Wind powered energy is an essential part of any green energy solution for the United States. However, one problem with using land-based turbines is that movement from the Earth causes friction and turbulence that cuts down on their overall efficiency. To help overcome this limitation, NASA is experimenting with an approach that solves the problem by locating the turbines 2000 feet in the air, where high-velocity winds will keep them suspended like a kite.
Two Types of Airborne Power Systems
The space agency is currently looking at a pair of systems. One relies on a spinning windborne design to rotate the generating turbine. The resulting energy is fed to the grounds by a conducting tether. The other uses a large, commercially designed kite attached to a land-based spool. Electricity is created by a cable that reels in and out continuously as the kite gains and loses altitude.
The concept relies on the fact that 90% of the power generated by turbines is created by the outer edges of the blades because they spin faster than the sections closer to the hub. This allows the spinning kite to act as a single blade tip. It also takes advantage of the fact that winds are much stronger and steadier at 2000 feet than at ground level.
Kept in the Air by Software
Unlike conventional kites, which are usually flown by enthusiastic children on a windy day, the NASA versions will be controlled by pattern recognition software that will keep them continuously moving in a figure-eight pattern. The application that controls it is similar to Microsoft’s Kinect. It alters speed, position, and orientation on a second-by-second basis to keep the device airborne and operating at peak efficiency to produce the most wind powered energy.
NASA’s freedom from corporate ties allows it to experiment with unusual ideas that may not have the immediate payoff expected by private enterprise. Commenting on this, NASA engineer David North said, “we have the luxury of focusing very specifically on problems, and not having to worry about getting a commercial product fielded by a certain date.”
The prototype models used thus far have a 10-foot wingspan, but plans call for commercial models to stretch 200 feet across. The project is based at Langley Research Base in Virginia. Test flights thus far have been done at relatively low altitudes, but NASA is seeking permission to conduct them at a 2000-foot height, considered by engineers to be the “sweet spot” for airborne power generation.
Private Effort Underway in Italy
An Italian firm is in the midst of constructing their own version of a kite-driven generator near Berzano, Italy. Power yields so far are in the 1 GW per hour range, roughly equal to the output of a small nuclear reactor but with much lower operating costs. It is estimated that the facility could stay in operation 80% of the time over the course of a year, at a 90% cost savings benefit over more conventional sources.
Projects Rely on Continuous Bands of Wind
The power that can be harvested from wind increases by the velocity cubed. In simple terms, this means that doubling wind speed results in eight times as much energy that can be generated. This is why airborne power systems have such great potential.
A pair of massive wind bands continuously circle the earth at high altitudes, one in each hemisphere. This is free energy that literally blows right past us every moment of every day. By harnessing just a fraction of it, humanity’s electricity needs could be met by wind powered energy for centuries to come, without a trace of greenhouse gases formed in the process. To take advantage of this resource requires only that we have the vision to do so.