RINA review strengthens the investment case for air lubrication retrofits

Silverstream Technologies has obtained a third-party assessment from RINA covering the method it uses to measure the real-world fuel and energy impact of its air lubrication system. The class society examined how the company isolates savings, adjusts for vessel speed and operating conditions, and reports outcomes in a consistent way, concluding that the methodology is fit for evaluating in-service results. The development builds on an earlier RINA Approval in Principle linked to EEDI-related calculations and testing. Silverstream says it has now delivered 164 installations, with 19 RINA-classed ships already operating with the system and a larger pipeline taking that number to 37 when contracted newbuildings are counted.

For shipowners, the practical value of this development is not simply technical validation; it is the reduction of uncertainty around a retrofit business case. Air lubrication has long sat in the category of technologies that can look compelling in model tests and voyage narratives, but become harder to underwrite once a finance team asks how savings will be proven across variable draft, weather, route structure and speed. A class-reviewed methodology does not guarantee any specific percentage reduction in fuel burn, but it gives owners, chartering teams, lenders and technical managers a common language for discussing what is being measured and how baseline disputes are handled. That matters in contract negotiations, performance guarantees and post-installation claims management. In an environment where decarbonisation capex is increasingly screened through internal hurdle rates rather than ESG messaging, measurement credibility directly affects board-level approvals.

The timing is also significant. Owners are under mounting pressure from CII trajectory management, EU ETS exposure and FuelEU Maritime compliance costs, particularly in trades where fuel intensity and schedule reliability are difficult to balance. A technology that lowers net fuel consumption can create multiple value streams: lower bunkers, lower carbon cost pass-through, improved CII headroom, and in some cases more operational flexibility to maintain speed without the same emissions penalty. For RoRo, RoPax, cruise and PCTC operators in particular, where service speed and timetable integrity often matter more than on tramp trades, hull-efficiency technologies are attractive because they preserve commercial capability better than pure slow steaming. If a savings methodology is accepted as robust by a recognized class society, owners are better placed to model the annual compliance benefit rather than treating it as speculative upside.

There is also a yard and off-hire angle. Retrofit decisions today are constrained not just by economics but by access to installation slots, drydock timing and the opportunity cost of vessel downtime. Owners are comparing air lubrication against alternative efficiency investments such as propeller upgrades, hull coatings, wake equalizing devices, shaft generators and voyage-optimization software. In that ranking exercise, technologies that can demonstrate transparent post-installation verification gain an advantage, especially when management must prioritize a limited number of dockings over the next two to three years. For classed fleets, a methodology reviewed by class may also simplify internal governance because technical, commercial and compliance teams can align around a recognized framework rather than bespoke vendor assumptions.

RINA’s involvement is therefore best read as part of the market’s gradual move from “promising retrofit” to “auditable efficiency asset.” That shift is important as owners seek to turn decarbonisation spending into something closer to measurable operating leverage. The headline installation count is relevant here too: scale alone does not prove performance, but a larger installed base improves the industry’s ability to benchmark outcomes by segment and operating profile. If owners can compare verified in-service data across sister vessels or peer fleets, retrofit decisions become less dependent on marketing claims and more grounded in fleet economics.

That said, the industry should not overinterpret a methodology review as blanket proof of commercial returns. The central question for owners remains vessel-specific net benefit after accounting for installation cost, power demand, maintenance burden, air system reliability, hull condition, trading pattern and time spent in operating windows where the technology is most effective. A sound methodology can improve the quality of measurement, but it does not eliminate performance variability between a high-utilization PCTC on relatively steady service and a ship exposed to irregular speed profiles, frequent draft changes or adverse sea states.

There is also a broader comparability issue. Independent review by one class society is valuable, but buyers would still benefit from greater industry standardization in how efficiency technologies report baselines, exclusions and confidence intervals. Without that, owners may still struggle to compare competing retrofit options on a like-for-like basis. The market will likely want to see more published long-run operational evidence, including persistence of savings over time, maintenance implications and realized payback under current carbon-cost regimes rather than theoretical fuel-price scenarios.

RINA’s assessment does not settle the air lubrication debate, but it does make the conversation more investable. For owners weighing compliance costs against scarce retrofit capital, credible measurement may prove almost as important as the underlying efficiency gain itself; that is exactly the kind of distinction serious fleet strategy analysis should focus on.