By
Rebecca Gibson |
Two Fjord Line ferries will emit less NOx thanks to innovative gas engines, says Finn Arne Rognstad, vice president of marketing and sales, cruise and ferries, Rolls-Royce Marine.
Construction of two large cruise ferries is expected to be completed in the spring of 2013 to serve two routes for Fjord Line.
The 170-metre Stavangerfjord and Bergensfjord will operate on the existing Fjord Line service linking Hirtshals in Denmark with Stavanger and Bergen in west Norway, and a new passage between Hirtshals and Langesund, in south Norway. Each ferry will be able to carry 1,500 passengers in comfort, along with 600 cars or equivalent. The new capacity allows Fjord Line to offer a daily departure from each port at the same time.
Having originally planned for diesel engines with a view to rebuilding these to dual-fuel gas engines later in their lives – the oil-fuelled engines were already in place in the first hull – Fjord Line decided on a major change in direction for the two ferries. The company changed engine supplier and installed single-fuel gas engines with liquefied natural gas (LNG) as the sole fuel.
Fjord Line managing director Ingvald Fardal explains: “We have a clear environmental strategy. Using LNG in single-fuel gas engines will allow us to fulfil it. We are also proud to have the first and largest cruise ferry to run on LNG as its sole fuel type. As Rolls-Royce is the leading manufacturer of these engines we are very pleased to have their technology on board.”
The engines have a very high thermal efficiency of around 49 per cent and significantly they can work with CP propellers in a twin-engine mechanical transmission to maintain a high total propulsion efficiency over the full range of ship speeds. This engine technology has been developed over many years and hundreds of gas engines have been sold. The marine version has seen five successful years of intensive LNG operation in cross fjord ferries.
Reducing emissions is Fjord Line’s goal and the company is achieving this on several levels. The Rolls-Royce gas engine reduces nitrogen oxide (NOx) emissions by around 92 per cent compared to a diesel engine. Gas is burned cleanly, with no smoke or soot from the exhaust, while total greenhouse gas emissions are around 23 per cent lower than those from comparable oil-fuelled installations. Sulphur emission is virtually eliminated. Although LNG fuel involves a somewhat higher capital cost because insulated gas tanks are more expensive than oil tanks, this is justified. Norway levies a tax on NOx emissions, but the country’s NOx fund provides support for measures that reduce these.
“It is support from the NOx fund that makes the project possible,” says Fardal. “In addition, our new cruise ferries will be operating in emission control areas, so if we had taken our original path we would have needed to use expensive low sulphur distillate fuel, or apply special clean-up systems to diesel engines. With our Rolls-Royce gas engine solution we automatically meet our environmental strategy and support from the NOx fund helps to bridge the system cost difference.”
The new Fjord Line cruise ferries will each have two gas tanks with individual capacities of 290 cubic metres. The plan is to refuel the ships every second day, but the bunkering port is still to be decided.