The desire of owners to enjoy nature and the world’s finest panoramas to the full is inspiring many shipyards to build yachts fitted with hybrid propulsion systems, to contribute to more sustainable and eco-compatible cruising and to preserve the planet for future generations
by Gian Piero Repetti
A PROMISE IS A PROMISE! The promise I made was to discuss real-world hybrid propulsion projects, hands-on solutions and my experience in the field in recent years. Our dream is of cruising in silence and perhaps being able to contribute to more sustainable and eco-compatible yachting. I’ll be speaking of my personal impressions rather than drawing up a ranking or making judgements, but I intend to highlight certain features of the systems and the differences between alternative technologies. My involvement refers to several different units and comes from the perspective of someone working alongside higher profile partners, although all liaising with the common intent of creating valid and functional systems together. Each project was new and each was addressed with the currently widespread spirit of willingness to develop prototype solutions virtually that nevertheless incorporate the very highest levels of technical excellence.
So, working chronologically, let’s take a look at the projects one at a time.
I’ll travel back in time by a few years to illustrate a system created for the Italian Sea Group’s Admiral shipyard, in collaboration with electric propulsion system manufacturer Auxilia. The Emotion 55 series Quinta Essentia is a mega yacht with an aluminium hull and superstructure, equipped with an advanced hybrid propulsion system composed of two 1,400 hp MAN diesel engines and two 150 kW electric motors coupled to variable speed generators.
The Emotion 55 series Quinta Essentia is a mega yacht featuring an aluminium hull and superstructure, equipped with an advanced hybrid propulsion system composed of two 1,400 hp MAN diesel engines and two 150 kW electric motors coupled to variable speed generators. The driveline uses the Auxilia solution: an integrated system interposed between diesel engine and gearbox that allows the electric motor to be engaged and disengaged by a centrifugal clutch.
The driveline uses the Auxilia solution: an integrated system interposed between diesel engine and gearbox that allows the electric motor to be engaged and disengaged by a centrifugal clutch (FIGURE 1).
Power Management is provided by an Emerson system, which combines the hotel and propulsion services. The propulsion unit, the assembly engineering of which supplied by Vulkan Italia, features a dual-stage suspension system (anti-vibration mounts located under the main engine and under the single bed shared by motor and inverter), with a thrust bearing (propeller thrust force) installed on the driveline, to guarantee the enhanced level of vibration and acoustic and isolation required (FIGURE 2).
A complex system, capable of combining the pleasure of silent electric cruising with a highly sophisticated propulsion system, painstakingly engineered in every detail to ensure that the design phase was not nullified by the conventional section, i.e. diesel engine and mechanical couplings, to produce a boat that can guarantee absolute comfort in all operating conditions. Let us now turn to a more recent project in the form of two 50-metre Tankoa S501 Hybrid series aluminium superyachts.
Powered by an MTU 4000 V8 diesel engine, Binta d’Or is equipped with an E-motion hybrid system interposed between engine and gearbox, with a 300 kW axial-flux motor. Electric drive is engaged and disengaged by a dog clutch to guarantee the utmost passive safety. Engineering of the integrated mechanical propulsion system was carried out by Vulkan, and it features the engine mounted on flexible supports on a skid with a separate thrust bearing to ensure the maximum isolation of structural noise.
Two very similar boats, with two very different propulsion systems. Binta d’Or, powered by a 4000 hp MTU V8 diesel engine and E-motion hybrid, is equipped with a hybrid system interposed between engine and gearbox, with a 300 kW axial-flux motor. Electric drive is engaged and disengaged by a dog clutch to guarantee the utmost passive safety. Vulkan’s engineering of the integrated mechanical propulsion system features the propulsion unit installed, via flexible mountings, on a skid with a separate thrust bearing to ensure the maximum level of structural noise isolation (FIGURE 3).
The second unit of S501 Hybrid by Tankoa, powered by a 1,800 hp MAN V12 diesel engine and an Esco-Power hybrid system, differs from the first ship due to the 180 kW motor mounted on an axis parallel to the main engine axis.
While both boats offer the same functional performance, this latter solution features a different engine room layout and different maintenance modes. (In this latter solution the electric motor can be disconnected without interfering with the propulsion driveline) (FIGURE 4).
Tankoa S501 is powered by two 1,800 hp MAN V12 engines and an Esco-Power hybrid system. This vessel differs from Binta d’Or due to the 180 kWelectric motor mounted on an axis parallel to the main engine axis. While both boats offer the same functional performance, this latter solution features a different engine room layout and allows the adoption of different maintenance modes. In the latter solution the electric motor can be disconnected without interfering with the propulsion driveline.
The 37 metre Benetti B.YOND uses the Siemens SISHIP EcoProp system, which is yet another interpretation of hybrid propulsion. Two 1,400 hp MAN V12 engines are combined with 180 kW Siemens motors mounted on the ZF gearbox PTI, with the mechanical transmission system engineered by Vulkan.
The Siemens SISHIP EcoProp hybrid propulsion system offers the freedom of working in four different modes. Enhanced Comfort, ideal for night cruising and coastal passages; Eco Cruise/hotel mode, a system to cruise or anchor with zero emissions; Extended Range, the perfect option for the longest passages, guaranteeing minimal energy consumption; and Eco Transfer, the option that allows the yacht to cruise with a single engine, although driving both propeller shafts, with benefits in terms of reduced engine running hours and higher efficiency.
Finally, another interpretation of hybrid propulsion, this time on the inverter PTI: the Siemens SISHIP EcoProp system is a typical example of this type of solution, and it was installed on a 37 metre Benetti B.YOND (FIGURE 5).
The shipyard’s objective was to give their clients a choice between conventional and hybrid propulsion, creating the hybrid system with the least possible impact in terms of engineering and layout with respect to conventional diesel propulsion. The same components are therefore used in both propulsion systems, with engine and gearbox installed on flexible mounts on a single bed; in the hybrid version the Siemens 180 kW motor is mounted on the ZF gearbox PTI, with the transmission engineered by Vulcan. Performance specifications are comparable to the other systems, with perhaps the only difference being that the power generation function is available only when cruising.
Experience working with different partners has revealed the differences between the various systems, their pros and cons in terms of on-board layouts, and the major and minor divergences in terms of use and operating logic, although all systems meet similar performance targets.
My conclusion? Each system can be customised to meet the needs of the shipyard and, more importantly, the owner. In the final analysis, if we disregard the current popularity of the “hybrid propulsion factor”, users are interested in silent cruising with a reliable system customised to match their requirements and configuration of the vessel. There are many different manufacturers, offering a range of different but equally reliable proposals. How to choose? It’s no easy task… and it is precisely this starting point, immersed in the role of the client, and having handled multiple installations, that resulted in the new VULKAN HYBRID ARCHITECT project: an ad-hoc solution engineered to the client’s specifications, with the result guaranteed by the systems integrator responsible for identifying the right solution with the ability to deliver the required performance, operating transversely across suppliers (choice of components/partners free of branding restrictions that could impact on the operating logic).
I’m quite sure that everyone would want to enjoy silent, low environmental impact cruising, to increase the range of their yacht or obtain higher propulsion power, charging the batteries while cruising to enjoy a quiet anchorage without being disturbed by generator noise. My opinion is that of an owner and keen seafarer. I think the goal must be to enjoy the sea and the boat in absolute comfort, and to respond to the desires of people whose lives are closely tied to their yacht. How to achieve this goal, and through what choices, can be left to the professionals – they must look to maximise comfort by making proportionate decisions, starting from the solutions available on the market.
(Sailing in Silence 3, more and more green – Barchemagazine.com – March 2021)
