Hybrid Power Retrofit for Edison Chouest Offshore

Scope of Work

Turnkey — Design, Approval, Build, Supply, Installation and CommissioningInstalled scope:

• 2 x 4000A shaft generator isolation air circuit breakers
• 2 x 2500A battery energy storage air circuit breakers
• Modification of 450VAC main switchboard control circuits and instrumentation
• Hybrid power management system
• Integrated automation and machinery control system
• New extension alarm system
• New dead man alarm system
• New tank gauging and valve control systems
• Interface to the DP system and the stability and loading computer

Design and engineering:

• Single line diagram
• General arrangement drawings and layouts
• Main switchboard electrical schematics
• Short circuit calculations
• Protection study
• Load balance
• Harmonic analysis
• I/O list and alarm list
• IAS mimic screen design
• PMS system design
• Tank gauging system design

Class approval:

MJR Power & Automation was responsible for DNV approval of the full electrical power and automation design, with FAT of the integrated automation and machinery control system and the power management system carried out at ELSYS in Vigo.

Solutions Delivered

The Starting Point — A conventional AHTS power plant

Two main bus bars at 440V, 60Hz. Two 350kW auxiliary generators, two 2,400 kW shaft generators, and the vessel's thrusters and heavy consumers distributed across the two sides. In normal DP mode the main engines run at constant speed, the bus ties are open, and each shaft generator feeds its own side of the board — port side supplying the stern thruster and azimuth thruster, starboard supplying the bow and stern thrusters.

It works, and it is how these vessels have always operated. It also means the main engines run whenever the vessel needs electrical power, including through long periods of standby when very little of that power is doing anything useful.

The Modification — New breakers, and a board with no room for them

Two changes to the switchboard made the hybrid architecture possible. New air circuit breakers connect each 375kWh battery system to its respective main busbar, and further breakers were added to isolate the shaft generators from the heavy consumer busbars — the latter being what allows the main engines to be shut down while the thrusters keep running.

Both had to be fitted into a switchboard with very limited spare space, in a compartment with no room to extend it.

The First Gain — Peak shaving and spinning reserve

In normal DP mode the batteries sit connected to their busbars in standby. They absorb load peaks that would otherwise have to be met by generation, and they stand as spinning reserve against the loss of a shaft generator or a main engine. That second point is a safety improvement as much as an efficiency one. On a conventional plant, losing a shaft generator during DP means an immediate scramble for power. With batteries connected, the gap is covered instantly.

The Main Gain — Low power loitering with the main engines stopped

The largest savings come when the vessel is standing by outside the 500 metre safety zone. In the hybrid configuration the main engines can be stopped entirely, with two thrusters operated at low power from the batteries and auxiliary generators.

The sequence is worth stating plainly, because it is the heart of the project: the azimuth thruster and one stern thruster are started from the shaft generators while those are still running, the batteries are connected, the shaft generators are then disconnected and isolated by opening the new breakers, and the main engines are stopped. The main busbars are then supplied from the auxiliary generators and batteries, with the auxiliary generators either running continuously in parallel or starting and stopping automatically on battery state of charge, starting at 30% and stopping at 90%.

Other modes are available, including battery-only operation in port with the auxiliary generators periodically starting to recharge.

The Control — Hybrid power management and VAMOS

At the heart of the upgrade is the ELSYS VAMOS vessel automation and machinery operating system, installed together with an advanced power management system to automate the vessel's new hybrid generation architecture. Operator stations were installed on the bridge DP console and in the engine control room, with VAMOS 21" colour LED displays, alongside software synchroscope HMIs fitted to each generator, a local main switchboard HMI, and extension alarm system panels on the bridge and in the crew mess.

Delivery & Approval

Basic and detailed design ran through 2024. Electrical hardware was manufactured at MJR's Teesside facilities and the automation system at ELSYS in Vigo, Spain, where the FAT of the integrated automation and machinery control system and the power management system was carried out.

In late 2024, with the assistance of Navship shipyard in Brazil, MJR Power & Automation and ELSYS carried out the installation and commissioning of the supplied system. MJR was responsible for DNV approval of the full electrical power and automation design, including the upgrade from DPS-1 to DPS-2 with Battery (Safety) notation.

Project Outcomes

Main engines can be stopped during standby.

In low power loitering mode the vessel holds position on two thrusters supplied by batteries and auxiliary generators, with the main engines shut down entirely — which is where the fuel saving comes from.

Class notation upgraded from DPS-1 to DPS-2.

With Battery (Safety) notation. The vessel became eligible for work she previously was not, which is a commercial outcome rather than a technical one.

Peak shaving and spinning reserve in normal DP.

The batteries absorb load peaks and stand ready against the loss of a shaft generator or main engine, improving both efficiency and safety during normal operations.

Battery-only operation in port.

With auxiliary generators starting periodically to recharge — removing engine running, noise and emissions alongside.

A modern automation platform across the vessel.

VAMOS operator stations on the bridge and in the ECR, extension alarm panels, dead man alarm, tank gauging and valve control, with interfaces to the DP system and the stability and loading computer.

A twenty-year-old vessel positioned for the next decade.

The conversion addresses the operating cost and emissions profile that increasingly determines whether an older vessel keeps winning work.