| So, you don’t like the idea of a long rope pulling a gigantic wind sail? Perhaps another way wind energy conversion could be scaled up is by allowing the wind to pull ship equipped with large propellers through water. Wind has been used for thousands of years to move ships on the seas. Imagine a large ship that can deploy a million square feet of sail. Suppose that the sail drags the ship, which has large propellers beneath the water. The spinning propellers would generate electricity. Perhaps smaller pilot ships in front of the main ship could be used to help control the sail for different wind conditions. The large propellers would act as sea anchors, slowing down the actual surface movement of the ship. The wind might be blowing at 30 MPH but the ship might only be moving at 10 MPH. |
| Perhaps each of these wind-reaping ships would go out to sea, collect energy and store it in some form. When the ship docked in a harbor, the energy would be quickly off-loaded. When the energy had been transferred, the boat would head back out to sea for another energy harvesting period. Perhaps a coastal city would own a fleet of such ships to help supply their electrical energy needs. |
| Using the wind power equation above, a million square foot sail could produce up to 146 million watts of power from a 30MPH wind, if all the energy could be captured. Assuming only 20% of that power were converted to electricity, the ship could generate 30 million watts of electrical power. During a period of 7 windy days, the ship could store 5 billion watt-hours of energy. Assuming the energy could be sold at $0.10 per kilowatt-hour, the ship’s cargo of energy could be worth $500,000 for a week’s worth of wind energy harvesting. If the ship could make 40 such trips per year, it could produce up to 20 million dollars worth of electricity per year. |
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Lighter wind conditions would require the ship to stay out at sea longer, before its cargo hold was full of energy. On the other hand, a period of heavy wind conditions would speed up the process. As an example, a 45-MPH gale would allow the ship to fill its cargo three times faster than a 30-MPH breeze. |
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It is not clear what energy storage method would be used for such a system. Perhaps gigantic flywheels or maybe some new super capacitor technology would work. Wind sail and rope materials that would do the job already exist. A one-inch diameter rope made from “Vectran” material has a tensile strength of 110,000 pounds. Such a rope weighs 34 pounds per 100 feet so even a mile of it would only weigh 1,795 pounds, or about 2% of its tensile strength. |
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The idea is still rough. There are all kinds of things that would have to be worked out. As an example, there may be some concerns about trapping birds in such large sails. Perhaps the sail would be designed with holes in it, allowing birds to fly through. Environmentalists may dislike the idea of large under water propellers. But, I do think these concerns could be minimized. This sailboat energy generator idea does have the advantage of not using up dry land but it does require that the energy be stored in some way. |
