For the past decade, wind has been the fastest growing energy technology worldwide, with an annual growth rate of over 30 percent. By the end of 2012, wind turbines supplied 282.5 GW of electricity worldwide and wind energy comprised 3.5 percent of US energy generation. However, technical and cultural barriers have thus far prevented wind power from contributing more substantially to world energy needs. Most significantly, winds are intermittent, and other sources of baseload power are needed when wind speeds are too low or too high for turbines to generate electricity.
A new generation of wind technologies may provide a solution. High-altitude wind power takes advantage of the fact that winds become more powerful and more dependable with increasing height above Earth’s surface. Although conventional wind turbines have been built up to 530 feet tall, their height is ultimately limited by the need for increasingly massive and expensive steel and concrete towers.
Next-generation “airborne” wind technologies circumvent this problem by combining a flying component that harnesses wind energy with a tether that holds the aircraft in place and transmits the energy to the ground. A range of prototypes are being tested, including kites, airfoils, blimp-like balloons, and planes. For the near-term, many of these technologies are aimed at reaching an altitude of 1,600 feet, where wind intensities plateau and remain constant up to an altitude of about 6,600 feet. For some researchers, a long-term goal is to devise airborne wind technologies to tap into the powerful jet stream at 30,000 feet.
Over 20 research groups at private companies and government labs are working on airborne wind technologies, with funding from sources that include NASA, the Advanced Research Projects Agency-Energy (ARPA-E), and Google. This May, the start-up company Makani Power completed the first-ever fully autonomous flight of a kite power system – a 30 kW system with a 26-foot wingspan. Future prototypes with 92-foot and 213-foot wingspans will have generation capacities of 600 kW and 5 MW respectively. The company aims to eventually produce power at a cost of 6 cents per kWh at offshore installations.
In addition to tapping into more powerful and dependable winds, airborne technologies are expected to have the benefits of a smaller footprint and a lesser visual impact on the skyline as compared with conventional wind turbines. However, both technical and policy challenges remain. In addition to perfecting the design of wind harnessing devices, researchers must work within the federal regulatory framework to prevent interference of their technologies with other aircraft, and the Federal Aviation Administration is currently developing policies specific to airborne wind energy.
Scientific analyses confirm the availability of a virtually unlimited supply of high-altitude wind energy. In a study published in Nature Climate Change this February, researchers from Lawrence Livermore National Laboratory and the Carnegie Institution for Science report that high altitude winds could theoretically supply over 1,800 TW of power – 100 times more than the present global power demand of 18 TW. The authors further note that 18 TW of wind power extraction evenly distributed across the globe would be unlikely to substantially affect earth’s climate. By tapping into this reliable and abundant energy source, airborne wind technologies could become a major player in Earth’s energy future.
Brittany Huhmann, AGI Policy Intern