The mammoth 800-plus meter (2625 ft) tall tower will instantly become one of the world's tallest buildings. Its 200-megawatt power generation capacity will reliably feed the grid with enough power for 150,000 US homes, and once it's built, it can be expected to more or less sit there producing clean, renewable power with virtually no maintenance until it's more than 80 years old. In the video after the jump, EnviroMission CEO Roger Davey explains the solar tower technology, the Arizona project and why he couldn't get it built at home in Australia.

How Solar Towers Work

Enviromission's solar tower is a simple idea taken to gigantic proportions. The sun beats down on a large covered greenhouse area at the bottom, warming the air underneath it. Hot air wants to rise, so there's a central point for it to rush towards and escape; the tower in the middle. And there's a bunch of turbines at the base of the tower that generate electricity from that natural updraft.

It's hard to envisage that sort of system working effectively until you tweak the temperature variables and scale the whole thing up. Put this tower in a hot desert area, where the daytime surface temperature sits at around 40 degrees Celsius (104 F), and add in the greenhouse effect and you've got a temperature under your collector somewhere around 80-90 degrees (176-194 F). Scale your collector greenhouse out to a several hundred-meter radius around the tower, and you're generating a substantial volume of hot air.

Then, raise that tower up so that it's hundreds of meters in the air - because for every hundred metres you go up from the surface, the ambient temperature drops by about 1 degree. The greater the temperature differential, the harder the tower sucks up that hot air at the bottom - and the more energy you can generate through the turbines.

The advantages of this kind of power source are clear:

• Because it works on temperature differential, not absolute temperature, it works in any weather;
• Because the heat of the day warms the ground up so much, it continues working at night;
• Because you want large tracts of hot, dry land for best results, you can build it on more or less useless land in the desert;
• It requires virtually no maintenance - apart from a bit of turbine servicing now and then, the tower "just works" once it's going, and lasts as long as its structure stays standing;
• It uses no 'feed stock' - no coal, no uranium, nothing but air and sunlight;
• It emits absolutely no pollution - the only emission is warm air at the top of the tower. In fact, because you're creating a greenhouse underneath, it actually turns out to be remarkably good for growing vegetation under there.

Source: Gizmag