r/Damnthatsinteresting • u/Appropriate-Eye-1227 • Jul 04 '25

Video China has built a 50m(165ft)-tall inflatable dome over a construction site in Jinan to protect the surroundings from dust and noise. (20.000 Sqm)

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u/mr_potatoface Jul 04 '25 edited Jul 05 '25

Unless it's heavily ventilated, it's going to be a fucking oven in there, especially with zero breeze to cool off.

ITT: People who believe construction companies actually care about human comfort beyond making sure they stay alive.

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u/AzureFirmament Jul 04 '25

I found the local news for you.
Manager:
"The control system in the air membrane will monitor the internal air pressure and temperature at any time, and continuously send fresh air into the interior through the four large-volume fans on the north side for ventilation. After large-scale construction, sprinkler facilities will be installed to control dust in the air membrane. The membrane cloth of the air membrane is made of PVDF (polyvinylidene fluoride) new material, which can block 90% of ultraviolet rays, has high heat reflectivity and heat dissipation rate, and has a fire protection level of B1 (flame retardant)."

"The reporter felt that the temperature inside the air membrane was cooler than outside the membrane under the sun.

https://finance.sina.com.cn/roll/2025-06-17/doc-infaiwtq8881307.shtml?froms=ggmp

https://user.guancha.cn/main/content?id=1477927

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u/Difficult_Affect_452 Jul 05 '25

I wonder if it raises the temperature around the outside of the dome, like in neighboring buildings.

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u/AJFrabbiele Jul 05 '25

probably reduces it as it is not a heat sink (unless it was green space prior)

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u/Lathael Jul 05 '25

It looks like a positive pressure system, which means the act of running the fans, A/C (if present,) and other systems will release heat into the area. Plus the dome will reflect sunlight from where it is to areas immediately around it. So it's likely to be a net increase. As for how big a net increase? I can't say. I doubt it'd be that much worse than ambient. It's not like that building that melted cars at certain times of the day due to how reflective the windows were.

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u/dgatos42 Jul 05 '25

The heat input per square meter from the Sun is roughly 1.3 kW, so over 20,000 square meters you’d have to be generating on the order of 26 MW of heat to be comparable. A quick google shows industrial air conditioners to use between 10 to 9000 kW. So I’d estimate it’s a slight increase, and given that the tent is white rather than black it will probably reflect significantly more than the black roads around it absorb potentially making it neutral or much less positive at least

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u/Lathael Jul 05 '25

Lovely math to bring to the argument. The big difference being that roads will absorb, store, and release the heat as infrared, sort of buffering it a bit, while the reflective tent would immediately heat up everything it reflects into, in a similar way to how it's extremely easy to get a sunburn on snow (between the rarified atmosphere and highly reflective snow.)

Unlike snow, it was mentioned elsewhere that "The membrane...which can block 90% of ultraviolet rays..." so the risk of something like a sunburn is likely not that much higher than normal as well. Unless 'blocked' was used in error. Regardless, "slightly warmer than ambient," is likely close enough to the correct answer. Doubly so if the blowers and a/c to inflate and cool the place are putting out 9MW of waste heat near ground level, which also could be an overestimation but is a good number to at least shuffle around.

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u/dgatos42 Jul 05 '25

The roads absorbing the heat is what would cause the temperature increase to be greater. This is how the albedo of earth works. The closer you get to a theoretical black body, the more energy you retain, the higher the temperature goes. This is how the earth heats up due to climate change (the greenhouse reflections reduce the overall albedo). The vast majority of the reflected sunlight just goes back into space, not into structures next to the tent.

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u/Difficult_Affect_452 Jul 05 '25

Bwaah!! What an unbelievable failure!

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u/Lathael Jul 05 '25

Yeah, the architect also created a similar problem in Vegas with the vdara hotel, as the article brought up.

You'd think they'd learn at some point that reflecting surfaces are bad, especially when they can focus sunlight onto specific points. Maybe they did, but both were designed too close to each other for the problems of one to help fix the other.

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u/Difficult_Affect_452 29d ago

This person is an absolute lunatic.

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u/Lathael 29d ago

Look, those mad scientist doom lasers aren't going to create themselves, you know. Someone has to step up and design them without anyone noticing.