RINA Proposes Fuel-Flexible Mermaid Hybrid Ship Architecture

A new approach to a commercial vessel

RINA has unveiled Mermaid, an energy-system concept designed for ships facing an uncertain fuel transition. Its August 2026 report describes a propulsion architecture that can use the main engine for onboard electricity generation.

The concept is developed for commercial ships and should not be treated as a ready-made propulsion package for superyachts. It is relevant as part of the wider engineering discussion on how vessels handle varying loads.

Making more of the main engine

The arrangement combines a shaft generator, a clutch in the propeller shaft and battery energy storage. In port, the propeller can be disconnected while the main engine supplies electrical power or charges batteries.

RINA argues this can reduce reliance on less-efficient auxiliaries under certain operating conditions. The benefit depends on the actual vessel’s machinery, load profile and operational pattern.

Energy flexibility over a vessel’s life

The concept also aims to match propulsion equipment more closely to reduced-speed operation and provide resilience through stored electrical energy. RINA describes it as fuel-agnostic, giving owners options as future rules and fuels evolve.

Its published claim of savings exceeding 1,000 tonnes of fuel per year applies only to some commercial applications. Such a figure must not be transferred to a yacht or quoted as a universal reduction.

Why the wider industry should watch

Hybrid systems, energy storage and resilient hotel power are also areas of interest to larger yacht designers. Different engine types and operating profiles require independent engineering rather than direct adoption of a commercial vessel’s solution.

RINA’s official press release and Mermaid-specific concept image establish what has been proposed. Independent vessel-specific analysis is needed before any application to yacht design.