One of the goals set in the DeRisk project focusses on biofouling. Biofouling is a difficult phenomenon to predict as it varies significantly from region to region, and from season to season. It is most problematic at depths of 0-40m, which is a zone rich in plankton and oxygen, and with high levels of light.
The ocean rods on the CorPower Ocean WECs are subject to biofouling, which can, in the best case, increase friction between the seals and the rods, and in the worst case, damage the dynamic sealing systems. Neither of these outcomes are desirable, and therefore different strategies for removing biofouling are being investigated.
One of the strategies to remove biofouling is by mechanically scraping the rods using scraping components in the sealing system. It is important to understand the relation between how often this scraping needs to be done, how much
excess friction is created over time, and how much hard fouling can be tolerated by the sealing system. All of these have a direct impact on the operations and maintenance cost of the WEC system, which in turn affects the levelised cost of energy (LCOE).
To investigate these phenomena a test campaign is planned in which scaled ocean rod samples will be deployed in the water at two test sites: one at the Kristineberg Center for Marine Research and Innovation on the west coast of Sweden, and one in Lisbon, Portugal.
The samples will be deployed for a total of 12 weeks, and will be mechanically scraped at various intervals using a bespoke scraping rig (shown in the pictures below), which will measure the friction required to remove the fouling.
The samples themselves consist of a rod and a scraping system. The rods are coated with the same metal alloys used to coat the WEC ocean rods, and the scraping ring is a scaled version of the seal gland on the WEC.
By testing at two different sites simultaneously it is hoped that the differences between fouling in different regions can be assessed.
The test campaign will run over the course of the summer to align with the barnacle season, with final scrapings planned for September 2021.