Robert Ewan Harris

CONTROL OF LOW-FREQUENCY MOTIONS OF SINGLE-POINT MOORED VESSELS

This paper describes the development of a number of control systems which aim to reduce the peak hawser loads in a single-point mooring system. Two fundamentally different methods of achieving this objective have been evaluated using instrumented scale models in a wave basin facility. The first involves control of the low-frequency motions of the vessel with the aim of suppressing the low-frequency component from the hawser force record. The second technique involves the deployment of an active tension compensation device fitted to the mooring winch to suppress the wave frequency component of the hawser force. The paper outlines the control theory and experimental work performed with a PID controller and self-tuning regulator .

Biodiversity characterisation and hydrodynamic consequences of marine fouling communities on marine renewable energy infrastructure in the Orkney Islands Archipelago, Scotland, UK

Abstract As part of ongoing commitments to produce electricity from renewable energy sources in Scotland, Orkney waters have been targeted for potential large-scale deployment of wave and tidal energy converting devices. Orkney has a well-developed infrastructure supporting the marine energy industry; recently enhanced by the construction of additional piers. A major concern to marine industries is biofouling on submerged structures, including energy converters and measurement instrumentation. In this study, the marine energy infrastructure and instrumentation were surveyed to characterise the biofouling. Fouling communities varied between deployment habitats; key species were identified allowing recommendations for scheduling device maintenance and preventing spread of invasive organisms. A method to measure the impact of biofouling on hydrodynamic response is described and applied to data from a wave-monitoring buoy deployed at a test site in Orkney. The results are discussed in relation to the accuracy of the measurement resources for power generation. Further applications are suggested for future testing in other scenarios, including tidal energy.