Variable speed generator ‘hits the sweet spot,’ reducing fuel consumption on CSOV

The first use of the VSG, on Olympic’s new commissioning service operation vessel (CSOV) Olympic Boreas, has resulted in what Ulstein Group described as "record-low" fuel consumption of 2.7 tonnes a day during a week of DP operations.
“Running the engines at variable speed optimises power production based on the vessel’s energy demand,” said Ulstein. “Technical measures on board have reduced power demand to 250-300 kW under certain conditions.

“With such low power requirements, variable speed is significantly more efficient than constant speed, contributing to greatly reduced energy consumption per kWh produced.”

Developed by Ulstein Power & Control, the VSG improves fuel consumption, reduces emissions and improves overall performance, while also reducing maintenance costs.

“The shipowner experienced big fuel savings on Olympic Boreas,” said Ulstein Power & Control, citing a near 50% reduction in fuel consumption compared with other CSOVs.

The VSG makes use of advanced load sharing between fixed and variable speed generators operating in parallel. Unlike conventional fixed-speed generators – which operate at a constant speed regardless of demand – the VSG dynamically adjusts its speed to match load requirements, delivering power to the ship’s grid in what the Norwegian company described as “the sweet spot of energy efficiency.”

The company describes the VSG powertrain as "the core component of the system," adjusting the generator’s rotational speed to deliver optimised power output based on real-time demand.

For quick response, an energy storage system supports dynamic power demand during more challenging operations. A power and energy management system monitors and controls the generator’s speed and use of the energy storage system, ensuring enhanced performance and efficiency.

The company says the VSG is suitable for a wide range of vessels, including offshore vessels, expedition cruise vessels and aquaculture vessels.