On Design and Building of a U-OWC Wave Energy Converter in the Mediterranean Sea: A Case Study

Abstract

Since the nineties, the OWC (Oscillating Water Column) plants were developed at full scale to produce electrical power from ocean waves [1]. A prototype was built into a caisson breakwater of the Sakata Port, in Japan; other plants were built in India, in Scotland at Islay, in Portugal at the Azores. A new plant was built in Mutriku (Spain) recently. A new kind of OWC caisson, named U-OWC or REWEC3, was proposed by Boccotti [2]. With respect to a traditional OWC, a U-OWC plant includes an additional vertical duct, which enables to tune the eigenperiod of the plant to the peak period of the wave pressures acting on the converter-breakwater. In this way, resonance conditions can be reached without phase control devices and the wave pressures into the air pocket are increased in amplitude, amplifying the performance of the plant. In 2012, a full scale U-OWC (REWEC3) breakwater has been designed in Italy, for the harbour of Civitavecchia (the port of Rome – Port Authority of Civitavecchia). Such a breakwater embodies 19 caissons, each including 8 cells, 34m long. The paper disseminates the key issues pertaining the design stage. Further, it describes the main phases of the construction stage. The building of the caisson started in October 2012. The first caisson has been completed at the end of 2012. It is the first device for wave energy in the Mediterranean Sea and one of the biggest in the world.

Wave Energy Exploitation System Integrated in the Coastal Structure of a Mediterranean Port

“…This breakwater embodies 19 caissons, each including 8 cells, 34 m long [22]. The vertical duct is 1.60 m wide and the U-duct opening is located 2.00 m below the mean water level, so that the opening is not always below the free surface; the pneumatic chamber is 3.20 m wide.…”

“…In this way, the flux of air crosses a turbine which can operate in both directions [16][17][18][19][20]. Additionally, the U-OWC system presents a further vertical duct, before the air chamber, which increases the oscillating period of the system and makes such a period close to the typical wave periods of sea waves, so increasing the overall performance of the device [21,22].…”

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

“…A new kind of OWC embedded into a caisson breakwater, named REsonant Wave Energy Converter 3 (REWEC3), is under construction at the harbour of Civitavecchia in Italy. The REWEC3 prototype is the first full-scale WEC incorporated into a caisson breakwater in the Mediterranean Sea and one of the biggest in the world [11]. The cost is funded by the Port Authority of Civitavecchia and by the Italian Government.…”

“…A great number of wave energy converters (WECs hereinafter) have been developed over the last twenty years in order to transform wave energy into electrical energy (e.g., [1][2][3][4][5][6][7][8][9][10][11][12]). Despite large efforts made by several countries, none of these innovative technologies is ready for the commercial stage.…”

Full-Scale Prototype of an Overtopping Breakwater for Wave Energy Conversion

“…The first two devices consist both of an oscillating water column (OWC) systems integrated into vertical breakwaters situated at the port of Mutriku in Spain (Torre-Enciso et al, 2009;Torre-Enciso et al, 2009) and the port of Civitavecchia in Italy (Arena et al, 2013).…”