The Motorship | HYBRID POWER FOR SHORT-SEA BULKERS


Self-sustaining, efficient tonnage for bulk trading in northern Europe (credit: Aasen Shipping).Self-sustaining, efficient tonnage for bulk trading in northern Europe (credit: Aasen Shipping).



Progressive, long-term design thinking underpins a Norwegian project for two ships to serve the humble but vital North European bulk cargo traffic, writes David Tinsley.

Drawing on Norwegian government funding support for the enlightened shipboard energy arrangements chosen, shortsea specialist Aasen Shipping has ordered two self-discharging bulkers incorporating hybrid powering.

The 9,200dwt minibulkers ordered from Dutch shipbuilder Royal Bodewes are scheduled to join Aasen’s fleet of self-unloaders by 2022, and are claimed to be the first of their kind to have been specified with diesel-electric hybrid propulsion.

While the intra-north European bulk commodity trades in which the shipowner is primarily engaged constitute typically low-margin shipping business, the capital cost premium for the hybrid solution is justified by the prospective, long-term payback. The environmental benefits associated with the incorporation of a battery pack also promise certain operating advantages, giving a commercial edge, over the coming years.

Each newbuild will be fitted with a travelling deck gantry-mounted excavator for loading and unloading at up to 900t per hour, conferring broader trading scope than gearless tonnage plus cost savings for shippers through vessel self-reliance in cargo handling as regards both equipment and personnel. Hatch covers will be lifted by dedicated panel-handling, movable gantries fore and aft of the excavator. The hydrodynamically-optimised hull design is just under 120m in length overall and 15.8m wide, with a maximum draught of 7.5m.

Aasen sought the advice of technology group Wärtsilä as to the merits of a hybrid installation, and the latter determined that the extra initial investment required for the incorporation of battery power would be more than offset by a high level of achievable fuel cost savings. Wärtsilä has been retained to supply the battery pack, direct-current (DC) switchboard and power management system as well as the small-bore, medium-speed main diesel engine, reduction gearbox and controllable pitch propeller.

The shipowner was keen to ensure that Wärtsilä Norway would cooperate closely with the shipbuilder’s subcontractor for the electrical equipment, so as to better ensure the development of an innovative yet comparatively simple solution.

Each vessel will be able to run her deck-mounted, electric excavator on battery power, and will have the means of feeding the shipboard net from the shoreside grid when alongside, eliminating the need to fire up gensets in port.

The specific nature of coastal and intra-regional bulk cargo shipping using such vessels typically involves multiple short voyages over time and transits at maximum speed, frequent waiting at or off ports due to tides or shoreside working shifts, and variable load demands on the discharge excavator during the cargo transfer process, all of which makes for wide and frequent fluctuations in energy requirements. This scenario was regarded as affording ample scope for the hybrid option, whereby battery packs and electrical feed can exert a load levelling effect as well as dispensing altogether with main or auxiliary diesel power in certain situations.

Noise reductions achievable in harbour through the use of the batteries, potentially when in manoeuvring mode as well as when alongside, rank as an increasingly important factor, given the increasing lack of tolerance among waterside inhabitants in many parts of Europe as to noise issues, no matter how long a port or terminal has existed.

The shipowner has indicated an expectation of fuel savings of more than 350t per annum through the arrangements nominated for the new ships. Specified battery capacity is understood to be some 340kWh, and the pack will be housed in a compartment right aft on the enclosed deck above the engine room.

Initially, the owner considered powering arrangements based on an LNG-capable, dual-fuel main engine, but decided against this option on account of comparatively high costs, coupled with what was perceived to be limited climate gain as regards emissions plus certain logistic and operational challenges as to LNG sourcing relative to trading profile.

Enova, the agency which promotes eco-friendly energy technologies under the aegis of the Ministry of Climate and Environment, has allocated NOK 7.35 million (US$790,000) towards the hybrid engineering aspects of the project, on the strength of the attributes as to energy savings and reduced climatic impact within the Norwegian regime.

The main machinery selected for each ship is an eight-cylinder model of the L26 engine, rated at about 2,600kW. The Wärtsilä four-stroke is among the shortest and lowest in its class, minimising engine room space requirements. Its relatively low component count also holds advantages as to maintenance needs.

Located at Mosterhamn, on the coastal island of Bomlo between Bergen and Stavanger, family-owned Aasen Shipping currently deploys eight self-dischargers with carrying capacities in the 3,500-7,650t range. The vessels are primarily engaged in contracts with industrial customers, carrying stone, salt, cement, grain, scrap, round timber and other commodities, but are also suited to breakbulk and project shipments.The company retains full commercial and technical management of the fleet, and also controls covered and open storage at Mosterhamn.

The award of the shipbuilding contract to Royal Bodewes at Hoogezand represents another string in the bow of the industry in the Netherlands’ northernmost provinces, resilient and innovative in the production and design of small commercial vessels.



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