Efficient new low-profile coaster enters North Sea trade

Ultra-efficient coaster ‘Tharsis’ has diesel-electric propulsion and twin screws; she entered service between Duisburg, in the Ruhr heartland, and the UK inland port of Goole Ultra-efficient coaster ‘Tharsis’ has diesel-electric propulsion and twin screws; she entered service between Duisburg, in the Ruhr heartland, and the UK inland port of Goole

David Tinsley examines a new Dutch-built inland/coastal cargo ship with diesel electric propulsion.

Underscoring the Dutch maritime cluster’s business resolve and remarkable range of capabilities in the small-ship sector, a highly efficient new design of sea/river coaster has entered North Sea trade, linking industrial regions of Germany and England. The nature of the design and engineering concept embodied in the 2,300dwt Tharsis, coupled with the ship production philosophy applied, have provided a basis for better ensuring long-term viability in the ever-challenging environment of European short-sea cargo vessel operations.

The project has added significance for the fact that there has been a paucity of investment in the under-3,000dwt category of the small-ship market over some years now, against a backcloth of weak freight rates and the inexorable shift towards greater scale economies. Where newbuild projects in this segment have been implemented in recent years, Dutch shipbuilders, owners, ship management companies and equipment suppliers have been most prominent. The Tharsis constitutes the latest response by the industry to the need for new solutions that can stimulate the modernisation of fleet capacity able to sustain or offer seaborne freight movements direct into inland ports and berths.

Tharsis has been built to Dutch account by Scheepswerf De Kaap in accordance with the latter’s Kaapcoaster design concept, characterised by exceptional fuel economy resulting primarily from the adoption of a diesel-electric power and propulsion system employing small main generator sets. Co-operating with the yard in the bid to attract further orders for the vessel type and possible derivatives, DSM Shipbrokers is also promoting the design concept as the Green Cape Trader. Both De Kaap and DSM are located in Meppel, on the Dutch inland waterway system.

De Kaap is qualified in turning out seagoing and inland cargo vessels and tankers up to 135m in length, using a transverse building slip of 110m. Dutch shipbuilders are longstanding practitioners of the business model whereby hull fabrication is subcontracted to yards in eastern Europe and/or sections are supplied from yards elsewhere in the Netherlands. However, De Kaap has continually invested in the wherewithal to undertake full construction in-house at its own premises, as has been the case with Tharsis. The yard has devised the design and its potential variants for serial production, with a focus on ensuring both competitive newbuild prices and very short delivery times.

The new entrant to the Dutch fleet is ascribed to Tharsis Sea River Shipping, representing several individuals from the Dutch shortsea community, and management has been entrusted to the Delfzijl firm Banier Scheepvaart.

At just under 88m in length overall and of 11.4m maximum breadth, the Kaapcoaster 2300 type represented in Tharsis has a laden draught of 3.7m, with a corresponding air draught of 5.3m. In ballast condition, the air draught is 6.1m. ‘Flattening down’ for navigation under bridges and other crossings is achieved by lowering the hydraulic pillar-mounted wheelhouse, and dropping the folding masts. The low-profile and shallow draught parameters render her especially well suited to trade to inland ports on the Rhine, the Rhone, the Albert Canal, the Seine, and the Humber region.

Exemplifying her dual sea/river-going qualities, Tharsis entered the regular line operated by Rhenus Maritime Services(RMS) between Germany’s Ruhrgebiet and the UK inland port of Goole, some 50 miles from the North Sea. In her debut assignment, she conveyed a 1,885t shipment from the inland hub port of Duisburg, arriving on October 4 at the covered Steel Terminal at Goole, on the River Ouse, and made the return voyage to the Rhine with a 1,700t cargo.

Pivotal to the attractive fuel consumption properties and the ‘green’ concept on which the twin-screw Kaapcoaster is predicated, the powering arrangements are based on three 400kW main gensets, incorporating Volvo Penta D13MG diesels. Propulsion is by two electric motors of just 375kW, driving two fixed-pitch propellers of 1.6m diameter through Reintjes reduction gearboxes.

The engine type, as the marine genset (MG) version of the manufacturer’s 13-litre D13 six-cylinder diesel, was launched at the 2011 Nor-Shipping exhibition. Each of the prime movers in Tharsis drives a Leroy Somer alternator and delivers its maximum 400kW at 1,800rpm. The power plant is compact in nature, a factor contributing to the optimisation of the hull envelope for revenue-earning purposes.

The Ridderkerk-based company D&A Electric was responsible for the design, turnkey delivery, implementation and commissioning of the complete drive system, including the generators, the main propulsion motors and the electric motor for the bow thruster, the main switchboard, power management system, Eprop (propulsion) and Ebow (thruster) panels and the two static converters for the board net.

Since service results from Tharsis are as yet limited, and given the influence of actual trading profiles on fuel usage, the shipyard is understandably cautious in quantifying the design’s fuel consumption performance. However, while stating that “the vessel consumes substantially less gas oil than similar vessels with normal, diesel-driven main engines”, it has indicated that obtainable savings are in the order of 20% or more, with parallel benefits in reduced exhaust emissions.

In advocating the concept under the Green Cape Trader designation, DSM Shipbrokers asserts that operation at up to about 70% of available power could mean a consumption rate of less than 3,300 litres per 24 hours in comparison with 4,400 litres-plus by similar capacity ships, subject to the master’s judicious use of the engines. But DSM acknowledges the crucial influence of weather and river conditions as well as operating profile, and is therefore also guarded in its quantifications in these as yet early days for the innovative, small-ship type, although the prognosis is very favourable.

The propulsion arrangements give a service speed of about 10 knots laden. The fact that the system is based on two drivelines imbues redundancy and makes for operating flexibility, such that an engine may be shut down when steaming at lower speeds or running downriver with the current. The diesel-electric system and configuration, in comparison with conventional diesel power and mechanical drive, is claimed to offer a range of additional benefits including a reduced overall power requirement, space and weight savings, easier and less costly plant maintenance, and reduced noise and vibration.

Having twin propellers and twin Promac hydrodynamic profile rudders confers a high degree of manoeuvrability, a vital asset in trade to small ports and river berths. Ship handling at restricted or tidal berths and in narrow waterways and fairways is assisted by a 350kW Van Wijk bow thruster. The unit is electrically powered via the D&A Ebow panel off the main board.

Tharsis has a single box-like hold, bounded by a 1.15m-wide double skin and 1.00m double bottom. The hold affords an obstruction-free volume of 3,272m³ (about 115,550ft³) over a length of 60.6m, width of 9m and free height of 6m, and is conducive to the efficient working and stowage of a wide range of general cargo and bulk commodities, including grain, coils and other steel products, timber, coal and IMDG-categorised dangerous goods. The headroom is also sufficient for two tiers of containers. The tanktop is strengthened for 15t/m², and the cargo space can be compartmentalised in various ways using two moveable bulkheads. The hold ventilation system ensures six air changes per hour.

The hatchway is closed by 10 pontoon-type covers, and handling is effected in characteristic Dutch coaster/shortsea vessel manner by a travelling gantry crane, the cargo access outfit having been supplied by Coops & Nieborg.

The Kaapcoaster concept lends itself to adaptation to owners’ specific requirements, and it is understood that the shipyard is flexibly disposed in this regard. Modifications may include a different length overall, the nomination of a fixed rather than an elevating wheelhouse, and the adoption of cargo handling gear such as a deck-mounted excavator.

Furthermore, and in response to growing environmental controls and the anticipated development of an LNG bunkering network, consideration is being given to a gas-electric version of the design, and also to dual-fuel machinery. Permutations of these various elements could be offered in a single vessel.

Principal particulars--THARSIS

Length oa 87.95m
Length bp 84.32m
Breadth, maximum 11.40m
Depth to main deck 5.80m
Draught, loaded 3.70m
Draught, ballast 2.91m
Air-draught, loaded 5.30m
Air-draught, ballast 6.09m
Deadweight 2,300dwt
Gross tonnage 1,595gt
Hold capacity 3,272m³
Propulsion system Diesel-electric
Main diesel generators 3 x 400kW
Propulsion motors 2 x 375kW
Propellers 2 x fixed-pitch
Service speed 10.1 knots
Bow thruster 1 x 350kW
Class Bureau Veritas
Flag Netherlands³

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