New materials for wave energy substructures

The aim of the project was to develop a method for protection of subsea offshore structures against corrosion and scour. The method involves the production of a protective layer “Seacrete” on subsea steel structures by electrochemical deposition. One of the goals of the project was to investigate the production of Seacrete in the laboratory and subsequent demonstrate the technology under real conditions. Seacrete is mainly composed of the minerals Aragonite (CaCO3) and Brucite (Mg(OH)2) and the ratio between the constituents was found to be highly important for the material properties. In the project a model was developed capable of predicting the composition and amount of material produced based on water temperature and applied current density.

Field tests were conducted at two sites in Denmark (Nissum Bredning and Hanstholm) and one site in the North of Italy (Isola di Bergeggi) representing cold and warmer water regions respectively. In both cold and warm water locations material was deposited on the structures which was composed of a mixture of aragonite and brucite. The cold-water location produced less material with higher aragonite fraction. Material with high fraction of aragonite was found to have similar properties to concrete, and thus may be implemented in some structural applications in constructions as a sustainable alternative to cementitious materials.

A Design Concept was developed featuring Resenwaves wave energy technology coupled with mineral deposition technology for an offshore installation at Hanstholm harbour. Using only 1-2% of the total energy produced for a 3kW wave energy unit, it is expected to be possible to protect the subsea structure
and at the same time create an artificial reef. With a preliminary life cycle assessment, we could verify that the potential for CO2 reduction compared to the use of concrete is significant.