Power take-off and electrical export

The Pliosaur Energy electrical system has been designed around a simple principle: use proven technology wherever possible and focus innovation on the engineering challenges that are unique to marine renewable energy. This approach reduces technical risk, avoids unnecessary development expenditure and supports a more reliable route to commercial deployment.

Electrical Power Take-off

The Pliosaur Energy turbine rotates at a very low speed of approximately 1–2 rpm, producing mechanical power at exceptionally high torque. Converting this slow, high-torque rotation into electricity presents a significant engineering challenge, particularly where installation space is limited and bespoke generating equipment would be costly to develop.

Our solution uses a large-diameter ring gear attached to the side of the turbine rotor. The ring gear drives a smaller spur gear at approximately 30 rpm, bringing the rotational speed into a range comparable with that used by established wind turbine drivetrains.

The spur-gear shaft is designed to connect with a proven wind turbine gearbox and generator assembly. By adapting existing technology rather than developing an entirely bespoke drivetrain, Pliosaur Energy can reduce development cost, shorten the engineering programme and benefit from equipment that already has an established operating history.

The use of a conventional wind turbine gearbox also provides an integrated braking system, removing the need to develop a separate turbine-rotor brake.

Modular Electrical Architecture

The electrical system forms part of Pliosaur Energy's wider modular platform architecture. Reinforced-concrete platform sections are constructed onshore, floated to site and connected together to form a much larger offshore generating structure.

This approach enables much of the structural and electrical integration work to be completed under controlled onshore conditions, reducing offshore construction complexity and allowing generating capacity to be increased by adding further modules.

The use of reinforced concrete also reduces the corrosion and coating-maintenance requirements associated with conventional steel floating structures. Because the platform is intended to remain offshore throughout its operating life, it avoids the need for routine dry-docking and the disruption and cost associated with towing a large generating asset back to port.

Intra-array Cabling

Within a Pliosaur Energy array, turbines are arranged in a line and connected by electrical cables routed between the generating units. This reduces the extent of seabed cable excavation required within the array and limits disturbance to the marine environment.

Keeping the intra-array connections accessible also simplifies inspection, maintenance and replacement compared with electrical systems that rely extensively on buried subsea cables. The arrangement reduces exposure to seabed movement and avoids the need for a separate voltage-limiting inductive coupling at every turbine.

Fixed Electrical Export

Dynamic export cables are one of the principal engineering challenges associated with floating offshore renewable energy. Where a cable is connected directly to a moving floating structure, continual movement caused by waves, tides and platform motion can create repeated bending and fatigue.

Pliosaur Energy's large modular platform allows the electrical export system to be arranged around a dedicated seabed-mounted caisson with a switchroom positioned above the waterline. The array cable is connected to the fixed export point, while the main export cable runs from the caisson to shore.

By transferring the principal export connection from the moving platform to a fixed structure, the design reduces dynamic cable movement and removes a major source of fatigue, subsea intervention and lifetime maintenance cost.

The caisson also provides an accessible location for electrical switching, protection and isolation equipment. Maintenance can therefore be undertaken from above the waterline rather than through complex subsea operations.

Integration with Offshore Wind Infrastructure

A Pliosaur Energy array could be installed within or alongside an offshore wind development, subject to site-specific engineering, environmental assessment and grid-connection requirements.

With suitable modification, the Pliosaur Energy export system could connect through an offshore wind turbine foundation or dedicated electrical caisson. Generated power could then be exported through uprated shared infrastructure or through a parallel cable route to the offshore or onshore substation.

Combining marine and wind generation could improve the utilisation of existing electrical infrastructure and provide a more diverse renewable-energy supply. Because tidal generation is predictable and wave conditions do not necessarily coincide with peak wind output, the technologies may provide complementary patterns of electricity generation.

Reduced Seabed Intervention

The principal buried cable requirement is the export connection between the fixed offshore caisson and the shore or grid-connection point. Reducing the amount of cable excavation within the generating array lowers installation complexity and helps minimise disturbance to seabed habitats.

The turbine can operate in comparatively shallow water while the floating platform concept also allows deployment in deeper locations. This flexibility creates the potential to position arrays closer to suitable grid connections where environmental, navigational and planning conditions permit, reducing export-cable length and improving project economics.