by Allie Comeau on June 21, 2009 1 comment Wind blows harder and faster at higher altitudes than it does on the ground. So it makes sense that more wind power could be harnessed by using high-altitude machines than with terrestrial windmills.
The very best ground windmills have a wind-power density of less than 1 kilowatt per square meter. But up in the higher altitudes near the jet stream, the wind power density can reach 16 kilowatts per square meter. This means that the potential for high-altitude wind energy is 16 times that of ground windmills. According to this article on CNN, high-altitude wind power machines could meet the global energy demand 100 times over (or at the very least power a big city like New York). The only problem is that high-altitude wind power is subject to the same problem as traditional wind power – intermittency. In other words, the wind isn’t always blowing. And because there’s currently no way of storing wind power, this type of energy alone is not enough to power the world, or a city, 24 hours a day. “The resource is really, really phenomenal,” said Christine Archer of Cal State University-Chico, who co-authored a paper on the work published in the open-access journal Energies. “There is a lot of energy up there, but it’s not as steady as we thought. It’s not going to be the silver bullet that will solve all of our energy problems, but it will have a role.” The idea of high-altitude wind power is not new. Scientists in the 1970’s attempted to harness it with two different high-altitude wind machine designs. One machine is like a kite, the other like a power plant in the sky. According to the article on CNN, several private sector wind power start-ups are working on similar prototypes at this time, though it’s mostly shrouded in secrecy. While working prototypes may not be far off, it will require a lot more than machines to power entire cities with high-altitude wind power. Because even in the windiest of areas, the wind will fail at least 5% of the time. “This means that you either need backup power, massive amounts of energy storage, or a continental- or even global-scale electricity grid to assure power availability,” said co-author Ken Caldeira, an ecologist at Stanford University. “So, while high-altitude wind may ultimately prove to be a major energy source, it requires substantial infrastructure.”