The design concept envisions a container feeder vessel with a full open top, 1,000 TEU intake including 150 reefer slots. The open-top design reduces loading and unloading time, allowing the vessel to sail at reduced speeds, whereas a conventional, faster vessel has to spend more time in port. The ship features standard principal dimensions but a reduced design speed of 15 knots to minimise the required propulsion power. There are two power generation rooms, situated forward and aft, respectively. The vessel uses two podded propulsors for primary propulsion and a “take-me-home” thruster for extra manoeuvrability and drive redundancy. The vessel would rely on a 5 MW fuel cell system for propulsion, made up of ten linked 0.5 MW modules. The 920 m3 of LH2 fuel stored in multiple pressurised, C-type tanks would be sufficient to power the vessel over a typical ten-day round trip.
Based on GL’s 2009 study for an LNG-fuelled container feeder vessel, an estimated six per cent of the TEU capacity of the vessel would need to be sacrificed for the hydrogen fuel tanks. These are arranged forward and aft to support a dual-bunkering approach and achieve a three-hour refuelling time. Since fuel cells typically cannot generate peak power rapidly, a 3-MWh battery system, charged by the fuel cell system, would store power for peak usage.
Untapped Wind Energy
For a true “zero”-emission vessel, it is necessary to go beyond the emissions from the ship itself and account for the production of its fuel as well. The GL design concept proposes a bunkering station that uses wind energy to produce LH2. The 2020 target for offshore wind farms operating in the German Exclusive Economic Zone (EEZ) is an installed capacity of approximately 3 GW. One of the disadvantages of existing forms of renewable energy, however, is the intermittent supply. The current grid infrastructure and the lack of mature storage technologies often prevent wind turbines from reaching their full production potential. Studies estimate that as much as 30 per cent of an offshore wind farm’s potential energy output is lost because it cannot be fed into the grid. This means that across the EEZ up to 3,600 GWh of unused power generation potential per year could be utilised for extra purposes, such as the production of LH2. Based on these estimates, a 500 MW wind farm could produce up to 10,000 tonnes of liquid hydrogen per year by using this surplus power to serve the bunkering needs of up to five feeder vessels of the size described above.
Competitive with MGO
The hydrogen produced could be liquefied and stored in tanks. Intermediate storage of LH2 for up to ten days would require the installation of insulated tanks of up to 5,000 m3. With the wind farm operating approximately 4,000 hours per annum, the price of LH2 would be about US$7,500/t. These costs include production, liquefaction and on-site storage. GL estimates that liquid hydrogen produced by wind power could be commercially attractive sometime between 2020 and 2030, provided that the price of marine gas oil (MGO) increases to US$2,000/t. The pressure to reduce greenhouse gases will continue to grow over the coming years, and the pivotal year 2020 is within the lifetime of many vessels currently operating. The CO2 reduction goals will not be reached unless new technology is embraced. GL’s vision of a zero-emission vessel demonstrates that new technology can pave the way towards meeting ambitious targets and can indeed propel the industry into the future.