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Trim Optimisation

Trim optimisation is the operational practice of selecting the longitudinal trim of a ship (the algebraic difference between the forward and aft draughts) that minimises the total resistance and the propulsive power required to maintain a given service speed, displacement and sea state. The principle exploits the fact that for most modern hull forms the trim that minimises resistance changes with speed and draught, often differing materially from even keel and from the Class-loaded design trim. Selecting the optimum trim for each operating condition typically reduces main-engine fuel consumption by 1 to 4% with no hardware modification beyond redistribution of ballast water or cargo. Trim optimisation is recognised as a mandatory candidate measure in the SEEMP Part I operational plan and as an innovative energy-efficient operational measure under MARPOL Annex VI Regulation 22A; the realised savings translate directly into CII rating improvement and EU MRV reported intensity reduction. Modern trim optimisation systems combine pre-computed computational fluid dynamics (CFD) trim tables indexed by draught and speed, real-time shaft-power and torque telemetry from instrumented bearings, weather and current data, and onboard advisory software to recommend the optimum trim for each voyage leg. ShipCalculators.com hosts the principal computational tools: the Trim Optimisation calculator computes the recommended trim for a given draught and speed; the Trim Optimization fuel-savings calculator estimates the annual fuel and emissions reduction; the Trim from Weight Shift calculator computes the trim change from a discrete weight movement; the Trim Moment / MCT1cm Usage calculator implements the moment-to-change-trim-one-centimetre relationship. Companion guides are linked from the calculator catalogue and the trim and list reference article.

Contents

Background and physics

Trim, draught and displacement

In ship hydrostatics, trim is defined as the algebraic difference between the aft draught ($T_A$) and the forward draught ($T_F$), measured at the load line marks at the perpendiculars:

$$ t = T_A - T_F $$

A positive value indicates trim by the stern (aft draught greater than forward draught, the conventional loading state for almost all merchant ships); a negative value indicates trim by the bow (rare for laden ships, occasionally seen in light-ballast condition); a value of zero is even keel. Trim is conventionally reported in metres or centimetres (SI units), and in feet and inches in legacy US Coast Guard documentation.

The mean draught ($T_M = (T_A + T_F)/2$) and the displacement are linked through the hull’s hydrostatic curves; for any given displacement there is a continuum of admissible $T_F$ and $T_A$ pairs that satisfy the longitudinal centre of buoyancy / longitudinal centre of gravity equilibrium condition. The naval-architecture relationship that links a given trim change to a longitudinal weight movement is the moment to change trim one centimetre (MCT1cm), tabulated in the hydrostatics and Bonjean curves and computed by the Trim Moment / MCT1cm Usage calculator.

For a more exhaustive treatment of the underlying hydrostatic relationships see trim and list, hydrostatics and Bonjean curves, block coefficient and hull form design. For intact stability and damage stability implications of trim selection see the related stability articles. The role of trim in ship resistance and powering is the principal subject of the present article.

Resistance components affected by trim

The total hull resistance ($R_T$) of a displacement ship at a given speed and displacement is conventionally decomposed (after Froude) into:

  • Frictional resistance ($R_F$), proportional to the wetted surface area and to the square of the speed; the dominant component for slow-speed bulk carriers and tankers, typically 60 to 80% of $R_T$ at design speed.
  • Residual resistance ($R_R$), comprising wave-making resistance, viscous pressure resistance and wave-breaking resistance; rises sharply with speed and dominates above the design Froude number.
  • Air resistance ($R_A$), proportional to the projected above-water area and to the square of apparent wind speed; small for laden tankers and bulkers, material for high-freeboard container ships and car carriers.
  • Appendage resistance ($R_{app}$), from rudders, bilge keels, propeller bossings, bow thrusters and stabiliser fins.

Trim affects each component in characteristic ways. Trim by the stern increases the aft draught and the submerged transom area; for a flat-stern hull form (typical of post-2000 bulk and tanker designs) this can increase the wave-making resistance by submerging more of the transom into the wake. Trim by the bow increases the forward draught and may submerge the bulbous bow more deeply into the wave system, sometimes reducing wave-making resistance at low Froude numbers but increasing it at high Froude numbers. The wetted surface area changes with trim because the change in draught is not symmetric fore and aft; the integrated frictional resistance therefore varies non-monotonically with trim.

The net effect is that the optimum trim is a function of speed, displacement and hull form. For a given hull at a given displacement, the optimum trim can vary from 1 m by the stern at low speed to 0.5 m by the bow at high speed, or vice versa; the curve is bespoke to each hull form and must be determined empirically (by model testing) or computationally (by CFD). See the ship resistance and powering article for a full treatment of resistance prediction methods.

Static, running and dynamic trim

Three trim concepts are used in operational practice:

  • Static trim is the trim measured at rest, alongside or at anchor; it is the value reported in the load line survey and in the draught survey for cargo measurement.
  • Running trim (also dynamic trim or squat-corrected trim) is the trim of the ship at service speed, including the effects of squat (the localised reduction in under-keel clearance from the dynamic pressure field) and of any trim wedge induced by the propeller race. Running trim differs from static trim by typically 0.05 to 0.30 m at service speed.
  • Equivalent CFD trim is the trim used as input to a CFD trim curve; it is conventionally the static trim adjusted to the displacement at the operating draught.

Modern trim optimisation systems use static trim as the controllable variable (since it is what the bridge can adjust through ballast or cargo redistribution) but model the resulting running trim when computing the resistance. See squat effect for the related under-keel-clearance phenomenon and ship motions for the dynamic pitch component.

Why even keel is rarely optimum

The naval-architecture intuition that “even keel is always best” is wrong for almost all modern displacement hulls. Three reasons:

  1. Modern hull forms have flat sterns. Post-2000 designs, particularly bulk carriers and tankers, use flat or near-flat transoms to maximise block coefficient and cargo capacity; the resulting wake field at the transom is sensitive to draught.
  2. Bulbous bows are tuned to a single draught and speed. A modern bulbous bow is optimised for the design draught and design speed; off-design operation, especially in slow steaming at part-load draught, can leave the bulb partly emerged, producing a slamming wave train that increases wave-making resistance.
  3. Propeller immersion sensitivity. A change in aft draught of 0.5 m can change the marine propeller immersion ratio significantly; emerged tip vortices increase propeller-induced cavitation and erode propulsive efficiency.

These three effects combine to produce a trim-resistance curve that is typically U-shaped for each operating point, with an optimum that is often 0.5 to 1.5 m off even keel.

Methodology

CFD trim curves

The dominant method for determining the optimum trim is computational fluid dynamics. A CFD trim study computes the calm-water resistance of the hull at a grid of operating points: typically 5 to 7 draughts (covering ballast, intermediate and laden conditions), 4 to 6 speeds (covering economic to design speed) and 5 to 9 trim values (typically -1.5 m to +2.0 m in 0.5 m increments). The result is a trim table of fuel consumption (or equivalently shaft power, propulsive power or resistance) indexed by draught, speed and trim.

The CFD code most commonly used is STAR-CCM+ (Siemens), with OpenFOAM as the open-source alternative; both implement the RANS (Reynolds-Averaged Navier-Stokes) equations with a free-surface volume-of-fluid scheme. Model-test validation of the CFD trim curves is conventionally undertaken at one or two operating points to anchor the calibration; the model basin most commonly used is MARIN (Wageningen), with HSVA (Hamburg), SSPA (Gothenburg), Krylov (St Petersburg) and NMRI (Tokyo) as alternatives. See hull form design and ship resistance and powering for the underlying methods.

A typical CFD trim study costs USD 30,000 to USD 80,000 per hull form and takes 4 to 8 weeks; the resulting trim table is delivered as a CSV or JSON file and is loaded into the onboard advisory software. For sister-ship hulls the same trim table can be re-used; for hulls with significant modifications (lengthening, bulbous bow retrofit, air lubrication installation) a fresh CFD study is required.

In-service measurement and validation

The CFD trim table is calibrated against in-service shaft power measurements. The required instrumentation is:

  • Shaft torque meter (typically strain-gauge based or magnetoelastic), measuring shaft torque in kN·m to ± 1% accuracy.
  • Shaft RPM sensor, measuring shaft revolutions in rpm to ± 0.1 rpm accuracy.
  • GPS speed-over-ground and Doppler speed-through-water sensors, providing actual ship speed and the implied current.
  • Wind sensor at masthead, providing apparent wind speed and direction.
  • Wave height sensor (radar-based, e.g. Miros WaveX, Rutter WaMoS II), providing significant wave height and dominant period.
  • Draught sensor (typically pressure-based at the bow and stern), providing real-time fore and aft draughts.
  • Engine fuel meter (typically Coriolis flow meter at the supply and return), providing main-engine fuel consumption to ± 0.5% accuracy.

The instrumentation suite is typically installed during a planned drydocking and integrated through a vessel performance monitoring system (VPMS); modern VPMS implementations follow the ISO 19030 series of standards (Measurement of changes in hull and propeller performance) for normalising the measured data to standard conditions. See shaft power monitoring (within the CII corrective action plan article) and the related VPMS discussion.

Onboard advisory systems

Once the CFD trim table is loaded and the in-service instrumentation is providing real-time data, the onboard advisory system computes the recommended trim for the current operating point. The recommendation is typically displayed on the bridge as:

  • The current static trim (read from the draught sensors).
  • The recommended static trim (interpolated from the CFD trim table at the current draught and speed).
  • The expected fuel saving in tonnes per day or percent of current consumption.
  • The trim adjustment instructions: tonnes of ballast water to transfer between specific tanks, or cargo to redistribute, to achieve the recommended trim.

The advisory is non-binding: the bridge officer retains discretion to ignore the recommendation if it conflicts with stability, sea-keeping or operational considerations. See intact stability, damage stability and seakeeping for the constraints.

Closed-loop optimisation

Some modern systems implement closed-loop optimisation, in which the system not only recommends the trim but also automatically initiates the ballast transfer through the ship’s existing ballast control system. Closed-loop optimisation is more common on newbuilds (where the ballast valves can be specified for remote actuation) than on retrofits (where the existing ballast valves are typically locally operated). The closed-loop approach is favoured by NAPA Voyage Optimisation and Eniram Trim (acquired by Wartsila in 2016 and integrated into the Wartsila Fleet Optimisation Solution); the open-loop advisory approach is favoured by Hempel TROOP, ABB OCTOPUS-Onboard and Hoppe HyTrim.

Implementation in operational practice

Voyage planning

Trim optimisation is integrated into the standard voyage planning workflow. At the pre-departure stage, the loading computer (which is required onboard for intact stability and damage stability compliance) is used to compute the loading plan that achieves the recommended trim for the planned voyage speed and the as-loaded displacement. The plan must satisfy:

The loading plan is then executed during cargo loading and ballasting; the realised trim is monitored throughout loading and adjusted by ballast transfer if necessary. See bill of lading, cargo securing manual and stowage planning for the related cargo-side workflow.

En-route adjustment

During the voyage, the recommended trim changes as fuel is burnt, ballast is exchanged, fresh water is consumed, and weather conditions change. Most trim optimisation systems recommend a mid-voyage ballast transfer (typically 200 to 800 tonnes between forepeak and aftpeak tanks) to maintain the optimum trim as the displacement decreases. The ballast transfer is undertaken in compliance with the Ballast Water Management Convention requirements for ballast water exchange and treatment.

For bulk carriers and container ships on long ocean voyages, the en-route ballast adjustment is typically once or twice per leg. For chemical tankers and LNG carriers the ballast adjustment frequency is constrained by tank-cleanliness requirements and may be less frequent.

Integration with weather routing

Trim optimisation is conventionally integrated with weather routing so that the trim recommendation accounts for the expected sea state as well as the calm-water resistance. In a head sea, the optimum trim is typically more by the stern (to keep the bow above the wave crests and reduce slamming); in a following sea the optimum is closer to even keel. Modern voyage optimisation suites (NAPA, Wartsila FOS, DNV Veracity, Kongsberg Vessel Insight) provide integrated trim-plus-route optimisation as a single calculation. See weather routing, just-in-time arrival and the SEEMP I, II, III for the operational context.

Vendors and systems

The principal commercial trim optimisation systems in 2024 are:

  • NAPA Voyage Optimisation (NAPA Ltd, Helsinki). Combines NAPA’s loading computer (used by approximately 80% of the world fleet for stability calculation) with a CFD-based trim advisory and a weather-routing module. Approximately 3,000 vessels are equipped with the NAPA loading computer; an estimated 600 to 800 are running the full Voyage Optimisation suite including trim advisory.
  • Wartsila Fleet Optimisation Solution (FOS), formerly Eniram Trim (Eniram acquired by Wartsila 2016). One of the original commercial trim advisory systems, deployed on approximately 400 vessels at acquisition; integrated into the Wartsila FOS suite alongside engine optimisation and route advisory.
  • Hempel TROOP (Trim and Roll Optimisation Programme), developed by paint manufacturer Hempel as part of its SHAPE (Ship Performance) suite. Open-loop advisory, integrated with Hempel’s hull coating performance monitoring.
  • ABB OCTOPUS-Onboard (ABB Marine and Ports). Combines trim advisory with motion monitoring and engine optimisation; deployed on approximately 200 vessels including several major cruise lines.
  • Hoppe HyTrim (Hoppe Marine, Hamburg). Open-loop advisory targeted primarily at bulk carriers and tankers; approximately 150 installations.
  • DNV ECO Insight (DNV). Cloud-based fleet performance platform that includes trim advisory as one module; provides benchmarking against the wider DNV-classed fleet.
  • Kongsberg Vessel Insight (Kongsberg Maritime). Cloud-based platform integrating trim advisory with engine and route optimisation; principally deployed on Kongsberg-equipped newbuilds.
  • FORCE Technology SeaTrend (FORCE Technology, Lyngby). Performance monitoring with trim advisory; predominantly Scandinavian fleet penetration.
  • MARIN MultiFlex (Maritime Research Institute Netherlands). Trim advisory derived from MARIN’s CFD and model-test capability; principally consultancy delivery rather than commercial product.

A 2023 review by DNV (Maritime Forecast to 2050) estimated that approximately 5,000 vessels worldwide are equipped with a trim advisory system, representing roughly 10% of the world merchant fleet by number and approximately 25% by tonnage (because larger vessels are more likely to be equipped). Penetration is highest among container ships (approximately 40% by tonnage), LNG carriers (approximately 35%) and large bulk carriers (approximately 20%); penetration is lowest among general cargo ships (under 5%) and small chemical tankers (under 5%).

Performance and economics

Typical fuel savings

Independent peer-reviewed and industry studies place the typical fuel saving from trim optimisation in the range of 1 to 4% of main-engine fuel consumption. Specific findings include:

  • MARIN (2014): 1.5 to 3.0% saving on a Suezmax tanker across a range of laden and ballast conditions, validated against full-scale shaft power measurements.
  • DNV (2018, EEDI study): 2 to 3% typical, 4 to 6% for some container ship hulls with strongly speed-dependent trim curves.
  • Lloyd’s Register (2016): 1 to 4% range, with the higher end concentrated on hulls operating at slow steaming speeds significantly below the design speed.
  • NAPA (2020 customer dataset): average 3.0% saving across approximately 200 reporting customers; range 0.5 to 7.5%.
  • DNV Maritime Forecast to 2050 (2023): 1 to 4% typical, 4 to 7% on hulls with significant off-design operation.

The wide range reflects the fact that trim optimisation savings depend strongly on:

  • Hull form: container ships and ro-ro vessels with strongly speed-dependent trim curves benefit most; hulls with weak trim sensitivity (some bulkers) benefit least.
  • Operating profile: hulls operating at a wide range of speeds and draughts benefit more than hulls operating at near-design conditions.
  • Pre-existing trim discipline: hulls already trimmed to design recommendations (e.g. those operated by quality-conscious owners) have less headroom for further savings; hulls trimmed by bridge intuition alone have more headroom.

The Trim Optimization fuel-savings calculator implements the IMO MEPC.1/Circ.815 method for estimating the savings.

Capital cost and payback

A trim optimisation system typically costs USD 50,000 to USD 250,000 per vessel installed, depending on the level of instrumentation and the level of integration with the loading computer and weather-routing software. The principal cost components are:

  • CFD trim study: USD 30,000 to USD 80,000 (one-time, per hull form).
  • Onboard instrumentation: USD 20,000 to USD 100,000 (shaft torque meter, draught sensors, wind sensor, fuel meters).
  • Software licence: USD 10,000 to USD 30,000 per year, typically subscription-based.
  • Installation and commissioning: USD 10,000 to USD 40,000 (drydocking time, integration with existing ship systems).

For a typical Capesize bulk carrier burning 35 t/d of HFO at USD 600/t, a 2.5% saving represents approximately 0.9 t/d, or USD 540/d, or approximately USD 165,000/y at 305 sea days. The payback period on a USD 100,000 system is therefore approximately 7 to 8 months; on a USD 250,000 system it is approximately 18 months. See the Trim Optimization fuel-savings calculator for the full payback calculation.

CII improvement

Beyond the direct fuel saving, trim optimisation contributes to CII rating improvement through the corresponding reduction in Annual Efficiency Ratio. A 2.5% fuel saving translates directly into a 2.5% reduction in CO2 emissions and therefore a 2.5% reduction in the Attained CII. This is typically sufficient to move a vessel one CII rating band (the band widths are approximately 5% on each side of the C boundary), and may be sufficient to avoid the CII corrective action plan trigger. See EU MRV regulation for the analogous reporting in the EU framework.

EU ETS and FuelEU Maritime exposure

Under the EU ETS for shipping, a 2.5% fuel saving on a vessel calling EU ports translates directly into a 2.5% reduction in EUA surrender obligation. At a 2024 EUA price of approximately EUR 70/t and a typical CII-relevant emissions level of 25,000 t-CO2/y for a Capesize, the saving is approximately EUR 44,000/y in EUA cost on top of the fuel saving, materially shortening the payback. Under FuelEU Maritime, the same saving reduces the GHG intensity of the energy used and therefore reduces the pooling, multiplier and penalty exposure.

Notable deployments

Maersk fleet-wide rollout (2014 to 2018)

A.P. Moller-Maersk undertook a fleet-wide trim optimisation rollout between 2014 and 2018, installing the Eniram Trim system (subsequently rebranded as Wartsila FOS after the 2016 acquisition) on the bulk of its operated container fleet. Maersk reported in its 2017 Sustainability Report that trim optimisation alone delivered approximately 1.5% fleet-wide fuel saving, equivalent to approximately 200,000 t/y of HFO and approximately 620,000 t/y of CO2.

MSC and CMA CGM

Mediterranean Shipping Company (MSC) and CMA CGM, the two other members of the container-shipping “big three”, have undertaken similar fleet-wide rollouts with NAPA Voyage Optimisation and ABB OCTOPUS-Onboard respectively. Both report fleet-wide savings in the 1.5 to 2.5% range from trim alone, with additional savings from the integrated weather routing and engine optimisation modules.

Cruise sector

Major cruise lines including Carnival Corporation, Royal Caribbean Group and Norwegian Cruise Line Holdings have deployed trim optimisation across the bulk of their fleets, principally through ABB OCTOPUS-Onboard and Wartsila FOS. The cruise sector benefits particularly from the integrated motion monitoring (which is important for passenger comfort) and from the high fuel intensity of cruise operations (a typical large cruise ship burns 200 to 250 t/d of marine gas oil or marine diesel oil in emission control areas).

LNG sector

LNG carrier operators including NYK, MOL, K Line, GasLog, Maran Gas, NJ Lottos (Knutsen) and Cool Company have widely deployed trim optimisation, both for the direct fuel saving and for the indirect benefit of reduced boil-off rate management complexity. Trim optimisation in LNG carriers is integrated with the LNG fuel system cargo-handling and the methane slip calculation in dual-fuel engines.

Bulk and tanker uptake

Uptake among bulk carriers and crude oil tankers has historically been slower than in the container and cruise segments, principally because the time-charter market structure and the spot-voyage business model leave the fuel-cost benefit with the charterer, not the owner; the owner therefore has limited incentive to invest in optimisation systems. The BIMCO CII Operations Clause (when implemented) and the Sea Cargo Charter reporting framework are gradually realigning the incentives. See also the Poseidon Principles for the analogous bank-side framework.

Trim optimisation is one component of a broader portfolio of operational energy-efficiency measures required under the SEEMP Part I and SEEMP Part III frameworks. The companion measures include:

For the regulatory framework see MARPOL Annex VI, the IMO Net-Zero Framework, the EU MRV Regulation, EU ETS for shipping, FuelEU Maritime, UK ETS for shipping, China DCS and the CARB at-berth rule.

Safety and stability considerations

Trim optimisation must always be subordinated to safety and stability constraints. The principal constraints are:

Intact stability

The recommended trim must satisfy the intact stability criteria of the IMO 2008 IS Code, in particular the GZ curve requirements at the operating displacement and trim. Excessive trim by the bow can reduce the area under the GZ curve at large heel angles; excessive trim by the stern can reduce the freeboard at the stern and increase the risk of pooping in following seas. Modern loading computers automatically check the IS Code compliance for the recommended trim; a recommendation that fails the check is suppressed and an alternative is offered.

Damage stability

The damage stability condition under SOLAS Chapter II-1 and the relevant cargo-ship damage criteria must be satisfied at the recommended trim. For bulk carriers the Loss of Hold Stability (LOHS) criterion of SOLAS Chapter XII is typically the binding constraint at large drafts; for container ships the probabilistic damage stability criterion of SOLAS II-1/B-1 typically binds.

Slamming and bow flare loading

Excessive trim by the stern in head seas can leave the bow exposed to slamming and to bow flare loading, both of which can damage the forward hull plating. The forepeak draught is constrained by the requirement to keep the bulbous bow submerged in the design wave, typically requiring at least 5.5 to 7 m of forward draught for a Capesize bulker. The classification society (e.g. DNV, Lloyd’s Register, ABS, BV, CCS, NK, KR, RINA) loading manual specifies the minimum forepeak draught.

Propeller immersion

The aft draught must be sufficient to keep the marine propeller fully submerged at all sea states; emerged tip vortices can cause severe cavitation erosion of the propeller blades and significant loss of propulsive efficiency. The minimum propeller immersion ratio (immersion above the propeller tip relative to the propeller diameter) is typically 0.25 to 0.30 for a fully submerged propeller; below this the recommendation is suppressed.

Rudder immersion

Similarly, the rudder must be fully submerged at all sea states to maintain steering authority; the minimum immersion is typically 1.0 to 1.5 m above the rudder top in calm water.

Bridge visibility

SOLAS Chapter V Regulation 22 requires that the bridge view of the sea surface ahead is not obscured by more than two ship lengths or 500 m, whichever is less. A laden bulker or container ship trimmed by the bow can violate this requirement; the loading computer checks the bridge visibility constraint as part of the recommendation.

Limitations and risks

Off-design hull-form sensitivity

CFD trim curves are valid for the modelled hull form. Hull modifications during the vessel’s life (lengthening, bulbous bow retrofit, air lubrication installation, energy-saving devices, rudder modifications) invalidate the existing trim curve and require a fresh CFD study. Hull fouling also shifts the trim curve, particularly at high speeds; the curve should ideally be recalibrated against in-service measurements at each drydocking interval.

Charterer / owner incentive misalignment

In the time-charter market, the fuel cost is borne by the charterer but the trim optimisation system is purchased by the owner. The owner therefore has limited direct financial incentive to invest in the system, despite the fuel saving accruing to the charterer. The BIMCO CII Operations Clause, BIMCO ETS Clauses, BIMCO FuelEU Maritime Clause and the Sea Cargo Charter reporting framework are gradually realigning the incentives, but the misalignment remains a structural impediment to trim optimisation rollout in the bulk carrier and tanker sectors.

Operational disruption

Trim adjustment requires ballast water transfer, which itself consumes auxiliary engine fuel for pump operation and which is constrained by the Ballast Water Management Convention requirements for treatment. The net energy benefit must be computed including the pumping cost; for short voyages or for large trim adjustments the pumping cost can erode 20 to 30% of the calm-water trim saving.

Measurement uncertainty

Validation of the realised savings against the predicted savings requires accurate baseline measurement of fuel consumption, which is challenging in the presence of variable wind, waves, currents, hull fouling and engine condition. The ISO 19030 series of standards provides a normalisation framework, but the residual uncertainty in the realised saving is typically ± 1 to 2 percentage points, comparable in magnitude to the saving itself. Reliable validation requires multi-month before-and-after datasets and statistical regression to separate the trim effect from confounders.

Future outlook

Machine-learning trim curves

Conventional CFD trim curves are static, indexed by draught, speed and trim only. Machine-learning trim curves under development by NAPA, Eniram (now Wartsila), Hempel and several research consortia (notably the EU H2020 DEMOPS project) extend the indexing to include wave height, wave direction, wind speed, wind direction, hull fouling state and engine condition; the resulting dynamic trim recommendation is potentially more accurate than the static CFD prediction. Field trials in 2021 to 2024 suggest an additional 0.5 to 1.5 percentage points of saving from the dynamic approach over the static CFD approach.

Integration with autonomous shipping

For partially or fully autonomous vessels, the trim recommendation must be integrated with the autonomous voyage execution system. Trim optimisation is one of the simpler optimisation modules to automate (the recommendation is unambiguous and the actuation is via existing ballast valves) and is therefore likely to be one of the first integrated subsystems.

Wider regulatory pressure

The progressive tightening of the CII rating reduction trajectory under the IMO Net-Zero Framework, the rising EUA price under the EU ETS for shipping, and the FuelEU Maritime penalty escalation are all increasing the financial value of trim optimisation. DNV’s Maritime Forecast to 2050 (2023) estimates that trim optimisation penetration will reach approximately 25% of the world fleet by number and 50% by tonnage by 2030.

Combination with air lubrication and wind-assist

Trim optimisation is increasingly bundled with other operational and technical measures into integrated fleet performance packages. The combination of trim optimisation, weather routing, air lubrication systems and wind-assisted propulsion on a single hull can deliver compound savings of 20 to 40%, with each measure reducing the fuel basis on which the other measures are calculated. See the integrated SEEMP Measures Combined calculator for the cumulative-savings calculation.

See also

Operational efficiency measures

Hull form, hydrostatics and stability

Regulatory and reporting frameworks

Voluntary frameworks

Cargo and ship operations

Ship types

Calculators

References

  • IMO MEPC.1/Circ.815: Guidance on Treatment of Innovative Energy Efficiency Technologies for Calculation and Verification of the Attained EEDI. International Maritime Organization, 2013.
  • IMO MEPC.1/Circ.866: Guidance for the Development of a Ship Energy Efficiency Management Plan (SEEMP). International Maritime Organization, 2017.
  • ISO 19030-1:2016, ISO 19030-2:2016, ISO 19030-3:2016: Ships and marine technology, Measurement of changes in hull and propeller performance. International Organization for Standardization.
  • DNV. Energy Efficiency Operational Indicator and Trim Optimisation. DNV Position Paper, 2014.
  • MARIN. Trim Optimisation: A Validation Study on a Suezmax Tanker. MARIN Report, 2014.
  • Lloyd’s Register. Trim Optimisation: An Operational Energy Efficiency Measure. LR Technical Briefing, 2016.
  • DNV. Maritime Forecast to 2050. DNV Energy Transition Outlook, 2023.
  • A.P. Moller-Maersk. Sustainability Report 2017. Maersk Group, 2018.
  • NAPA. Voyage Optimisation: Customer Performance Benchmarking 2020. NAPA Ltd, 2021.
  • Wartsila. Fleet Optimisation Solution: Trim Advisory Module. Wartsila Marine Solutions, 2022.
  • Hempel. SHAPE: Ship Performance Suite Technical Overview. Hempel A/S, 2022.

Further reading

  • BIMCO. BIMCO CII Operations Clause for Time Charter Parties. BIMCO, 2022.
  • DNV. EEXI: Frequently Asked Questions. DNV Maritime, 2022.
  • IMO. Resolution MEPC.336(76): 2021 Guidelines on Operational Carbon Intensity Indicators and the Calculation Methods (CII Guidelines, G1). International Maritime Organization, 2021.
  • ICS. Catalysing the Fourth Propulsion Revolution. International Chamber of Shipping, 2022.
  • ITTC. Recommended Procedures and Guidelines: Predicted Power of Ships in Service. International Towing Tank Conference, 2017.