Direct generation savings from H Nordic turbines are less sensitive to trade route wind patterns than a first assessment would suggest. The vessel's own forward motion creates a persistent apparent wind that makes the turbine largely independent of ambient conditions. Routes with higher ambient wind do produce higher savings -- but even on routes with modest wind resources, the venturi effect and apparent wind from vessel speed ensure useful generation throughout the passage.
When a vessel is underway, wind speed at the turbine has two components: the ambient wind that the weather forecast measures, and the apparent wind created by the vessel's own forward motion.
A vessel cruising at 10 knots (approximately 5.1 m/s) generates 5 m/s of apparent wind from forward motion alone -- before any ambient wind is added. At 12 knots, this component exceeds 6 m/s. This apparent wind is present continuously for the entire passage, regardless of the trade route's wind climate.
On many commercial routes, the forward motion component is the dominant input to turbine wind speed for a large fraction of operating hours. Ambient wind is additive to this baseline -- it makes a good site better, but its absence does not make a poor site useless.
Above the apparent wind baseline, the venturi effect further amplifies the effective wind speed at turbine positions. At 3 m/s ambient wind -- well below what most people would consider windy conditions -- effective airflow over the deck reaches 9 m/s or more on a typical cargo vessel. Even at 1 m/s ambient wind, the venturi adds meaningfully to the apparent wind from forward motion.
The venturi effect is driven by the vessel's geometry and speed -- not by the ambient wind climate. It is available on every route at every time of year.
Despite the stabilising effect of apparent wind and venturi amplification, trade route wind patterns do affect the final generation figures.
Ambient wind adds to the baseline. A North Sea crossing in winter adds substantially more ambient wind -- consistently above 8 to 10 m/s -- than a passage through the Malacca Strait in calm conditions. This additional ambient wind pushes effective turbine wind speed well above rated output for extended periods, increasing average output for the passage.
Wind direction affects drag reduction. The aerodynamic drag reduction benefit -- the second component of fuel saving -- depends partly on the angle of the wind relative to the vessel's course. Beam and quartering winds produce the strongest vortex disruption at the superstructure edges. Head winds also produce useful drag reduction, as the turbines intercept the airflow at the bow-facing superstructure face.
Routes with predictable, consistent wind allow better modelling. For vessels on fixed regular routes -- ferries, short-sea traders, vessels on defined tramping patterns -- H Nordic can model route-specific performance using actual meteorological data for those passages. This produces a more accurate savings projection than the generic baseline.
Vessels operating on the North Sea, Baltic Sea, and North Atlantic passages benefit from wind climates that regularly exceed 8 to 12 m/s at sea. On these routes, ambient wind pushes turbine generation well into the rated output range for extended periods. The conservative 6,500-hour baseline and moderate average output used in the standard calculation understate actual performance on these routes.
For operators on these routes, the conservative published figures are particularly conservative.
Vessels on consistently low-wind routes -- tropical Pacific, equatorial Atlantic, passages in the lee of landmasses -- see less ambient wind contribution. However, forward motion and the venturi effect maintain generation throughout the passage at levels that are not reached by the ambient wind alone.
On a vessel cruising at 14 knots in genuinely calm conditions, apparent wind from forward motion is approximately 7.2 m/s. With venturi amplification, effective wind speed at turbine positions may reach 12 to 15 m/s -- above rated output for H Nordic turbines -- based on vessel speed alone.
Low-wind routes therefore do not produce zero generation. They produce less than high-wind routes, and the generation comes proportionally more from vessel motion than from ambient wind.
See also: How fuel savings are calculated · Full fuel savings model
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