The merchant world fleet gradually shifted from sail to a full engine powered fleet from about 1870 to 1940. Steamships burning coal dominated up to 1920, and since then coal has gradually been replaced by marine oils, due to the shift to diesel engines and oil fired steam boilers. The shift from wind to coal was driven by the developments in steam engines, and offered the opportunity for more reliable transit times, to a large extent independent of the weather conditions and prevailing wind directions. The following shift, from coal to oil, was driven by increased efficiency, ease of handling, and cleaner operations.
The main drivers leading to the advent of alternative fuels in the future can be classiied in two broad categories:
■ Regulatory requirements and environmental concerns, and
■ Availability of fossil fuels, cost and energy security.
The upcoming requirements for reduced sulphur content in the fuel will increase the cost of the fuel. This effect will be more pronounced after 2020 (or 2025, depending on when the new regulations are enforced), when the sulphur content globally will be at 0.5% (or 5,000 ppm), which is lower than current levels for the ECAs. Introducing exhaust gas after treatment systems, such as SOx scrubbers and urea-based catalysts for NOx reduction, can add significantly to the cost of a ship. These systems are both space-demanding and costly, while they can increase the fuel consumption by 2–3%. On the other hand, they allow for the use of less expensive, high sulphur fuels. Introducing new, sulphur-free fuels can be a viable solution for this problem, provided that these fuels and the necessary technology are offered at competitive price levels.
The fuel consumption in the ECAs is estimated at approximately 30–50 million tons of fuel per year and it is going to increase if more areas are included in the ECAs in the future. These figures are important for evaluating the potential of each one of the alternative fuels presented in this report for replacing oil-based fuels.
Overview of potential alternatives
Over the next four decades, it is likely that the energy mix will be characterised by a high degree of diversification. LNG has the potential to become the fuel of choice for all shipping segments, provided the infrastructure is in place, while liquid biofuels could gradually also replace oil-based fuels. Electricity from the grid will most likely be used more and more to charge batteries for ship operations in ports, but also for propulsion of relatively small vessels. Renewable electricity could also be used to produce hydrogen, which in turn can be used to power fuel cells, providing auxiliary or propulsion power. If a drastic reduction of GHG emissions is required and appropriate alternative fuels are not readily available, carbon capture systems could provide a radical solutionShip electrification and renewables
for substantial reduction of CO2. While renewable energy, eg. solar and wind may have some potential to mitigate carbon emissions, this is not seen as a
viable alternative for commercial shipping. Certainly, vessels equipped with sails, wind kites or solar panels may be able to supplement existing power generating systems, but the relative unreliability of these energy sources make them appropriate only for special cases where favourable weather conditions prevail.
Recent developments in ship electrification hold significant promise for more efficient use of energy. Renewable power production can be exploited to produce electricity in order to power ships at berth, cold ironing and to charge batteries for fully electric and hybrid ships. Enhancing the role of electricity on ships will contribute towards improved energy management and fuel efficiency on larger vessels. For example, shifting from AC to on board DC grids would allow engines to operate at variable speeds, helping to reduce energy losses. Additional benefits include power redundancy and noise and vibration reduction, which is particularly significant for passenger ferries. Energy storage devices are critical for the use of electricity for ship propulsion, while they are also important for optimization of the use of energy on board in hybrid ships.
There are several energy storage technologies currently available. Battery powered propulsion systems are the most popular ones, and they are already being engineered for smaller ships. For larger vessels, engine manufacturers are focusing on hybrid battery solutions. Challenges related to safety, availability of materials used and lifetime must be addressed to ensure that battery- driven vessels are competitive with conventional ones, but the pace of technology is advancing rapidly. Other energy storage technologies that could find application in shipping in the future include flywheels, supercapacitors, and thermal energy storage devices.
Electrification has generated strong interest, particularly for ship types with frequent load variations. Significant growth in hybrid ships, such as harbour tugs, offshore service vessels, and passenger ferries should be expected in the next few years.The way forward
The introduction of any alternative energy source will take place at a very slow pace initially as technologies mature and the necessary infrastructure becomes available. In addition, introduction of any new fuel will most likely take place first in regions where the fuel supply will be secure in the long-term. Due to uncertainty related to the development of appropriate infrastructure, the new energy carriers will first be utilised in smaller short sea vessels, and small ferries are expected to be some of the first movers. As technologies mature and the infrastructure starts to develop, each new fuel can be used in larger vessels.
The adoption of LNG will be driven by fuel price developments, technology, regulation, increased availability of gas and the development of the appropriate infrastructure. The introduction of batteries in ships for assisting propulsion and auxiliary power demands is also a promising low carbon energy source. Ship types involved in frequent transient operations (such as frequent manoeuvring, dynamic positioning, etc.) can benefit most from the introduction of batteries through a hybrid configuration. Moreover, energy storage devices can be used in combination with waste heat recovery systems to optimise the use of energy on board. Cold ironing could become a standard procedure in many ports around the world.
It is very likely that in the future there will be a more diverse fuel mix where LNG, biofuels, renewable electricity and maybe hydrogen all play important roles. Electrification and energy storage enable a broader range of energy sources to be used. Renewable energy such as wind and solar can be produced and stored for use on ships either in batteries or as hydrogen. Besides IMO rules and ISO standards, development of appropriate Rules and Recommended Practices is necessary for the safe implementation of any of these technologies in the future. To achieve this, the role of Class Societies will be crucial. Adopting new technologies is likely to be an uncomfortable position for shipowners. To ensure confidence that technologies will work as intended, Technology Qualification from neutral third parties, such as classification societies, is also likely to be more widely used.