Shipping industry eyeing hydrogen fuel cells as possible pathway to emissions reduction; work by Germanischer Lloyd and DNV
|Germanischer Lloyd’s concept hydrogen-fuel cell container feeder vessel is fueled by liquid hydrogen. Source: GL. Click to enlarge.|
Although technical and operational efficiency improvements in conventional propulsion systems may lower CO2 emissions from ships by as much as 20% across the global fleet, such marked gains in efficiency will not stop the steady increase of total emissions from shipping or meet the ambitious reduction targets of the future. One possible pathway being explored by the shipping industry is the use of hydrogen fuel cells.
At a presentation at the GMEC (Global Maritime Environmental Congress) held earlier this month in Hamburg, Dr. Pierre Sames, Germanischer Lloyd’s Head of Research and Rule Development, examined the potential use of fuel cells in shipping, the use of renewable energy to produce hydrogen for use as fuel, the economics of the technology and looked at two concept designs for fuel-cell driven, hydrogen-fueled vessels.
Separately, DNV has released a position paper, “Fuel cells for ships”, exploring the potential for fuel cell technology in on-board marine applications and the current status of the technology. The paper also discusses certain safety aspects, and highlights the development of mathematical models for assessing performance and operational aspects of shipboard fuel cell systems via simulation.
The paper examines the Phase 1 results of the DNV-led project FellowSHIP (Fuel Cells for Low Emissions Ships, earlier post), the first large-scale fuel cell installation operating on board a merchant ship. The first phase of the FellowSHIP project wrapped in 2010; in 2011, DNV kicked off a continuation of the FellowSHIP project named HybridShip. HybridSHIP is concerned with introducing batteries for on-board energy storage, integrated with fuel cells and gas engines.
Germanischer Lloyd. In his presentation Dr Sames set out GL’s design concept for a zero-emission container feeder vessel (above). The concept design, which targets Northern European feeder services, uses liquid hydrogen as fuel to generate power with a combined fuel cell and battery system.
The design concept addresses typical feeder services with a full open-top 1,000 TEU intake and 160 reefer positions at a service speed of 15 knots. The vessel is powered by a fuel cell system which delivers up to 5 MW to two podded propulsors. A battery system provides peak power. Multiple type C tanks hold 920 m3of liquid hydrogen to facilitate a roundtrip equivalent to ten full operating days.
With strict limits on sulphur emissions set to come into effect in 2015 in the Baltic Sea, ferry owner and operator Scandlines turned to FutureShip, GL’s consulting subsidiary, to help them develop a fuel-cell-driven concept design with for their Baltic ferry lines.
This design is for a double-ended ferry for with space for 1,500 passengers and 2,200 lane-meters for vehicles. Located on deck, the hydrogen tanks can accommodate 140 m3—enough for a passage of 48 hours, Dr. Sames noted. The fuel cells offer a rated power of 8,300 kW and the storage batteries a capacity of 2,400 kWh. 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 3 MW pod drives draw additional current from the batteries. Flettner rotors on deck add to the energy efficiency of the design.
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 using wind energy to produce LH2. A 500 MW wind farm could produce up to 10,000 tonnes of liquid hydrogen from surplus power it is unable to feed into the gird. GL estimates that liquid hydrogen produced by wind power could be commercially attractive between 2020 and 2030, provided that the price of MGO increases beyond US$2,000/t.
In 2020, current estimates are that approximately 3GW of offshore wind energy generation capacity will be installed in the German Exclusive Economic Zone alone. But up to 30% of the generated power may not be put into the grid and therefore could be available for hydrogen production (up to 3,600 GWh/a).
Two recently opened projected in Germany, Dr Sames pointed out, have demonstrated how using hydrogen to store surplus energy was already a viable technology. The two plants, at Prenzlau and Falkenhagen, have been in operation for the better part of a year and use wind energy to generate Hydrogen through electrolysis, which can be then stored and used to power vehicles (Prenzlau), or fed directly into the natural gas pipeline system (Falkenhagen).
|Fuel cell system integration in the Viking Lady. Source: DNV. Click to enlarge.|
DNV FellowSHIP. In the FellowSHIP project, a 330 kW fuel cell was successfully installed on board the offshore supply vessel Viking Lady, and demonstrated smooth operation for more than 7,000 hours. When internal consumption was taken into account, the electric efficiency was estimated to be 44.5%, and no NOx, SOx and PM emissions were detectable. When heat recovery was enabled, the overall fuel efficiency was increased to 55%. Nevertheless, noted DNV Research and Innovation, there remains potential for further increasing these performance levels.
Although fuel cell technology is not new, and has been tested before on ships, the FellowSHIP project marked the first large-scale fuel cell installation operating on board a merchant ship. Viking Lady is also the first vessel to use high-temperature fuel cell technology.
The project used a molten carbonate fuel cell (MCFC), developed by MTU in Germany and modified for operation in a marine environment. LNG is the main fuel in the gas-electric propulsion system of Viking Lady; no additional fuel system to support the MCFC was needed. In the current installation, the MCFC delivers power to a direct current (DC) link that is connected to the ship’s alternating current (AC) bus through power converters. The ship’s electric propulsion system therefore consume fuel cell power equivalently to power provided by the main generators.
The fuel cell stack, together with the required balance of plant, is located in a large, purpose-built container (13 x 5 x 4.4 m). Project-specific electrical components (transformers, converters and DC bus) designed to protect the fuel cell from potentially harmful disturbances on the power grid, are situated in a standard 20-ft container. The total weight of the containers is 110 tons, but both weight and volume could be significantly reduced in future fully integrated systems, DNV noted.
|Fuel cell integration in the propulsion system. Source: DNV. Click to enlarge.|
Viking Lady began operations on the North Sea in April 2009, and, in September of the same year, had the 330 kW MCFC power pack installed. After initial testing, Viking Lady became the first vessel to obtain the class notation FC-Safety. The FellowSHIP fuel cell installation is not classed as main or auxiliary power, but is considered as supplementary power.
During the first year in operation, the fuel cell stack showed no signs of degradation. In January 2012, the fuel cell was cooled down and conserved for future demonstration projects.
Fully loaded, the fuel cells produced electricity at a measured electric efficiency of 52.1 % based on the lower heating value of LNG.￼
DNV has paved the way for safe and smooth introduction of fuel cells for ships. We recognize that it will take time before fuel cells can become a realistic on-board alternative, mostly restricted by costs, but the FellowSHIP project has taken some important first steps towards a future for fuel cells on ships.—DNV researcher Eirik Ovrum