Sailing on wind and solar energy

A yacht will have batteries on board anyway: the navigation and steering equipment runs on electricity, as do the lights, heating and other comfort facilities. However, batteries can only provide power for a limited period. On most yachts, the batteries are recharged while the boat is in motion, but this requires a loud, diesel-guzzling engine. That means a sailing boat without an internal combustion engine has to go to the quay to recharge its batteries.

A classical engine like this is particularly annoying for sailing yachts: it hardly fits the image of the sailor who sails solely by the wind and the waves, using only natural elements. This was also the opinion of Christophe Schepens, CEO of the Belgian company Optimus Yachtbuilders, which specialises in yachting technology. He wondered whether a sailing catamaran could still be seaworthy, with a long range, but with an electric motor, batteries and solar panels – without sacrificing onboard comfort.

Schepens got in touch with the battery storage experts at VITO/EnergyVille back in 2016. They found it an interesting issue to work on, especially with a view to testing and expanding their own expertise in the field of electrifying vessels. ‘We began with an energy management evaluation for what would be known as a zero-emission yacht,’ says Klaas De Craemer of VITO/EnergyVille. ‘Based on that, we calculated which batteries and which battery management system would be needed, and which solar panels would be the right fit.’
Optimus Yachtbuilders set to work with those results on building a prototype electric sailing catamaran. It would be able to sail when the wind was still or when entering and leaving the harbour, driven by two electric motors (one in each hull). ‘While sailing by wind, these motors would generate new power for the onboard batteries like a dynamo,’ says Peter Coenen of VITO/EnergyVille.

Innovative battery management system

Safety has been at the forefront of the design and construction of the prototype over the past two years. We made sure, for example, that the batteries could not overheat or undercool during the journey, and that they were protected from the outside air in a watertight manner,’ says Hans Rymenants of VITO/EnergyVille. But the most innovative aspect on board is the battery management system. ‘It's our showpiece. For example, the system continuously checks the charge in the batteries and relays this information to the boat's energy management system. This is vital, because incorrect communication between the two systems could mean that the yacht can't make it to the port in bad weather.’

VITO/EnergyVille developed a tailor-made solution for Optimus Yachtbuilders, enabling the first zero-emission yacht – sold under the model name OPTIMUS 45 – to be presented in 2020. 
The same technology and expertise can be applied to larger vessels with much more powerful engines. ‘Ferries are particularly interesting for electrification,’ says Coenen. ‘Ferries usually spend only a short time at sea, so they can recharge their batteries on land in between. These kinds of sailing cycles are ideal for batteries.’ VITO/EnergyVille is conducting research into electric ferries (among other things) within the European research project NAVAIS.
The electric sailing catamaran does not have to moor up when its batteries are empty. After all, it has solar panels on board so its batteries can also recharge at sea. Based on usage profiles for existing sailing yachts, VITO/EnergyVille studied a range of scenarios, so that the generation and storage of solar power would be tailored to the power demand as closely as possible. The experts also took into account the nearby and distant seas and coasts that the catamaran will be visiting. Coenen: ‘The yield from the solar panels depends on the location. From Antwerp to Norway to French Polynesia, the sun shines differently everywhere.’