Background

The mooring system is one of the most critical sub-systems for a floating offshore installation. Highly-dynamic floating bodies such as marine sensors, aquaculture platforms, floating wind, wave and tidal flow energy convertors require mooring lines with particular mechanical properties; the mooring system must achieve adequate station keeping whilst controlling mooring tensions within acceptable limits. This can be achieved through conventional mooring solutions, however these systems are highly complex and have large mooring footprints. This in turn presents a high cost of mooring for highly-dynamic floating bodies.

The dilemma for floating offshore installations such as marine renewable energy devices is that the capital cost of the mooring system is driven by extreme (peak load) conditions, whilst the revenue is generated under normal operating conditions. If peak loads can be mitigated the cost of mooring systems and associated structural elements, as well as deployment and installation costs, can be significantly reduced.

Technology Overview

The “Exeter Tether” is a novel elastomeric mooring tether designed to manage marine infrastructure such as renewable energy devices, aquaculture platforms, vessels and sensor buoys located in highly dynamic marine environments.

The invention functions with a significantly lower axial stiffness than conventional mooring systems by decoupling axial stiffness from the minimum breaking load of the line. By reducing axial stiffness, a reduction in mooring system stiffness is achieved along with a reduction in peak and fatigue loads without increasing mooring system complexity. Reducing these loads improves system reliability and allows a reduction in mass of both the mooring system and the floating body, thus reducing costs.

Benefits

Reduced axial stiffness resulting in a reduction of mooring system stiffness providing a reduction of peak and fatigue loads, without increasing mooring system complexity
Reducing these loads allows for improved system reliability
Reduction in mass of both mooring system and the floating body
Reduction in mass further reduces costs

Applications

Offshore renewable energy developments – wave energy, off shore floating wind energy, tidal flow energy, maritime operations, aquaculture.

State of Development

Results demonstrate that the Exeter Tether can be configured to achieve a significantly lower axial stiffness than conventional fibre rope and that the stiffness is selectable within limits for a given breaking strength.

The Tether is currently being deployed in the Bay of Biscay within the OPERA project, a European Union Horizon 2020 research and innovation program. The project aims to develop technology to enable a reduction in offshore operating costs, paving the way for a 50% long term reduction in costs, thus accelerating the establishment of international standards and reducing technological uncertainties and technical and business risks.

Opportunity

The University is seeking to license the technology and continue industrial research in collaboration with industry partners.

A Novel Mooring Tether for Highly-Dynamic Offshore Applications

Patents

IP Status

Seeking