Diesel Digest: by Capt. Jeff Werner
“AUGSBURG, Germany – Last year, the French submarine Aigrette was launched with diesel electric propulsion. MAN built the diesel engine for that underwater vessel.”
“VASTERAS, Sweden – This year, Vandal, a 245-foot-long, shallow draft oil tanker is plying the canals of the Volga-Baltic Waterway using diesel electric motors built by ASEA. The revolutionary design has a single diesel engine turning three generators to supply power to reversible DC motors.”
These two press releases demonstrate that in the maritime world, the use of hybrid propulsion is rapidly growing in both military and commercial applications. The question is, when will the yachting industry embrace this new technology?
In reality, these two press releases were never written – but if they were, the year would have been 1903. All the facts about Aigrette and Vandal are true, and more than 100 years ago both were the first vessels of their type to use hybrid engine technology. Superyachts have been using hybrid diesel electric technology since at least 1997, when Lürssen launched the iconic 316-foot Limitless.
Where is the intersection of hybrid propulsion technology and yacht building today? First some definitions:
Conventional propulsion – An internal combustion engine powered by diesel fuel, gasoline or liquefied natural gas (LNG) connected to a propeller shaft or pod drive system.
Electrical propulsion – A battery-powered electric motor turns the propeller shaft.
Hybrid propulsion – This system has an internal combustion engine, a generator, storage batteries and an electric motor that turns the propeller shaft. An example of this is the diesel electric system. The required hybrid components can be used in either a serial or parallel system.
Serial hybrid – A generator charges the battery that powers the electric motor to turn the propeller. When the battery is charged, the diesel engine running the generator shuts down and the electric motor runs on battery power to turn the propeller.
Parallel hybrid – This system offers more flexibility than a serial hybrid system because it offers three configurations. With the first option, the diesel engine drives the propeller directly (conventional propulsion mode). Using the second option, the generator charges the battery, which powers the electric motor to turn the propeller (serial hybrid mode). The final option is when a battery powers the electric motor to turn the propeller (electric propulsion mode). The parallel hybrid design has the diesel engine connected to a gearbox, which in turn drives the propeller. As a bonus the electric motor, connected to this same gearbox, can also operate as a generator, in addition to its regular function of rotating a propeller.
The major superyacht engine builders all have diesel electric products. The first diesel engine company to begin working in this arena was MAN. Another German competitor, MTU, offered 14 diesel engines with over 1000 horsepower output suitable for diesel electric drives. Cummins considers itself “one of the pioneers in diesel electric propulsion … with a decade of experience and hundreds of diesel electric packages in operation globally.” Caterpillar, on the other hand, marketed its first marine diesel electric propulsion systems in 2009.
Savannah, Feadship’s award-winning 274-foot superyacht launched in 2015, is billed as the “the world’s first hybrid superyacht.” Although that is a misnomer – Savannah is just the latest in the line of superyachts, including Octopus and Grace E, to incorporate hybrid propulsion technology – Savannah does incorporate green technology throughout the vessel.
Are there any barriers to deter owners of yachts like Savannah from incorporating hybrid propulsion systems into the design of their yachts? In a recent interview with Billionaire.com, “Marnix Hoekstra of yacht designers Vripack, speaking in relation to how sustainability is affecting the design process, says: ‘I don’t think innovation should be a struggle with anything — from class and regulations to taxes and sustainability — particularly with the yacht industry as it’s the most personal object that anyone can have built for themselves. Sustainability can certainly be inserted into that process.’”
It is clear that yacht captains and engineers should begin to become conversant with hybrid propulsion systems. That future, first glimpsed at the turn of the 20th century, combined with a variety of green innovations has finally arrived.
Capt. Jeff Werner is a 25-year veteran of the yachting industry as a captain on private and charter yachts, both sail and power, and a certified instructor for the RYA, MCA, USCG and US Sailing. He also owns Diesel Doctor (MyDieselDoctor.com). Comments are welcome below.