New findings from Germany’s Max Planck Institute for Biogeochemistry in regard to the nature of the jet stream that flows around the Earth’s upper atmosphere may put an end to hopes of harvesting its high-speed winds as an endless supply of renewable energy.
According to researchers, the assumption that high wind speeds in the jet stream correspond with high wind power are incorrect.
A study has found the lack of friction at high altitudes and the absence of any strong power source, the actual extractable energy from the jet stream is 200 times less than has been previously reported.
The jet stream is a region of continuous winds that occurs at near-space altitudes of 7-16km. This flow of air is governed by an accelerating force produced by atmospheric pressure and the “Coriolis Effect,” created by the rotation of the Earth. At upper levels of the jet stream, wind speeds can reach as much as 320km per hour.
Some companies and federal organisations – including NASA – believe that by developing the right technology, such as airborne wind turbines that could harness high-speed jet stream winds and funnel power back to Earth, the jet stream will become an unlimited source of renewable energy.
Not so, according to Dr. Axel Kleidon, head of the Max Planck Research Group Biospheric Theory and Modelling. Because the jet stream is so far removed from the influence of the surface and with low air density, the slow down by friction plays a very minor role. Hence, it takes only very little power to accelerate and sustain jet streams.
“It is this low energy generation rate that ultimately limits the potential use of jet streams as a renewable energy resource,” Keidon says.
Not only is the jet stream far weaker than first thought, to actually disrupt the delicate flow by creating drag with massive floating wind turbines could cause profound damage to the Earth’s climate.
The researchers estimate that if 7.5 terrawatts (TW) of energy were extracted from the jet stream using wind turbines, this would alter the driving force between the equator and the poles, depleting the jet stream of energy.
“Such a disruption of jet stream flow would slow down the entire climate system. The atmosphere would generate 40 times less wind energy than what we would gain from the wind turbines,” ex-plains Lee Miller, first author of the study. “This results in drastic changes in temperature and weather.”
