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Sustainability: Catamaran builders – Silent-Yachts


Austrian-owned Silent-Yachts, which builds in Italy, Thailand and China, is moving from niche to mainstream with its increasingly popular and increasingly large solar-electric ‘powercats’.


The Silent 55 was the company’s second production model, after the Silent 64


Founded by Austrian Michael Köhler, Silent-Yachts is one of the pioneers of solar-electric technology in yachting. Reflecting the increasing acceptance of solar power and the proven performance of the company’s catamarans, Silent-Yachts has quickly progressed from building a total of 10 units of the Silent 55 and Silent 64 in the last five years to predicting delivery in 2021 of about 15 units ranging from 55-80ft.


These include the first ‘front-exit’ version of the Silent 55 in China, the first units of the new Silent 60 under construction in Thailand and Italy, and the first hulls of the Silent 80, all being built in Italy. Even the flagship 80 Tri-Deck has already received four orders. Köhler believes green technology is going to become as popular in yachting as it’s slowly becoming in other transportation sectors.


“Tesla is an inspiration for us and has played the biggest role in the overall acceptance of electric mobility and the electric revolution we see today. For yachts, we expect a similar growth in overall electrification as we see in the automotive industry. Due to massive R&D in various industry sectors, further developments are just around the corner,” Köhler says.


The upper helm of the Silent 55 offers a close-up view of the solar panels


“The mindset of millions of people has already changed and this will continue. Governments will adapt to the consumer and adapt regulations and develop infrastructure in ports. We’ve already been introduced to projects about upgrading marinas to include electric charging stations. In 10 years, such installations will be the new normal.”


Prior to creating Silent-Yachts, the former lawyer and his wife Heike cruised on conventionally powered sailboats and motorboats for over two decades, spending over 5,000 days on board and cruising over 75,000nm. They eventually researched more efficient ways to supply yachts with energy.


“Even on a sailing yacht, you need to use the diesel engine when you leave a marina or bay and when the wind is too weak or blowing from the wrong direction. You’re forced to turn on the diesel engines for propulsion and energy generation way too often, and we realised the sun is more reliable than wind.”


After four years of research, Köhler launched the Solarwave 46 powercat in 2009 and “sea-trialled” it for four years before developing the Silent 64, which launched in 2016 and became the first production catamaran to cross the Atlantic Ocean on solar energy. The 55 further popularised the brand, with hulls shown at the Cannes Yachting Festival in 2018 and 2019.


Several units of the Silent 60 are being built at PMG Marine in Thailand


However, the new Silent 60 has already become the company’s best-seller, generating at least 16 sales before the first unit was completed, while the Silent 80 and 80 Tri-Deck have generated at least eight orders between them.



Silent-Yachts uses solar panels from US brand SunPower and high-end Panasonic lithium batteries, with the same cell structure as those used in the automotive industry.


The roof of a Silent 60 is equipped with SunPower MAX3-400 panels with a total output of about 17kWp, compared to almost 26kWp on the Silent 80. Köhler – who says the company is working on a bigger model with an output well above 40kWp – says such solar panels need to be mounted horizontally.


The original Silent 80 features a relatively small flybridge


“If they were mounted vertically on the hull, superstructure or on a mast, the output per day would only be a fraction of what our panels produce. If you want to maximise the power output, it’s of utmost importance to mount the panels so they can’t be shaded by other parts of the boat. As well as improving the efficiency of our hulls, we improve the roof design with every model to maximise the available surface for solar panels.”


The yachts feature electric motors with a 96 per cent efficiency factor and high-tech carbon propellers with about 80 per cent efficiency, Köhler says, leading to a drivetrain with an overall efficiency of about 75 per cent.


In comparison, a conventional diesel engine’s efficiency of about 35 per cent multiplied by a bronze propeller’s efficiency of about 55 per cent results in about 20 per cent total efficiency. “This means the Silent-Yachts drivetrain requires only a quarter of the energy of a conventionally powered boat,” he says.


An interior option for the Silent 80 and Silent 80 Tri-deck


In the more powerful E-Power+ version, the Silent 60 and 80 are equipped with twin 340kW electric motors on shafts that receive their power from a water-cooled lithium battery pack (286kWh on the 60; 429kWh on the 80).


The set-up means yachts can be driven during the day at six-eight knots and even at night at a reduced speed, without the need to start the generator. For a limited period, a top speed of 20 knots or more is possible depending upon the motor configuration.


“While at anchor in a bay or even when cruising typical holiday distances of 30 miles per day, there’s no need to engage the generator at all,” Köhler says.


The Silent 80 Tri-Deck has already received multiple orders


The company offers warranty of eight years on the battery banks, 25 years on the solar panels and lifetime on the electric motors. In terms of recycling and reducing electrical waste, the modularity of the solar panels and batteries mean these components can be replaced by new-generation versions and re-used in a house, for example.


In addition, all models can be equipped with an automatic kite-sail system, as will be seen on the first Silent 60. The kite flies at altitudes between 70-140m, generating up to 10 times as much power/sqm as a conventional sail.

Silent-Yachts unveils 62 Tri-Deck

The Austrian-owned company has already sold three units of its newest solar-electric catamaran, which develops upon the popular Silent 60.

Silent-Yachts uses carbon-fibre in its efforts to lower yacht weight, while for interiors, it offers a variety of alternatives to leather or teak wood such as compressed paper, recycled plastic, as well as basalt and hemp fibres.


“We try to implement as much sustainable and naturally-sourced materials into our yachts as possible, striving to enlarge this offering with every sensible possibility. Silent-Yachts was created to build solar-electric yachts, so reducing the carbon footprint and striving for sustainability is part of our DNA.”

Silent-Yachts strengthens Advisory Board

Volkswagen’s Michael Jost has joined the Silent-Yachts Advisory Board and started a JV with the solar-electric boat builder in Croatia.