this part are described all operations that are made on board of the
ships. Independent of its specialty to carried out the marine adventure
of carry goods from a port to another and vice versa, and they need the
use of equipment’s and systems of the ship. The use of the before
mentioned equipment imply an energy consumption which one must be made
in the most efficiency way. The first equipment that is analysed are the
diesel engines and its load during the performance of the same.
The importance of the index that best defines the efficiency of a diesel engine, such as specific consumption, that is, the amount of fuel it consumes for each kilowatt hour it produces, kg/kWh, since it is very important know that diesel engines are designed to be the most efficient at 80% of their maximum effective power. This implies that we must always try to make the engine work at 80% of its maximum power or in the vicinity of it. This will keep the fuel consumption of the engine to a minimum.
As indicated in the previous paragraph, in the case of having to reduce the speed of the ship, for reasons of economy, try to ensure that the engine works as close to the power of minimum consumption and if this reduction in the speed has to remain for a long time, it is necessary to make the corresponding modifications to the engine to reduce fuel consumption and avoid engine breakdowns. It must be borne in mind that reducing the speed of the ship exponentially reduces fuel consumption, but fuel consumption increases sharply for each kilowatt-hour produced.
In the case of auxiliary engines for the generation of electricity on board, as more than one diesel engine is available for reasons of safety and guarantee of supply, it is necessary whenever possible, that the electricity supply is carried out through single engine operating to the nearest 80% of maximum effective power.
With regard to the electrical load, it is of great importance that no electrical equipment is operating in a vacuum. The air conditioning equipment must work to give a temperature on board cruise ships, fundamentally, not lower than 24ºC. In addition, they must be in accordance with the weather of the area in which you are sailing.
The reduction of electricity consumption, and therefore of fuel, of auxiliary equipment, such as pumps, compressors and fans, etc. They must be designed for the power that corresponds to each service and an oversize or undersized should be avoided, as this will lead to inappropriate consumption. Auxiliary equipment that moves fluids and is driven by electric motors will always consume the same energy at different workloads, something that must be avoided by using electric motors with variable speed that adjust to the power demanded at all times.
In fluid machines, good maintenance must be carried out and dirt in the ducts that cause a loss of load and an increase in fuel consumption must be avoided.
The use of steam on board ships is very important. It is used for propulsion, in the case of the ships with steam turbines as propulsion, case of the LNG ships, to generate electricity with steam turbines that use steam produced with the heat of the exhaust gases of the engines in a exhaust gas boiler, and to heat the cargo carried, the fuel used by the engines or for heating of the ship. Currently the 90% of the world merchant fleet has fitted a steam boiler, mainly for auxiliary services.
All systems that use steam, like turbines, heat exchange, water generators, etc. must have a high-level cleanness and maintenance to get the higher efficiency.
The water used in the boiler is a water chemically treated to avoid the corrosion and plugging of the pipes, due to the salts solved in the steam.
The combustion in the boiler must be made with the air excess index right avoid loss of heat y efficiency. The steam pipes of furnace must be cleaned to assure a very good heat transmission.
To the aim to get the maximum efficiency of the boiler she should be working close the 80% of workload and the distribution system of the steam like valves, pipes, etc. must be convenient insulated to avoid heat loss and avert all kind of steam leakage.
An important way of reduce the fuel consumption is using the heat of the exhaust gases in a steam boiler called waste heat recovery system that produce steam to feed a steam turbine that driven a electric alternator AC producing the electricity on board.
The crude oil tankers need for safety reason to inerting of the tanks, therefore the inert gas system use the exhaust gases of the boiler, with a minimum quantity of O2 like inert gases. The exhaust gases of the engines can´t be used like inert gases due they have a high level of O2.
are used to know the best possible trim for their vessel using sea
worthiness as main and only criteria. Usually best trim is 30.48 cm
astern. Even keel loading in the port is quite common especially with
the small ships operating from small harbours. Today more important
criteria are energy efficiency and emission reduction and if these two
criteria fills up with the trim, result is excellent. Trim is normally
defined as the difference between the aft draft and the forward draft.
Optimum trim is trim where required propulsive power is minimal. Optimum
trim is achieved via the proper planning and ship ballasting plan. A
ship’s resistances and trim are closely related to each other. Trim
affects to hulls wetted surface area and therefore increases or
decreases forces that is slowing the ship (MariEMS 2017).
Using optimum trim, it can have 2% to 4% reduction on fuel consumption. However, this reduction can be higher or lower depending on the vessels type and operation draft. And when there are ways to save environment and money all possible measures should be taken care of. Therefore even 5 to 10 centimetres difference on trim can cause higher fuel consumption and this causes emission increases.
Nowadays the accuracy has improved so much that, trim tables based on use of Computational Fluid Dynamics (CFD) software tool calculations can be comparable to the results from resistance model test. However, both resistance test and CFD methods tend to ignore the impact of the propeller: this may have significant impact on evaluations of vessel with light drafts. Normally when Trim is being calculated the test are made at both forward and aft trims. Often forward trim is not even possible for the lighter drafts due to restriction in the propeller’s submergence. Because of the recent energy efficiency regulation, more shipping companies have chosen to do trim optimization calculations using the CFD software (MariEMS 2017).
talking about energy efficiency and emission reduction on ships, the
trim isn’t the only factor that affects to ship’s propulsion fuel
consumption. One almost as big thing to keep on mind is hull and
propeller cleaning and maintaining.
Hull surface roughness can be divided to two categories, physical and biological. These two categories are normally divided to two subcategories micro roughness (less than 1mm) and macro roughness (more than 1mm). The physical micro-roughness is normally human made mistakes or mechanical failures like, mechanical damage, failure of the applied coating and even improper preparation of the surface and/or improper application of a new coating. Biological roughness (fouling) comes when some organic growth sticks on the hull of the vessel (slime, algae, barnacle etc.). Roughness has significant impact on resistance. Light slim covering the entire wetted surface can increase total resistance by 7-9 %. Heavy slime increases resistance by 15-18%, and small barnacles and weed can push up to 20 to 30% increase in total resistance. Therefore, hull resistance has significant factor to fuel consumption and emission reduction and energy efficiency. Cleaning the hull and changing the hull coating to better working coating can save 10-12% on fuel consumption (MariEMS 2017).
Like the hull roughness, Propellers suffer also decreased performance due to surface roughness. The absolute reduction in ship energy efficiency due to propeller roughness is less than those seen on hull roughness, but propeller roughness can increase propulsion fuel consumption up to 6%. Propellers suffer physical surface roughness created by corrosion, cavitation erosion and impingement attack. These damages can be cleaned and polished which will reduce the propellers frictional and rotational losses. Fouling is not problem on propellers that are constantly moving, therefore vessels that are anchored or in harbour for extended periods should rotate their propellers for short period once a day to prevent fouling on the propellers. In a long run the fuel saving that have gained by preventing the fouling by rotating propeller outweighs the fuel consumption that is used to do so. Polishing roughened propeller can decrease fuel consumption by 3%. Cleaning and polishing the propeller can give 6% improvement on fuel consumption. Divers can clean a 5 blade 10 m diameter propeller in about 3-4 hours and that costs about US $3,000 in Far East and about double of that in Europe (MariEMS 2017).
effective way of improving the energy efficiency of a ship is to
upgrade ship-board technologies to more energy efficient ones. Upgrading
of technologies is not a ship-board activity but nevertheless, the
ship-board staff could always engage in proposing such technologies. A
number of technology upgrades can be considered for energy efficiency
and emission reduction. It should be noted that applicability of such
technologies will depend on ship type, ship size, operation profile and
other factors (MariEMS 2017).
The devices used to technical upgrade on the ship are: Devices forward and aft of propeller, duct propeller, fore-body optimization and bulbous bow, waste heat recovery, high efficiency electric motors, fuel oil homogenizers, etc.
Plimsoll line or Load line is placed mid-way between the forward and
after perpendiculars of the ship and give the draft of the ship that is
the legal limit to which a ship may be loaded for specific water density
and temperature. Temperature can influence the draft of a ship because
warm water provides less buoyancy as it is less dense than cold water
but this factor is not really taken into account in cargo calculations
except by the use of Load line Zones of areas that have been defined in
the International Load line Convention (MariEMS 2017).
International Load lines Convention applies to all commercial vessels of over 24m length and requires that every ship is surveyed and issued with a Load line certificate every 5 years. If the ship does not have its certificate up to date, then it can be detained by the Flag State or Port State inspectors. The survey mainly consists of checking the vessel to ensure that the watertight integrity of the structure as a whole has been maintained (MariEMS 2017).
It is pertinent to note that as regard to loading aspects, trim and ballasting, ships such as bulk carriers do not have much scope for changing trim without shutting out cargo and reducing the load factor as the holds are often full (MariEMS 2017).
Ships are designed to carry a certain amount of cargo at a certain speed for a certain fuel consumption that generally results in a particular trim for the vessel when fully loaded and in ballast. Trim has a significant influence on the resistance of the ship through water and of the effectiveness of the rudder and propeller. Optimized trim can give significant fuel savings and for any draft there is a trim condition which will give minimum resistance and increase the efficiency of the engine (MariEMS 2017).
One of the key tasks for ship’s master is to pre-calculate weight of the cargo for stability and trim. In this regard, the ships master must rely on the ship loading computers and ships final drafts to ensure that stability is maintained throughout the intended voyage, taking into account the consumption of fuel oil and any international load-line requirements. The overall efficiency of the ship is a function of the ship's size. As the ship grows, a lower fuel consumption and lower CO2 production per cargo will be achieved. Operationally, energy efficiency can be increased by concentrating the transportation of cargo on larger ships that can reduce the energy consumption of the shipping industry as a whole. These smaller feeder ships will be less efficient anyway than the large ships and there will also be some extra GHG emissions penalties in the additional discharging and loading operation for trans-shipment. So, the use of economies of scale is as effective as it can be, but it is a good idea to make a lot of money. This means that the overall energy efficiency may also be improved for smaller vessels with access to more ports and cargo types and able to fill cargo holds to full capacity (MariEMS 2017).
Another key factor is the Ballast water (BW) Management. BW is essential to control trim, list, draught, stability and stresses of a ship. Ballast water activities are largely regulated not only because of the above ship’s safety implications but also since they have been recognized to be a pathway for the movement of undesirable and alien bio-species from their natural habitat to other ecosystems. The impact of Ballast Water Management (BWM) on a ship’s fuel consumptions is not normally considered despite the evidence that, regardless of the management method established, the overall energy efficiency of a ship is affected by ballast water because the ballast exchange requires the additional use of the ballast water handling equipment and in particular pumps. Ballast water impacts the ship’s energy efficiency in two additional ways: The change in ship displacement; thus wetted surfaces and ship resistance and change in ship trim (MariEMS 2017).
The best ways to implement best practices for a sustainable fleet with a view to environmental protection and cost reduction are:
A sustainable comprehensive fleet management policy must include:
• A policy to reduce risks and costs, e.g. accidents
• A policy for the protection of the environment
• A policy for the efficient planning of trips
• A policy to increase competitiveness
• A shipping company’s internal structure can be seen in the diagram below;
Ships come in a variety of types and sizes. Some ship types are the following; tankers, bulk carriers, container ships, refrigerated vessels, Roll-on–Roll-off (Ro–Ro) vessels, ferries, passenger ships, fishing vessels, service/supply vessels, barges, research ships, dredgers, naval vessels, sometimes a combination vessels and other special purpose vessels. The types of ships are usually even further categorized in sub-types depending on the size of the ship. To measure the size of a ship we have to take into consideration its weight carrying capacity and its volume carrying capacity.
There is a large variety to the cargo carried by ships like the ships themselves. The cargo of a ship can be consumer goods, unprocessed and processed food, livestock, industrial equipment and even raw materials. All these different cargos come with a variety of packaging all to make the cargo handling more efficient.
operate between ports. Ports are used for resupplying and for
discharging waste. Ports impose physical limitations on the size of the
ships and charge fees for their services. Port operations involve a lot
of people, both at management level and at operational level. The port
is a physical entity and is managed by a port authority. In addition,
depending on the size of the port, any number of businesses may be found
Issues of governance, control and ownership are very important to any discussion of environmental management in ports. The majority of ports are characterized by privately owned dock facilities and in these instances, control of property and operations lie with each private property owner. One of the main issues that ports are facing is local air quality. This is caused due to air pollutants, in particular the CO2 emissions. In ports, air emissions and energy consumptions are primarily due to ships. Around 85% of emissions come from containerships and tankers but despite that the most contaminants ships in ports are the cruise ships. Containerships have short port stays, but high emissions during these stays. However, there are other facilities that contribute to air emissions and energy consumption in ports. Future forecasts indicate that most of shipping emissions in ports are estimated to grow fourfold up to 2050, with Asia and Africa seeing the sharpest increases in emissions, due to strong port traffic growth and limited mitigation measures. Despite the fact that a lot of ports have developed regulations to reduce shipping emissions, they would need wider application in order to be truly successful (MariEMS 2017).
Ships operate between ports. Ports are used for loading and unloading cargo as well as for loading fuel, fresh water, other supplies and for discharging waste. Ports impose physical limitations on the dimensions of the ships that may call in them (ship draft, length and width), and charge fees for their services. Sometimes ports are used for trans-shipment of cargo among ships, especially when the cargo is containerised. Major container lines often operate large vessels between hub ports and use smaller vessels to feed containers to/from spoke ports. In many countries, ports authorities that are in overall charge of regulating ports are different from those authorities that are in charge of regulating shipping.
A ship may consume hundreds of tons of bunker fuel per day at sea and there may be significant differences in the cost of bunker fuel among bunkering ports. Thus, one has to decide where to buy bunker fuel. Sometimes it may be worthwhile to divert the ship to enter a port just for loading bunker fuel. The additional cost of the ship’s time has to be traded off with the savings in the cost of the fuel. Bunker procurement is overall a commercial decision-making process but nevertheless it has large implications for routine operation decision making as well. Additional cost of ship diversion may not occasionally come into perspective due to split-incentive issues relating to who pays for what when it comes to ship costs. Bunker procurement not only involves operational considerations but also technical considerations.