Rederij Doeksen’s new catamaran ferries are not just more environmentally friendly than conventional ferries because they fully operate on LNG. The ships are also equipped with a waste heat recovery system based on Organic Rankine Cycle (ORC) technology.
The 70 metres long Willem Barentsz and Willem de Vlamingh are the first (single-fuel) LNG-powered ferries in the Netherlands as well as the first ships in the world in which single-fuel LNG engines directly drive rudder propellers with fixed propellers. They can carry up to 66 vehicles and around 700 passengers each. The hull is made out of aluminium and not, as usual, out of steel to reduce weight and as a result fuel consumption.
The Willem Barentsz entered service on the ferry link to the Dutch Wadden Islands Vlieland and Terschelling on Friday 3 July. The other one will follow in September.
The Willem Barentsz (by Rederij Doeksen).
Generating electricity from waste heat
The waste heat on board is utilised with Orcan Energy’s efficiency PACKs from the 50.100 class. Based on ORC technology, the two efficiency PACKs on board use the exhaust gas and jacket cooling water waste heat from the propulsion and auxiliary engines to generate electricity.
In order to do that, a heat exchanger transfers the waste heat from the exhaust gases to the ORC. The jacket cooling water is being routed through the efficiency PACKs directly. Here, the refrigerant is evaporated – a non-toxic, non-flammable hydrocarbon – and routed to the expansion machine as superheated vapour. The highly-pressurised refrigerant is expanded, thereby driving the expansion machine. The rotational energy is used to drive a generator that produces electricity.
When the engines operate at full power, the efficiency PACKs will provide 154 kW of additional electrical net power. The recovered energy is stored in battery packs during crossings. In port, where the ferries manoeuvre themselves into position for disembarking passengers, the batteries supply electricity to the ships’ bow thrusters. This means that the bow thrusters are effectively powered by waste heat.
‘In ship propulsion systems more than half of the energy contained in the fuel is lost as waste heat, it simply dissipates into the atmosphere. That we can now utilise this waste heat to produce electricity is a decisive step forward and a must-have for any modern ship,’ says Paul Melles, managing director of Rederij Doeksen.
Applying waste heat recovery is said to save 318 tonnes of CO2, 260,000 liters of fuel and 462,600 kilowatt-hours of electricity per vessel per year.
Picture (top): An Orcan Energy PACK in the engine room.