energy generated will be. Hence, most of the overtopping concept has attempted to maximize the inclusion of water in the reservoir by optimizing geometrical parameters, particularly the ramp angle. However, the studies corresponding to ramp shapes geometries have not been adequately reviewed. Most studies only focused on the usage of linear overtopping ramp shape. There is still limited knowledge on the influence of different ramp shape parameters towards the overtopping wave. Thus, this paper aimed to push the border of available knowledge by investigating the influence of the ramp shape parameters to the overtopping wave discharge through simulation and experimenting approaches. Seven different ramp shapes have been tested under Malaysia’s wave condition and a new ramp shape parameter allowing for maximized overtopping wave on OBREC is presented.

Integrated assessment of the hydraulic and structural performance of the OBREC device in the Gulf of Naples, Italy

The aim of this work is to analyze the performance of the Overtopping Breakwater for Energy Conversion (OBREC), developed by the team of the University of Campania and installed at prototype scale in the port of Naples. It is a multifunctional coastal structure aimed to protect harbors and produce energy, based on the overtopping principle. This device has been preliminary analyzed by means of experimental and numerical investigations.This contribution provides for the first time an integrated assessment of the OBREC hydraulic and structural performance, by means of the measurements collected at the prototype installation and of numerical modelling i.e. methodologies not affected by the scale effects. The numerical model, developed in the openFOAM environment, is calibrated on the field data gathered during a storm event and is then applied to extend the information related to the OBREC response under the typical wave climate. The results obtained are proposed in terms of overtopping discharge rates and pressures acting along the OBREC profile, under several sea states.Based on these results some recommendations and indications regarding the optimal cross section design are given to maximize the energy production, without compromising the structural stability, and to promote the device exploitability.

Empirical overtopping volume statistics at an OBREC

The results of a new experimental campaign on an Overtopping BReakwater for Energy Conversion (OBREC) device are presented. Previous 2D model tests carried out at Aalborg University (DK) made it possible to define new prediction methods that were used to design the first OBREC prototype breakwater which has been operating at Naples Harbor (Italy) since January 2016. The new tests were carried out at the Hydraulic Laboratory of the Catania University aiming to provide reliable methods for evaluating the energy extracted by the device. In particular, the new tests investigate the probability distribution of the individual overtopping volumes which enter the OBREC reservoir. The methods presented and validated here allow for a reliable estimate of the time distribution of the input flow, which along with the characteristics of the device, can be used to predict the energy produced by OBREC devices.

Lifecycle Environmental Impact Assessment of an Overtopping Wave Energy Converter Embedded in Breakwater Systems

Overtopping breakwater systems are among the most promising technologies for exploiting wave energy to generate electricity. They consist in water reservoirs, embedded in piers, placed on top of ramps, higher than sea-level. Pushed by wave energy, seawater fills up the reservoirs and produces electricity by flowing back down through low head hydro turbines. Different overtopping breakwater systems have been tested worldwide in recent years. This study focuses on the Overtopping BReakwater for Energy Conversion (OBREC) system that has been implemented and tested in the harbor of Naples (Italy). The Life Cycle Assessment of a single replicable module of OBREC has been performed for analyzing potential environmental impacts, in terms of Greenhouse Gas Emissions, considering construction, installation, maintenance, and the operational phases. The Carbon Footprint (i.e. mass of CO2eq) to build wave energy converters integrated in breakwater systems has been estimated, more specifically the “environmental investment” (i.e. the share of Carbon Footprint due to the integration of wave energy converter) needed to generate renewable electricity has been assessed. The Carbon Intensity of Electricity (i.e. the ratio between the CO2eq emitted and the electricity produced) has been then assessed in order to demonstrate the profitability and the opportunity to foster innovation in the field of blue energy. Considering the impact for implementing an operational OBREC module (Carbon Footprint = 1.08 t CO2eq; Environmental Investment = 0.48 t CO2eq) and the electricity production (12.6 MWh/yr per module), environmental benefits (avoided emissions) would compensate environmental costs (i.e. Carbon Footprint; Environmental Investment) those provided within a range of 25 and 13 months respectively.

FULL-SCALE PROTOTYPE OF AN OVERTOPPING BREAKWATER FOR WAVE ENERGY CONVERSION

The Overtopping BReakwater for Energy Conversion (OBREC) is a new typology of overtopping wave energy converter (OTD) integrated into a traditional rubble mound breakwater. The device can be considered as an innovative non-conventional breakwater that has the same functions as the traditional structures with the added-valued of the energy production. The paper presents a comprehensive overview of the OBREC, offering a synthesis of the complete design process, from the results of the two complementary test campaigns in small scale carried out in 2012 and 2014 at Aalborg University, to the description of the full-scale device installed in Naples in 2016. The device represents the first OTD device in full-scale integrated into an existing rubble mound breakwater and it has been equipped by an instrumental apparatus to measure its response to the wave interaction. The monitoring of the full-scale device in the port of Naples, particularly during storm conditions, is aimed to study the scaling effects in wave loading and the overall performance of this breakwater-integrated OTD, included performance in terms of the energy production.

2DV RANS-VOF NUMERICAL MODELING OF A MULTI-FUNCTIONAL HARBOUR STRUCTURE

This paper is focused on the analysis of a multifunctional structure developed by the Second University of Naples, named OBREC, which is an Overtopping Breakwater for Energy Conversion. The hydraulic and structural performance are evaluated by means of the 2DV numerical model IH-2VOF developed by the University of Cantabria, in terms of average discharge rate, wave reflection coefficient and pressures acting on the structure. The results are compared with the laboratory experiments carried out at Aalborg University (Denmark) and with recent formulae and a new Artificial Neural Network. Furthermore, the numerical model is used to obtain information related to the wave loadings where experimental data were not available. This numerical analysis is a useful support to the ongoing monitoring of the prototype installation in the port of Naples.

Wave loadings acting on innovative rubble mound breakwater for overtopping wave energy conversion

The Overtopping BReakwater for Energy Conversion (OBREC) is an overtopping type wave energy converter, totally embedded into traditional rubble mound breakwaters. The device consists of a reinforced concrete front reservoir designed with the aim of capturing the wave overtopping in order to produce electricity. The energy is extracted through low head turbines, using the difference between the water levels in the reservoir and the sea water level. This paper investigates the nature and magnitude of wave loadings exerting on various parts of the structure. The results improve the overall knowledge on the device behavior, completing the highlights from the complementary test campaign carried out in the same wave flume in 2012 (Vicinanza et al., 2014). The formulas provided have been used to design the first OBREC prototype breakwater in operation since January 2016 at Naples Harbour (Italy).

Numerical Simulation of Wave Flow Over the Overtopping Breakwater for Energy Conversion (OBREC) Device

A number of Wave Energy Converters (WEC) have been proposed by many researchers, but most of them are not economically competitive as a contender in the energy market. This article intends to contribute to the development of very viable concept, which called as Overtopping Breakwater for Energy Conversion (OBREC) aims to fully utilize traditional breakwaters and capturing wave energy. The OBREC and its concept have been physically modeled and tested in Aalborg University since 2012 until 2014 and showed the promising results. In present work, the most-recent CFD of FLOW 3D technology is used to provide a more reliable approach in analyzing wave flow over the structure, in particular, OBREC device. Thus, the numerical simulations are carried out for validating overtopping discharge performance from the previous experimental and prediction methods. The result shows a good agreement with the experimental data. Hence, FLOW 3D is highly capable in handling coastal issues, especially for evaluating overtopping wave parameters.

Economic Assessment of Overtopping BReakwater for Energy Conversion (OBREC): A Case Study in Western Australia

This paper constructs an optimal configuration assessment, in terms of the financial returns, of the Overtopping BReakwater for wave Energy Conversion (OBREC). This technology represents a hybrid wave energy harvester, totally embedded in traditional rubble mound breakwaters. Nine case studies along the southern coast of Western Australia have been analysed. The technique provides tips on how to estimate the quality of the investments, for benchmarking with different turbine strategy layouts and overlapping with the costs of traditional rubble mound breakwaters. Analyses of the offshore and nearshore wave climate have been studied by a high resolution coastal propagation model, forced with wave data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Inshore wave conditions have been used to quantify the exploitable resources. It has been demonstrated that the optimal investment strategy is nonlinearly dependent on potential electricity production due to outer technical constraints. The work emphasizes the importance of integrating energy production predictions in an economic decision framework for prioritizing adaptation investments.

Hydraulic Performance of an Innovative Breakwater for Overtopping Wave Energy Conversion

The Overtopping BReakwaterfor Energy Conversion (OBREC) is an overtopping wave energy converter, totally embedded in traditional rubble mound breakwaters. The device consists of a reinforced concrete front reservoir designed with the aim of capturing the wave overtopping in order to produce electricity. The energy is extracted through low head turbines, using the difference between the water levels in the reservoir and the sea water level. This paper analyzes the OBREC hydraulic performances based on physical 2D model tests carried out at Aalborg University (DK). The analysis of the results has led to an improvement in the overall knowledge of the device behavior, completing the main observations from the complementary tests campaign carried out in 2012 in the same wave flume. New prediction formula are presented for wave reflection, the overtopping rate inside the front reservoir and at the rear side of the structure. Such methods have been used to design the first OBREC prototype breakwater in operation since January 2016 at Naples Harbor (Italy).

Prediction of Energy Performance by Adopting Overtopping Breakwater for Energy Conversion (OBREC) Concept in Malaysia Waters

Prediction of Energy Performance by Adopting Overtopping Breakwater for Energy Conversion (OBREC) Concept in Malaysia Waters

Wave loadings acting on Overtopping Breakwater for Energy Conversion

ABSTRACT Vicinanza, D., Norgaard, J.H., Contestabile, P. and Andersen, T.L., 2013. Wave loadings acting on Overtopping BReakwater for Energy Conversion. Any kind of Wave Energy Converter (WEC) requires information on reliability of technology and on time required for the return of the investment (reasonable payback). The structural response is one of the most important parameters to take in to account for a consistent assessment on innovative devices. This paper presents results on wave loading acting on an hybrid WEC named Overtopping BReakwater for Energy Conversion (OBREC). The new design is based on the concept of an integration between a traditional rubble mound breakwater and a front reservoir designed to store the wave overtopping from the incoming wave to produce electricity. 2D hydraulic model tests were carried out at the Department of Civil Engineering, Aalborg University (Denmark). The analyses of hydraulic model tests have identified the main shapes assumed by wave surfaces at the breakwater ...