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 Hybrid retrofit power train on MS Nadorias keeps inland waterways clean in Holland

the speed and pitch of the propeller to be optimised for efficiency. The vessel is now powered by a diesel-electric hybrid propulsion

systemfromHSP using a VaconNXP Liquid CooledDrive and twoDanfoss drives. A newmain switchboard equipped with Vacon NXP Liquid CooledDrives was installed in the engine room. To eliminate the need to run a separate generator for the ship’s 50Hz on-board grid when sailing, they also built a VaconNXP MicroGrid inverter into the switchboard. This converts the variable frequency fromthe new generators to a fixed 50Hz clean ship’s grid. It ismuchmore fuel-efficient than operating a diesel generator at low load with a poor fuel efficiency. “We savemore than 15 per cent on fuel due to the hybrid

propulsion system. The ship now travels on the same route as it did before the conversion and we have been able to compare the fuel consumption over a long period,” says Sebastiaan van der Meer, who together with brotherDominic and business partner Edwin Green own the Sendo Shipping company. They are very satisfied with the new propulsion system. “The ship runs 98 per cent of the time in electricmode and the crew has become very skilled in operating the ship in economymode without the need for full throttle.” As another positive side effect, the ship is extremely quiet,

because the two generators are located far away fromthe bridge and accommodation area. “We went froma noise level of 60dBA in the wheelhouse to just 42dBA, which is really quiet,” adds van derMeer. The retrofit had its challenges however. One of themain hurdles

was finding space in the engine room. KoedoodDieselservice BV andHybrid Ship Propulsion BV (HSP) performed the retrofitting project. They solved the space problemby replacing the original main engine with a new compact systemcomprising a new engine and a high-torque shaftmotor. The two new generators were placed in the bow of the ship and the electrical power was fed back


 Autonomy is easier.  River boats: silent study of wild life.  Ski boats, record breaking: best acceleration.  Leisure submarines: fun, independence for anyone.  Military: little or no heat or sound signature attracting missiles.  Energy independence by harvesting such energy sources as sun, waves, tide and wind is easier.  Workboats: provide electricity at destination for equipment and disaster recovery.  Tugboats:maximumpower fromstationary and holding positionmore precisely. Lowest upfront cost for small vessels and potentially lowest cost of ownership formost vessels.  Reducing deaths & sickness of humans and wildlife from local air and water pollution.

12 /// Environmental Engineering /// February 2017

to the engine roomat the stern through two new cables. The generators can run either as single units or in parallel.

CABLE-LAYING In drilling or cable-laying vessels, anything up to amile of cable has to be paid out over the side during passage. The weight of the cable is somassive that the drivemotor has to reverse its function frommotor to generator, in order to brake the cable reel. Air- cooled resistors have heating elements enclosed within a fan- cooled cabinet. Thismakes themsuitable for deckmounting, often on anti-vibrationmounts. An important benefit of using an electric drive is that reliable

systems of regenerative and dynamic braking are available to complement or replace traditionalmechanical braking systems. The advantages of electric braking include, just as in cranes, lifts, hoists and conveyors, the control, reliability,mechanical simplicity, weight saving and, in certain cases, the opportunity tomake use of the regenerated braking energy. In such applications, air cooled resistors are common, but in

mediumvoltage, high-power applications, liquid-cooling wins. According toDavid Atkins, projects director at Cressall Resistors, “Amedium-voltage drive running off a 3.3kV supply to turn a 500kWmotor will put a severe heating load on the application’s power transistors, hence the need for water cooling. As a rule of thumb, if 1MWormore of heat needs to be dissipated, direct water coolingmakesmore sense.” Cressall’s new EV2 advanced water-cooledmodular resistor

range for low- andmedium-voltage applications is designed to function in severe environments, like those in whichmarine systems have to function. This patented design encapsulates and completely separates the resistor elements fromthe coolant. A typical 1MWfresh water-cooled brake resistor formarine use

is basically a 10ft (about 3m) tube with large heating elements similar to those found in common household kettles. The braking electricity that is being regenerated powers these elements.Most ships have a chilled water system, which circulates cool water throughout the vessel, used for both air-conditioning and equipment cooling. There is also a sea water variant with construction and ratings

similar to the fresh water designs, but with titanium-sheathed elements in higher-grade stainless steel vessels, suitable for continuous duty in hot sea water. The problemis that heating elements cannot be used here at an operating voltage ofmuch above 1.5kV, whereasmedium-voltage drives will typically use a 3.3kV supply. Cressall’s EV2 resistor is not limited by this restriction. This is a

25kWunit available singularly or as a block with a common cable box attached to 250kWbraking power input using a common water supply. Cold water comes in one end and hot water comes out the other. The EV2 has the advantage of higher operating voltage, lower weight and compactness, and is therefore ideal for marine applications. EE

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