STOK Electric completed the first project in 2022, they converted a 56ft classic sailing yacht “Elysium” into a hybrid sailing yacht. Read what choices have been made by STOK Electric and what renovations have been carried out by Hutting Yachts.
The Elysium is a Hoek Design Truly Classic sailing yacht built in 2001. It's new owner plans to live on the yacht and sail around the world. To accomplish this the yacht first needed a major refit due to its age. There were problems with the existing diesel motor and the pilothouse was leaking badly. Because the new owner of the Elysium will be working onboard, a decent amount of energy is required to be able to work through a full day without having to start a loud diesel motor.
Comfort, safety and the adventure of being self sufficient are the reasons this beautiful sailing yacht is refitted with an electric propulsion system.
A 40kW nominal and 70kW peak electromotor replaces the original diesel motor. This small motor can provide enough power to propel the ship and also stop it quickly if necessary. The motor is liquid cooled and doesn't require any maintenance, with good alignment it is also directly mounted to the propeller shaft, without a reduction box. This fitment ensures maximum efficiency of the propulsion system.
To provide the powerful electric motor with sufficient energy a new battery bank is placed underneath the beds in the aft cabins. This battery bank has a capacity of 38 kWh at 350 V. This is more then enough energy to use the electric motor for long runs.
Because the owner plans to seriously use the yacht and it's also meant to be used to cross oceans, a diesel generator is installed. This generator is developed by STOK Electric to be optimized for our system. The base of the generator uses a modern Yanmar engine block, fitted with a flywheel mounted dynamo it can provide up to 28 kW of electric power and 20 kW nominal. This is enough to support the batteries when long motoring is required, or rapidly charge them in a little more than an hour.
To ensure the system is compatible with the yachts electric system a powerful DC/DC converter is installed to link the propulsion battery to the household battery. This converter can supply power in both ways, enabling the use of a large battery bank for all household appliances. While also enabling the 350 V propulsion bank to be charged with conventional 24 V chargers, eliminating the need of specialized equipment and keeping the system simple.
The demand and interest in hybrid and electric sailing yachts is increasing growing. This is 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 blue ocean sailing, reliable in connection with the, often long, sailing trips, and easy to maintain. It concerns craftsmanship and customization because each sailing yacht requires a different system. The custom-made energy system for sailing yacht 'Elysium’ was developed by STOK Electric, where Hutting Yachts offers all support in the field of renovations and installation.
STOK Electric delivered the entire electrical propulsion system.
The hull of the ship was converted to a 3D model based on the old drawings available, this way the best solution for the system placement could be decided. Together with Hutting Yachts the old diesel motor was removed from the engine compartment and a new electric motor and diesel generator were installed. Some customization work was done to ensure that all components would fit.
Once all components were in place some dry testing was performed in the Shipyard, consisting of turning the motor, charging the batteries and investigating any possible failure points.
When the yacht was ready to be relaunched after the refit many test were done together with the owner of the yacht, to ensure everything operates properly and to get the owner familiar with the system.