There is a clear need to provide the master of ships and those responsible for the safety of the vessels ashore with modern proven tools to make marine navigation and communication more reliable and hence reduce errors, especially those with the potential for loss of life, injury, environmental damage and undue commercial costs. Navigational errors and failures have been significant in overall incidents that require a full investigation. IMO considers the implementation of e-navigation in the world’s fleet as a long term objective. E-navigation implements also many other shipboard and shore side management elements than just navigation with the aim of ensuring the highest standard in environmental protection and safety. The system may combine measures like passage planning with dynamic real time monitoring to ensure that the pre-planned under-keel clearance is maintained during the whole passage. Also the ships' route can be analysed in real-time in relation to GHG emissions to look for ways to reduce fuel consumption, emission reductions and costs (MariEMS 2017).
It is clear that any reduction in collision and grounding will lead to the reduction of ship generated pollution. E-navigation could be used also to reduce carbon, sulphur and nitrogen emissions from ships. It has also been proposed to use e-navigation data to audit the measurement of emissions data if and when they need to be reported.
The international convention for safety of life at sea (SOLAS) will soon require that the paper charts shall be replaced by approved electronic charts and an approved Electronic Chart Display and Information System (ECDIS). The ECDIS can however do much more as it also has, as a minimum, the speed, water depth and position input from sensors so these other ship’s information are accessible by it and can be seen at all times. The ECDIS is used to include the ships passage plan on and it has the ability to analyse the ships route and provide alerts for better ship course control. The ECDIS will also alert the “officer of the watch” of deviations from any pre-programs safety zones set by the officer or master. The above capabilities are relevant to energy efficiency measures such as weather routing and route planning (MariEMS 2017).
The main advantage of ECDIS is that it is capable of accurately plotting and monitoring the ships position in real time to ensure that the ship follows the optimum course to the destination. An ECDIS fitted to the ship has the ability to be linked to a track pilot that can improve the vessels ability to keep on track and alter course at just the right time to minimize the distance travelled. This will ensure that the ship take the minimum distance between the departure and destination port, thus reducing GHG emissions. An ECDIS can also give a quick method of calculating estimated time of arrivals (ETAs) at the port of arrival taking into account the current position of the ship, the distance to go and the tidal rates and directions without doing a complicated calculation. This information gives the information to accurately adjust the speed of the vessel so that it arrives at the pilot station or start of the pilotage passage at exactly the right time when on coastal passages or approaching the port. This can be used to adjust the speed for better fuel efficiency and for more convenient time of arrival (MariEMS 2017).
The ECDIS has the potential to improve the fuel efficiency of a vessel on an ocean passage also when the ship is operating at her full service speed. The ECDIS can follow a Great Circle curved track that requires the ship to constantly alter the ship’s course, as the ship follows a circular path to take the shortest route between two points on the earth’s surface.
The passage plan is the most important part of the voyage plan. Careful planning and execution of the passage plan can achieve an optimum route and improved efficiency. The ECDIS can be an important part of any passage planning and implementation. The stages of a passage plan are:
- Appraisal: An overall assessment of the intended voyage, made by the master, in consultation with the navigating officer and other deck officers who will be involved.
- Planning: The navigating officer carries out the planning process. The detailed plan would cover the whole voyage, from berth to berth, and includes all waters where a pilot will be on board.
- Execution: The execution of the finalised voyage plan.
- Monitoring: Monitoring of the vessel’s progress along the pre-planned, which is a continuous process.
For energy saving purposes, the route planning needs to take extra dimensions such as avoiding shallow waters, avoiding sea currents, etc. combined with overall voyage planning. Thus, a fuel-efficient operation should be part of the ‘passage planning’ and taken into consideration at the appraisal stage above (MariEMS 2017).
When operating in areas of high traffic density, it may be necessary to deviate substantially from the intended track by an alteration of course to comply with the collision regulations. In such cases, any considerations to reduce CO2 emissions are outweighed by an international obligation to comply with the international regulations for the prevention of collision at sea. The international regulations for prevention of collision at sea require all ships to comply with its regulations. It may be necessary to ignore energy saving measures when operating in such areas. Navigational safety and good seamanship must always take priority. Ships may operate in an area of restricted visibility for several days which may require them to reduce speed significantly or even wait with subsequent need for over steaming that overall will result is a significant increase in fuel consumption but yet again navigational safety must take priority (MariEMS 2017).
The fuel consumption for a ship not only depends on speed, but also on water depth and weather conditions. The impact of shallow water operation on fuel consumption was discussed earlier. The weather condition includes wind and wave. A one Beaufort increase in sea state could result in 4% increase in fuel consumption due to the head wind. Waves may also have a significant impact on route selection. In order to take waves into account one has to know their height and direction along the route. Such knowledge may allow selection of the route and of power setting for optimal fuel consumption and transit time (MariEMS 2017).