We all know it is critical for us to curb consumption of fossil fuels, not only because most of this "ancient sunlight" comes from unstable parts of the world (and will eventually run out), but also because it damages the future of the only planet we have.
     We need to substitute, where possible, biofuels, hydrogen or electricity to power our transportation, and we need to get as much electricity as possible from sources other than coal, and especially from renewable energy sources. Large renewable energy sources include hydroelectric, wind, solar, and geothermal. Most potential hydroelectric sources are already developed; of the other three renewables, wind power is (so far) more widely
deployed than the other two, despite their huge potential.
     Denmark, Germany and Spain, for example, produce large portions of their electricity from ground-based wind turbines. Even the United States has built a number of "wind farms", mostly in the Southwest and West. Engineers have evolved standard turbine designs that
call for up to 300 ft. diameter three-bladed propellers driving generators mounted on towers up to 300 feet tall. Groups of these devices are located in high wind areas and can generate enough electricity, enough of the time, to be competitive with coal-fired generating plants at less than 10 cents per kilowatt-hour. But these turbines are expensive to build and controversial with local residents despite that they are, at least to some, quite beautiful. An important weakness is that they don't work when the wind is too light, or when it is too strong. Winds Aloft Are More Reliable Aviators and meteorologists know that "winds aloft" are much stronger than surface winds, as well as much steadier, and are therefore a tempting source of power. Between Latitudes 30 degrees North and 50 degrees North, and above 3000 feet, the wind is several times stronger than on the ground. Ground-based turbines obviously cannot reach these winds, but some entrepreneurs and engineers in the US and Italy are developing ingenious new ways to use this higher altitude wind for power, and the costs appear to be extremely promising. In fact, these new designs may be able to deliver electricity at 1-2 cents per kilowatt-hour, a fraction of ground-based wind turbine costs, and highly competitive with any other source of power. But How to Reach Those Winds Aloft? Inventors have been thinking about this question for years, and have developed various designs for capturing the wind energy available above the ground. One such design looks like a twin rotor helicopter that hovers in auto-rotation on a tether while the rotors run generators aboard and the power runs down a wire incorporated in the tether. This method has been shown to work, but is complex, expensive and conjures up images of helicopters crashing and causing damage.
     People have experimented with kites reeling out from spools which run generators on the ground; the same spool then reels the kite back in at a lower altitude, consuming much less power than was generated during the "outstroke". This approach also works; it requires multiple kites flying at the same time to produce a net positive output, and it is complex to design, build and operate.
Enter a Technology Transfer of a Different Sort A sport called kite-boarding has evolved from hang-gliding and wind-surfing. It allows a sailor on a "short-board" with foot straps to control very accurately a semi-circular, semi-rigid fabric kite above his head that tows him around at high speeds on the surface of the water in reasonable safety. It is much more fun than water skiing, especially since it does not require a powerful speedboat. The key to the sport's growth beyond slightly crazed risk-takers to more ordinary athletes is the development of reliable controls for "powering up", steering and "de-powering" the kite at will.
     These are recent developments and potentially important ones for wind-generated electricity.
     Environmentally-aware kite boarders began to see that their highly developed kites generate a lot of controllable power and might be used for other purposes, such as generating electricity. A group of such people has started a company in Alameda, CA, called Makani Power, which can be visited at www.makanipower.com (makani = "wind" in Hawaiian). They are being stealthy about publicizing their approach, but a little information about them can be gleaned from public sources.
Enter Google…Stage Left Google apparently learned of this company and has funded it to the tune of ten million dollars. Given Google's spectacular profitability, its brand acceptance and its "socially conscious" corporate culture, it is hard to imagine a better investor for Makani to have. Google is very conscious of the energy consumption of its uniquely large server farms; this is widely regarded as the reason for their locating an enormous data storage facility in The Dalles, OR, where hydropower and water-cooling are cheap and plentiful.
     Most intriguing is how Makani plan to convert the power available from kites into meaningful amounts of usable power on the ground. In one variation they intend to build large individual kites fitted with a combination motor/generator. The motor is used for vertical take-off and to gain enough altitude for the wind to take over, whereupon the motor becomes a generator sending power down the tether to the ground. Through the control lines, the kite is made to describe high speed "figure eights" in the sky, greatly accelerating the relative wind over the generator/propeller, and increasing the power generated by the square of the increase in apparent wind speed.
     We looked into another design idea from Italy that makes good sense to us. This involves building a large diameter "carousel-like" horizontal wheel that would rotate slowly in one direction and be connected through gearing to generators. The wheel would be driven by standard semi-rigid fabric kites attached at various points around the periphery of the carousel. Each kite would be automatically powered up on one side of the wheel and de-powered on the other side, using standard control lines connected to a straightforward mechanical control system.
     It would be the same principle as an anemometer, writ large. It would overcome the need to transmit power along what is essentially a kite string that might be over 3000 feet long.
     Preliminary analyses indicate that these designs could generate a great deal of power (ca. 1 to 100 megawatts per installation) in a relatively small space at reasonable cost. In fact, one engineer calculated that the airspace that must be restricted (for safety reasons) near a nuclear power plant, could, if fitted with these sorts of wind generators, produce roughly the same amount of power as the nuclear plant itself would produce!
     Of course, many issues need to be resolved and many unknowns explored before this dream becomes a reality. But it is heartening to learn just how many original ideas are sparked by the increasing attention this subject is getting as appreciation of the gravity of the problem grows.
      - DLA