By combining diesel-direct, diesel-electric propulsion and battery power the vessel can achieve average fuel savings of up to 30% and up to 40% reduction of emissions. The Bernardus still has a bollard pull of 60 tonnes.

The Bernardus. Click to enlarge.

Damen used existing technology for the ASD Tug 2810 Hybrid. One additional clutch was been added to the vessel and a 230 kW water-cooled electric propulsion engine between each main engine and the rudder propeller. One fire-fighting/generator set is installed to feed the electric propulsion engines or to drive the 1200 m³/hr fire-fighting pump.

The generator/fire-fighting set engine is fitted with an exhaust gas after-treatment system consisting of a Selective Catalytic Reduction (SCR) system, a Diesel Oxidation Catalyst (DOC) and a half open, Diesel Particulate Filter (DPF).

The fire-fighting/generator set engine can deliver 695 kW at 1800 rpm and is fully compliant with the IMO Tier 3 regulations being introduced in 2016. Each main engine has a maximum power of 1840 kW at 1600 rpm and is IMO Tier 2 compliant.

The captain can choose one of the following operating modes from the wheelhouse and then the Hybrid Control Unit manages everything automatically:

• Stand-by mode (with battery pack). All diesel engines will shut down and the battery pack feeds the normal electric system and the electric propulsion engines that are driving the rudder propellers. When the battery pack becomes empty the system will switch to free sailing mode automatically and the battery pack will be charged. The stand-by mode can be used for station keeping, maneuvering and free sailing at speeds of up to 5 knots.

• Free sailing mode. The generator/fire-fighting set starts and feeds the electric propulsion engines that are driving the rudder propellers. The main engines are not running and the auxiliary generator set is feeding the normal electric system. The free sailing mode can be used for station keeping, maneuvering and free sailing at speeds of up to 8 knots.

• Towing mode. Main engines start and drive the rudder propellers. The generator/fire-fighting set is not running and the auxiliary generator set is feeding the normal electric system. The towing mode has to be used during push/pull operations and free sailing of up to 13 knots.

• Fire-fighting mode. The fire-fighting mode has to be used during fire-fighting operations. Main engines start and drive the rudder propellers. Generator/fire- fighting set starts and drives the fire-fighting pump. The auxiliary generator set is feeding the normal electric system.

During station keeping, maneuvering and low speed sailing (up to 5 knots), the Bernardus will utilize battery packs to operate under 100% electric power. The same batteries will be used when the tug is at the quayside at night, doing away with the use of generators.

Harbor assisting tugs typically operate in polluted areas with high levels of particulates and NO_x, so being green is becoming a more and more important selling point. The coming decade will see a lot of changes happening in engine rooms as they become greener and cleaner.

This delivery demonstrates that the shipbuilding industry has the knowledge and ability to build greener vessels. But we need more support from governments in terms of subsidies because being green has to be commercially attractive too.

—Damen Product Director Tugs Coen Boudesteijn

Damen has four other hybrid tugs under construction at present. This includes three for the Royal Netherlands Navy in response to developments in emissions reduction and environmentally friendly shipping and one for stock.

Damen has also built an electrical patrol vessel for the canals of Amsterdam that runs on 100% battery power (charged at night by a small Steyr engine). Furthermore, the company now has definite plans to construct an LNG inland shipping vessel, otherwise known as the Ecoliner, and an LNG-powered tug.