Green feeding from Denmark

by | 4th April 2017 | News

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The Naval Architect: April 2017

The shipping industry’s ageing and polluting feeder fleet is in need of an emissions angel. In 2005, 35% of Sulphur deposition in coastal areas originated from international shipping while 20% of Nitrogen deposits in coastal areas came from ships, according to the same report (Main Report Shipping, 2013).


Danish-led initiative, Green Ship of the Future (GSF), set out to change this, undertaking the Regional ECOFeeder project in 2016 to inspire a “responsible” renewal of the feeder fleet.


The project involved an array of participants from every strata of the maritime industry and has now concluded with the release of a feeder ship design from Odense Maritime Technology (OMT), a Danish design, production engineering and project managing company for the maritime industry.  


The overarching aim was to demonstrate that a large proportion of necessary emissions reductions from shipping can already be obtained by applying available technology. “From the beginning we were not after a ‘fantasy ship’,” says Thomas Eefsen, business development director for containerships at OMT.  “We wanted something that is ready for now, or at least the very near future”. However, this sentiment does not mean that ongoing searches for the next generation of fuels will grind to a halt; rather that shipping has the power to be substantially more efficient right now with the promise of even greater gains in the future.


According to those involved in the project, the Regional ECOFeeder design achieves at least a 30% reduction of CO2 per transported container compared to world fleet average, Sulphur 2020 compliance (0.5% S), NOx Tier III compliance, as well as reduced particulate matter and a reduced black carbon footprint.


A second aim was to reduce the cost per TEU per nautical mile compared to current levels in terms of operation and manning, adding financial weight to the environmental argument for change.
OMT defined the project’s main objectives in terms of emission targets, but left the identification of solutions to the partners to encourage creativity. Suggested technologies were then assessed in combination with others in order to ensure their benefit to the ship system as a whole. Through three phases, the partners ideated, shared knowledge and evaluated the suggested solutions in order to reach the project’s main objective and emission targets.


Regional ECOFeeder has been conceptualised to provide basic container carrier functionality with a design that centres on operational simplicity and possesses a compact arrangement. This called for a box-shaped, open top design with containers stowed as closely as possible in cell guides. The nominal capacity is 2,500TEU without LNG tanks and 2,422TEU with LNG tanks, while for transit of the Kiel Canal it can be loaded with 1,100TEU at 14t/TEU.


A wide-beam, maximised to 32.5m for passage of the Kiel Canal, has been used to optimise container capacity. Eefsen explains that “considering speeds are lower than 5-10 years ago, wide beam designs have become more effective.” The design choice improves intake, both by directly providing more space for containers, but also by increasing stability, which reduces the need for ballast water and increases the vessel’s payload. Slim ballast tanks have been selected as a corollary design feature, offering a lower vertical centre of gravity that also helps to improve container intake; container positions below can be maximised as a result.


The 32.5m beam is said to improve container intake by more than 10% compared with a typical containerships of the same length. In terms of drawbacks, propulsion power must be increased because of the wider beam, but partners in the project say: “considering the operational speeds of the vessel design, the net fuel reduction per transported container is still positive”.


Regional ECOFeeder’s open top allows for easy loading and lashing with the aim of reducing time spent in port. The vessel has five open cargo holds with cell guides to the 13th tier and semi-automatic stack splitters at the 10th tier of containers. In this way, 20 or 40 foot containers may be loaded to the 13th tier of containers without hatches and without lashing. This application reduces harbour turn-around time by up to two hours per port call. According to GSF, feeder vessels can spend up to 50% of their time in harbour, so by cutting this time vessels will be able to improve their efficiency between itinerary stops, travelling slower and using less fuel.


The vessel’s high coamings/side-structures serve the following purposes. Firstly, to ensure the flooding angle is large enough to allow hatch covers to be omitted; secondly, to support the top of the stack-cells; and, thirdly, to provide necessary hull girder strength without excessive scantlings.


In order to save cost and space, the ship’s crew was reduced and a major overhaul of the vessel’s accommodation was undertaken. This involved shrinking and sinking the accommodation block within the ship to allow containers to be stored above it. The crew cabins are located along the ships side at A-deck level, with five cabins in each side. The cabins occupy the outboard two rows in each side, leaving the remaining eight rows for cargo or LNG-fuel tanks.


A particularly novel arrangement of the deckhouse was formulated. Following hotly on the heels of developments in the fields of smart and autonomous shipping, cameras and sensors (though not allowed by SOLAS and flag states currently) in the front, aft and side of the vessel are replacing the traditional bridge layout for officers on the bridge. A control room located in a lower and optimised deck house arrangement allows the vessel to be controlled from the aft of the vessel and is intended to be used by on-duty officers to manage look-out duties. Container gains as a result of these measures stack up to approximately 100TEU, while the arrangement of the accommodation is optimised with fewer staircases.


The vessel is designed with LNG powering based on a 2-stroke dual fuel engine, which reduces direct CO2 emissions by approximately 20% per transported container and almost eliminates sulphur emissions. Eefsen says: “Discussions were held about hybrid systems, but our conclusion was that when you have the space [for a 2-stroke engine] it is very hard for other systems to compete, as there are too many transmission losses in electric systems.” NOx Tier III requirements are met by an EGR NOx abatement system. The vessel has four cylindrical C-type tanks with total capacity of 1,300m3, which provides endurance of around 15 days or around 5,000nm.


The oil fuel tanks are located forward of the engine room and below the chain lockers, outside of useful cargo space. LNG is carried in four cylindrical tanks located above the accommodation, but larger LNG tanks may be adopted at the cost of more container slots.


Power is generated by an in-line shaft-generator to improve fuel efficiency and is backed up by two diesel gen-sets.


“The power for auxiliary systems and reefer containers is approximately 10-15% of the total installed power,” explains GSF. “Considering the 20% higher energy efficiency of 2-stroke engines compared to 4-stroke engines, auxiliary power is provided by a 2,000kW PTO shaft generator producing electric power for the auxiliary systems and reefer containers. Compared with typical electric power generator systems with separate 4-stroke auxiliary engines, the estimated overall energy efficiency is around 6% higher for a roundtrip.”


A 1MW battery pack is included in order to reduce generator load peaks. The engine load on the auxiliaries is continuously optimised for optimum specific fuel consumption, and in harbour mode the electric bow thruster is effectively powered by the battery. This has the effect of reducing power consumption by 1-2% and means that the number of required auxiliary engines is reduced by one auxiliary genset.


In addition, an Organic Rankine Cycle (ORC) unit has been considered for Regional ECOFeeder that utilises exhaust gas heat to produce electricity. Use of low-sulphur (<0.1 %) fuel enables cooling of the exhaust gases without issues of sulphuric acid formation on the boiler tubes. The ORC unit is designed based on the assumption that no service steam is required for HFO preheating, etc. due to the use of low-sulphur fuel. Space heating demands are covered by heat from the HT cooling water. For ISO conditions, fuel savings of 3.3 % compared to the fuel energy used in the main engine can be obtained. For winter conditions, fuel savings of 2.3% can be obtained. By including scavenge air and EGR cooler heat, the fuel saving potential will increase.


The ship is propelled by a single large controllable pitch propeller with high efficiency Kappel propeller blades. It is directly coupled to the engine and possesses a similar propeller efficiency to a fixed pitch propeller, according to Eefsen. The solution also offers improved load flexibility in combination with the shaft generator as well as significantly better manoeuvring characteristics – an important feature for container feeder vessels with numerous terminal calls.


Air lubrication has also been included in the design, utilising corporate partner Silverstream Technologies to provide a solution tailored to the vessel. Silverstream’s solution uses micro bubbles to reduce resistance working on the ship’s hull. CO2 reductions for Regional ECOFeeder are estimated to be around 6% at speeds above 15knots.


In addition to the above-mentioned technologies and solutions selected, the design includes frequency control of pumps and fans, which are already widely accepted by the industry, and the vessel may be supplied with necessary equipment for cold ironing in ports, should this be available at the terminals. GSF clarifies that these technologies have not been considered when calculating the reduction potential in terms of energy and CO2 emissions in this project (the results of which can be found below). However, they proceed to add, it is proven that relatively large electric power savings can be obtained by including frequency control of selected pumps and fans.


Emissions reductions for two case study schedules
Emissions reductions have been predicted for two typical feeder schedules in Northern Europe based on the dimensions and capabilities of the Regional ECOFeeder design.


The blue route illustrates a schedule between Netherlands, UK and Scandinavian countries, while the red route illustrates a schedule between Hamburg and Baltic countries including transit of the Kiel Canal.


In terms of IMO’s Energy Efficiency Operational Indicator (EEOI), there is an estimated reduction of 35% for the blue schedule and 30% for the red route compared with the typical reference vessel, which is based on MGO. 


Following suit, the Energy Efficiency Design Index (EEDI) for Regional ECOFeeder shows a significant reduction compared with the IMO baseline and reference design. A reduction of almost 40% is achieved compared with the IMO baseline, while a reduction of approximately 30% is achieved compared with the reference vessel.

Note: Green Ship of the Future is a public private partnership working to reduce emissions from the maritime industry. Members include: ABB, Alfa Laval, Bureau Veritas, Corvus Energy, Danfoss VLT Drives, Danish Maritime, DNV GL, DTU Mechanical Engineering, HOK Marineconsult, Lloyd’s Register, MAN Diesel & Turbo, Rolls Royce Marine, Silverstream Technologies, and VP Solutions.

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