Ask Hackaday: Saving The World With Wacky Waving Inflatable Arm Flailing Tube Men

This is a solution to global warming. This solution will also produce electricity, produce rain in desertified areas, and transform the Sahara into arable land capable of capturing CO2. How is this possible? It’s simple: all we need to do is build a five-kilometer tall, twenty-meter wide chimney. Hot air, warmed by the Earth’s surface, will enter the base of the chimney and flow through turbines, generating electricity. From there, air will rise through the chimney, gradually cooling and transferring energy from the atmosphere at Earth’s surface to five kilometers altitude. This is the idea behind the Super Chimney, It’s an engineering concept comparable to building a dam across the Strait of Gibraltar, a system of gigantic mirrors in Earth’s orbit, or anything built under an Atoms for Peace project. In short, this is fringe engineering.

This is also, ‘saving the world with wacky waving inflatable arm flailing tube men.’

The idea of building tens of thousands of fabric chimneys, placing them all around the globe, and cooling the Earth while sequestering carbon dioxide is fantastic. Ideas are simple, implementation is something else entirely. There are also obvious problems with the physics presented in the Super Chimney presentation, but these problems don’t actually make a Super Chimney impossible. We need more eyes on this, so we’re opening this one up as an Ask Hackaday. What do you think of this audacious scheme, and is it even possible?

Actually Building the Tube Man

A schematic of the Super Chimney. Credit Click to embiggen.

Before we get to the science of the Super Chimney, attention must be paid to the engineering and construction of this bizarre device.

The Super Chimney would be the tallest man-made structure on the planet. It would be made out of fabric — specifically, the same material used for hot air balloons, sourced from AliBaba. At the base of the structure are several openings lined with air turbines to produce electricity. At the top of the chimney, air is redirected downwards by a ‘mushroom cap’ to provide lift.

This is an exceptional engineering project. A single Super Chimney would require 300,000 square meters of fabric, a tremendous amount of land for the proposed guy wires, and the initial erection of the Super Chimney would mean carrying 112 tons to an altitude of 5 kilometers. Lifting the Super Chimney is actually easy when your tongue is planted firmly in your cheek — it only requires building the largest hot air balloon ever made. A dozen of the largest helicopters ever made or a pair of the largest airships currently flying could lift the Super Chimney.

If this is starting to sound dumb, you’re right. However, we’re only dealing with the crazy and impractical right now, and not the impossible. We’re not even dealing with zoning, land use rights, or FAA clearance at this point. What about the science?

Someone Failed a Physics Exam

Compression and expansion of air inside the Super Chimney. Credit

The key scientific concept of the Super Chimney is adiabatic cooling. That’s a link to a Wikipedia page, the text of which contains a bit of the script for the Super Chimney video. The basic idea of the Super Chimney is as follows: hot air, warmed by the Earth’s surface, is drawn into the chimney. The hot air rises through the chimney. The pressure on the hot air rising through the chimney decreases, allowing it to expand. Since the hot air is contained in a chimney, it has nowhere to expand and simply speeds up when traveling through the chimney. When the hot air gets to the top of the chimney, it’s traveling at 500 km/h. If you put some turbines at the base of the chimney, you’ll be able to generate about 100 Megawatts of power.

However, the video for the Super Chimney uses a slightly incorrect analysis for why the chimney works. The word ‘adiabatic’ is used and gets a few points for that. The Wikipedia explanation of ‘parcels of air’ is still used, though. The correct way of analyzing the Super Chimney is continuously, and the air pressure doesn’t change anyway; atmospheric pressure is, as always, a function of the column of air.

How Do You Analyze This?

And so we come to the Ask Hackaday segment of this post. How, exactly, do you analyze this very interesting physics problem? If I had to throw out a few ideas for this problem, we’re dealing with an increase in air speed throughout the Super Chimney, so Bernoulli’s principle will come into effect. Additionally, what happens when the Super Chimney is sitting in a temperature inversion, or when the atmosphere at the surface is cooler than the atmosphere at altitude?

This is one of the weirder engineering debunkings we’ve ever seen. We know the Batterizer is a terrible idea simply by looking at datasheets. A Solar Roadway is dumb because tires like traction. A five kilometer tall wacky waving inflatable arm flailing tube man is so far outside the usual set of problems that it seems no one has any idea where to start. So what say you, Hackaday? What do you make of this idea? Is there a seed of an idea that could do something amazing — with the realities of execution just needing to be solved? Are there assumptions with fundamental flaws that make this impossible?

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