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Scaling/Rating Exercise WindLode
Scaling – In this example, the WindLode radius is put at 100 feet and a circumference of 628 feet, with the annular framework holding 70 blades suspended at intervals of 9 feet. The blades are scaled 6 feet x 33.3 feet, for 200 sq. ft. of lift surface, each blade. This yields a total of 14,000 sq. ft. of lift surface, this total multiplied by one-half to yield 7000 sq. ft., the figure used in calculating a rating.
Rating WindLode – Assumptions: turbine rotates with negligible friction; 50% of blades used in the calculation; wake effect at downwind side of turbine; biplane effect of little consequence; Coefficient of Lift = 2; turbine speed and the speed of true wind put at 30 mph.
Methodology: This exercise is meant as illustrative. In the calculation of a rating, torque is computed from the aggregate motive lift of one-half of the turbine blades, those blades located within two sectors of the circuit, each sector one-quarter of the whole circuit and altogether comprising one-half of the blades, or 35 blades with 7,000 square feet of aggregate lift surface. The two sectors are opposed, one sector located at the upwind side of the circuit and the other at the downwind side. The rating is calculated for a true wind speed of 30 miles per hour and a rotating blade with a forward speed the same. A wake effect is postulated, and aggregate lift at the downwind sector is reduced by an arbitrary figure. It should be noted that the blades of WindLode do not generate the vortices that are generated at the blades of a Hawt.
Rating: At any given wind speed, the value of motive lift varies from point to point on a blade’s circuit. To derive a rating, an average value of motive lift is computed for the two sectors and thirty-five blades used in this computation, at a 30 mph true wind, with blade forward speed the same. The resultant average is 75 # per sq. ft. of motive lift, using a coefficient of lift of 2. Using a radius of 100 and rpm of 4, and standard constants we have:
7,000 sq. ft. x 75 #/sq. ft x 100 x 4 / (5252 x 1341) = 30 megawatts
The 30 megaWatts is adjusted downward to 25 megaWatts in accounting for the postulated wake effect at the downwind sector.
Note that load recovered as motive torque is not factored into the rating. If load so recovered increases turbine power by, say, 30%, the 25 megaWatt rating computes to about 32 megaWatts. A final rating depends on a determination of the efficiency of the inventive, single-camber blade and the factor used for determining the recovery of load for power. With a coefficient of lift of 2.5, the rating computes to 25% more, to 40 megaWatts.