Building competitiveness into operations

Mika Koli, The Switch, and Mårten Storbacka, WE Tech Solutions Oy explain how next generation drive trains based on permanent magnet (PM) technology are game changers when it comes to reaching the highest energy efficiency, lowering the costs of operation and complying with future environmental legislation.

Stricter environmental regulations and lower profit margins are forcing ship builders, owners and operators to rethink conventional power configurations. This has opened the way for advanced technologies that are revolutionizing the way ships generate and use energy for the good of the environment. By building competitiveness into shipping operations, solutions such as these enable ships to stay afloat and profit. 

Permanent magnet machines for green solutions

During the past few decades, traditional shaft generator systems have been one option for ship power generation. The main benefit of adding a shaft generator is to produce electrical power with the main engines, thereby significantly reducing the use of auxiliary generators. The downside, however, used to be that the propulsion machinery can only be run at constant speed.

The other option has been to operate without a shaft generator. In this case, ships continue to take advantage of the main engine’s variable speed operation while auxiliary generators produce electricity on board. The downside here is that the ship operator is exposed to higher fuel consumption from generating electricity with significantly poorer efficiency of the auxiliary generator prime movers as well as increased generating set maintenance costs.

Now merchant vessels can get the best of both worlds by using a game-changing solution that combines variable speed PM shaft generators with variable frequency drive technology. The advanced drive trains enable vessels to produce electricity with better efficiency for the entire ship’s network. This lowers costs by keeping auxiliary generators off and allows the main engines to operate at variable speed and to generate electricity.

A shaft generator solution based on permanent magnet technology and a variable frequency drive enables high efficiency when compared with other types of generators, especially at part loads, where ships normally operate most of the time.

With a variable speed shaft generator solution, the operation point of the main propulsion engine can be optimized and allow auxiliary generators to be turned off during sailing.

Proven performance for profitable results

Although relatively new to the shipping industry, PM technology has reached unprecedented success in numerous other industries, such as wind power, where it ensures the highest energy efficiency and lowest cost of operation. For marine applications, the PM machine is typically 2-4% more efficient at full load and 10% more efficient at part loads compared with induction machines. These efficiencies result from a lack of current losses in the rotor, the absence of an exciter, and reduced winding losses.

A synchronous PM machine contains Neodymium-Iron-Boron (NdFeB) magnets, materials with a very high flux density, which makes them ideal for variable speed generators throughout the entire speed range. The magnetic field is created with almost zero rotor losses. Thanks to their high power density, PM machines can be more compact, lighter in weight and smaller in size.

PM drive trains comply with the standards of leading classification societies in the world. They have been tested, approved and certified to ensure the highest possible reliability of the vessels and to comply with the strict international safety and environmental standards. Even under extremely harsh operating conditions, they deliver excellent performance with corrosion resistance and temperature tolerance as well as reliability and durability.

Frequency drives allow variable speed

Adding a frequency drive to a shaft generator allows a ship to control its speed and ensure a stable source of electricity for the ship’s network. The frequency drive allows the ship to choose between taking power from the main engine or from the auxiliary generators, as deemed best.  The frequency drive is based on IGBTs with advanced vector control technology and is optimized to work with PM machines for the best overall system efficiency.

Multiple options improve flexibility: Take Me Home/Take Me Away operating modes, safe return to port with the auxiliary propulsion drive, or boost modes for low-load optimization or ice boost mode. This technology enables the use of a PM machine to be operated as a motor or a generator according to the application requirement. Additional AFE benefits include lower harmonics, resulting in better electricity quality.

Frequency drives offer a modular, lightweight design with air or liquid cooling and exceptional thermal management. Their small footprint makes them easy to locate within limited vessel space and they feature a rugged IP54-class cabinet. The design is intended for harsh environments and is easily accessible for installation and maintenance.

Written by Mika Koli, Business Development Manager, The Switch, and Mårten Storbacka, Managing Director, WE Tech Solutions Oy

 The views presented hereabove are only those of the author and not necessarily those of  GREEN4SEA and are for information sharing and discussion  purposes only.

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The Switch together with WE Tech Solutions Oy, provide solutions focusing on shaft generator applications for 4-stroke and 2-stroke main engines that use a PM shaft generator which give ship owners the options of flexible hybrid propulsion systems that include Power Take Out (PTO), Power Take In (PTI), boost modes as well as efficient power distribution.

 Mika Koli is the  Business Development Manager of The Switch

Mårten Storbacka is the Managing Director of WE Tech Solutions Oy