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Comment by chroem- | Hacker News Reader

Whoever made this assumes that the chimney wall would be a perfect insulator, which absolutely cannot be the case if it's supposed to be a thin cloth or film barrier. The air would cool to the same temperature as the surrounding atmosphere.

This will not work.

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Chimneys do not require perfect insulators otherwise no chimneys would work. The biggest thing they do is prevent air mixing which in turn prevents a lot of energy exchange. This could work.

You realize that other chimneys have an outside energy source and that this essentially amounts to a free energy device, right?

I can scarcely believe that this is an actual level of argument that's occuring on HN.

I am not qualified to evaluate the actual possibility of this device, and there are many points that don't seem plausible to me.

However, the author is not arguing free energy. That would be like arguing wind turbines are "free energy". It's very clearly a solar powered device, with solar energy providing the heat that drives the air movement.

I'm not qualified either but this is an important point, the energy is definitely available and photoelectric semiconductors are merely one way to harness it.

Regarding the practical issues, what happens at night? Does it collapse under its own weight? How do you get it up in the sky in the first place?

The upper troposphere cools as well, resulting in a maintained differential.

This is absolutely not a free energy device. It may be bunk, but it is an attempt at a heat engine. Or rather, an attempt to make an existing heat engine more efficient/ faster/ controlled. There is outside energy and it is already doing work. We want more heat transfer and more controllable weather.

where is the outside energy source? If it's ambient solar light, then it hit (mostly) evenly, so can't possibily be an energy source for this chimney!

More light is absorbed at the bottom than at the top. This energy is already doing work as weather.

If the air under the chimney needs to be warmer than the air beside it,this could be achieved with mirrors or a broad greenhouse.

The author also states in the FAQ that the air in the chimney will not undergo adiabatic cooling. If that were possible it would also not undergo expansion and would remain denser than the surrounding atmosphere.

It only has to be a reasonably good insulator. And anything that can stand up to winds at kilometer altitudes will do fine.

I doubt it has to be a good insulator. The air is travelling up the tube at high speed and there isn't time for it to cool significantly before it emerges.

No, it would have to be a very, very good insulator. You're talking about three miles of tubing exposed to high speed winds and large convective heat losses. Anyone who's taken a course on thermal power systems would know that this is absolutely preposterous.

I'm not saying it's feasible or anything, but he's talking about moving air at over 100 miles per hour. It would only take a couple of minutes to get to the top.

Right, plus it's a 30 metre diameter tube. The bulk of the air moving up the centre would be insulated by the outer layers of air near the inner skin of the tube.

That's not how convection works. It won't be moving quickly in the first place if it cools off. This whole farce of a thread is really tempting me to sink time into calculations to prove that this is absolute bullshit.

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