Wärtsilä launched a series of four new container feeder vessel designs at this year's Nor-Shipping exhibition being held in Oslo from June 2 to 5. The designs are based upon achieving optimal fuel efficiency, while being compliant with all known current and future environmental regulations. The four ship designs (the WSD80-1500, WSD80-2400, WSD80-4000 and WSD84-2400) feature low fuel consumption. Each design is available in three versions; 'conventional' using HFO as fuel, 'environmental' using HFO with exhaust cleaning scrubber systems…