Tidal stream energy

Patent publication No.: 3090753

“SUPPORTING STRUCTURE FOR THE TRANSPORT AND IN SITU INSTALLATION OF MARINE ENERGY CAPTURE MODULES”

(Official French title: « STRUCTURE PORTEUSE DE TRANSPORT ET D’INSTALLATION IN SITU DE MODULES DE CAPTAGE D’ÉNERGIE MARINE »)

Tidal stream energy is clean, inexhaustible, regular and highly predictable. The Channel area — particularly Normandy, the Channel Islands and the United Kingdom — has one of the strongest tidal resources in Europe. It is therefore well placed to make tidal stream energy a strategic component of a secure, low-carbon energy mix.

In its tidal stream version, HydreManche® is a ballastable offshore support structure designed for relatively straightforward construction using proven materials such as concrete and steel.

Functional advantages

  • The HydreManche® support structure can be adapted to existing tidal turbine technologies.

  • Each tidal turbine module frame is connected to ballastable caissons. Their buoyancy can be controlled by compressed gas during the installation or removal of the HydreManche® support structure. The combined assembly — support structure and tidal turbine modules — forms a particularly stable self-supporting offshore structure.

  • The combined effects of a very low centre of gravity and a very low point of application of the hydrodynamic loads generated by the current reduce the overturning moment and make it possible to install the support structure on high-current sites.

The use of the HydreManche® support structure can significantly increase productivity by enabling the exploitation of powerful tidal currents and allowing installation on irregular seabeds, including slightly sloping seabeds. Its high stability in floating mode can also widen the usable weather windows for offshore operations.

The electrical connection of the machines is grouped into a single connection.

  • By considerably reducing towing operations and avoiding offshore lifting and subsea works during installation, maintenance and decommissioning, the HydreManche® support structure offers improved reliability and safety by helping to prevent and reduce accident risks throughout its operational life.

Economic advantages and productivity gains through shared infrastructure and array-based design

The HydreManche® support structure can potentially accommodate between 3 and 20 tidal turbines, depending on port infrastructure and on the power rating of the selected machines. By grouping several tidal turbine modules on a single support structure, transport and installation costs can be significantly shared and reduced per installed turbine.

Significant reduction in installation and decommissioning costs

  • Thanks to its ballast system, the HydreManche® support structure does not require offshore lifting operations during installation, maintenance or end-of-life decommissioning.

  • Grouping several tidal turbines on a single HydreManche® support structure can substantially reduce installation, removal and decommissioning costs per power-generating module. For example, under conventional arrangements, the installation and subsequent removal of 14 tidal turbines would require a total of 28 offshore lifting operations (2 × 14), together with numerous towing operations. With the HydreManche® support structure, such operations can be reduced, in principle, to one tow-out and one tow-back phase, with no offshore lifting required.

Eliminating offshore lifting operations also reduces weather-window constraints.

Significant reduction in operating maintenance costs

Operating several HydreManche® support structures, with the possibility of on-site module swap-out, could help avoid prolonged interruptions in electricity production. The premature failure of one or two turbines mounted on a support structure would not necessarily require the immediate replacement of the entire structure.

The HydreManche® concept therefore makes it possible to adopt a preventive maintenance strategy, with maintenance intervals genuinely adapted to machines exposed to demanding subsea conditions.

Construction and deployment rooted in the regional industrial base

Manufacturing, maintaining and operating tidal stream energy can support long-term, skilled and rewarding jobs. The HydreManche® concept is well aligned with the capabilities already present in Normandy and, more broadly, in the Channel maritime area: port infrastructure, marine operations, civil engineering, metalworking, offshore maintenance, SMEs and mid-sized companies.

The United Kingdom and the Channel Islands, which share the exceptional tidal resource of the Alderney Race / Raz Blanchard area, could also play complementary roles through project development, finance, marine operations, monitoring and maintenance coordination.

 

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