Precise Maneuvering and 26% Fuel & CO2-Saving
Gearless, diesel-electrical Torque-Drive System proves safe and reduces operating costs
Led by calls to reduce emissions (CO2, NOx, PM-values), while at the same time increasing energy efficiency with a long-term eye on the diminishing supply of fossil fuels, it is clear for all that “alternatives” — even under the aspect of higher investment costs — will pay back in the future.
Beside economic and safety-related aspects, more and more questions about environmental protection as well as health hazards due to the emission of harmful substances into the environment play an essential role in shipbuilding.
Unfortunately, hitting environmental targets while maintaining efficient operations is becoming ever more difficult with conventional drive systems, requiring costly additional components, such as exhaust after-treatment systems.
Low operating costs, precise maneuvering and a high starting torque at lowest propeller speed as well as a low-noise operation pays back in many respects.
For these reasons, today more than ever there is a call for investment in new and emerging propulsion technologies to meet all criteria.
And these mentioned facts open the chance, with an innovative propulsion concept, to ensure the competitiveness of the shipping industry, further increasing existing advantages.
Torque Marine IPS GmbH & CO. KG based in Hamburg, has developed in 2010 its High Torque Power Drive (HTP) — an innovative diesel-electric propulsion system for all kinds of vessels, from river to coastal to tugboats — which is outclassing the conventional systems with combustion engines, reduction gears and drive systems.
The idea of diesel-electric ship propulsion system is nothing new: Already in 1838 Professor Moritz Hermann Jacobi experimented on the river Neva in Russia with an electric driven paddlewheeler.
Ronald Schröder, Business Development Manager at Germanischer Lloyd, addresses the advantages of diesel-electric drive applications:
• High redundance of the entire ship
• High torque already at lowest
• Reduction of the initial ship
• Reduction of the operating costs
• Increase of transport security
• Reduction of pollutant and
“We, the GL, see a great potential with this new HTP-Drive system for the shipping industry,” he said.
To reduce fuel consumption and emission values, the development center for ship technology in Duisburg, were, on behalf of the German Federal Environmental Ministry, deeply engaged with the subject many years ago. The conventional diesel-electric drive could not fulfill the preconditions, e.g. weight and volume reduction. Hence new possibilities had to be developed.
“The idea to develop something new in this field kept me busy from this moment on,” said Claus-D. Christophel, General Manager Torque Marine IPS.
After extensive research and development work, together with the development center for ship technology, DST, in Duisburg, Torque Marine IPS successfully converted in 2010 a twin-propeller river freighter, MS ENOK, with a Torque Drive System. Measuring 84 x 9.5m, ENOK can load 1,500 to of cargo at a load draft of 2.86 m.
ENOK is worldwide believed to be the first motor vessel, which has been equipped with a permanent magnet motor (PM drive) as a gearless electrical direct drive. Since mid of 2010 the vessel runs in regular cargo service on European Waterways.
Rudi Koopmans (64), captain of the vessel is more than satisfied with the results: “Within five seconds I can bring the propellers to a standstill. It’s a complete new world. Each second, we can react faster, is more safety. Since 14 years I am captain on this ship, but such an fantastic handling with this new Torque-Drive I never experienced before. The power of the shaft is steplessly available. Today we have a noise level in our cabins of measured 47 dB(A). I don’t want to have something else anymore.”
The High Torque Power (HTP) Drive-Concept
The modular system consists of, according to power requirements, encapsulated diesel engines with water-cooled, permanently excited generators in modular design and water-cooled redundant torque units, as well as weight and power optimized converters.
Hence, for diesel-electric operations modern and compact torque drives are available, which, based on their low power-to-weight ratios, offer the following possibilities:
• Propulsion redundancy
• Extremely high torque which, via a shaft thrust bearing, is direct available at the propeller,
• Low noise emission and
• Almost maintenance free operation.
For the time being driving power per shaft and propeller up to a maximum of 1,890 kWe are available. To drive generators (power producer/gensets) diesel engines are still indispensable; but already now combustion engines operating on LNG are considered for further torque drives. And also fuel cell techniques will be introduced in the future.
The installations of the genset modules are independent of the propulsion elements with the shaft drive units. Hence, further optimizations in ship building are visible, e.g. engine compartment configuration (shifting of the center of gravity) in respect of the ships shallow water characteristics, optimization of the propellers based on the higher available torque. In the case at hand, two gensets had been installed in the foreship and two in the stern main engine compartment.
Despite the fact that ENOK is an “old” vessel, meaning it did not feature an optimal hull form and its propellers were not matched to the new drive system, there were nonetheless impressive advantages: efficiency increase of around 26%, stepless rpm adjustment of the torque drive unit from 20 rpm up to maximum rpm.
The reversing of ahead/astern occurs via phase commutation of the converter. Hence, very precise maneuvering and speed control, e.g. during lock passages, with speeds from as low as 20 rpm are given. Elimination of costly mechanical rotational direction units like reversing gears or variable pitch propeller devices are additional advantages.
The water-cooled permanent exited, PME, synchronous generator
Basically this one is predestinated for applications where low weight, a compact design and a very high efficiency is required. The particular advantages of the PME-generators compared to conventional synchronous generators are the increased efficiency, the reduced power-to-weight and -volume as well as the loss of collector rings. ENOK’s early installed generators featured “pasted on” magnets on their rotors. That was to the disadvantage of efficiency, temperature rise and finally to the performance capability.
In November and December 2011, further developed PME-generators were installed. Via so-called ‘buried magnets,’ the generator temperature could be reduced and the efficiency, on the other hand, increased by 1.5% points – to now 97% at full load.
Results after almost two years of “Torque-Operation”
The ship operation with the Torque-system has been, to date, safe and trouble-free. Since the drive-unit modification, there have not been any breakdowns or malfunctions that have interfered in the ships unrestricted operational readiness.
During a voyage from Amsterdam to Stuttgart in January 2012 the Torque-system proved its function impressively. The ship was loaded with 1,000 to soy shred. Draft at this time was 2.2m.
The flooded river Rhein featured at this time a countercurrent of 7–8 km. At that the ENOK had still a ground speed of around 6 km. The average load on the diesel engines was around 70%. Since it’s commissioning in August 2010 around 2,000 operating hours have been recorded in the ships log-book.
Thereby 1,200 hours (60%) only with one genset, around 600 hours (30%) with two and about 200 hours with three engines. The drive system of Torque Marine fulfills all requirements of the legislators according to energy efficiency, NOx limit values as well as noise protection regulations.
The Torque-System as Torque Converter
The knowledge that ship propulsions require power for the speed is the basis for the design of the necessary driving power. But this power is used only very seldom. In some applications, river / tugs etc, this utilization is at an average of 45% of the installed power.
The classic diesel mechanical drive has its maximum torque, according to its completion, between 40 to 80% of speed. To reverse the drive system at lowest possible propeller speed, power of the engine is defined on the required torque at lowest engine speed.
As a consequence diesel mechanical drives are basically oversized.
The Diesel Engine and its Torque
Unfortunately a diesel engine requires a certain low speed (idling speed) to run independently. Below this lowest speed the engine has no torsional force: it dies! In addition, at idling speed the combustion engine supplies no torque.
But low engine respectively propeller speeds are essential for particular drive conditions. Also the very often common installation of transmissions helps somewhat to nothing. The attached power-torque-diagram of a modern ships diesel engine shows very plainly that, not until an engine speed of around 40% of the rated speed, is there a noticeable torque starting. For many drive conditions, such as frequent lock passages, long channel passages, maneuvering support by tugs and AHTS, high torque at lowest propeller speeds are essential.
Low Speed, High Torque
Here comes the new drive concept of TORQUE Marine IPS on the table. With this diesel electric drive, gensets and electrical drive units, the necessary low propeller speeds are reached exactly as required. The reason for the extreme low propeller speeds are based in the high torque of the permanent exited drive units. The Torque-Motor supplies its full torque already from the first rpm over the entire speed range (see diagram). This high torque is generated by the Torque-Motor directly; it is developed from reciprocation between magnets and the runnier current through the stator winding. This drive system offers an almost wear- and maintenance free operation And as a specific “treat” customers receive fuel and emission reductions on top. www.torquemarine.de
(As published in the August 2012 edition of Maritime Reporter - www.marinelink.com)