In the world of international container shipping, "slow steaming" has long become widespread practice. With the optimization of hulls and innovative designs, FutureShip played an appreciable role in the successful implementation of the concept. Together with shipping company Scandlines, this subsidiary of GL is going one step further: the development of double-ended ferries that are totally emission-free. The FutureShip engineers took a completely new course and approached the matter in a holistic way: from fuel-protection, through energy conversion and storage, and up to optimization of the ship design. For example, the surplus electricity generated by wind turbines in northern Germany and Denmark is to be used to produce hydrogen. This can be transformed back into electrical energy by the fuel cells on board the ship in order to supply the electrical pod drives. Any excess electricity is stored in batteries to cover peaks in demand. Modern hull lines, optimized propeller shapes and efficient procedures in port play a vital role in reducing the overall energy needs.
For GL, this design project was an ideal platform to show what is already possible today with modern - and above all, available - technology. "Short-sea applications are simply predestined for our zero-emission concept," says Fridtjof Rohde, development engineer at FutureShip. The energy requirement of the Scandlines ferries is lower; moreover, it is possible to bunker more often. On the other hand, ships that have to cover large distances would be much more difficult to "get green" - the total energy requirement is too high.
First and foremost, the need is for propulsion and also for the catering operations. Diesel engines and gas turbines had to be ruled out, with a mix of photovoltaic systems, fuel cells and Flettner rotors crystallizing out as being the most suitable solution. The design process yielded a double-ended ferry with space for 1,500 passengers and 2,200 lane metres for vehicles. Located on deck, the hydrogen tanks can accommodate 140 cubic metres - enough for a passage of 48 hours. Deep down in the belly of the ship, where they do not take up space unnecessarily, the fuel cells offer a rated power of 8,300 kilowatts and the storage batteries a capacity of 2,400 kilowatt-hours. The nominal speed of the ferries is set at 17 knots - the parameter used for sizing the fuel cells. To accelerate up to 18 knots, the four three-megawatt pod drives draw additional current from the batteries.
The energy balance is compelling. Whilst today's diesel-powered ferries burn about a tonne of fuel per crossing and expel about three tonnes of C02 in addition to sulphur and nitrogen oxides, the new ferry is entirely emission-free. The power provided by the Flettner rotors was not even included in the energy balance. Rohde estimates this "bonus" to be about ten per cent: "It is a windy area," is his justification for the large number. With regard to capital expenditure, the new ferries would only cost about 25 per cent more than a conventional design. "The technology is there - it just has to be applied to shipping," says FutureShip expert Rohde.
