Innovative and reliable products abound in the genset market, despite challenges from alternative technologies
The genset market has been relatively volatile in recent years, reflecting the general overcapacity in the market and consequent lack of newbuildings. In certain markets gensets are also coming under pressure from battery-based hybrid systems, which in some instances mean that there will be reduced need for onboard power generation.
Despite all this, there is still demand for efficient generating sets and no shortage of equipment options available. Wärtsilä’s Auxpac range of gensets covers a wide range of power requirements. Its most recent additions, the Auxpac 32 and smaller Auxpac 16, were introduced concurrently to the market as pre-engineered generating set packages based on Wärtsilä’s proven four-stroke diesel engine technology. The engines feature direct fuel injection and charge air cooling, and are suitable for auxiliary power applications on all classes and sizes of vessel. They are based on the Auxpac 20 and 26 engine packages, of which there are approximately 1,000 in operation with over 6 million cumulative hours of running.
The Wärtsilä Auxpac 32 is the most powerful generating package in the range, capable of an output of up to 4,160kW electrical (kWe), and its compact design provides a high power-to-space ratio. As a pre-commissioned standard package, installation time is reduced and reliability increased. The package is available with six-, seven-, eight- or nine-cylinder engine configurations, starting with the W6L32 specification rated to deliver 2,400 kWe. There are four more ratings in the range, with the maximum power output being over 4,000 kWe. Capable of 50Hz or 60Hz frequencies, the packages are suitable for a wide range of vessel types, and particularly aimed at the power requirements of tankers, bulk carriers and large container vessels.
The Auxpac 16 is of similar design and is available based on five-, six- or seven-cylinder engine configurations. The package includes an integrated multi-functional, digital automation system with electronic governing to ensure smooth control. This also provides rapid and stable response to sudden transients in load demands. The smallest W5L16 packages are capable of delivering 455 kWe at 50Hz or 525 kWe at 60Hz, with the W7L16 configurations offering 635 kWe and 735 kWe at 50Hz and 60Hz frequencies respectively.
The standard package scope of both products includes automation systems with serial bus communication interfaces for monitoring and safety systems, this arrangement minimising external cabling and interface connections. Baseframes are designed for resilient mounting directly onto the vessel hull structure, allowing simple installation and reliable alignment of the generating set. Resilient mountings reduce levels of structure-borne noise transmission from the generating sets to the vessel's hull, increasing the comfort for crew. Both Auxpac 16 and 32 units are capable of operation on the lowest LFO viscosity of circa 2.0 cSt to levels of 700 cSt seen in HFO (based on 50°C fuel temperature). The engine can also operate on fuel oils with sulphur contents below 0.01 per cent sulphur.
The Wärtsilä Auxpac 16 serves the lower end of the market, from approximately 500 kWe to 750 kWe per generating set. The Wärtsilä Auxpac 20 goes up to approximately 1,700 kWe, the Wärtsilä Auxpac 26 serves power needs up to 2,800 kWe, and finally, for the uppermost power range required typically by large container vessels, the Wärtsilä Auxpac 32 offers between 2,400 kWe and 4,500 kWe.
Electrical outputs are available at 400V, 690V or 6.6kV at 50Hz, with the same at 60Hz other than the lowest voltage, where 450V is the equivalent. Protection class is to IP23 as standard, with an option to increase this to IP44 if required. Temperature rise and insulation is to class F standards in all cases.
A more recent innovation has seen the increasing use of dual-fuel technology for main genset installations. This will be the case on the forthcoming Tallink 27-knot ropax Megastar, in the shape of two Wärtsilä 8L20DF medium-speed prime movers and a single 6L20DF model. LNG fuel will also be used by two 3,000kW thermal oil heaters, sized to meet the vessel’s considerable heating load.
The prime movers for the five main generators are three 12-cylinder models of the Wärtsilä 50DF engine and two six-cylinder versions, making for an aggregate output of 45,600kW on the basis of the nominal maximum continuous engine ratings. The overall generator output is 44,000kW.
The engines can be run on natural gas, LFO or HFO without any difference in delivered power, and will automatically switch to fuel oil back-up in the event of any interruption in LNG supply while in operation. Both the gas admission and pilot-oil fuel injection are electronically controlled.
The multi-genset configuration and electric drives will enable the operator to closely match the number of engines in service at any one time to the ship’s fluctuating power requirements, in accordance with scheduling needs, voyage profile, weather and ice conditions, and ‘hotel’ electrical load. Selected engines can then be used at their nominal power, where the efficiency is highest.
MAN Diesel & Turbo’s most recent engine to have proved its value as a genset is the 175D, which is now globally certified for marine propulsion (diesel-mechanic and diesel-electric) and genset applications with a power output of up to 185 kW/cylinder by the Classification Societies ABS, BKI, BV, CCS, DNV/GL, KRS, LR, NK, RINA and RS.
In fact, it was announced in July this year that, after more than 10,000 running hours on testbeds and a successful DNV GL type approval, an MAN 12V175D MEL Genset including SCR equipment had been installed on board the platform supply vessel Edda Fonn since 2016.
The Edda Fonn from Østensjø Rederi is an advanced, cost-effective, flexible 90m vessel used for inspection, maintenance, survey and light construction service. The vessel is equipped with a DP2 system, and is designed for the most challenging sea applications.
The retrofit into an offshore service and supply application with its challenging load profile – low engine load during working mode and high engine load during transit – was selected in order to ideally demonstrate the ease of installation and commissioning of the 175D into already existing rooms, and its efficient operation and reliability.
An existing genset was exchanged with the MAN 12V175D-MEL Genset, rated at 1,920kW, at 60Hz. The MAN 175D is engineered with all auxiliary components attached on the base-frame, while fitting into the existing vessel foundation.
Since the end of 2016, the genset has collected over 4,000 running hours. Chief engineer Nils Are Hermansen said: “The genset has been running smoothly for a few thousand running hours. It’s more efficient than our former propulsion set-up, both in terms of fuel consumption and maintenance efforts and costs. Due to the compactness of the genset and its small footprint, we could within a week and without any major modifications install it into the existing vessel system.”
Caterpillar’s marine generator sets span 11kW electrical output to over 7.7MW. Indeed, few companies can offer such a wide range of marine generating sets as Caterpillar, enabled through a combination of its traditional Caterpillar Marine products and heavy-duty packages from its MaK business unit. Its M25E and M32E engine platforms are suitable for propulsion duties as well as generator applications.
The M32E was designed for offshore markets with particular focus on diesel electric and generator set applications. Output speeds have been raised and there are now options of 720 rpm and 750 rpm drives. These speeds improve compatibility with electrical generators and, in turn, reduce generator costs and increase electrical efficiencies. The boost in cylinder power to 550kW has extended the M32 power range close to 5MW. Generator packages are now available with electrical outputs of 3,165 kWe with six-cylinder engines to 4,747 kWe with nine-cylinder engines, based on generator efficiencies of 96 per cent and a power factor of 0.8.
Using similar technological developments, the smaller MaK M25E generator package offers electrical outputs from 2,016 kWe to 3,024 kWe, the engine having a 5 per cent power increase and reduced fuel consumption compared with the M25C from which it was developed. The package uses a combination of proven features including the MaK FCT camshaft system and waste-gate and cylinder-bypass technology. As with the M32E, the M25E meets both EPA Tier 2 and IMO II requirements. Remote condition monitoring and diagnostic maintenance programmes are available to ensure engines continue running in optimum condition and at the highest efficiency levels.
Power and efficiency improvements have been achieved through a series of developments including a new-generation turbocharger system and an optimised, smaller charge air cooler. The engine design itself is more compact and weight has been reduced. Importantly, MaK has retained its policy on output ratings, which can be maintained when operating in any conditions, making high ambient load reductions unnecessary. The company offers an optimisation kit, which improves efficiencies when generator sets are running at load factors of 47 per cent or less.
The M20C product is the smallest package in the MaK marine generator set range, and is available in six-, eight- and nine-cylinder in-line engine configurations. Packages are based on a common single-piece base-frame, designed for ease of installation and reliable alignment. Auxiliary equipment is mounted on-package, including the fuel supply system, which is also suitable for both medium and heavy fuel oil duties. As a generating package, the M20C has power capabilities from 1,224 kVA to 2,160 kVA. At the top of the range, the MaK 9M46DF generator set has the largest bore engine and the highest power output, at 7,768 kWe, but it is closely matched by the 16-cylinder VM32C package, rated at 7,680 kWe in 50Hz operation.