5.1 The search for energy efficiency and carbon intensity improvement across the
entire transport chain takes responsibility beyond what can be delivered by the
company alone. A list of all the possible stakeholders in the efficiency of a single
voyage is long: obvious parties are designers, shipyards and engine manufacturers
for the characteristics of the ship; and charterers, fuel suppliers, ports and
vessel traffic management services, etc. for the specific voyage. All parties
involved should consider the inclusion of efficiency measures in their operations
both individually and collectively.
5.2 Fuel-efficient operations
Improved voyage planning
5.2.1 The optimum route and improved efficiency can be achieved through the careful
planning and execution of voyages. Thorough voyage planning needs time, but a number
of software tools are available to assist in voyage planning.
5.2.2 The Guidelines for voyage planning, adopted by resolution
A.893(21), provide essential guidance for the ship's crew and voyage
planners.
Weather routeing
5.2.3 Weather routeing has a high potential for efficiency savings on specific
routes. It is commercially available for all types of ship and for many trade areas.
Just in time
5.2.4 Good early communication with the next port should be an aim in order to give
maximum notice of berth availability and facilitate the use of optimum speed where
port operational procedures support this approach.
5.2.5 Optimized port operation could involve a change in procedures involving
different ship handling arrangements in ports. Port authorities should be encouraged
to maximize efficiency and minimize delay.
Speed optimization
5.2.6 Speed optimization can produce significant savings. However, optimum speed
means the speed at which the fuel used per tonne mile is at a minimum level for that
voyage. It does not mean minimum speed; in fact, sailing at less than optimum speed
will consume more fuel rather than less. Reference should be made to the engine
manufacturer's power/consumption curve and the ship's propeller curve. Possible
adverse consequences of slow speed operation may include increased vibration and
problems with soot deposits in combustion chambers and exhaust systems. These
possible consequences should be taken into account. For LNG carriers speed
optimization means, quite often, a higher speed at the start of laden passages to
control tanks pressure and at the end of ballast passages to use the operational LNG
quantity needed for cargo tank cooling in propulsion instead of wasting in GCU or
condenser steam dump. Charterers are generally aware of the improved efficiency of
this speed pattern.
5.2.7 As part of the speed optimization process, due account may need to be taken of
the need to coordinate arrival times with the availability of loading/discharge
berths, etc. The number of ships engaged in a particular trade route may need to be
taken into account when considering speed optimization.
5.2.8 A gradual increase in speed when leaving a port or estuary whilst keeping the
engine load within certain limits may help to reduce fuel consumption.
5.2.9 It is recognized that under many charter parties the speed of the ships is
determined by the charterer and not the operator. Efforts should be made when
agreeing charter party terms to encourage the ship to operate at optimum speed in
order to maximize energy efficiency.
Optimized shaft power
5.2.10 Operation at constant shaft RPM can be more efficient than continuously
adjusting speed through engine power. The use of automated engine management systems
to control speed rather than relying on human intervention may be beneficial.
5.2.11 When optimizing shaft power, due attention should be given to overall power
system efficiency. For example, in some cases reducing load or shaft speed below the
minimum necessary to operate energy recovery systems and shaft generators may
increase overall emissions.
5.3 Optimized ship handling
Optimum trim
5.3.1 Most ships are designed to carry a designated amount of cargo at a certain
speed for a certain fuel consumption. This implies the specification of set trim
conditions. Loaded or unloaded, trim has a significant influence on the resistance
of the ship through the water and optimizing trim can deliver significant fuel
savings. For any given draft there is a trim condition that gives minimum
resistance. In some ships, it is possible to assess optimum trim conditions for fuel
efficiency continuously throughout the voyage. Design or safety factors may preclude
full use of trim optimization.
Optimum ballast
5.3.2 Ballast should be adjusted taking into consideration the requirements to meet
optimum trim and steering conditions and optimum ballast conditions achieved through
good cargo planning.
5.3.3 When determining the optimum ballast conditions, the limits, conditions and
ballast management arrangements set out in the ship's Ballast Water Management Plan
are to be observed for that ship.
5.3.4 Ballast conditions have a significant impact on steering conditions and
autopilot settings, and it needs to be noted that less ballast water does not
necessarily mean improved energy efficiency.
Optimum propeller and propeller inflow considerations
5.3.5 Selection of the propeller is normally determined at the design and
construction stage of a ship's life but new developments in propeller design have
made it possible for retrofitting of later designs to deliver greater fuel economy.
Whilst it is certainly for consideration, the propeller is but one part of the
propulsion train and a change of propeller in isolation may have no effect on
efficiency and may even increase fuel consumption.
5.3.6 Improvements to the water inflow to the propeller using arrangements such as
fins and/or nozzles could increase propulsive efficiency power and hence reduce fuel
consumption.
Optimum use of rudder and heading control systems (autopilots)
5.3.7 There have been large improvements in automated heading and steering control
systems technology. Whilst originally developed to make the bridge team more
effective, modern autopilots can achieve much more. An integrated Navigation and
Command System can achieve significant fuel savings by simply reducing the distance
sailed "off track". The principle is simple: better course control through less
frequent and smaller corrections will minimize losses due to rudder resistance.
Retrofitting of a more efficient autopilot to existing ships could be considered.
5.3.8 During approaches to ports and pilot stations the autopilot cannot always be
used efficiently as the rudder has to respond quickly to given commands.
Furthermore, at certain stages of the voyage it may have to be deactivated or very
carefully adjusted, i.e. during heavy weather and approaches to ports.
5.3.9 Consideration may be given to the retrofitting of improved rudder blade design
(e.g. "twist-flow" rudder).
Hull maintenance
5.3.10 Docking intervals should be integrated with the company's ongoing assessment
of ship performance. Hull resistance can be optimized by new technology-coating
systems, possibly in combination with cleaning intervals. Regular in-water
inspection of the condition of the hull is recommended.
5.3.11 Propeller cleaning and polishing or even appropriate coating may significantly
increase fuel efficiency. The need for ships to maintain efficiency through in-water
hull cleaning should be recognized and facilitated by port States.
5.3.12 Consideration may be given to the possibility of timely full removal and
replacement of underwater paint systems to avoid the increased hull roughness caused
by repeated spot blasting and repairs over multiple dockings.
5.3.13 Generally, the smoother the hull, the better the fuel efficiency.
Propulsion system
5.3.14 Marine diesel engines have a very high thermal efficiency (~50%). This
excellent performance is only exceeded by fuel cell technology with an average
thermal efficiency of 60%. This is due to the systematic minimization of heat and
mechanical loss. In particular, the new breed of electronic controlled engines can
provide efficiency gains. However, specific training for relevant staff may need to
be considered to maximize the benefits.
Propulsion system maintenance
5.3.15 Maintenance in accordance with manufacturers' instructions in the company's
planned maintenance schedule will also maintain efficiency. The use of engine
condition monitoring can be a useful tool to maintain high efficiency.
5.3.16 Additional means to improve engine efficiency might include use of fuel
additives, adjustment of cylinder lubrication oil consumption, valve improvements,
torque analysis, and automated engine monitoring systems.
5.4 Waste heat recovery
5.4.1 Waste heat recovery systems use thermal heat losses from the exhaust gas for
either electricity generation, heating or additional propulsion with a shaft power
take in.
5.4.2 It may not be possible to retrofit such systems into existing ships. However,
they may be a beneficial option for new ships. Shipbuilders should be encouraged to
incorporate new technology into their designs.
5.5 Improved fleet management
5.5.1 Better utilization of fleet capacity can often be achieved by improvements in
fleet planning. For example, it may be possible to avoid or reduce long ballast
voyages through improved fleet planning. There is opportunity here for charterers to
promote efficiency. This can be closely related to the concept of "just in time"
arrivals.
5.5.2 Efficiency, reliability and maintenance-oriented data sharing within a company
can be used to promote best practice among ships within a company and should be
actively encouraged.
5.6 Improved cargo handling
Cargo handling is in most cases under the control of the port or terminal operators
and optimum solutions matched to ship and port or terminal requirements should be
explored. However, in cases where ships use their own cargo handling equipment (e.g.
cargo cranes, self-unloading booms, cargo pumps (tankers)), procedures should be in
place to efficiently utilize the energy produced from any additional generators
required to operate the equipment.
5.7 Energy management
5.7.1 A review of electrical services on board can reveal the potential for
unexpected efficiency gains. However, care should be taken to avoid the creation of
new safety hazards when turning off electrical services (e.g. lighting). Thermal
insulation is an obvious means of saving energy. Also see comment below on shore
power.
5.7.2 Optimization of reefer container stowage locations may be beneficial in
reducing the effect of heat transfer from compressor units. This might be combined
as appropriate with cargo tank heating, ventilation, etc. The use of water-cooled
reefer plant with lower energy consumption might also be considered.
5.8 Fuel type
The use of emerging alternative fuels may be considered as a CO2 reduction
method, but availability will often determine the applicability.
5.9 Other measures
5.9.1 Development of computer software for the calculation of current fuel
consumption, for the establishment of an emissions "footprint," to optimize
operations, and the establishment of goals for improvement and tracking of progress
may be considered.
5.9.2 Renewable energy sources, such as solar (or photovoltaic) cell technology, have
improved enormously in recent years and should be considered for onboard
application.
5.9.3 In some ports shore power may be available for some ships but this is generally
aimed at improving air quality in the port area. If the shore-based power source is
carbon efficient, there may be a net efficiency benefit. Ships may consider using
onshore power if available.
5.9.4 Even wind-assisted propulsion may be worthy of consideration. Various systems
are available for retrofit, including Flettner rotors, wing sails and aerofoil
kites.
5.9.5 Efforts could be made to source fuel of improved quality in order to minimize
the amount of fuel required to provide a given power output.
5.10 Compatibility of measures
5.10.1 These Guidelines indicate a wide variety of possibilities for energy
efficiency improvements for the existing fleet. While there are many options
available, they are not necessarily cumulative, are often area and trade dependent
and likely to require the agreement and support of a number of different
stakeholders if they are to be utilized most effectively.
Age and operational service life of a ship
5.10.2 All measures identified in this document as applied to part I of the SEEMP are
potentially cost-effective in case of high oil prices. The financial feasibility of
a specific energy efficiency enhancement can be evaluated by various means. One way
would be to estimate the return on investment (ROI) time. However, while measures
with lower ROI may have the lowest cost, this does not guarantee the best results in
energy efficiency performance improvement. Clearly, this equation is heavily
influenced by the remaining service life of a ship and the cost of fuel.
Trade and sailing area
5.10.3 The feasibility of many of the measures described in this guidance will be
dependent on the trade and sailing area of the ship. Sometimes ships will change
their trade areas as a result of a change in chartering requirements, but this
cannot be taken as a general assumption. For example, certain types of wind-enhanced
power sources might not be feasible for short sea shipping as these ships generally
sail in areas with high traffic densities or in restricted waterways. Air draft
limitations may also affect the feasibility of wind assistance technology and
certain other emission reduction measures. Another aspect is that the world's oceans
and seas each have characteristic conditions and so ships designed for specific
routes and trades may not obtain the same energy efficiency benefits by adopting the
same measures or combination of measures as other ships that operate in different
areas. It is also likely that some measures will have a greater or lesser effect in
different sailing areas.
5.10.4 The trade a ship is engaged in may also determine the feasibility of the
efficiency measures under consideration. For example, ships that perform services at
sea (pipe laying, seismic survey, OSVs, dredgers, etc.) may choose different methods
of improving energy efficiency when compared to conventional cargo carriers. The
length of voyage may also be an important parameter as may trade specific safety
considerations. The pathway to the most efficient combination of measures will be
unique to each vessel within each shipping company.
5.10.5 Environmental conditions and the nature of cargo carried also varies between
regions. For example, some routes may carry greater volumes of goods requiring
careful temperature conditioning, or some transit regions may be subject to frequent
severe adverse weather conditions. This may lead to an increase of emissions of
ships serving those routes and regions.