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GTT, DNV GL and CMA CGM release feasibility study on LNG containership

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LNG Industry,

Gaztransport & Technigaz (GTT), DNV GL and CMA CGM have released a feasibility study for a new mega box ship. The Piston Engine Room Free Efficient Containership – or PERFECt – is an LNG-fuelled concept vessel powered by a combination of gas and steam turbines and is electrically driven. The concept has the potential to be more efficient, flexible and environmentally friendly than the 20 000 TEU two-stroke diesel engines that currently drive large containerships.

Remi Eriksen, the Group President and CEO of DNV GL, said: “The shipping community has realised that LNG enables the implementation of new propulsion concepts such as demonstrated by the PERFECt design that can increase a vessel’s efficiency, reduce fuel consumption and therefore offer a commercially interesting solution. I am confident that the utilisation of LNG as ship fuel will increase over the next few years.”

Gerd Würsig, the Business Director for LNG-fuelled ships at DNV GL – Maritime, added: “The impulse behind this study was our interest in seeing how a modern ultra large container ship design could benefit from utilising COGAS, which is a system for combined gas and steam turbine power generation […] A modern, land-based combined cycle LNG-fuelled power plant will reach fuel-to-power efficiency ratios of up to 60%, which is higher than conventional diesel engines, which can achieve up to 52%. In addition, the power density by volume and weight is much higher for a COGAS system.”

Jean-Baptiste Boutillier, the Technology & Information Director at CMA Ships, said: “CMA CGM and its subsidiary CMA Ships position themselves as pioneers by contributing to this worldwide leading innovation. This concept rethinks the ship’s design. The COGAS system with electrical propulsion gives us a great deal of freedom in the general arrangement and in tailoring the installed power to the actual operational requirements […] The lower footprint of the machinery system and increased flexibility of the electric propulsion system means we can increase the capacity of the vessel, despite LNG tanks requiring more space than traditional fuel oil tanks, thereby generating greater revenues and reducing the payback time for the additional CAPEX required.”

Arthur Barret, the LNG Bunkering Program Director at GTT, said: “Gas turbines associated with steam turbines in co-generation mode are ideal for the efficient utilisation of LNG as a fuel. This new design combines the exceptional volumetric efficiency of membrane containment technology with flexible electric propulsion to save even more cargo space compared to a conventional design […] In addition to being a cleaner fuel, LNG is very abundant and could be made available for bunkering cost effectively for this kind of trade much sooner than commonly admitted today.”

Making full use of the DNV GL COSSMOS tool, a comprehensive analysis of the potential power production and propulsion system was carried out in order to analyse the COGAS system. The COSSMOS tool made it possible to attain highly detailed data for the calculating the overall efficiency of the fuel in a complete round voyage. By using a global FEM analysis, the partners in the project were also able to evaluate the impact the changes made to the general arrangement.

Both of the LNG fuel tanks have a capacity of 10 960 m3 and are located below the deckhouse, thus enabling the vessel to have enough fuel for Asia/Europe round trip. In addition to this, as the steam and gas turbines are integrated at deck level in the same deckhouse as the LNG tanks, space that is normally taken up by a conventional engine room, is able to be used as additional cargo capacity.

As the electric power generation is dissociated from the electric propulsion, the electric plant can be moved away from the main propulsion system. This offers flexibility and means that an engine room is redundant. In addition to this, all three electric main motors are arranged on a single common shaft, and are able to be operated entirely independently of one another. This provides increased redundancy and reliability, as well as safety.

Due to gas turbine-driven power production and the utilisation of clean fuel, the machinery systems of the vessel will be more robust. This simpler, sturdier design will lead to new maintenance methods, which are already in use in aviation. These strategies would reduce both costs and crew.

The study also found that the minimisation of the size of the steam turbine, a reduction of power capacity and condenser cooling, as well as using a two-stage pressure steam turbine and steam generation, would further improve the efficiency of the system. The propulsion system will be the focus of the next stage of the study, in which even greater efficiency and cargo capacity will be sought after.

Edited from various sources by David Rowlands

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