Performance figures used by the shipping industry when buying clean technologies are still often produced in controlled settings, on a single hull, and during favourable operating windows. In air lubrication — a technique that reduces frictional resistance between a ship's hull and the surrounding water by injecting or drawing air to create a cushion of bubbles along the underside of the vessel — standard reference points frequently come from sea trials conducted in light or ballast conditions, when compressors face less hydrostatic pressure and the system can be shown at its strongest. As a result, the relevance of those figures to another ship, at another load level, or on another trade can be much lower than a headline savings number suggests.

Independent findings have reinforced that concern. An insights summary published this year by the Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping, based on input from owners and charterers operating active, compressor-driven systems, reported real-world net savings ranging from zero to six per cent. The results varied according to hull form, draught, speed and sea state. That range differs materially from the figures commonly presented to the market and underlines that a single headline number gives an owner limited insight into how a system will perform on a particular vessel.

The consequence is a procurement environment in which owners may struggle to compare the systems being offered to them with confidence. Some have paused purchases while they wait for the evidence base to become more mature. That slows shipping's decarbonisation pathway — the industry accounts for roughly three per cent of global greenhouse gas emissions and faces International Maritime Organization targets to reach net-zero by or around 2050 — and also affects credible suppliers that have invested in engineering but must compete in a market still focused heavily on headline performance claims. The underlying issue is a credibility gap, which grows whenever a system fails to deliver against a broad promise made on paper.

Shipowners therefore need to change the question they ask, according to Alex Routledge, CEO of Armada Technologies. Rather than asking, "what has this system achieved in someone else's test conditions?", owners should ask, "what do you predict it will do on my ship, in my trades, at the draughts and speeds I actually operate?" Vessel-specific evidence should be the baseline expectation before any capital expenditure is committed, and a system that cannot be modelled at that level of specificity should not be purchased.

The issue has become more important because ship operating patterns have changed. Tightening carbon-intensity regulations — principally the IMO's Carbon Intensity Indicator and Energy Efficiency Existing Ship Index requirements that entered into force in 2023 — together with volatile fuel costs are pushing vessels toward slower and more variable steaming. Ships now spend significant time below the design speeds at which headline figures are typically recorded. A technology that performs within a narrow speed band is therefore very different from one designed to deliver across the full range of speeds and conditions in which a vessel actually operates.

Most compressor-based, cavity-style air lubrication systems are designed around a limited productive window. Below the lower threshold of that window, they are intended to drop out of useful operation, with compressors working only to keep cavities filled rather than to generate net savings. A vessel that operates high-speed legs and slow ballast returns can therefore spend much of its time in conditions where such first-generation systems provide little or no benefit. These trading patterns are also the same conditions toward which regulatory compliance is steering the global fleet.

Armada says it has developed its Passive Air Lubrication System, or PALS, to address that operating profile. The system uses the vessel's own forward motion to draw and distribute air, without a compressor, and is designed to continue producing positive net performance across slower and more variable profiles.

However, developing an improved system is only part of the challenge. Producing credible evidence for a specific ship is an accuracy problem: how will a system behave on a hull on which it has not yet been installed, at the integration proposed by the owner, and within that owner's real operating envelope? That question cannot be answered simply by pointing to what the technology has achieved elsewhere. A large installation base does not necessarily demonstrate depth of understanding, and a high volume of orders on a single vessel type may amount to repeated data from an unrepresentative sample of individual ships.

Addressing the issue requires rigorous experimentation and a modelling programme built around the variables that determine performance. Those include full-scale cavitation tunnel testing on individual pods, model-scale towing tank work across multiple hull forms, full-scale pilot installations and multi-phase CFD analysis, corroborated independently by industry-leading partners. Such a foundation allows a supplier to stand behind its predictions contractually and, ultimately, to discuss performance guarantees with commercial consequences for under-delivery.

In a market where claims have often moved ahead of what can be verified on the specific ship in front of the owner, a willingness to offer that level of accountability is presented as one of the clearest signals that a supplier's modelling can be trusted. Shipping's decarbonisation depends on owners being able to rely on what they are sold. That starts with shipowners demanding the right evidence and remaining unwilling to commit a single pound of CAPEX without it.

Source: By Alex Routledge, CEO, Armada Technologies.