FAQ | Charge Offshore

Fundamentals

Operations

Installation

Safety Integration

Economics

Fundamentals

Why is offshore charging considered essential for wind O&M fleets?

Regulatory bodies are gradually introducing greenhouse gas emission reduction requirements for vessel operations, with high taxes or fines imposed on non-compliant fleets.
Battery-powered vessels (fully or partially) address that issue, without the requirement for a high-CAPEX & OPEX supply chain to provide alternative biofuels/hydrogen to shore bases or quaysides.
A single charge at port will not provide sufficient autonomy for a CTV or SOV to operate fully electrically without burning alternative fuels, so offshore charging infrastructure enables flexible, fast, and safe battery pack deep charging in the field.

Can offshore charging enable CTVs and SOVs to operate entirely electrically at wind farms?

Yes, the 0.5MW to 8MW charger product range enables fast charging of the vessel battery pack during operational idle periods.
Charge Offshore can assist operators and vessel owners with battery pack and charger sizing assessments, based on expected operational profiles and vessel consumption estimates, to help them choose the best Aquarius product.

Can charge offshore design and supply electrical and control systems to interface with any asset and vessel configuration with the charger?

Yes, Charge Offshore, with 25 years of expertise in delivering marine electrical systems, can design and supply any of the required specific ancillary interface systems for both asset and vessel sides.

Typically:

Transformers and protective gear
Power regulation units to connect to the Vessel bus bar
Switchgear
PMS and AIS

Operations

What are MetOcean's limitations for charging?

CTVs can connect when able to push on briefly at the boat landing (Hs 2m to 2.5m, CTV capabilities dependent). Charge and disconnection have a higher threshold, as no push on is required.
SOVs can connect in sea states above the limits for personnel and cargo transfer (Hs 3m to 3.5m; SOV capabilities dependent). Charge & disconnection have higher thresholds limited only by SOV's ability to hold station.
Charger location on the asset is optimised to allow for the widest weather-vanning charging sector. This guarantees the vessel can maintain a safe “blow away from asset” position in prevailing tidal/wind conditions.

Can the vessel charge if there is no wind or the turbine is not operational?

Yes, the charger is supplied from the array network connected to the grid, guaranteeing permanent availability of charging power.

What happens if the vessel is unable to charge?

As per classification society requirements, vessels will always have backup emergency generators capable of temporarily charging batteries or providing propulsion and hotel load until charging is possible, or allowing for the safe return to the shore base.

Can a single charger unit service both CTVs and SOVs?

yes :

It can be used in a standard set-up for equipment up to 2.5MW
For requirements above 2.5MW, an additional voltage-step-down transformer is required on the asset to serve the high power SOVs.

What are the maintenance requirements, and how durable is the system

The on-asset charger design ensures equipment remains accessible and free of the splash zone at all times, minimising OPEX.
The system is designed for durability, using proven, standard marine-grade gear and main dynamic components that are subject to an intensive fatigue-testing programme.
Routine visual inspection can be performed by the operator’s maintenance team every six months after a simple familiarisation training programme from Charge Offshore.
Yearly maintenance is performed by a team of two Charge Offshore personnel with regular tooling. All components can be split and re-fitted onsite for easy replacement in case of failure or wear, without requiring a return to shore.

Installation

Where is the charger installed, and how many are needed on site?

Chargers can be installed on any fixed offshore infrastructure: TP, offshore substation (OSS), dedicated small-pile, or even a decommissioned TP.
Installation on newly built farms where integration is considered at the design stage is straightforward and economical.
Retrofitting to existing fields is possible in most cases for substations. The charging capacity limit will be driven by charging power and the availability of integration locations on the asset.
The standard recommendation is 2 chargers per field for redundancy and access optimisation under all weather conditions. If installed on an OSS, both chargers can share a common power supply to optimise CAPEX.

What are the typical requirements for installing a charger on an offshore asset?

- Asset charger characteristics:

Equipment weight: 12T
Max. live operational loads on charge cable: 4.5T max
Reserved volume: 3.8m Width x 4.5 Long x 3.5 High
Mounting base footprint: 1.5m x 1.5 m

- Power supply from the asset to the charger unit :

6.6 kV AC 3 Ph for chargers up to 4MW
11kV AC 3Ph for chargers 5MW to 8MW

- Communication :

Optional intranet connection to allow Operator real-time monitoring & management of charge operations from shore control DCS/SCADA system.

Can a charger be installed at any stage during the life of the field?

Yes, provided the asset has been designed “charger-ready”.

Safety Integration

How safe are offshore charging operations for personnel, assets, and vessels?

The system has gone through extensive failure mode and effect analyses, and solution robustness has been validated through comprehensive onshore and offshore validation programmes, with key focus on:

Fully unmanned operations are controlled by a vessel bridge crew: no manual handling required, and no personnel exposed to hazard at any stage of the process.
Charge cable tension under strict control through redundant passive and active load control mechanisms - guaranteeing neither asset, vessel, nor charge system is overloaded above the design threshold.
Several levels of manual, automated, and passive emergency disconnection systems will fully release the vessel from the charger in less than 3 seconds, even in a full blackout.
Vessel remains at a safe distance and in a “blow away” position from the asset throughout the whole charging process.
A strict electrical isolation philosophy guarantees that an electrical fault cannot propagate to the asset or vessel systems.
The charger can be reconnected immediately after an emergency release, without any maintenance or cleaning required.

Does the equipment hold the necessary certification for installation on both assets and vessels?

The system is built in compliance with all relevant DNV and IEC marine codes.
Key components are DNV-type approved. Type approval for the whole system has been submitted.

Economics

Are electrical O&M fleets economically viable?

Yes:

Vessel CAPEX:

Hybrid -fully electrical CTV and SOV fleets are growing, and with battery pack pricing dropping steadily, e-vessel build CAPEX is equalising fast with standard diesel versions.

Vessel OPEX:

The offshore energy offtake price vs diesel is the central economic lever. Behind-the-meter charging from the wind farm itself can deliver energy at marginal cost (~£0–10/MWh during curtailment, or avoided CfD top-up payment value), versus marine diesel on an equivalent energy-content basis.
Even at full grid export price (~£90/MWh @ Cfd 2024), electricity remains 2 to 3 times cheaper per MWh than diesel at low 2025 rates.
The ratio becomes even more favourable with ETS taxation already in force for large SOVs and when oil prices become volatile.
This differential alone can recover any CAPEX premium within a few years on a high-utilisation SOV.

Charger infrastructure CAPEX:

Charger CAPEX can, in large part, be offset through UK or EU Grants and Incentivization Schemes.

What are the installation CAPEX and licensing requirements?

On-asset charger integration requires minimal CAPEX at newly built sites when interfacing is considered during asset design.
Licensing is simple, as no additional subsea infrastructure is required (cables, anchors, trenching, rock dumping). Additionally, the charger does not interfere with navigation & does not introduce any environmental or visual disturbances.

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