Lürssen Yachts — Pioneering Propulsion

German yacht builder Lürssen has been at the forefront of its field for more than a century, pioneering the way forward for the industry since they built the world’s first motor boat in 1886. Today, with green yachting and sustainability being such a huge topic, it is no surprise that the world-leading shipyard is working on developing innovative eco-propulsion systems. Navigator talks to Peter Lürssen about the future of yacht power.

Why is Lürssen involved in the future of propulsion technology?

P The issues surrounding CO2 emissions is ever-present in all our lives, both on land and sea. The International Maritime Organization (IMO) committed itself to reducing the CO2 emissions of shipping by 50 percent by 2050 compared to 2008 levels, which includes those of the yachting sector. This is a challenging target for everyone involved, but I believe it is a necessity and at Lürssen we want to do our part to build our yachts in the most environmentally friendly way possible.

 

To give yacht propulsion some context, what are the basics?

P For a long time the combustion engine has served as a reliable power source in propelling yachts. However, over the years what was required of propulsion technologies kept increasing, while at the same time knowledge and technological developments pushed the boundaries of power. The use of the first diesel-electric propulsion systems as an alternative to a conventional direct mechanical prop-shaft drive made yachts even quieter and cruising became more comfortable. Then came hybrid-drive concepts, which were introduced at the end of the 1990s by Lürssen with the launch of the first hybrid propulsion motor yacht LIMITLESS. Now everyone in the industry is working toward emission-free cruising, and Lürssen is at the forefront of research and development in this area.

What are the current propulsion systems available?

P The current options for propulsion are the conventional diesel-mechanic system, the diesel-electric system (with or without Azipods), and a hybrid system (with or without Azipods). The diesel-mechanic type of propulsion is still very dominant today – it is an efficient system for most motor yachts that takes little space on board, with good reliability. It is the easy solution for most shipyards but it has its issues, the main being its inefficiencies when cruising at low speeds.

 

What is the diesel-electric alternative?

P Diesel-electric is a combination of electric propulsion motors and diesel generators that provide electrical power for both propulsion and the hotel load (the running of the equipment on board). If you add Azipods, the yacht’s maneuverability is greatly improved as the turning capability is much higher than that of a conventional propeller and rudder system. However, this type of propulsion system is usually only suitable for large yachts as it requires more space in the engine room for the converters and other parts.

 

What is the difference between diesel-electric and hybrid propulsion?

P The hybrid system combines the advantages of both the efficiencies of a diesel-mechanical system at higher speeds and the efficiencies of a diesel-electric system at slower speeds. Connected to the yacht’s electrical grid, the gear box drives the propellers to move the boat when required, while it also feeds the grid to power the hotel load. It has the advantage of low noise, no smoke, little vibration and, when cruising at low speeds you don’t have to start your main engines to move around in a bay or when leaving port. At higher speeds, the main engines are added and used together with the electric motor for maximum performance. This mode avoids electrical conversion losses and thus ensures more fuel efficiency. You can actually switch off your generators and use the main engine for your hotel load by taking the power from the main engines and converting them to electrical power. This saves running hours on the generator engines. And when you add an Azipod to the hybrid propulsion system you have a system with further improved maneuverability. The only drawback is the complexity of the power management system, but this is the propulsion system that is being used the most on yachts under construction today.

Do you have a preferred solution that you recommend?

P The propulsion and power production system on a yacht is down to the client’s preferences in much the same way as the size and type of yacht is their choice. To find the best solution you need to take the client’s specific requirements into account. If their desire is to cruise in the Mediterranean and spend a lot of time at anchor or in port, for example, we will recommend a different system than we would to a client looking to cruise greater distances and venture further afield. The components should be designed in such a way that the yacht’s power consumption is maximally efficient and as sustainable as possible.

 

You mentioned the new IMO Tier 3 regulations enacted in 2016. Has this been the big driving factor in the eco-conscious approach of Lürssen?

P It is certainly an additional motivator as regulations obviously need to be adhered to, but I think the whole yachting industry knows how important it is to care for the oceans and the environment. The new regulation required a clean-up of the exhaust emissions for a yacht to be allowed to certain areas. It forced us to develop a new filtration system, which we had used before, but we expanded on this and developed a complete new set of filters. All yachts with their keels laid after January 1, 2016, have been fitted with a stateof- the-art exhaust after-treatment system that reduces the nitrogen oxide and noise emissions. We managed to create an extremely compact system through which can filter out 90% of the nitrogen oxides, thereby protecting the environment.

Where do you see the future of propulsion?

P I think fuel cells will be the future – either driven directly by hydrogen or driven by hydrogen created from reformation of methanol, which is actually the solution we are aiming for. Since 2009, we have been involved in research projects aimed at using fuel cells on ships in order to advance sustainable shipbuilding. We don’t just want to use the latest technology on our yachts – we want to advance the status quo. Since 2012, the development of a modular fuel cell system using methanol has been underway – this is a government-sponsored research project that runs under the name Pa-X-ell.

 

How will this work on board a superyacht?

P Essentially, methanol is converted into hydrogen, which is then used in fuel cells to generate electricity. Unlike liquid hydrogen, which needs to be pressurized and stored in extensive structures, methanol has a higher energy density and can carry a lot of hydrogen within its chemical composition. It also can be stored in structural tanks in the yacht’s hull for long periods. Methanol is already available in almost every port in the world, and, despite its low flash point, it is as safe and as easy to handle on board as diesel fuel. The core of the system is the fuel cell from our partner Freudenberg. The hydrogen from the reformed methanol generates electrical energy with oxygen from the ambient air. Extremely low in pollutants and combined with regeneratively-produced methanol, it is also carbon neutral. Warm, moist air is the only by-product.

Does it have other advantages?

P Thanks to the modular construction the methanol fuel cell system can be adjusted to a customized yacht to keep space requirements and costs as low as possible and the total efficiency of the system as high as possible. Fuel cells cause almost no noise or vibrations, require minor maintenance and are more efficient than diesel engines. But most importantly, emissions like nitrogen oxygen, soot and even CO2 can be avoided. Due to the low dynamic capability of fuel cells, the system layout and the combination with other energy converters and storage is the key for a successful fuel cell power system.

 

Will we see this on a yacht in the near future?

P We actually are already building a superyacht with a fuel cell installed for a pioneering and technology-driven client. Of course, we had to prove the practical value of the new propulsion including the range, autonomy and sustainability. This zero-emissions technology will allow the owner to spend more than 15 nights at anchor or cruise more than 1,000 nautical miles completely emission-free. It is an extremely exciting project for Lürssen. I believe this will be a game-changer for the yachting industry.

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Photo Credit: Tom van Oossanen