Seadeck 7 is the first model in Azimut‘s hybrid series. The propulsion system is based on Volvo Penta’s new pilot helm-to-propeller hybrid-electric package
The new Seadeck 7 Full Hybrid was presented at the Cannes Boat Show last September. This is the first model in Azimut’s hybrid series. Azimut is one of the reference boatyards in Italy and around the world and builds yachts between 13 and 38 metres long organised in seven lines (it is part of the Azimut-Benetti group, the world’s leading superyacht manufacturer, which has been at the top of the sector’s reference rankings for 24 consecutive years). The Seadeck 7 Full Hybrid displayed at the show is a pilot project designed to address consumption, emissions, and sustainability comprehensively. It is a planing vessel capable of reaching speeds of 30 knots, measuring almost 22 meters in length and weighing 43 tons. The hull and superstructures are made from composite materials with extensive use of carbon fiber, which helps reduce the overall weight of the structure.
As far as the propulsion system is concerned, the Seadeck 7 Full Hybrid is a collaboration between Volvo Penta and the Azimut|Benetti Group R&D Department.
The system is based on Volvo Penta’s pilot helm-to-propeller hybrid-electric package.
This prototype installation, which required over a year of design work, was created in parallel with the final development stage of the Seadeck 7 to guarantee total integration, including validation, certification and type approval, and risk assessment for management of the lithium batteries and the high voltage systems. The maximum levels of safety and reliability are certified by RINA.
Volvo Penta and Azimut will continue to develop and optimise the hybrid-electric package on the Seadeck 7 throughout 2024. First deliveries of the Seadeck 7 are expected in 2026.
«The Seadeck», according to the shipyard, “epitomises the solutions available today to reduce fuel consumption and CO2 emissions, allowing a careful owner to reduce emissions by up to 40% over a year of average use compared to boats of comparable weight and size with a shaft drive and a traditional hull». -30% is due to the yacht’s advanced naval architecture, integrating the extensive use of carbon to reduce the boat’s structural weight through high-efficiency hulls and propulsion systems. The remaining -10% results from the hybrid architecture and innovative electrification technology.
The hybrid system of the Seadeck 7
On board the Seadeck 7 prototype the hybrid system consists of two 735 kW (1000 hp) Volvo Penta D13 1350 diesel engines working in parallel on the same drive shaft with two marine electric motors from Danfoss ((da 160 kW @900 rpm, torque 1700Nm @900 rpm). These are complemented by a 392 kW lithium battery pack from Akasol.
There are four operating modes of the system: with Hybrid Standard the boat starts in electric mode and then switches to diesel when the required power is too much to be handled by electric; with Hybrid Boost the diesel engine is flanked by the electric one which helps in acceleration when necessary; with Pure Electric the system is forced not to switch on the diesel engines. Then there is the fourth mode, which is not present on the prototype but will be operational in the standard versions of the Seadeck 7, the Cross-over mode: one diesel engine powers both drives, optimising efficiency and prolonging time between engine maintenance. Depending on the chosen drive mode, the system automatically controls whether the boat should be powered by the electric marine engine, the combustion engine, or both, ensuring seamless operation.
The on-board hybrid-electric system allows the Seadeack 7 to sail at a maximum of 11 knots in electric mode. When sailing in hybrid mode, up to 8 knots of speed the electrics are in operation and then the endothermic propulsion takes over.
The 220V consumers are powered by the lithium battery pack, which can be recharged at the dock and during navigation or at anchor via the heat engines. There is no on-board generator. In Fast Charging mode, keeping the engines running at idle in the roadstead for just one hour recharges the batteries so that you can spend the whole night with air conditioning and stabilisers on (80 to 100kW are needed).
If recharging takes place while sailing at medium speeds (around 16 knots), the recharging time is further reduced and in just over two hours you arrive at the roadstead with the batteries 100% charged and able to power all on-board services for up to 12 hours.
The importance of an integrated hybrid system
Andrea Piccione, Head of Marine Business Volvo Penta Italy, explains Volvo Penta’s new pilot helm-to-propeller hybrid-electric package. It is a fully integrated package with Volvo Penta controlling all components from helm to propeller.
«Before talking about the new hybrid system, I would like to make a premise about the Volvo Penta philosophy. We have been differentiating ourselves from our competitors for more than 60 years by the fact that we supply the entire propulsion system, not just the engine, leaving the shipyard to pair the engine with transmission, shaft, exhaust, and steering… I mention this because our hybrid solution for the nautical world stands out for its total integration».
What are the features of the new hybrid system?
We started with our proven IPS platform – a propulsion system using
counter-rotating, steerable pod propellers, oriented towards the bow launched some 20 years ago and revolutionised nautical propulsion, increasing efficiency considerably compared to shaft drives, by around 30%. – And we enriched it with the electric part. So we inserted the electric machine between the diesel engine and the transmission; we then added a battery pack and created a complete package under the Volvo Penta umbrella.
Our integrated system includes two 1000 HP Volvo Penta D 13 internal combustion engines, two 160 kW electric machines from Danfoss, IPS technology, a 392 kW battery pack, and the provision of all control systems, Power Management, Battery Management, etc.
How did you approach the integration of the conventional engine and electric motor?
We started with the ultimate goal: to develop a system that is easy to use. The hybrid boats present today are not user-friendly. For us it was essential that any skipper or owner should be able to sail without any problems. Our system is very similar to those in the automotive industry, and this too is a plus that comes from product integration. Moreover, from an aftermarket perspective, it is Volvo Penta that takes care of everything with its international network.
The transition from electric to diesel and vice versa was the most delicate phase to develop from a technical and technological point of view. Managing acceleration from electric to diesel, and deceleration from diesel to electric, is particularly challenging given the 1000 HP diesel engines and 160 kW electric motors involved. Once again, having full control over the system proved invaluable, as we understand all the torque and power data, both for the engine and the transmission, as well as for the electric motors.
What technology did you use for the diesel-electric dialogue?
The technology we are using on the pilot project exhibited in Cannes is a freewheel mechanism. The electric motor is mounted coaxially on the crankshaft, with a freewheel managing which of the two engines provides traction. This might not be the final solution, as we are still studying the best option in terms of work cycle durability, but it’s currently yielding excellent results.
The on-board battery pack is definitely important…
Today there is an oversized battery pack of 392 kW on board, on the standard model it will be 142 kW, and if the owner wants more autonomy, either for propulsion or hotel mode, additional 70 kW modules can be added. However, weight becomes a factor that could penalize the boat.
Currently we have fitted Akasol batteries but but in the future we will use Volvo Group’s own batteries. At Volvo Penta we then developed the Battery Management System.
What are the on-board autonomies in electric mode?
With today’s configuration there is about four hours of autonomy sailing at 7 knots; at 11 knots, the top speed, the range drops by about half. In the standard version, the top speed will not change but the range will be less. It has to be said that these systems involve a change of approach in the use of the boat, as is the case with cars. Electric mode becomes crucial in manoeuvres, in ports and to be able to enter certain protected areas, as well as for spending the night at anchor with air conditioning and onboard systems running without the need for a generator. For long-distance navigation, electric propulsion isn’t viable. Our diesel systems are at the cutting edge of technology, they are clean and efficient solutions. In recent years there has been a lot of focus on the energy source on board, electric, hydrogen, dual fuel etc.. I believe the solution lies in the transmission, how efficiently we transfer energy from the boat to the water. And IPS are certainly the best answer today. Nevertheless, we are studying all the alternatives, keeping all options open, always convinced of the importance of the efficiency of the whole system.
by Paola Bertelli
