The Elysium is a 21 year old Hoek Design Truly Classic sailing yacht built by Holland Jachtbouw. With such an age, it was due for a complete refit. The original diesel engine became unreliable and limited the sailing area, and the woodwork started to leak. As this is a well-built yacht that can easily last ten years with proper maintenance, the owner has decided to make it truly future-proof by extending the refit to the interior and exterior by converting the diesel engine to a hybrid propulsion system.
The end goal? The owners, Harry and Jill, are currently realizing their sailing dream of living and working aboard full-time and sailing around the world. Read their blog here. The first step was taken in 2019, when they bought this Truly Classic Corner Design in Lymington, UK. Harry and Jill are convinced that a hybrid propulsion will greatly increase the value of their sailing yacht and above all that it will prepare the yacht even better for a trip around the world.
Converting a diesel-powered ship with electric propulsion is quite a challenge. Why? The engine room is too big for the electric motor and the other compartments too small for a large battery bank. This was one of the big design challenges for STOK Electric to make their hybrid propulsion system truly flexible so that it would fit into any ship and configuration. This is one of the reasons why a „serial hybrid“ system is best suited.
In a serial hybrid system, the diesel generator and electric motor are not physically connected by a shaft and coupling, but are electrically connected by wires. This allows the diesel generator to be placed almost anywhere on the ship in any direction. This also means that the diesel engine can be smaller because it does not have to deliver peak power. He only needs to keep track of the average power consumption of the electric motor.
To get a large battery bank, STOK Electric chose to use Super-B Nomada batteries. These batteries are like bricks, you can stack them side by side and build a big battery bank. In addition, the batteries use a chemical called Lithium Iron Phosphate (LiFePo4 or LFP). This chemistry, unlike other lithium-ion chemicals commonly used in EVs and almost any other electronic device, is completely safe and fireproof.
The batteries are distributed between the two aft cabins of the yacht and are connected in the middle with a manual switch, which allows the batteries to be completely disconnected from the rest of the system.
Because the electric motor is so powerful, the voltage at which the hybrid system runs had to be increased to 350V, in order to reduce the current and thus the fire risk and increase safety. 350V may sound scary to many people, but it is much safer than a lower voltage system in these situations. Higher voltages are easier and more reliable to protect because of the energy it stores, insulation monitoring is used to detect ground faults in the system and shut it down automatically. Also, many EVs go to even higher voltages, and you still feel safe in that.
To reduce the need for special equipment compatible with the high voltage, the existing 24V household system is kept in place. But to increase living comfort, a small inverter has been placed between the high-voltage and low-voltage system. This converter essentially links both battery banks together and allows one huge battery bank to be used for all home appliances. It also ensures that the high voltage system can be charged in the same way as the domestic system. With the added benefits of charging both battery banks from the generator or hydrogenation.
While the hybrid system was fully thought out and all necessary parts were ordered, Hutting Yachts carried out an extensive refit of the exterior. For example, the teak deck on the cabin roof has been completely renewed, the damage has been removed and all the woodwork has been repainted.
The entire hull has also been sanded and checked for damage. Minor repairs have been carried out where necessary, the underwater hull has been provided with antifouling and the hull has been repainted. The mast and boom were also inspected and treated after they were repainted as a finishing touch.
The demand for and interest in making hybrid sailing yachts is increasing enormously. Not surprising, when you look at the developments within the automotive industry. However, making a hybrid sailing yacht involves many aspects and, above all, specific expertise. For example, the energy system must be safe enough for very water-rich environments, reliable in connection with the often long distances and easy to maintain. It concerns craftsmanship and customization, because each sailing yacht requires different capacities. The custom-made energy system for ‚SY Elysium‘ was developed by STOK Electric, with Hutting Yachts offering all the support in the field of renovations and installation. Check here for more information or contact us or go to www.stokelectric.nl.