Combining Parallel SuperKites with Winches and Cranks

Combining Parallel SuperKites with Winches and Cranks

A system of four parallel batteries of superkites with four-line control may drive electrical generation gear using winches and clutches for a systems of up to 1 MW or winches and crankshafts for more powerful systems. Large tower-based wind turbines of 200-feet diameter rotate as slow as 10 r/min and the blade tips can exceed 100 ft/s. A system of superkites can pull through winches to drive a crankshaft and electrical generation equipment at 10 r/min or 6 s/r.. The stroke of the wind-driven crank may vary between the stroke of steam railway locomotives (3 ft) and large marine diesel engines (up to 8 ft). Crankshaft roller bearings would be required given the low rotational velocity and tremendous shear forces that would be exerted on the crankshaft.

For extreme stroke, a vertical single-throw crankshaft may be appropriate. Each battery of kites would exert a tensile force on cables attached to large-diameter winches that in turn drive small-diameter winches. The tensile force on four cables spaced at 90° intervals would drive the crank. The equivalent "gear ratio" of 9-to-1 combined with a crank stroke of 7 ft at 6 s/r would mean that each battery of kites would cover the equivalent horizontal distance of 63 ft within 6 s, yielding a kite velocity of 10.5 ft/s. We may assume the high-altitude wind to be blowing at a velocity of at least 66 ft/s.

The wind drag on a stationary kite of 200-feet width by 50-feet height, with air density of 0.065 lb/ft³ , and velocity of 66 ft/s would calculate to 33,820 lbf for drag coefficient (C_d) of 1. A battery of 10 kites would yield 338,200 lbf at C_d=1 or drop to 250,000 lbf for a C_d=0.74. A battery of 10 kites moving at 10.5 ft/s in a wind of 60 mi/h (88 ft/s) would yield a drag force of 350,000 lbf for a C_d= 0.75. The power of each battery of kites moving at 10.5 ft/s would be over 4900 kW or 4.9 MW. A high-altitude wind speed of 90 mi/h (132 ft/s) would yield a drag of 858,000 lbf with C_d=0.75 and a power level of 12.2 MW for each battery of kites moving at 10.5 ft/s during each power cycle. Cables and bearings would have to be designed for side forces or shear loadings that could exceed 10,000,000 lbf.

Kite angles would be reset to reduce drag after each power generation cycle. Other batteries of kites that are amidst the power generation cycle would "pull back" the non-working batteries of kites. Depending on location, the kite cable system along with the crankshaft and its bearings may be designed for power output levels that exceed 30 MW. Some researchers have suggested that high-altitude energy kite installations could attain 50-MW levels of output.

Harry Valentine

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