Air Lubrication For Ships Is Real. The Air Still Isn’t Free.

Air lubrication technology for ships, which reduces hull friction by injecting air beneath the hull, has long been recognised as a method to cut fuel consumption. However, the true challenge lies in the net savings after accounting for the energy required to compress and deliver the air. Everllence and Silverstream have introduced an innovative approach that utilises engine scavenge air—pressurised intake air from the main engine’s breathing system—instead of relying solely on dedicated compressors. This method aims to lower the overall fuel penalty associated with air compression, potentially making the system more efficient and economically viable. The concept hinges on whether tapping into the engine’s scavenge air imposes a smaller fuel consumption penalty than traditional electrically driven compressors across various real-world operating conditions, including different speeds, sea states, and engine loads. Early estimates suggest that Everllence’s engine-supported air lubrication can yield net fuel savings of around 3.5%. While this figure is modest, it is significant enough to impact ships with high fuel costs and increasing carbon regulations, though it is not a standalone solution for maritime decarbonisation. Air lubrication has moved beyond theoretical discussions, with Silverstream already deploying systems on hundreds of vessels, particularly LNG carriers, container ships, and cruise ships. These large vessels benefit most due to their size, hull shape, and operational profiles, which maximise the friction reduction effect. However, the technology is not universally applicable; its effectiveness depends heavily on vessel-specific factors such as hull form, air retention under the hull, and the balance of compression energy costs. Despite its promise, air lubrication should be viewed as part of a broader efficiency strategy rather than a central pillar of shipping’s green transition. Shipowners must weigh it alongside other measures like advanced hull coatings, propeller improvements, slow steaming, and emerging technologies such as wind assist and hybrid propulsion. For short-sea and inland vessels, electrification and shore power offer more substantial decarbonisation benefits by eliminating combustion altogether, whereas air lubrication remains more relevant for large deep-sea vessels reliant on liquid fuels. In the context of deep-sea shipping, where alternative low-carbon fuels are still costly and limited in supply, even modest efficiency gains from air lubrication can reduce the volume of such fuels needed, supporting incremental emissions reductions. While a 3.5% net fuel saving is not transformative on its own, it represents a valuable contribution to the layered approach required for maritime decarbonisation, especially for operators seeking to optimise fuel use and reduce carbon exposure in the near term.