Hydrogen appears to be one of the most promising clean fuels with potential shipping application, but it also raises serious technical challenges. Catherine Austin examines recent progress towards an emerging marine fuel.
The first half of the twenty-first century will likely be remembered, in shipping circles at least, for a monumental shift in fuels of choice. In the past two centuries shipping’s power and propulsion has progressed from sail to steam to diesel, and today the industry is on the verge of another historic flux.
Twelve months ago, the IMO ignited a mighty catalyst with its decision to implement a global cap on fuel sulphur content of 0.50% by volume, revising the current 3.5% cap from 2020. A change of fuel or the installation of emission abatement technology, such as a scrubber, will be the only option. The fuel mix that powers our ships will shift away from the predominant use of heavy fuel oil.
The decarbonisation of the industry is also an issue, gaining serious traction on the IMO agenda thanks to recent developments on the global climate change stage. As a result, pressure to increase the availability of cleaner fuel options and emission abatement technology is at an all-time high.
One aspect over which the industry is fretting is the supply and price of lower sulphur fuels. Greater demand will be placed on the fuel supply as oil refiners adapt to new market requirements. This uncertainty provides an extra incentive for ship operators to explore long-term cleaner fuel alternatives that, before the storm of regulatory limits, were reserved only for proactive green forerunners.
Research, trials and even some first applications on in-service ships of alternative fuel options such as LNG, methanol, biofuels (including bio-methanol), LPG (Liquid Propane Gas), DME (Dimethyl Ether) ammonia, nuclear and hydrogen (including bio-hydrogen) are taking place. Whilst LNG is by far the most heavily promoted alternative fuel in shipping, it is still a fossil fuel and therefore not a perfect solution.
Similar in many ways to LNG, hydrogen fuel could play an important role in the future, even though opinions on its application remains to be hotly debated. Once constrained to research studies and small-scale fuel cell trials, hydrogen is now moving from pre-commercial markets to commercialisation in the shipping industry.
As with many other renewable energy sources, the use of hydrogen as ship fuel presents a plethora of technical, safety and regulatory challenges. The attraction, particularly given current environmental tensions in the shipping industry, is that it offers zero-emission operations – making it a mighty contender in the quest for shipping industry decarbonisation.
When someone talks about hydrogen fuel, fuel cells come to mind. However, the two types of hydrogen fuel use for ships need to be considered. Hydrogen internal combustion engines can burn hydrogen to produce water as the only waste product. Fuel cell systems on the other hand use an electro-chemical reaction to generate electricity. The efficiency of fuel cells is relatively high, at around 45%, compared to internal combustion engines (roughly 20%).
Hydrogen can be produced from many energy sources, fossil and renewable. It is produced by electrolysing water, supported by solar or wind power or from reforming hydrocarbon fuels. Today, the most important feedstock for hydrogen production is natural gas.
Naturally, the cost of producing liquid hydrogen is strongly linked to the feedstock price. Hydrogen can therefore be costly to produce through the reformation of hydrocarbon fuels. For natural gas-based hydrogen, a range of €2,200-3,330/tonne was estimated in a 2011 study. The initial costs required for the supply chain infrastructure are generally higher than for petroleum-based fuels due to the lack of initial economies of scale.
A number of hydrogen liquefaction plants already exist, but the current supply network of hydrogen as ship fuel is very limited. The ability of ships to carry large amounts of liquefied hydrogen (LH2) worldwide is therefore one key component to the exploitation of hydrogen by the shipping industry. Over the past two years, ClassNK has been involved in a series of technical demonstrations to identify issues facing commercialisation of the hydrogen supply chain. The demonstrations have been conducted by the Hydrogen Energy Supply-Chain Technology Research Association (HySTRA) which is promoted in Japan by the New Energy and Industrial Technology Development Organization (NEDO). HySTRA has developed a roadmap for operational stages that need to be addressed to deliver a viable LH2 carrier, ranging from initial cool down, loading and unloading of liquefied hydrogen to sea-going operations using a newly built pilot LH2 terminal in Kobe. The first LH2 carrier is expected to debut as soon as 2020.
Supply chain issues
Hayato Suga, director of ClassNK’s plan approval division notes that the project responds to “potential calls for practical solutions” to ensure that liquefied hydrogen production is economically viable and that it is carried through a safe supply chain to the place of consumption. “Movement by ship represents the most efficient long-distance transportation option,” he says.
ClassNK has also staked its claim as a leader in the new fuel through its recently-published guidelines covering ships able to carry liquefied hydrogen. The publication signals increasing demand from within the industry.
There are many technical challenges related to the use of hydrogen as ship fuel. One key factor is the weight and volume impact of the hydrogen fuel storage system required on board, presenting even tougher handling and storage challenges at sea than LNG.
Hydrogen fuel must be kept at temperatures below −253°C to maintain its liquid state under atmospheric pressure. Although the most commonly used hydrogen storage system today is high-pressure gas cylinders, the low volumetric density is considered a key limitation for application onboard ships. Large spaces are required for very well insulated storage tanks, estimated to be 4-7 times in volume of the traditional fuel oil tanks and a refrigeration unit is also required if the hydrogen is stored in a cryogenic state which adds extra cost.
For fuel cell applications, the biggest challenges include high investment cost, dimensions and weight, expected lifetime and dynamic response. Power requirements can also be an issue as fuel cell systems with at least 500kW of power would be required for larger ships.
From a safety perspective, hydrogen has a lower boiling temperature than methane, for example, as well as lower density, higher upper flammable limit and lower ignition energy. Ventilation, alarm systems and fire protection, as well as the introduction of other measures to limit the likelihood and consequences of hydrogen leakage, would be needed.
Dr Carlo Raucci, a consultant at UMAS, used high-powered modelling tools to explore conditions that would favour the significant uptake of hydrogen in the industry. He concluded that key circumstances could include: the introduction of an emissions cap and a market-based measure mechanism in shipping; a hydrogen price ranging between US$4-8/kg and competitive investment costs for fuel cell and hydrogen storage technologies onboard ships; and the supply of hydrogen mainly based on natural gas and biomass, with carbon capture and storage or electrolysis technology.
Raucci told The Motorship: “If the shipping industry seriously commits to a decarbonisation, there are good reasons to think that hydrogen may play an important role. Ships are the largest vehicles in the world, so they will require a significant amount of hydrogen in a few specific locations – favouring economy of scale – in comparison to cars that require a sophisticated network of refuelling stations. This gives shipping a hydrogen supply advantage.”
Raucci also predicted that shipping could itself unlock the potential of the hydrogen economy by investing in hydrogen more other sectors. “Ports may find ways to integrate this energy carrier (hydrogen) to other land-based demands,” he explained.
Hydrogen has political support in the form of an EU commitment to invest in a new fuel cell system for marine purposes, as part of the Fuel Cells and Hydrogen 2 Joint Undertaking, which is supported by the European Commission, Hydrogen Europe, and research groups.
The use of hydrogen by ships to date spans a number of demonstration projects and some hydrogen-powered ships are actually in service. European projects are numerous and include; H2SusBuild, HySafe, HyApproval, the European Integrated Hydrogen Project (EIHP2), HyWays, Zemships and FellowSHIP.
In December 2009 the world’s first hydrogen fuel cell powered ship, Eidesvik’s offshore support vessel Viking Lady, docked in Copenhagen. Last year, a catamaran built by Cheetah Marine became the first ever vessel to sail 100km powered by a hydrogen internal combustion engine – the Honda outboard of the 9.95m vessel works in the same way as traditional petrol engine except it burns hydrogen and produces harmless water vapour as the only emission.
The feasibility of hydrogen-powered high-speed ferry SF BREEZE was proven earlier this year following an extensive study. The 150-passenger commuter ferry, powered entirely by proton exchange membrane (PEM) fuel cells, is designed for a top speed of 35 knots. Using renewable LH2 – the hydrogen is derived from biomass or electrolysis of water using renewable electricity – well-to-water greenhouse gas emissions have been slashed by 75.8% compared to a comparable diesel fuelled ferry.
The total installed power of the vessel is 4.92MW, consisting of 41 racks, each containing four 30kW fuel cell stacks. The fuel, 1,200 kg of LH2, is contained in a single Type C cryogenic storage tank on the top deck.
Following the project, ABS concluded that there were no technical show-stoppers preventing the use of hydrogen fuel cells. However, the cost and space required was significantly higher than conventional power systems.
Cruise operator Royal Caribbean has also announced plans to use hydrogen fuel cell technology as a means of additional power on their new LNG-powered Icon-class vessels, which are expected to be delivered in 2022 and 2024. Another hydrogen pioneer is Norway’s Fiskerstrand Holding, which is working on a hydrogen-powered ferry as part of a wider project, HYBRIDShips. The project was formally launched with a kick-off on January 9 this year and Fiskerstrand has set an ambitious goal of having the ferry ready by 2020.
Despite the growing number of hydrogen-related marine projects, industry opinion on the suitability of the fuel remains divided – perhaps the best indication that any significant uptake remains several years off.
Japanese class society ClassNK told The Motorship that they believe hydrogen – as a zero-emissions fuel with availability around the world – has the potential to transform modern society. “As a low carbon energy source, the use of hydrogen as a fuel offers significant potential to solve environmental problems caused by fuel emissions,” says Hayato Suga.
Daniel Cronin, vice president class standards & software, ABS explains that the class society believes hydrogen will be part of the future fuel mix, but is hesitant to make bold predictions. In the short to mid-term, they see conventional fuels continuing to dominate the marine industry.
Cronin says: “We see hydrogen and fuel cells as one of many alternative fuels and alternative technologies that will emerge in the next 10 to 20 years. But it is likely to only play a significant part in the marine sector in the longer term.”
Maurice Meehan, director of shipping operations, Carbon War Room, is optimistic. “Although at an early stage of development for the shipping market, hydrogen could well be the high-impact, truly low-carbon propulsion solution the industry needs,” he notes. “Energy efficiency based on fossil fuels can only get shipping so far down the road to decarbonisation, and new fuels will be a major force in broadening the industry’s horizons and opportunities.”
A lot will depend on both marine engineering companies and shipowners. MAN Diesel & Turbo told The Motorship that a two-stroke engine can be easily built to use hydrogen fuel, using the same ME-GI concept used for gas fuels. But a significant challenge is how to store hydrogen onboard, and in particular the associated storage equipment costs and space demands.
MAN Diesel & Turbo has examined hydrogen fuel through dedicated projects, but quickly realised that the cost of the whole onboard arrangement onboard was too high. Given experience with LNG, where the cost of storage tanks has not decreased in ten years, hydrogen storage costs would likely remain as high as those for LNG, if not higher, for the foreseeable future.
René Sejer Laursen, promotion manager, ME-GI, MAN Diesel & Turbo explains that due to this fact, their exploratory work had changed direction to examine converting hydrogen into methanol as a carbon-free ship fuel for their ME-LGI engine series, which is already in service.
Laursen says: “I don’t think we will see hydrogen as a fuel for future shipping. If hydrogen can be converted into methanol then it will have a chance in the shipping market.”
That dose of realism from one of the industry’s leading engineering groups highlights the technical work that remains to be done before this challenging, but very promising, clean fuel can play a wider role in shipping’s evolving fuel mix.