Work Package 6

Lifetime offshore logistics


Objective: To reduce uncertainty on, and optimise, risk and cost of offshore operations.

In offshore wind OPEX is roughly a third of cost of energy, of which offshore operations typically is the major contributor. Offshore operations also have a major impact on Life Cycle CO2 emissions. Although similar importance is expected in wave energy farms, the lack open-sea experience shared across the sector introduces major uncertainty on expectable OPEX in wave farms, which introduces a costly business risk in wave energy projects. Documenting and sharing information on offshore operations in OPERA is a major opportunity to achieve decisive progress on this front.

This Work Package focuses on lifetime offshore logistics of floating OWC with a goal to reduce the uncertainty on, and optimise, the risk and cost of offshore operations.

For these purposes, this Work Package will:

  • Improve operational models to more precisely reflect logistic requirements for floating OWC
  • Identify and optimise maintenance and operational procedures to lower life-cycle costs
  • Perform, improve and document required offshore operations during the open-sea testing period
  • Provide figures for OPEX calculation based on real open sea operations
  • Produce guidelines and recommendations that minimise risk and cost of offshore operations for wave energy

Task to be performed

Logistics needs characterisation

The characterisation of the installation, operation, maintenance and decommissioning of the device will be based initially on the procedures carried out for its deployment and testing at real sea (i.e. baseline prototype configuration) and adapted to specific OPERA requirements. In particular, this task will update the initial planning of maritime operations developed by OCEANTEC prior prototype deployment and produce:

  • Detailed inventory of offshore operations needed
  • Hazard identification, risk assessment and mitigation actions
  • Planning and scheduling of maritime operations
  • Required functional and operational specifications of vessels/equipment and competences of key people
  • Weather window thresholds for the various marine operations depending on the vessel, HSE and activity being performed
  • Applicable codes, standards, legislation and recommended practices (including environmental issues)

Installation includes on-site port activities before the device is deployed at sea, device towing, heavy lifting or submerging, ballasting, securing to the seabed and connection to the grid. Apart from the device itself, installation operations will also encompass wave resource instruments, mooring, and turbine, generator and power electronics. Operations will comply with bimep procedures and international regulations.

The inspection, repair and maintenance levels/frequency will be adjusted to the reliability considerations of the prototype and the limitations on weather windows accessibility to the site, including provisions for emergency situations. Unscheduled maintenance actions will be simulated in order to reduce risks and estimate realistic operating costs. In-service inspections and small repair will be done onsite, whereas large maintenance actions will be done at Bilbao port. Decommissioning operations and costs will be considered with attention to the expected duration of a commercial project and its consequences on the lifetime cycle.

Improve offshore logistics and cost models

Existing operational models for the estimation of the OPEX will be refined with data collected under real operating conditions. However, since most components are not expected to fail during the project life (2-3 years of operating data) service life will be estimated based on data collected, main drivers for components fatigue (e.g., operating temperature and peaks for the power conversion chain, loads in the mooring, etc.) and indications of the personnel involved in the operations (e.g. mariners, offshore crew, port authority etc.). The SCADA condition monitoring system will be customised to trigger alarms base on real operating conditions.

The operational model in this work package will be focused on the cost of offshore operations, whereas the cost of components to be replaced and other running costs such as insurance will be integrated in the overall cost model in WP7. The task will also collect information from all the other WPs on the probability of failure and the need for replacement of the equipment on board. Results will be used to feed into operational models for the OPEX calculation and O&M scheduling and will be validated against the effective failures and replacements occurring on site.

Modelling site accessibility assessment with estimation of weather windows and validation against real sea operations is also necessary to realistically assess the waiting time and costs. The analysis of maritime strategies will be completed using models for the operational simulation of offshore renewable devices when it is not possible to gather this information directly from the open-sea experience (limited to a single unit). These tools might include optimisation methods and techno-economic analysis to aid in the decision making and will be validated against the case offered by the real sea operations at bimep.

Monitoring of safe offshore operations and logistics

The implementation of all phases of the offshore operations will be carefully monitored and documented to update and reduce the uncertainty on the initially identified risks and risk levels. Current procedures applied at the test site will be analysed and checked against existing standards and regulations from the offshore industry. Applicability of existing guidelines from offshore oil and gas will be reviewed also in consideration of the health and safety requirements for renewables. The approach for risk assessment implemented in the project will have identified prior to commencement of the test programme failure modes and survival scenarios (such as hull breach situations, mooring failure and power take off malfunction). Real operations will be analysed to reduce time and associated equipment to produce a more cost-effective and risk-free solution.

The plan of offshore activities developed in the first task will be compared with the real operating experience. Detailed monitoring and recording will be used to systematically identify opportunities for better specifying required vessels, diver and equipment, dock and crane, and necessary weather windows. The planning of offshore operations will be continuously updated with this information and the reduction in uncertainties achieved from open-sea implementation recorded to be used for final project assessment by WP7.  Subcontracting to vessel/equipment and qualified personnel will follow standard offshore procedures and practice with the constant concern and record to identify specific requirements for wave energy as well as specific opportunities for cost-reduction.

Recommendations and guidelines

The offshore logistics and procedures documented will be synthesized as actionable recommendations, focussing on decision-support and uncertainty reduction for issues facing wave energy project developers at various levels. Specific issues will include de-risking operations, evaluation of site accessibility, refining assessment of vessel access limits, optimising maintenance schedule and grouping operations, spare part storage, conditions-based monitoring and contingency plans. Practical lessons will be included such as recording of maritime operations and design requirements to facilitate maintenance operations such as easier connection/disconnection, safer design access and necessary room for maintenance operations inside the hull.

Where they are important, these newly de-risked specifications for wave energy shall be compared to relevant offshore oil & gas requirements, which still guide maritime operations in ocean energy despite presenting fundamentally different risks to human life and the environment. The offshore logistics experience will be extrapolated to different scenarios of larger deployment using state of the art methods and in particular the wave farm design tools developed by the H2020-DTOcean project, with a view to better assess economies of scale and identify logistics bottlenecks when deployed in large arrays.

Involved Partners

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654.444