Turnkey contracts dominate diesel electric market

Increasingly, yards are turning to single-source `turnkey` contractors for diesel electric propulsion machinery, say manufacturers. Vendors are assuming responsibility not just for the supply and installation of propulsion and power generation equipment such as prime movers, converters and motors, but also associated equipment such as dynamic positioning systems.

Cruise ships continue to form the majority of references for diesel electric installations, but increasingly diesel electric is the preferred choice for many other types of sophisticated vessel.

For ships such as floating production, storage and offloading (FPSO) vessels, drillships, offshore vessels, and others with high demands for on board power or reliable, redundant propulsion, diesel electric combines operational flexibility with safety, reliability, reduced noise and vibration and reduced maintenance requirements.

The latest addition to Festival Cruises` fleet is the 1,200-passenger Mistral. Although somewhat smaller than many modern cruise newbuildings, Mistral also makes use of a diesel electric power plant based on four of diesel alternators, each of 7,650kW, generating 6.6kV current.

Typically, says Alstom`s Michel Double, Alstom recommends synchro-converters for applications such as cruise ships. The arrangement of a synchro-converter with a synchronous motor provides excellent overall efficiency and reliability with a reduced number of components, and a high operating flexibility because of the system`s ability to deliver maximum torque over the entire speed range.

Manufacturers such as Siemens and ABB agree with Alstom`s assessment of the suitability of synchro-converters on cruise ships, whereas for specialised applications – such as icebreakers, where up to twice the rated torque may be required at zero speed – cyclo-converters are the generally preferred choice, given their high dynamic performance and ability to provide high torque at low speeds.

However, one of the most notable features of Mistral is that the diesel electric installation makes use not of synchro-converters but the company`s new Onix converter technology with pulse-width modulation (PWM) and insulated gate bipolar transistors (IGBTs).

Another Meyer Werft newbuilding, Superstar Virgo, also has a diesel electric propulsion and power system. This installation is based on four MAN B&W 14 V 48/60 diesel generators, which develop 14,700kW at 515 rev/min. ABB also supplied the electric propulsion motors, which have an output of 20,000kW. The motors transfer power via the ship`s shafts to FP propellers.

ABB has delivered electrical power generation and distribution systems for a number of floating production, storage and offloading platforms (FPSOs) and a number of drillships, including Petrojarl 1, Gryphon A, Petrobras XV111, Petrojarl Foinaven, Balder FPU, SPU 550, and Varg FPSO.
More recently, it has delivered the power generation and distribution systems for the FPSO and the shuttle tanker serving the Terra Nova development on Canada`s Grand Banks.

DIESEL-ELECTRIC

Booster drive `adds another cylinder` to an engine.

Diesel electric booster drives can supplement a main engine and protect it from damage, claims Siemens.

Danish shipowner Maersk has become the launch customer for a new type of diesel electric booster drive on board its container ship newbuildings. The drive was developed by Siemens in Germany using experience gained from its work on shaft generators, including generators with drive operating modes.

The first examples of the diesel electric booster drives was fitted to the seventh ship in Maersk`s on-going series of S-Type post-Panamax newbuildings at Odense shipyard, and a total of nine shipsets have so far been ordered.

Siemens claims that fitting a diesel electric booster station can provide a ship with the equivalent of another cylinder on its main engine, without a reduction in cargo carrying capacity, and says that the advantages of the system are such that the cost of installing the drive and required diesel generating capacity is quickly recouped.

The system takes electrical energy generated by the ship`s network and turns it into propulsion power rather like a stepless, automatic gearbox. In this way, the diesel electric booster engine supports the main engine, particularly during critical operating conditions, such as when starting, while accelerating, and at maximum output power.