The technologies of diesel-electric and fully-electric propulsion systems are continuing to develop in Norway, according to recent reports, thereby allowing for cuts in shipping costs and the reduction of noise produced by ship propulsion systems. This could potentially result in ships nearly as silent as modern submarines.
Amongst those in the Northern European country working on such technologies is the Siemens-employed Odd Moen, based out of Trondheim.
Moen’s teams have already outfitted over 200 ships with hybrid-electric power-trains over recent years.
“We use diesel-electric propulsion systems for many ships,” Moen stated. “In these installations, the ships’ propellers, or ‘screws,’ are turned by inverter-fed electric motors that get their energy from diesel-powered generators. This arrangement gives us much finer control of the screws, which results in fuel savings.
“In order to maintain a vessel’s position at sea or to move at very slow speeds, the amount of propulsion needed is sometimes so minimal that it need not be more than the power to adjust the pitch of the propeller blades,” explained Moen. “The propeller turns at a constant speed. As a result, the diesel engine also does so.”
In this hybrid system, the frequency converter controlling the propeller rotation speed directly allows for slower turning and cost savings.
“In ships where the load on the propulsion system changes frequently, the savings provided by this type of hybrid system more than compensate for the loss in efficiency due to converting the mechanical energy produced by the diesel engine into electrical energy.”
Altogether, diesel-electric ships use up to a third less fuel than purely diesel-powered ships, as demonstrated by the company’s first use of the technology back in 1996 on a supply boat for drilling platforms, The Skandi Marstein.
“That ship was a milestone for us,” explained Moen. “On a three-day cruise, the Skandi Marstein used 35% less energy than a diesel vessel.”
Speaking on the growth of the technology since 1996, Moen noted: “The complexity of a project grows as the complexity of the individual components increases. Although the Skandi Marstein was advanced for its time, it is actually no more than a floating truck. It delivers supplies to a drilling platform and hauls away trash. But the new pipeline ships will have to operate under much more extreme conditions, hold their exact positions in deep water, and provide plenty of energy for welding, insulating, and laying pipelines.”
With regard to future developments, Moen commented that there appears to be a lot of potential for drives not dissimilar to those currently utilized in hybrid cars — utilizing batteries as a means to compensate for fluctuations in propulsion power.
Such an approach has been used by Siemens before, in the hybrid-powered Prinsesse Benedikte — which is a 140-meter ferry that connects Denmark and Germany, and can transport over 300 cars and 1,000 passengers a trip. The ferry is powered by 17,440-kW diesel engines that generate the electricity that then drives the electric motors with the aid of frequency converters. As mentioned before, a battery was integrated into the system, one with a storage capacity of around 2,900 kW-hours. This allows for the motors’ varying energy requirements to be compensated for — resulting in a more evened-out level of operation, thereby saving up to 15% on fuel-use, and reducing wear on the engines.
All-electric drive systems are also a possibility — though, of course, owing to the energy requirements this approach is seemingly best suited for short trips with long port calls, which allow batteries to be fully recharged in between uses, and the potential of running out of energy to be greatly minimized.
The first such entirely-electric ferry in Norway is currently set to enter service next year — bringing cars and people across a major fjord in the country.
Another major use for electric drives is in the “quieting down” of ships — many research ships, for instance, require very quiet environments, which electric drives can provide.
Many other kinds of vessels have also been equipped with Siemens drive technology. For instance, research ships benefit because they require particularly quiet drives (almost as quiet as those used for submarines). And in the case of fishing boats, ship designers at Siemens have been able to increase onboard storage space by 40%. Since the diesel engines no longer have to be directly connected to the propellers, the drive system can be installed with more flexibility. As a result, available space can be used more effectively.
The future does seem to possess a number of other possibilities as well with regard to electric ships — it’ll be interesting to see what comes of the technology (or technologies) over the next few decades.
SOURCE:GO Media - written by James Ayre - Image Credit & Source: Siemens