The Intertropical Convergence Zone Upper Wind Resource
- Here is good news for Nigerian & equatorial AWE generally-
The Intertropical Convergence Zone (ITCZ) is a rainy band of high convectivity at the convergence of Northern & Southern Hadley Cell circulation. While this prevailing Easterly wind is slower overall than upper-latitude Westerlies, there is nevertheless a rough power equivalence or even greater power lurking overhead. One hidden world-class energy source is the latent-heat-of-condensation stored in Tropical humidity. Every storm cell has a powerful upward jet at its core powered by this heat. This vertical power is missing in horizontal flow measured wind maps. Another reason for high power overall is that the Equatorial Tropopause is roughly twice as high as the Upper-Latitude Tropopause, with a double volume of wind flowing overhead. Global wind maps topping out around 10,000m simply omit much of the highest altitude wind along the Equator.
The ITCZ slowly wanders a few degrees north & south with the solar year, but it runs far straighter & thicker than the Jet Stream. A multi-storm field is a patchwork of ascending & descending air; in the case of the ITCZ ascending air predominates, feeding the vast upper return flows of the Hadley Cells. Its really a quite different wind, a river in the sky made of storms, not clear-air, & the specialized AWECS required to effectively tap it might be a many kilometers broad horizontal kite-mesh racked by transverse waves from meso-scale turbulence. Smaller systems able to navigate the complex wind aloft can find nice local concentrations of energy in the convective tails. Southern countries with uncongested airspace have a big advantage for AWECSs that take huge amounts of sirspace or hunt widely for upper wind.
The surface trade winds feeding into the towering ITCZ from both sides are of course superb kite winds, the easiest global pickings of all. W still see the attraction of chasing cross-country to stay in optimal wind or having a quiver of kites to adapt optimally to the changing conditions at a fixed location, but in the Tropics, less chasing or quiver is demanded. As with the Jet Streams, some major mountain ranges & large deserts squeeze the ITCZ around them, with an accelerating effect. Bad places to harvest wind are directly in front of or within these planetary-scale obstacles. Flying kites moderately higher in lower latitudes is all it takes to match stronger winds at higher latitudes or "ideal" wind sites. Wind towers do not grow so easy as just adding kiteline. ITCZ surface-windpower limitations will not be critical, it will only be necessary to tow leading kites up past surface calm to trigger a large cascaded launch.