Understanding Wind Energy From Kites
At any moment the winds in extreme high-altitude jet streams can hold about 100 times more energy than all of the electricity being consumed on earth, with wind speeds about ten times faster than on the ground.i The kites that would be needed to capture this energy would so high that passing airplanes would be required to steer around them. The process works in two phases following the “reverse Yo-Yo” concept. The first phase is known as the retraction phase where the kite is flying cross-wind and pulling on the rope with optimal force and speed. The next phase is known as the recovery phase where the wing returns back to its original starting point.ii The ground station holds the generator which collects the electrical power, and when required, actuates the kite from the energy it collects. The electricity is then transported to an electrical grid which, in an ideal situation, is designed on a national scale. A similar model being produced by KiteGen and is similar to a carousel, where several kites are tethered to a central hub and each kite’s flight pattern is controlled from the ground to capture the most wind. As the kites catch wind and pull on their tethers a pulley system is triggered which converts the motion into electricity. After analyzing wind currents it was determined that the most likely places for implementation would be Tokyo and Seoul because they are affected by the East Asian jet stream while places such as Mexico City and Sao Paulo are too tropical and are rarely affected by jet streams.iii The main issue facing the high altitude kites is the fact that wind is so inconsistent. Even in places such as Tokyo and Seoul where wind currents are fairly consistent they are not stable enough and as a result they leave gaps in the flow of electricity. Using a battery that was large enough to fill in the gap, or running a backup generator would be expensive and improbable. If this minor hurdle is overcome then many manufacturers predict that the cost of high-altitude wind power will range from 2 to 4 cents per kilowatt-hour.
Alternative Energy: Kite Energy
As we continue on from last week’s solar energy blog, we are looking into another recent improvement in alternative energy. While turbines have been capturing wind energy for years, engineers recently began sending kite systems to high altitudes, above 200 meters, and letting the naturally occurring high altitude wind move the kite and in turn create energy. In general wind gets stronger and more persistent with increasing altitude, and because of this tower height in conventional wind turbines, it greatly affects their power output. However, the largest turbines are structurally limited from reaching heights of 200 meters and especially for deep water and offshore turbines the additional cost of foundations is a large deterrent.
The long term application for all alternative energy sources is to replace the dependence on fossil fuels and move toward a sustainable and environmentally friendly society. With current wind turbines achieving a fraction of what could be achieved in high altitude power generation, it is not out of the question to assume that soon turbines will not be seen on long drives in the country side, but will be replaced with farms of giant strings reaching into the sky. One researcher believes that if the technology for these kites advance far enough a single kite could be used to generate energy for a small city with little to no impact on the environment. When oil is no longer abundant or necessary it will be the other energy sources that are called upon to produce the energy that we need, and if wind power continues to improve as it does, then soon we may have little to worry about.
i Shepard, Ben PhysOrg “Kites Flying in High-Altitude Winds Could Provide Clean Electricity” Jun 24, 2010
ii EnerKite “Airborne Wind Energy” 2010
iii Dr. Roland Schmehl Wind Systems “Kiting for Wind Power” July 2012