Just six years ago, engine makers and the shipping industry were celebrating – or at least acknowledging – a century of motor propelled ships. The first motor ship may have appeared in 1912 but it would take more than half a century before steam engines completely disappeared, although with steam-turbine LNG carriers still being built some might argue that motors have never achieved a complete monopoly on ship power.
Most LNG carriers today may run on LNG but fewer steam turbine ships are being built and it is dual-fuel engines that power most. Dual-fuel engines are now also making their presence felt in several more ship types than the gas carriers and offshore where they have their main proponents. Bulk carriers, tankers, PCTCs and cruise ships can all be found running on LNG and whether the cycle individual engines employ is Diesel or Otto, the internal combustion engine is king.
For ships sailing with residual fuels, cat fines are a clear and present danger. Centrifugal separators remain the most importa…
However, after MEPC 72 there is a big question mark over the future of such engines. With a declared ambition of reducing CO2 emissions by 50% in 2050 compared to 2008, the IMO has thrown down a challenge to engine makers and shipowners alike that would seem to preclude the type of engines the industry is presently dependent on.
The efficiency of modern engines whether running on oil or gas fuels is at a level where improvements can only be achieved in ever smaller increments. A saving of around 15% in CO2 emission is possible by switching from oil fuels to LNG but much or all of that might be negated in the phenomenon known as methane slip is a problem on particular engines. Even if the methane slip is disregarded, and all ships are fitted with gas-burning engines, there is still a 35% reduction to be achieved.
The current EEDI regulations introduced several years after 2008, require that most ships types find 30% emission reductions by 2025. The early phase 1 reduction of 10% in 2015 was achieved relatively easily by a combination of methods. Firstly, it should be acknowledged that the baseline against which the reductions were measured was set relatively high as it was based upon the fleet of existing ships which included some vessels of a vintage when energy efficiency was less compelling than it became in the years of record fuel prices between 2008 and 2014. Other reasons the reductions were achieved included changes in engine design – longer strokes and lighter weights – and better matching of engines with propellers.
In a little over a year’s time in 2020, the Phase II of EEDI will kick in and the reductions achieved by new ships must be 20% below the baseline. Some owners and designers of recent newbuildings claim to have already achieved compliance with Phase II. In the main this has been achieved by reducing the design speed and consequent power requirement. In an over-tonnaged fleet this is a strategy that can be adopted but is less attractive when demand for shipping space outstrips supply even on a temporary basis as ships cannot speed up,
When Phase III arrives in 2025, the 30% reduction target will be much harder and will require innovations such as energy storage systems, waste heat recovery and more.
Going beyond that as the IMO now has ambitions to do is in the view of many analysts something that is unachievable without either a major breakthrough in engine technology or a new source of power onboard.
If making a 30% reduction is hard, then a 50% reduction will need something beyond what most engineers and scientists consider is possible. Furthermore, the IMO has also said that after 2050, the goal should be for zero emissions from shipping. If the presently discussed options are all that will be on the table, then the future of ship propulsion will either be fuel cells or perhaps an internal combustion engine running on a fuel that does not contain carbon or very little. Hydrogen is presently predicted to be the future but how close it is to being achieved as debateable.
Fuel cells back on the agenda
Fuel cells have been promoted as the future for many years now. EU funding for fuel cell projects stretches back almost to the turn of the century and yet the commercialisation seems as far away as ever. There have been fuel cells installed on ships – Viking Lady and Undine are probably the most high-profile ship projects but these were just small scale in terms of power. In 2013, Wärtsilä ceased its development of fuel cell technology for ships and interest from shipping generally seemed to wane.
There are several different types of fuel cells and their efficiency and waste products vary considerably. In the simplest fuel cell, hydrogen is combined with oxygen from the air in a reverse of the electrolysis process.
The result is an electric current and water emitted as steam. The steam may be used to run a turbine in order to increase the overall efficiency of the fuel cell which is in the region of 50% and thus on a par with conventional diesel engines.
Instead of pure hydrogen, some fuel cells use methanol as the fuel and in these the carbon from the methanol must be factored in to the overall chemistry.
As well as the electric current produced, a fuel cell powered by methanol will produce one molecule of CO2 for every two molecules of water. Therefore, while a fuel cell fuelled only with pure hydrogen might be considered emission free, one that uses methanol, LPG or LNG could not.
Earlier this year, it was announced that ABB and Ballard Power Systems had signed a memorandum of understanding (MoU) to jointly develop megawatt-scale containerised proton exchange membrane (PEM) fuel cell power systems for the marine industry. The two parties are already working together to provide fuel cells for Royal Caribbean’s Icon Class cruise vessels being built in Finland with the first scheduled for a 2022 delivery. Royal Caribbean has also said that it plans other projects involving fuel cells on some existing ships as well.
Projecting a green image is important for cruise operators not least because their past activities have come in for some undesirable criticism from environmentalist organisations and perhaps because as a luxury life style choice it is one area of the wider shipping industry that – unlike cargo carriage – can be considered as being unnecessary.
Operators of cargo ships have different concerns and whether the future lies with the current methods and a dropping of the IMO’s ambitious targets for emissions or with fuel cells or some as yet undeveloped technology remains to be seen.•