Large Axial Turbine
Windmill-powered vessels built by Jim Bates and Prof. Blackford represent small scale prototypes of future windmill-powered large vessels. The vessel built by Bates used a 3-bladed turbine of 33-feet in diameter and delivered sufficiently low torque to allow gear systems to transfer power from the wind-mill hub to the propeller. As the physical size of axial-flow wind turbines increases, rotational speed decreases, with torque increasing dramatically. In a 30-mile per hour wind, a 120-ft diameter turbine will deliver over 500-Hp at 50-RPM at over 50,000-lb- ft of torque.
When wind speed reached just under 60 miles per hour, power output would rise to over 3,600 Horsepower at 50 RPM and over 185,000-lb-ft of torque. As an alternative to costly and heavy gear trains, a multi-section
large-diameter hollow driveshaft installed an angle could carry power from a large-diameter wind turbine installed above the bow to a propeller located below the stern, where exit ducts could redirect the flow of water. There may be scope to install a pair of wind rotors that rotate in the same direction, at a distance apart from each other on the angled driveshaft.
Combined Wind Technologies
Some designs of wind turbines that directly drive propulsion technology have sailed vessels directly into headwinds and able to deviate up to 20 degrees from headwind direction. As angle between wind and sailing direction approaches 30 degrees, other wind power technologies such as deck-mounted air foil sails including telescopic versions, airborne kite-sails and deck-mounted rotating Flettner rotors become more effective than wind turbines as providing for vessel propulsion. Future wind-powered commercial vessels and passenger cruise vessels would include multiple different wind-power technologies to provide propulsion, including kite-sails for sailing with prevailing trade winds.
Conclusions
Boat builder Jim Bates and physics professor Brad Blackford proved that windmill-driven vessels could sail directly into a headwind. Sailboat enthusiast Peter Worsley has undertaken research into optimal blade angles for axial- flow wind turbines. His work with working scale-model wind- powered boats provides a basis for other enthusiasts and researchers to expand on researching and developing wind-powered technology capable of sailing vessels directly into trade winds, including on trans-oceanic voyages. Worsley’s findings provide a basis to undertake further research into adapting vertical-axis wind turbines to vessel propulsion that includes sailing directly into headwinds, with little directional deviation.
On very large vessels, large-scale vertical-axis wind turbines including typhoon capable versions offer the combined advantages of lower centre of gravity than axial-flow turbines and directly driving a propeller, including an axial-flow propeller combined with ducts to redirect water flow. While axial-flow windmills with gear drive would be suitable for smaller catamaran vessels, large-scale axial-flow turbines operate at low RPM with extreme levels of torque that make gear drive problematic. While a suitable typhoon capable axial-flow propulsion wind turbine is possible, it would need to use an expensive electrical generator and propulsion motor(s).
This article first appeared online on the Maritime Executive’s website and is republished here with our thanks.
THE REPORT | DEC 2023 | ISSUE 106 | 115
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