Decarbonization Technologies for Ships

A ship’s carbon intensity can be attacked from three directions at once: change the fuel, slow the ship down, or make the same voyage take less energy. This hub covers the third route, the onboard hardware and operational measures that cut energy demand or capture CO2 without waiting for a new fuel to arrive at scale. They matter now because the existing fleet has to comply with the IMO’s EEXI and CII regime with the ships that already exist, and most of these ships will trade for another decade or two. A new fuel changes the well-to-wake number; an energy-saving device changes the number this year, at the next drydock, on the hull the owner already owns. The CO2 emissions calculator translates a fuel-saving percentage into the tonnes of CO2 it removes from a voyage.

The technologies split cleanly by where in the energy chain they act. Some cut the resistance the hull pushes against. Some add thrust from the wind. Some recover energy the engine throws away as heat. Some replace engine power with shore or stored electricity. One captures the CO2 after combustion. The question to ask of each is the same: how much does it save, on which ships, and can it be retrofitted or only built in. This article groups them by that logic and routes down to the wiki articles and the cluster’s calculators that size each one. It sits under the decarbonization and alternative fuels hub and links across to the ship-efficiency indices the technologies are deployed to meet and to the alternative marine fuels that carry the rest of the decarbonization load.

One caution frames the whole field, and it is worth stating before any number: the savings percentages do not add up. A pre-swirl device and a boss cap fin both recover energy from the swirl behind the propeller, so fitting both recovers less than the sum of their separate figures, because they compete for the same loss. The honest way to size a package of measures is a hull-specific model or a sea trial, not an addition of the brochure percentages. The figures below are typical ranges from primary sources; treat them as the order of magnitude, not as guarantees for a specific ship.

Hull and propulsion energy-saving devices

Energy-saving devices (ESDs) are appendages added to the hull or propeller to recover some of the energy lost in the flow around them. They are the workhorse of existing-fleet efficiency, because most of them retrofit at a normal drydock and pay back in a few years of fuel. The losses they attack are real and measurable: a conventional propeller leaves a rotating wake that carries kinetic energy off the stern, the boss cap sheds a hub vortex, and the hull’s own wake is uneven, so the propeller works in water of varying speed. Each device targets one of those losses, which is why their gains overlap and why the energy-saving devices article works the wake-field physics that ties them together.

The duct devices reshape the flow into the propeller. The Becker Mewis Duct, a fixed duct with internal fins mounted ahead of the propeller, straightens and accelerates the inflow and pre-rotates it against the propeller’s turn; Becker Marine reports power savings of 3 to 8 percent depending on the hull and propeller interaction, with an initial sea trial on a 319-meter VLCC measuring about 5 percent. The duct works best on slow, full-form ships (tankers and bulkers) where the wake is thick and the propeller is heavily loaded, which is exactly where the IMO GreenVoyage2050 portal places the largest gains: at low Froude number, where frictional and wake losses dominate. The Mewis duct savings calculator sizes the gain against a baseline.

The swirl-recovery devices work on the propeller’s own losses. A pre-swirl stator is a set of fixed fins ahead of the propeller that pre-rotates the inflow opposite to the propeller’s rotation, so the propeller does less work to produce the same thrust; the GreenVoyage2050 portal gives up to 5 percent for pre-swirl or duct devices. A propeller boss cap fin (PBCF) is a finned cap that breaks up the hub vortex shed behind the boss; the PBCF maker reports 3 to 5 percent and the GreenVoyage2050 portal lists up to 2 percent, the lower figure reflecting that hub-vortex energy is a smaller slice of the total. The pre-swirl stator calculator and the PBCF savings calculator compute each. Because both clean up the same propeller-wake energy, an owner fitting both should expect less than 5 plus 2 percent.

The propeller and bulbous bow are the bigger structural items. A propeller upgrade (a new wake-adapted design, more blades, or a larger diameter at lower revolutions) is one of the highest-value retrofits where the original wheel was matched to a now-superseded operating profile; the GreenVoyage2050 portal gives 2 to 6 percent on main-engine fuel for propeller retrofitting. A bulbous-bow retrofit re-profiles the bulb to the speed and draft the ship actually trades at, which often differs from the design point it was built for, especially after years of slow steaming. The bulbous bow retrofit savings calculator and the bulbous-bow retrofit article work the case where a ship’s real operating speed has dropped below its design speed and the original bulb now adds resistance rather than cutting it.

Air lubrication sits apart from the wake devices because it attacks friction directly. An air lubrication system pumps a carpet of microbubbles or an air film under the flat of bottom, lowering the frictional resistance of the wetted hull. The IMO recognized it as a Category B-1 innovative energy-efficient technology under MEPC.1/Circ.815 in 2018, and the GreenVoyage2050 portal gives net annual energy savings of about 2 to 8 percent among successful installations, with the larger figures on wide flat-bottomed ships (large tankers, bulkers, and container ships) where the lubricated area is large relative to the air-compressor power it costs to maintain the film. The air lubrication savings calculator nets the gross friction reduction against the compressor’s parasitic load, and the air lubrication systems article works the bubble physics and the net-versus-gross trap that flatters poorly netted figures.

The wake-field caveat on every ESD figure

The single most misread thing about ESD percentages is that they are not properties of the device; they are properties of the device on a specific hull at a specific operating point. The Mewis duct that saves 7 percent on a heavily loaded slow tanker can save under 2 percent on a fine, lightly loaded propeller, because there is less wake energy to recover. The GreenVoyage2050 portal makes the point with the Froude-number rule: the maximum reduction is achieved at low Froude number, where frictional and wake losses dominate. So a fast container ship and a slow bulk carrier get different answers from the same device, and a figure quoted without the ship type, speed, and draft is not usable. The admiralty coefficient power calculator and the resistance estimators (Holtrop-Mennen, ITTC-57 friction) frame the baseline against which any saving is measured.

Wind-assisted propulsion

Wind-assisted propulsion (WASP) puts the wind back to work as a thrust source alongside the engine, not as the primary mover. The category is the fastest-growing in the field: the International Windship Association tracks the installed and on-order count climbing through the 2020s, and the 2023 EMSA study prepared by ABS, CE Delft, and Arcsilea frames it as a promising decarbonization route for the existing fleet because most systems retrofit on deck without touching the hull below the waterline. Three device families dominate, and the wind-assisted propulsion article works the aerodynamics that separate them.

The Flettner rotor is the most installed type. It is a tall spinning vertical cylinder (typically 15 to 30 meters high and 3 to 5 meters in diameter) that generates thrust through the Magnus effect when wind crosses the spinning surface, the same physics that curves a spinning ball. Single-voyage figures reach the headlines (E-Ship 1 recorded up to about 23 percent on a favorable Emden-to-Portugal run), but the realistic whole-year average is lower: Norsepower’s rotor-sail trial on a product tanker measured an 8.2 percent fuel reduction, inside its predicted 7 to 10 percent band. The rotor costs a small amount of electricity to spin, which the Flettner rotor drive-power calculator accounts for against the Flettner rotor thrust and the Flettner wind-assist savings calculator. Net thrust, not gross, is what reaches the propeller credit.

Rigid wing sails and soft sails are the second family. A wing sail is a symmetric aerofoil, often hard and articulated, that develops lift across the wind like an aircraft wing turned vertical; it produces more thrust per unit deck area than a rotor in some wind angles and folds or feathers for port and headwind. The rigid wing sail thrust calculator and the wing sail and kite wind-assist calculator size the thrust against the apparent wind. Towing kites are the third: a large parafoil flown several hundred meters ahead and above the ship on a tether, pulling from high-altitude wind that is stronger and steadier than wind at deck level. SkySails recorded about 5 percent on an average route mix and 10 to 12 percent on the windy North Atlantic and North Pacific, and the towing kite pulling-force calculator works the tether tension into a thrust.

The honest framing for all three is that wind assist pays in proportion to two things the owner does not fully control: the ship’s speed and the route’s wind. A slower ship spends more hours exposed to a given wind, so the cumulative push is larger; a route with steady beam-to-quartering winds (the trades, the Southern Ocean, the North Atlantic) feeds the device, while a route dominated by headwinds or calms starves it. The ITTC’s Wind-Powered and Wind-Assisted Ships work is building the performance-prediction procedures that turn a wind rose and a route into an expected annual saving, which is the number that matters for an investment case rather than the best-voyage figure.

Waste-heat recovery

A marine diesel engine throws away more energy than it turns into shaft power. Roughly half the fuel’s energy leaves as heat in the exhaust gas and the cooling water, and waste-heat recovery (WHR) reclaims part of it. The standard arrangement puts an exhaust-gas economizer in the funnel uptake to raise steam, drives a turbo-generator with that steam and sometimes with a power turbine on the exhaust bypass, and feeds the recovered electricity back into the ship’s grid, displacing the auxiliary diesel generators. The IMO GreenVoyage2050 portal gives 2 to 6 percent of total fuel consumption for waste-heat recovery, and the waste-heat recovery credit calculator sizes the electrical credit against the auxiliary load it offsets.

WHR favors large ships running steadily at high engine load, because the exhaust mass flow and temperature that drive the recovery are highest there. A large container ship on a long ocean leg at 70 percent load is the textbook case; a small ship on short hops with frequent load changes recovers little, because the boiler and turbine never reach steady output. The waste heat recovery system article works the thermodynamics of the steam and power-turbine loops and the part-load penalty that erodes the figure on a ship that does not steam steadily. WHR also competes for the same exhaust heat as an exhaust-gas-fired auxiliary boiler, so the recovered electricity and the recovered steam have to be balanced against the ship’s actual heat and power demand, which the boiler fuel calculator and the shaft-generator credit calculator help frame on the auxiliary side.

Shore power and cold ironing

Cold ironing, or onshore power supply (OPS), lets a ship shut down its auxiliary diesel generators in port and draw electricity from the shore grid instead. The emissions case at the berth is large: studies of container calls report on the order of 21 percent less CO2 and far larger cuts in local pollutants, around 89 percent NOx and 47 percent particulate matter, because the generators are off and the grid carries the load. The CO2 cut depends on how clean the shore grid is; a port on a coal-heavy grid moves less CO2 than one on hydro or wind, even though the local air at the berth clears either way. The cold ironing savings calculator works the auxiliary-load-times-hours-at-berth arithmetic against the grid’s carbon factor.

The reason shore power is regulated at the port rather than left to the voyage economics is that the ship spends most of its life at sea, where OPS is unavailable, so the voyage-average saving is small even though the berth saving is large. The benefit is local air quality in the port city, which is why the California Air Resources Board built it into a mandatory at-berth rule rather than an efficiency incentive. The CARB at-berth regulation article and the CARB at-berth compliance calculator work the specific control fractions and vessel categories that rule covers, and the cold ironing and shore power guide covers the connection standards, voltage and frequency matching, and the high-voltage shore-connection equipment the ship and the berth both need. Shore power is also a building block of the green shipping corridors that pair zero-carbon fuel supply at both ends of a route with shore power in port.

Hull cleaning and coatings

A fouled hull is one of the cheapest efficiency losses to fix and one of the most neglected. Biofouling (slime, weed, and shell growth) roughens the wetted surface and raises frictional resistance, and a hull left to foul through a docking interval can lose several percent of its speed-power performance before the next clean. The IMO GreenVoyage2050 portal gives 1 to 5 percent of total fuel for hull cleaning and the same 1 to 5 percent for a hull-performance coating, and the hull cleaning payback calculator works the fuel saved against the cost and out-of-service time of the clean.

The two measures work together. A high-performance coating (a low-friction foul-release or a self-polishing antifouling) slows the rate at which fouling builds, lengthening the clean interval, while in-water cleaning or grooming removes the growth that does accumulate. The combined target is to hold the hull near its smooth-condition resistance for the whole docking interval rather than letting it drift up between drydocks. The appendage and roughness allowance calculator frames the roughness penalty that a fouled or rough hull adds to the friction line, and the ITTC-57 friction coefficient calculator sets the smooth-hull baseline the penalty is measured against. The IMO’s biofouling management guidelines tie the cleaning question to the invasive-species question, because the same growth that costs fuel also carries non-native organisms between ports.

Weather routing and trim optimization

Two of the highest-return measures cost no steel at all, only software and discipline. Weather routing plans the voyage track and speed against the forecast wind, wave, and current to avoid the heavy weather that adds resistance and to ride favorable currents, trimming both fuel and the risk of weather damage. The saving is route- and season-dependent, larger on long ocean crossings through variable weather and smaller on short fixed-schedule runs, and the weather routing savings calculator frames the fuel difference between a great-circle track and a weather-optimized one.

Trim optimization adjusts the longitudinal distribution of ballast and cargo so the ship floats at the trim that minimizes resistance at the current speed and draft. The optimum trim is not intuitive; it shifts with speed and draft, and a ship trimmed by the stern out of habit can sit several percent off its best point at a given condition. The gain comes from running the ship at the model-tested or CFD-derived optimum for each loading rather than a fixed rule of thumb, and the trim optimization calculator works the trim-versus-resistance relationship for a loading condition. Both measures are pure operational levers: no capital, no drydock, just better decisions each voyage, which is why they are usually the first items on a ship’s energy-efficiency management plan and why they feed the operational CII rating directly.

Battery hybrid and solar

Electrification adds a second energy source alongside the engine. A battery-hybrid system stores electrical energy and discharges it to shave the peaks off the auxiliary load, so the diesel generators run fewer hours and closer to their efficient load band rather than idling lightly or chasing transient peaks. The fuel saving comes from keeping the generators in their sweet spot and switching some off entirely during low-demand periods, and it is largest on ships with spiky load profiles (offshore vessels, ferries, tugs) rather than on a steady-steaming ocean ship. The battery hybrid and peak-shaving calculator sizes the saving against the generator load profile, and the auxiliary engine load calculator and the fuel cell power calculator frame the rest of the auxiliary power picture.

Solar photovoltaic panels on deck are a smaller contributor, limited by the deck area available and the modest power density of marine PV under real conditions. On a ship with large flat deck space (a car carrier, a ferry) solar can offset a slice of the hotel and auxiliary load, but the contribution to total energy is small because the deck area is tiny against the propulsion demand. The solar PV on deck calculator works the panel area, irradiance, and capacity factor into an offset. Battery and solar both pair naturally with shore power and shaft generators in an integrated electrical plant, where the question becomes how to source each kilowatt-hour at the lowest carbon and cost rather than which single device to fit.

Onboard carbon capture

Onboard carbon capture (OCC) is the only end-of-pipe measure in the group: instead of burning less fuel, it captures the CO2 after combustion. The leading approach passes the engine exhaust through an amine-based absorber that strips out CO2, then liquefies and stores the captured stream on board for offload at port. Suppliers target 70 to 80 percent capture from the engine exhaust; Wartsila states its system can cut about 70 percent of CO2, and demonstrated and modeled tank-to-wake reductions on fitted vessels run around 74 to 78 percent. Solvang’s Clipper Eris is capturing on the order of 50 tonnes of CO2 a day in service. The onboard carbon capture article works the absorption chemistry and the energy and space penalties.

OCC is the least mature member of the toolkit, and three hard problems sit behind the capture-rate figure. The plant costs energy to run (the absorber regeneration takes heat and the liquefaction takes power), so part of the captured CO2 is offset by the extra fuel the capture plant burns. The plant takes space and weight that a working cargo ship is short of. And the captured CO2 has to be liquefied, stored in tanks, offloaded to a port reception facility, and then transported to permanent storage, a shore-side chain that barely exists at scale yet. Because it does not reduce fuel burned, OCC does not improve a ship’s energy efficiency or its EEDI; it reduces emitted CO2 on a tank-to-wake basis, which is the basis several regulations count. The SBTi shipping path calculator and the CO2 emissions calculator frame the captured tonnes against a decarbonization trajectory, and the Singapore GreenShip rebate calculator frames one of the incentive schemes that help fund the heavier retrofits.

Comparison of technology families

The table sets the families side by side on the three questions that decide a retrofit: how much it saves, which ships it suits, and whether it fits an existing ship or only a newbuild. The savings figures are typical ranges from the IMO GreenVoyage2050 portal, the EMSA wind-assist study, and the device makers cited; they are not additive across rows, because several measures compete for the same energy loss.

The pattern in the table is the substance of any retrofit plan. The cheapest gains are operational (trim, routing, hull condition) and the medium gains are the ESDs that fit at a normal drydock; the heaviest measures (waste-heat recovery, carbon capture, large batteries) want a newbuild or a major conversion. An owner planning a docking does the operational and ESD work first because the payback is short and the ship is already out of the water, and reserves the heavy measures for a newbuild or a once-in-a-life conversion. The wind-assist case sits in between: a deck retrofit is feasible, but the saving has to clear the capital cost against the specific ship’s speed and route, which is the calculation the wind-assisted propulsion article and the wind calculators work through.

Stacking measures: why the percentages do not add

The single hardest number in any retrofit plan is not the saving of one device; it is the saving of several together. Take a worked case. A slow bulk carrier fits a pre-swirl stator quoted at 4 percent and a propeller boss cap fin quoted at 3 percent. Adding the brochure figures gives 7 percent. The real combined figure is lower, often 5 to 6 percent, because both devices recover energy from the same rotational wake behind the propeller. The stator pre-rotates the inflow so the propeller leaves less swirl, which is exactly the swirl the boss cap fin was counting on to break up. Once the stator has taken its share, the fin works on a smaller loss. The two compete for one pool of energy, so the combined recovery is less than the sum.

The rule that separates stacking from cannibalizing is simple: measures that act on different losses add better than measures that act on the same loss. A hull coating attacks frictional resistance, a pre-swirl device attacks propeller swirl, trim optimization attacks the residuary resistance of the wrong floating attitude, and weather routing attacks the added resistance of waves. Those four touch four different terms in the resistance and propulsion balance, so a package of them stacks close to additively. Two swirl-recovery devices, or air lubrication plus a friction coating that both work the wetted bottom, overlap and have to be discounted. The wake fraction and thrust deduction calculator and the shaft and gearbox losses calculator frame which loss each device is claiming, which is the only honest basis for deciding whether two figures add or fight.

The order of fitting matters too, because each device changes the operating point the next one sees. A propeller re-pitched for a lower service speed shifts the wake the stator works in; air lubrication that lowers resistance lets the engine run at a lower power for the same speed, which moves the point on the engine map where waste-heat recovery and a shaft generator earn their credit. This is why a sea trial or a hull-specific CFD model, not a spreadsheet of added percentages, is the basis a class society and a financier will accept. The Holtrop and Mennen resistance calculator and the Wageningen B-series propeller calculator build the baseline resistance and propulsion model that a stacked package is measured against, and the Hollenbach resistance calculator covers the slower full-form hulls where ESDs pay best.

Cost, payback, and the abatement-cost question

A saving percentage is only half of a retrofit decision. The other half is what the saving costs to buy and how fast the fuel it saves pays the capital back. The operational measures (trim optimization, weather routing, hull cleaning) sit at the cheap end: software and discipline, with paybacks measured in months because there is little or no capital to recover. The ESDs sit in the middle: a duct, a stator, or a boss cap fin is a six-figure item installed at a drydock the ship was going to enter anyway, so the marginal yard time is small and the payback runs a few years of fuel at the device’s quoted percentage. Wind assist, waste-heat recovery, large batteries, and onboard carbon capture sit at the heavy end, where the capital is large, the payback is longer, and the case turns on the fuel price and the carbon price the ship faces.

The carbon price changes the arithmetic sharply. A ship inside the EU Emissions Trading System or paying the FuelEU Maritime penalty values every tonne of CO2 it avoids, not just the fuel, so a measure that looked marginal on fuel alone can clear its payback once the avoided allowances are counted. That is the link between the technologies in this article and the ship-efficiency indices and the carbon-pricing regimes: the same percentage saving is worth more to a ship that pays for its carbon than to one that does not. The honest framing is abatement cost, the cost per tonne of CO2 avoided over the device’s life, which lets an owner rank measures that have very different up-front prices and lifetimes on one scale. The CO2 emissions calculator converts a fuel-saving percentage into the avoided tonnes that an abatement-cost figure divides into, and the SBTi shipping path calculator frames whether a stacked package keeps the ship on a decarbonization trajectory rather than just trimming a single year’s bill.

The space-and-weight penalty is the hidden cost on the heavy measures. A waste-heat recovery plant, a carbon-capture absorber and its liquefied-CO2 storage, and a large battery bank all take volume and deadweight that a cargo ship sells for freight. The opportunity cost of that lost cargo capacity belongs in the payback alongside the capital, and it is the reason the heaviest measures favor newbuilds, where the naval architect designs the space in, over retrofits that have to find it in a hull already full of cargo. The admiralty coefficient power calculator and the auxiliary engine load calculator frame the propulsion and hotel power the heavy plant has to justify against the deadweight it consumes.

How the technologies meet the regulations

These measures exist because the ship has to hit a number. The EEXI sets a one-time design-efficiency line every existing ship above 400 gross tonnage had to meet, and a ship short of the line met it by limiting engine power or by fitting efficiency hardware; an ESD or air lubrication that lifts the attained EEXI can keep the ship’s installed power up while still passing. The CII rates the ship every year on its actual operational carbon intensity, so the operational measures (trim, routing, hull condition, shore power where it counts) feed the rating that determines whether the ship slides from a C to a D over successive years. The EEDI sets the design line for newbuilds, where the heavier measures (waste-heat recovery designed in, an optimized hull and propeller) earn their place. The full regime is the subject of the ship-efficiency indices hub.

The technologies are the supply-side complement to the demand-side levers. Slowing the ship down cuts fuel by the cube of the speed reduction, the single largest operational lever, and the efficiency hardware then cuts the fuel for whatever speed the ship runs. Switching to a lower-carbon fuel cuts the carbon per tonne of fuel, the other half of the problem, covered in the alternative marine fuels hub. A realistic decarbonization path for a given ship stacks all three: slow down where the schedule allows, fit the efficiency measures that pay back, and move to a lower-carbon fuel as the bunkering and the engine allow. The technologies in this article are the part the owner can act on at the next drydock, with the ship that already exists, which is why they carry the near-term load while the fuel transition builds out.

Limitations

The savings ranges in this article are typical figures from the IMO GreenVoyage2050 technology portal, the 2023 EMSA wind-assist study, and the named device makers; they are not guarantees for a specific ship. Every figure depends on the ship’s speed, draft, hull form, and operating profile, and a device that delivers the top of its range on a slow full-form tanker can deliver the bottom on a fine fast ship. The percentages are not additive: two devices that recover the same energy loss (a pre-swirl stator and a boss cap fin, for example) overlap, so a multi-measure package has to be sized by a hull-specific model or a sea trial, not by adding the brochure numbers. None of the linked calculators replaces that ship-specific analysis or the device maker’s own performance guarantee.

The wind-assist figures separate single-voyage records from annual averages on purpose, because the two differ by a large factor and the annual average is the one that matters for an investment case. The capture rates for onboard carbon capture are supplier targets and early demonstration figures; the technology is the least mature in the group, the shore-side CO2 reception and storage chain is not built out at scale, and the energy penalty of running the capture plant reduces the net benefit below the headline capture rate. The regulatory descriptions here are general; the specific EEXI, CII, and EEDI calculations, the at-berth control fractions under the California Air Resources Board rule, and the incentive schemes such as the Singapore GreenShip rebate are set by the controlling instruments and change with revisions, so a real compliance decision uses the current text and the class society’s verification, not this summary.

See also

• Decarbonization and alternative fuels: the parent hub covering fuels, operational measures, and these technologies together.
• Ship-efficiency indices: the EEXI, CII, and EEDI regime the technologies are deployed to meet.
• Alternative marine fuels: the fuel-switching half of the decarbonization problem.
• Energy-saving devices: the wake-field physics behind ducts, stators, and boss cap fins.
• Air lubrication systems: the microbubble friction-reduction method and its net-versus-gross trap.
• Bulbous-bow retrofits: re-profiling the bulb to a ship’s real operating speed.
• Wind-assisted propulsion: Flettner rotors, wing sails, and kites, and the route-and-wind dependence.
• Waste heat recovery system: the steam and power-turbine loops that reclaim exhaust energy.
• Cold ironing and shore power guide: the connection standards and the at-berth emissions case.
• CARB at-berth regulation: the California control fractions that force the shore-power connection.
• Onboard carbon capture: the amine absorption method and its energy, space, and storage penalties.
• Green shipping corridors: the route-level pairing of zero-carbon fuel and shore power.

Related calculators

The cluster’s tool page already surfaces the closest few; the calculators below are grouped by the family they size, so you can go straight to the one that matches the measure.

Hull and propulsion energy-saving devices:

• Mewis duct savings calculator: the duct gain against a hull baseline.
• Pre-swirl stator calculator: the swirl-recovery saving.
• PBCF savings calculator: the hub-vortex recovery from a boss cap fin.
• Bulbous bow retrofit savings calculator: the gain from re-profiling the bulb.
• Air lubrication savings calculator: the net friction saving after compressor load.

Wind-assisted propulsion:

• Flettner rotor thrust calculator: the Magnus-effect thrust from a rotor.
• Flettner rotor drive-power calculator: the electricity the rotor costs to spin.
• Flettner wind-assist savings calculator: the net rotor saving on a route.
• Rigid wing sail thrust calculator: the thrust from a wing sail at the apparent wind.
• Towing kite pulling-force calculator: the tether tension from a parafoil kite.

Waste-heat recovery and shore power:

• Waste-heat recovery credit calculator: the electrical credit against the auxiliary load.
• Cold ironing savings calculator: the at-berth saving against the grid carbon factor.
• CARB at-berth compliance calculator: the at-berth control-fraction compliance.

Operational and hull-condition measures:

• Hull cleaning payback calculator: the fuel saved against the cleaning cost.
• Weather routing savings calculator: the fuel difference between a great-circle and a weather-optimized track.
• Trim optimization calculator: the trim-versus-resistance relationship for a loading.
• Battery hybrid and peak-shaving calculator: the saving against the generator load profile.
• Solar PV on deck calculator: the offset from deck-mounted panels.

Propulsion baseline models:

• Holtrop and Mennen resistance calculator: the baseline resistance a saving is measured against.
• Wageningen B-series propeller calculator: the propulsion model behind any ESD figure.
• Wake fraction and thrust deduction calculator: which propeller loss a device claims.
• Shaft and gearbox losses calculator: the transmission losses in the power chain.
• CO2 emissions calculator: the tonnes of CO2 a fuel saving removes.