Some Clean Energy Projects Carry Considerable Technical Risk
One of the elements of new technology that investors hate is “technical risk,” the chance that a certain concept, when deployed in the real world, will simply fail to work. I run across things like this all the time and dismiss them without commenting publically. Here’s one that’s noteworthy, if only for its sheer size. As I just told the entrepreneur, “Wow, this is the poster child for technical risk. You want investors to back a project that will cost billions of dollars, and there is no working model, regardless of how small, showing that it will work? My hat is off to you!”
For the downdraft tower, the theory of operation is unclear. It is supposed to work by misting the hot dry air at the top, causing the air to sink at a high enough speed to drive wind turbines at the bottom. Although I could have missed it, I saw no figures for the proposed height of the tower. But up to the height that airplanes operate, temperature DECREASES with height, i.e., it decreases with height up to at least 30,000 feet. Whether there is a height above which temperature INCREASES, I don’t know but if there is such a height, it would have to exceed at least 30,000 feet. Building a tower to that height would seem somewhat impractical for many obvious reasons, both economic and technical. Also, pumping water up to that extreme height would require considerable power.
Unless the proposers can provide considerably more information, the entire idea would seem to be impractical.
I have seen this many years ago. Another advantage they were touting was the fact that the moist air would spread out across the ground around the tower and keep it moist making it good for farming without depending on rain. I don’t know how real that is but this is an old idea.
It would seem to me to make more sense to use a solar up-draft tower surrounded by a large greenhouse over a shallow sea water lake and to boost the evaporation rate by using high surface area cellulose evaporators (water vapour is lighter than air)
That was pretty much my reaction when I ran in to them last year:
http://www.altenergystocks.com/archives/2011/09/a_new_way_to_skin_the_renewable_energy_cat.html