Not necessarily. Lets say the lows at the top of the tower are maybe 40 degrees F. They're heating up the base to 180 degrees F during the heat of the day. Whether the thermal gradient ever inverts depends on whether the ambient nighttime temperatures are able to bring that 180 degree thermal mass (concrete? dirt?) down to 40 degrees in the time available before the sun comes back up. You'd have to do the math.

What you say is correct. If there's energy production at night using stored heat then it's pulling out power from the heat reserve and cooling it down. If, say, the system was 10% efficient at producing power directly and put 25% into heat reserves which are 80% efficient at releasing that heat and turing it into power, then yes, the bottom would, excepting rare cases (strange weather?), be warmer than the top.

I don't believe that is the case for two hand-waving reasons. The desert in northern New Mexico (where I lived) gets a thermal inversions. You can see that smoke from morning fires rises, hits the inversion layer, and goes horizontal. I believe this is common in deserts, at least those with mountains. From http://www.srh.noaa.gov/media/abq/LocalStudies/ABQthermalinv... there's an 5.8C difference for shallow (~155m thick) inversions, which occurs throughout the year, and there were "130 inversion cases" in that year. Thus, the "1 degree per 100 meters" rule of thumb only applies during the day. A power system would have to work against the inversion.

Second, power extraction is more efficient with higher differentials. It would, I believe, be better to extract more power during the day (when the difference is high and demand for cooling is also high) than to store it for energy production at night.

The previous comment proposed the "capacity to be much nearer to 100% than the opposite." I just don't see that as being likely.

For working against the inversion, a simple solution would be to implement some venting along the sides and vent at the height of minimum temperature for a maximum differential, assuming that if the inversion was strong enough and the minimum temperature was lower in altitude than the max height of the tower. Yeah, you're gonna lose efficiency, but you'd still be able to generate some power, but I think even with that amount of thermal mass you could still maintain a decent differential I think. Also, southwestern and northeastern Arizona are pretty flat and the southwestern part is much much lower in altitude than Albuquerque.

Also, where from NM are you? I'm from ABQ and Farmington.

But there isn't much power there, and we aren't good at extracting power efficiently from lower temperature differentials. I read that wind power goes as the cube of the wind speed, so you really want to maximize this system to extract power during the day time (when the temperature difference and hence wind speed is most), and not the night. Even if it can support 1/2 the wind speed, that's only 1/8th of the power production.

Yeah, ABQ's in the valley so it's probably more prone to thermal inversions. I get the idea (eg, from http://www.arizonensis.org/news/sonorandesertedition/news03_... "PHOENIX, Az. ... The perfume is most noticeable after dark when temperature inversions trap it close to the ground.") that mountains aren't required, and that it's a common feature of deserts, but I wasn't able to track down numbers.

I was in Santa Fe for 8 years. I come back about once a year for my green chile fix. ;)