high all electric ship concept

Marine Electrical High Voltage MEHV 14 / June 2008 /SULAIMAN 1 1

To Be A World Class Maritime Academy


HV Voltage Generation, Conversion , Transformation and Distribution in Ship

ALL ELECTRIC SHIP (AES) CONCEPT




Marine Electrical System • Maritime electric systems include power generation, distribution and

control, and consumption of electric power on supply- service- and fishing vessels as well as offshore installations.

• Electric propulsion has increased especially for vessels with several largepower consumers, for example cruise ships, floating production systems,supply- and service vessels.• Maritime electric systems are autonomous power systems. The prime

movers, including diesel engines, gas- and steam turbines, are integral parts of the systems.

• The power consumers are large compared with the total capacity of the system, as for example thruster and propulsion systems for DP operated vessels, drilling systems, HVAC systems on board ship




Marine Electrical System• The overall power train efficiency with DEP is around 87-

90%. Use of permanent magnets in electric generators and motors as well as general advances in semiconductor technology may improve this figure to around 92-95% in the near future. Electrical transmission will consist of three basic energy conversions:

• From (rotating) mechanical energy into electrical energy: E-generator

• From electrical energy into (rotating) mechanical energy: E-motor

• Some form of fixed or controlled electrical conversion in between: power converter




Systematic overview of existing typesE-generator

• Mechanical ==> Electrical: E-Generators• - DC Generators• - AC Generators

E-Motors

• Electrical ==> Mechanical: E-motors• - Driving motors• - Synchronous Motor• - Positioning motors

Power convertersElectrical ==> Electrical: power conversion or transformation• - Fixed transformers• - Controlled converters• - Static converters• -Inverter




Structure of a combined power plant for ships




Electric Propulsion System (AES) • Electric propulsion of ships has been know for a long time to human • Dynamic changes in human discovery has given several up and down in

history• Recent time have seen a a lot of Passenger ships being built with all

electric system for various advantage that over the conventional prime movers

• Early large passenger vessels employed the turboelectric system which involves the use of variable speed, and therefore variable frequency, turbo-generator sets for the supply of electric power to the propulsion motors directly coupled to the propeller shafts. Where, the generator/motor system was acting as a speed reducing transmission system.

• Electric power for auxiliary ship services required the use of separate constant frequency generator sets. System with generating sets to provide power to both the propulsion system and ship ancillary services.

• However fixed voltage and frequency system are suitable to satisfy the requirements of the ship service loads.




Electric Propulsion System (AES)• Other complication associated with earlier systems is difficulties in using multiple

motor per shaft when required propulsion power was beyond the capacity of a single d.c. motor .

• Developments in high power static converter equipment have – presented a very convenient means of providing variable speed a.c. and d.c. drives at the largest ratings likely to be required in a marine propulsion system.

• The electric propulsion of ships requires electric motors to drive the propellers and generator sets to supply the electric power. It may seem rather illogical to use electric generators, switchgear and motors between the prime-movers (e.g. diesel engines) and propeller when a gearbox or length of shaft could be all that is required.

• In the light of the above, hybrid of gas turbine or Diesel with electric couple with dual fuelling that include natural gas, is explorable option for existing vessels, all electric ship using natural gas is also a good option.

• Currently there is interesting development for new ship need exploration on technologies to improve integrated full electric propulsion with advanced power management systems:

• Improved converter and power electronics technology

• Improved generators and motors




Electric Propulsion System (AES)• The AES give widespread electrification of auxiliaries and the opportunity

to use upgradeable and flexible layouts. It will include a low risk, cost effective and comprehensive Platform Management System that has a standardized Human-Computer Interface supportable for its entire service life and the goal to be an Environmentally Sound Ship.

• The fit into the goals of the Environmentally Sound Ship where : freedom of operation in MARPOL special and restricted areas; unrestricted littoral operations; port independence; minimum onboard storage of waste and reduced manpower whilst reducing cost of ownership and port reception costs.

• the also promise potential for replacing the current traditional systems used in steering gear, fin stabilizers with compact, power-dense actuators.

• They also offer potentials for possible use of electric valve actuators that will simplify system architectures systematic integration of upper deck to machinery.




Electric Propulsion System (AES)

• A 2001 study concluded that fitting a Navy cruiser with more energy-efficient electrical equipment could reduce the ship’s fuel use by 10% to 25%.

• Ship fuel use could be reduced by shifting to advanced turbine designs such as an intercooled recuperated (ICR) turbine. Shifting to integrated electric-drive propulsion can reduce a ship’s fuel use by 10% to 25%.

• There is Potential alternative hydrocarbon fuels Like biodiesel and liquid hydrocarbon fuels made from coal

• Recent time has seen firms offering kite-assist systems to commercial ship operators.

• Solar power might offer some potential for augmenting other forms of shipboard power.

• Talking about the question now the electric propulsion , especially with hybrid system offer the best answer to problem of energy




Propulsion motor• For efficient operation of propulsion motor there is a

requirement for a compact, power dense, rugged electrical machine to be utilized for the propulsion motor.

• For the full benefits of electric propulsion to be realized the machine should also be efficient, particularly at part load,

• In order to achieve suitable compact designs rare earth permanent magnet materials may be required.

• The machine topologies available for PMM are deemed to be those based on radial, axial and transverse flux designs.




PMM




Electric Propulsion System (AES)

• Integrated electric-drive system derived from a commercially available system that has been installed on ships such as cruise ships requires a technology that is more torque-dense (i.e., more power-dense) .

• Candidates for a more torque-dense technology include a permanent magnet motor (PMM) and a high-temperature superconducting (HTS) synchronous motor.

• In addition, electric drive makes possible the use of new propeller/stern configurations, such as a podded propulsion ... that can reduce ship fuel consumption further due to their improved hydrodynamic efficiency

• Podded drives offer greater propulsion efficiency and increased space within the hull by moving the propulsion motor outside the ships hull and placing it in a pod suspended underneath the hull.

• Podded drives are also capable of azimuth improving ship maneuverability. Indeed, podded drives have been widely adopted by the cruise ship community for these reasons.

• The motors being manufactured now are as large as 19.5 MW, and could provide the total propulsion power.




Azipod Drive Unit




Power for LNG ships • These alternatives are more economical and offer greater overall efficiency

with an added advantage of providing greater flexibility and redundancy• Diesel plant also raises are inherited with problem of vibration on

membrane • LNG carrier it is necessary to understand the interaction between the

structural resonance that is excited by the diesel engine and the separate resonance that is created within the membrane containment system interacting with LNG.

• The traditional application of gas fired boilers for steam turbine propulsion systems is no longer the only available option for LNG Carriers,”

• Direct drive, slow speed diesel plants, coupled with an on-board liquefaction plant to handle the cargo boil off, or 4 stroke medium speed diesel electric propulsion or gas turbine with diesel electric drive appear to offer the greatest operational efficiencies for the new designs of large LNG carriers.




Power generation for LNG ships• Although slow or medium speed diesel engines have been selected for some of the

recent LNG carriers with dual fuel installation option that uses both gas boil-off and ordinary bunkers.

• Variations of the dual fuel arrangements include: -diesel engine or gas turbine driven generators with one propulsion shafting system and

a liquefaction plant; -diesel engine or gas turbine driven generators with two propulsion shafting systems

and a liquefaction plant; -diesel engine or gas turbine driven generators with two azimuth thrusters and a

liquefaction plant. • To date, slow speed diesel with re-liquefaction plant as well as a gas combustion

unit, and medium speed dual fuel diesel with gas combustion units, are the preferred options for the new large LNG carriers recently ordered in Korea.

• It would appear that gas turbine with simple and combined cycles using heat recovery units to drive steam turbo alternators are another alternative being explored. Industry is currently developing the fuel gas systems for these gas turbine options.




Power generation for LNG ships• A dual fuel diesel-electric system uses forced boil-off from the cargo tanks

as the primary fuel and marine diesel oil as back-up fuel. The arrangement can also be adapted to current LNG carrier designs.

• Shipbuilders and engine designers that are proponents of dual fuel systems point out that a gas-electric propulsion plant is more compact than the traditional steam turbine plant used for LNG carriers, increasing cargo capacity within the same dimensioned hull.

• The IMO Gas Carrier Code requires two means of utilizing boil-off gas on all LNG carriers. Conventional systems use the main boilers for generating steam for propulsion. When this cannot be used, excess steam is redirected to the condensers. Similar arrangements are required for the diesel propulsion systems. Current industry proposals for the alternative means of boil-off gas utilization are a liquefaction plant or a gas combustion unit.

• Risk assessment methods are recommended for option selection




Power Distribution• As the demand for electrical are 3.3 kV or 6.6 kV but 11 kV is

used on some offshore platforms and specialist oil/gas production ships e.g on some FPSO (floating production, storage and offloading) vessels.

• By generating electrical power at 6.6 kV instead of 440 V the distribution and switching of power above about 6 MW becomes more manageable.

• As for electrical Power increases on ships (particularly passenger ferries, cruise liners, and specialist offshore vessels and platforms) the supply current rating becomes too high at 440 V.

• To reduce the size of both steady state and fault current levels, it is necessary to increase the system voltage at high power ratings.




Component parts of an HV• The component parts of an HV supply system are standard equipment

with: HV diesel generator sets feeding an HV main switchboard. • Large power consumers such as thrusters, propulsion motors, air-

conditioning (A/C) compressors and HV transformers are fed directly from the HV switchboard.

• An economical HV system must be simple to operate, reasonably priced and require a minimum of maintenance over the life of the ship.

• Experience shows that a 9 MW system at 6.6 kV would be about 20% more expensive for installation costs.

• The principal parts of a ships electrical system operated at HV would be the main generators, HV switchboard, FV cables, HV transformers and HV motors.

• An example of a high voltage power system is shown




Ship HV Voltage system




HV Systems• In the example shown the HV generators form a central power station for

all of the ship's electrical services. • On a large passenger ship with electric propulsion, each generator may be

rated at about 10 MW or more and producing 6.6 kV, 60 Hz three-phase a.c. voltages.

• The principal consumers are the two synchronous a.c. propulsion electric motors (PEMs) which may each demand 12 MW or more in the full away condition.

• Each PEM has two stator windings supplied separately from the main HV switchboard via transformers and frequency converters.

• In an emergency a PEM may therefore be operated as a half-motor with a reduced power output. A few large induction motors are supplied at 6.6 kV from the main board with the circuit breaker acting as a direct-on-line (DOL) starting switch.




Ship High Voltage Systems These motors are:o Two forward thrusters and one aft thruster, ando Three air conditioning compressors

• Other main feeders supply the 440 V engine room sub-station (ER sub) switchboard via step-down transformers.

• An interconnector cable links the ER sub to the emergency switchboard. • Other 440 V sub-stations (accommodation,galley etc.) around the ship are

supplied from the ER sub. • Some installations may feed the ships sub stations directly with HV and step-

down to 440 V locally.• The PEM drives in this example are synchronous motors which require a

controlled low voltage excitation supply current to magnetise the rotor poles.• This supply is obtained from the HV switchboard via a step-down

transformer but an alternative arrangement would be to obtain the excitation supply from the 440 V ER sub switchboard.




Ship high voltage systems




Converter Types

The principal types of motor control converters are:

- >a.c.-d.c. (controlled rectifier for d.c. motors) . a.c.-d.c.-a.c. (PWM for induction motors)

- >a.c.- d.c.-a.c. (synchroconverter or synchronous motors) .

-> d.c.-a.c. (cycloconverter for synchronous motors)




Controlled rectification converter and d.c. motor




Synchroconverter Circuit




Twin Shaft EL Propulsion




FPSO Electrical system Layout




Shuttle Tanker Electrical System Layout




Drill Ship Electrical System Layout

high all electric ship concept

Documents