What makes the industry go round?

The world of marine propulsion is so diverse that a little background information can be very useful. What are the possibilities? Which types are well-known and have lasted the past decades and of which types will we be seeing more and more in the future? Join Maritime by Holland Magazine on the journey through marine propulsion.

Perhaps it is best to start at the beginning. Heavy fuel oil engines are still the prime source of propulsion and their ability to be adapted to higher power, and the relatively cheap cost of heavy oil is what makes them popular. Speed can be varied, where large powerful engines are often slow-speed, something that is now used to decrease the fuel costs. They do consume a lot of space on board a vessel and present limited options in their location. Naturally, high-speed and medium-speed engines are also available, though high-speed are more commonly found within smaller vessels. Some vessels have propulsion systems that have several engines of the same size to accommodate various speeds and waters, for example passenger ships or ferries. This also offers a better redundancy: should an engine fail at sea, there will always be a back-up.

Diesel or diesel-electric

Though diesel and diesel-electric engines may be a trend we are seeing, it is in fact quite old. In the early 1900s diesel-electric ships were also hard at work. A Russian tanker named Vandal, launched in 1903, was the first tanker with a fully diesel-electric transmission. These early vessels were direct current (DC) propulsion, necessary to achieve the required speed control. Nowadays the advent of power electronics has allowed the development of alternating current (AC) speed control systems. These are commonly found in many vessels along with thrusters, which make the vessel easier to manoeuvre. The advantage as stated above is several smaller fixed speed engines driving generators and flexibility of location in the vessels because cables bend but propeller shafts do not. These engines run at their optimum economic speed and produce fewer emissions, which in turn is even better for the environment. They are controlled by power management systems (PMS) that match the number of generators to the requirement of the propulsion at the time, ensuring that no engines are running when they do not need to be. An example of a diesel-electric vessel is the Kaapcoaster 2300 by shipyard De Kaap in the Netherlands. This extremely economic vessel, specially developed for coastal sea, is the first of a serial economic fuel consumption production.

The future possibilities

Looking toward the future, with new tighter emissions regulations, dual-fuel engines are now an environmentally friendly option. Based on a combination of marine grade diesel, heavy fuel oil, or liquefied natural gas (LNG), the various fuel options means vessels can rely on the most efficient fuel for the particular water or situation and even blend it when required.

The combination with LNG has proven to be the most effective and successful. What is the benefit of dual-fuel? Mainly the obvious fuel and operational flexibility, but also high efficiency, low emissions, and lower operational cost advantages. Not least the environmental aspect. The Argonon belonging to Deen Shipping in the Netherlands is a perfect example of a dual-fuel vessel, with a 80% LNG and 20% diesel engine possibilities. This combination significantly reduces the NOx and SOx emissions. The cryogenic tank on board of the vessel stops the LNG from warming and evaporating.

Liquified Natural Gas

Full LNG vessels are considered by many to be the future of propulsion. Many countries are now working on a full infrastructure to accommodate this growing market. LNG is a natural gas that is stored under pressure in a liquid state in tanks aboard the vessel, such as the cryogenic tank mentioned for the Argonon. A prime example of a full LNG propulsion vessel will be the Green Stream Tanker by Peters Shipyards and partners. This is a major step in the right direction for inland shipping. The vessel is powered electrically thanks to its generators fuelled by LNG. The emission reductions are enormous, 25% and 80% respectively. Not only that, but there is also no release of sulphur dioxide (S02) and particulates. The Green Steam Tanker will have four LNG PACK engines, meaning effective redundancy.

Innovating engines

Innovation is a constant process, where LNG has most focus a new innovation has sparked interest. Recently during the Maritime Awards Gala, Bas Goris was awarded the VNSI Wim Timmers Award (more information can be found in our article on the Maritime Awards Gala on page 32) for the O-foil propulsion system. The name O-foil stands for oscillating foil, or more commonly: a flapping wing. The propulsion lies in the wing generating power by creating lift in the water, much like a screw propellor. The difference being that the wing spans the width of the vessel, which means a larger contact surface with the water. The lift is generated by the winging moving up and down in the water whilst at the end of each stroke changing its pitch or angle of attack to the water so as to push the water behind it. This patented technology, developed by O-foil b.v., is based on the natural swimming motions of dolphins. This will result in 50% better efficiency and a cut in fuel consumption by up to 50%.

Anything is possible, that is key to marine propulsion. Costs, regulations and the environment now have precedent over speed. It will be interesting to see what the propulsion line-up will be ten years from now.

Rebecca McFedries