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Feasibility analysis to identify the most suitable method of providing power to the subsea control and monitoring system for the Perth Wave Energy Project

Le-Ray, Antoine (2012) Feasibility analysis to identify the most suitable method of providing power to the subsea control and monitoring system for the Perth Wave Energy Project. Internship Report, Murdoch University.

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Abstract

In April of 2011 CWE successfully tested CETO 3, completing the first stage of the Perth Wave Energy Project.

Stage 2 is a 2 MW grid connected plant. This plant will consist of up to 5 fifth generation CETO units deployed in 24 m water off the Coast of Garden Island with a plant to be constructed on the shore to facilitate the power generation and grid connection.

This document investigates the options for powering the offshore monitoring and control system. Various options were assessed and it was found that a grid connected hybrid umbilical running from the shore to the PLEM was the best option. Different voltage and power regimes were considered, and quotes sought from different vendors.

Legal requirements from relevant standards were established for the subsea power system, particularly with regards to design, safety and earthing.

A final system was chosen after analysing the system requirements and comparing it against the vendor's offerings. Once established this was then modelled to ensure compatibility. Further system design showed that the successful operation of the subsea power distribution system will rely on the operation of the node controller to manage the instantaneous power levels and implement safety and protection measures. These protection measures are required for maintenance and reliability and will allow divers to safely work on the subsea system.

The final design was for a 240 to 1200 VAC transformer located onshore, power transmission over a hybrid umbilical cable, stepping back down to 240 VAC at the PLEM, and finally, distribution to the individual pods at 240VAC. This system is controlled and protected by a node controller, which is required to limit the peak power and manage faults. The whole monitoring and control system should be installed in parallel with the mechanical components to allow for removal and maintenance of any item without having to move attached hardware. The longest lead time was for the Hybrid Umbilical at 16-18 weeks.

This feasibility analysis has shown the range of parameters that should be considered to develop a reliable subsea power system to power a small load. It has also shown the range of prices associated with different technologies and design options. The final cost of the system was $343,975.8 for the 1200 VAC system compared to $353,790.0 for the 900 VDC system. The bulk of this cost is associated with the cabling and not particularly sensitive between AC and DC. The advantages of DC may prove to be more attractive under different circumstances.

Publication Type: Internship Report (Bachelor of Engineering)
Murdoch Affiliation: School of Engineering and Energy
URI: http://researchrepository.murdoch.edu.au/id/eprint/13107
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