Solarwave 64 von Silent Yachts. Foto: Michael Köhler
Michael Köhler was a passionate sailor. But he was tired of being dependent on an engine in calm conditions. The Carinthian therefore switched from wind and diesel to solar power. On his solar yachts powered by electric motors, the sea can be experienced in a completely new way – quietly, self-sufficiently, comfortably and wonderfully decelerated.
A guest article by Günter Kast, published in the current eMove360° magazine in german language.
The Solarwave has barely left the sheltered bay of Port de Sóller on the northwest coast of Mallorca when it has to fight against a two-metre swell, even though there is virtually no wind. The catamaran’s slender keels cut through the waves with great ease and barely cause the yacht to buck. The sailing boats in sight have to fight harder. Michael Köhler refers to them somewhat derisively as “motorboats with masts” or “sailors without sails”. He is alluding to the fact that on days like this, they can barely make any headway with the canvas alone and are therefore reliant on their diesel engine. “It stinks, is loud and makes the whole boat vibrate.” Köhler wrinkles his nose.
Even under these difficult conditions, the Solarwave manages just under five knots, almost ten kilometers per hour. Without any wind. But also without the help of Rudolf Diesel. What the sailors can’t see: The roof of the catamaran is covered with solar modules. The electricity generated by these cells feeds two electric motors, each with 60 kilowatts, which make the Solarwave reach a top speed of eleven knots.
Silent gliding
Köhler checks the displays in the control center to see how much power the solar cells are generating and the electric motors are consuming at the same time. What he reads makes him nod with satisfaction. “We can sail for twelve hours straight,” he explains to Ellen Aschauer, one of his guests on board. The woman from Salzburg may be in her 80s, but she is mentally and physically in top shape. She knows the best sailing areas in the world. “On a trip to the Seychelles, friends raved to us about this solar yacht,” she says. ”My partner and I had to try it out, of course, and the new technology made us curious. In the meantime, we have already spent two weeks cruising between the Ionian Islands with Michael and his wife Heike. This silent gliding is wonderful. We never had to switch on the generator to produce electricity.”
Köhler, the inventor, invites us into the belly of the yacht. This is where the eight battery blocks that store the solar energy are located. “Our boat had surprisingly few teething troubles,” he emphasizes. Of course, he has made improvements here and there: over the years, the lead batteries have become lithium cells, which are lighter, smaller and more durable. “The battery blocks now take up just 0.6 cubic meters of space and weigh only 600 kilos.” This is important to him, because anyone who buys a boat for around two million euros is not used to living in cramped conditions. In general, this is his credo: “Electric propulsion will only prevail on water and on land if it is no more expensive and no less convenient than energy from combustion engines.” The lawyer from Klagenfurt should know. He is an authority on e-mobility on the water: the only one in the world to offer such a yacht ready for series production, for sale, for charter, for test drives.
A combustion engine is not an ideal sailing partner
However, it was a long journey until then. Whenever their time allowed, the Köhlers were out and about on the world’s oceans. They covered around 30,000 nautical miles in monohull sailing boats and later covered roughly the same distance in sailing catamarans. But at some point shortly after the turn of the millennium, they had to admit to themselves: “The wind is a very unreliable companion. We spend far too many hours sailing under engine power.” Unfortunately, a combustion engine is not an ideal sailing partner. Diesel engines generate noise, heat, vibrations, exhaust fumes and a film of dirt on the water. The generator (which is also noisy) also needs fuel to supply “power guzzlers” such as the refrigerator, navigation devices and air conditioning. Yachts that carry little fuel are limited in range to a few hundred nautical miles. The great feeling of freedom and adventure looks different.
So the Köhlers took a look at what the e-market had to offer. They quickly realized that it wasn’t much. In 2005, they therefore began initial tests for their own solar catamaran. How and where should the panels be installed? How much space do they need? How much electricity do they need to generate to power an electric motor? How much power is required for the on-board electronics? Over the following years, they covered 15,000 nautical miles with these questions in their luggage – in the Mediterranean, in the Caribbean and on an Atlantic crossing.
First e-yacht launched
In 2009, the Köhlers’ first e-yacht was built in a shipyard in Niederkassel near Bonn. After the Solarwave 46 was launched, it sailed across the Rhine, Main, Danube and Black Sea to the Aegean. No maintenance work was required during this very long voyage, neither on the solar system nor on the electric drive. The generator only rattled for around 50 hours – primarily to prevent it from rusting. The electric motors, on the other hand, ran silently for more than 2,500 hours. The Solarwave system received the Energy Globe Award, among others, for this success.
Köhler tells his guests this story in a quiet voice. No engine noise disturbs the peace and quiet. No sails have to be set or hauled in again. As the Solarwave turns into the bay of Santa Ponça, six hours have passed since it set sail, during which time it has covered 32 nautical miles. The battery charge has been reduced by a quarter.
Normally, Köhler would now drop anchor in a hidden bay and save himself the mooring fees of around 300 euros per night in the marina. After all, he is self-sufficient and doesn’t need a power socket or a petrol pump. But today, for once, he heads for the marina – a demonstration lesson! As he and his skipper Ufuk Türkes sail past the other boats, only a few leisure captains raise their heads. They read the words “zero emission – solar powered”, but don’t see the solar cells on the roof. Only when the Solarwave reaches its berth does it become an eye-catcher. People stop and ask questions.
Maritime e-mobility as easy as in the Raffaello advertisement
Anyone traveling with Köhler experiences maritime e-mobility as easily as in a Raffaello commercial. In fact, it is a complex business. Others have also tried to get such e-boats ready for series production. And failed. Some founders got bogged down because they wanted to offer everything from a single source and be a planning office, design company, shipyard and marketing company at the same time. However, that was never the Köhlers’ intention: “Building yachts is far too difficult a profession for that. Our role is to bring the know-how together.” The core team therefore consists of just half a dozen employees. The company is based in Austria and the design office is in Hamburg. “The 64-foot model is currently still being built in Turkey, while we have commissioned the German-Chinese shipyard Mazarin German Yachts for the 55 and 75-foot models,” explains Köhler.
70 to 80 miles effortlessly without a generator
In the late afternoon, dark clouds push in front of the sun. The cells on the roof of the yacht are producing less power at the moment, as you can see on the display. “No problem,” says Köhler, ”the batteries have stored enough energy.” This is easily enough for a typical charter week in the Mediterranean in the summer season, sailing from bay to bay, not covering too great a distance and anchoring again and again for swimming and snorkeling. “We can easily cover a distance of 70 to 80 miles, for example between Ibiza and Mallorca, without a generator. It’s a different story when we want to cross from Mallorca to the Spanish mainland,” explains Köhler. “This requires intelligent battery management. And we certainly have to switch on the generator for a few hours during the one-and-a-half-day crossing. Of course, we can’t drive at full throttle either. So it’s not for managers in a time crunch.” The small diesel generator is just an insurance policy in case the electric motor doesn’t get enough juice from the solar cells. After all, no one wants to drift across the open sea completely without propulsion.
Köhler has no problem with the generator. He sees himself as a pragmatist, not a purist. However, he doesn’t mind being called a visionary.
Silent Yachts: Silent Yachts was founded in 2016. Since then, the company has successfully developed various production-ready solar-electric yacht models. The 60 Series, 80 Series and 120 Explorer are the cornerstones of the current Silent model range. In addition, the first Tender Series and the Speed 28 were launched in 2022. The tenders are designed to be stowed and charged on our yachts, while the Speedboat illustrates the incredible performance potential of electric propulsion on the water. https://silent-yachts.com/de
