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Solar chimney thoughts

Pearl Sutton

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posted 6 months ago

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Question: if I took a tube, let’s say 6 inches diameter by 10 feet long, stood it on end so it would stay up but had a way to get good airflow off the ground:
Would it move air up like a solar chimney even if it wasn’t in sun?
How about in the middle of a chilly night?
What if it was 20 feet long?
How about at a 45 degree angle?

What is the lowest requirements for making air flow up a tube?

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C. Letellier

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posted 6 months ago

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How much air flow? Heat differential is the only requirement. Simple black pipe in full sun will do a little although not much(as in you can barely feel the air flow if you are lucky. Is round a requirement? A rectangle with more surface area to the sun will do more, because of more heat Assuming round it a requirement can you add a bigger reflector behind it to give more heat or can you give it a clear front to provide air isolation so it gets hotter?

Linking to my collector write up simply because it might give you a feel for what you might expect. The early testing included some convection numbers.

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R Scott

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posted 6 months ago

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What is the goal or application?

I am a fan of passive non-electric solutions, but the price of pipe and materials is so high these days that solar electric solutions are often cheaper.

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Pearl Sutton

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posted 2 hours ago

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Apologies for not answering, I lost track of this thread.

The idea is circulation of air, from lower to higher, without it needing to be heated by the sun. I'm thinking the cooler air is lower, higher is generally warmer, is that enough to move the air from here to there?

So in the winter, or in the shade, is the air inclined to go that way? It doesn't have to be heavy flow, just circulation flow.

I might be able to test this, I have some guttering downspouts, could put little wind spinners by them to see if the air moves.

I don't recall what exactly prompted this question, I'll try to remember what I wanted it for :D

M Ljin

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posted 43 minutes ago

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Pearl Sutton wrote:Apologies for not answering, I lost track of this thread.

The idea is circulation of air, from lower to higher, without it needing to be heated by the sun. I'm thinking the cooler air is lower, higher is generally warmer, is that enough to move the air from here to there?

So in the winter, or in the shade, is the air inclined to go that way? It doesn't have to be heavy flow, just circulation flow.

I might be able to test this, I have some guttering downspouts, could put little wind spinners by them to see if the air moves.

I don't recall what exactly prompted this question, I'll try to remember what I wanted it for :D

The cooler air is denser and should settle towards the bottom anyway. So too with the hot air, it is lighter and gravitates upwards. So that is just a static stratification of air and not circulation.

If the air inside is cooler than the surrounding air, it should move downward. The reverse if it’s warmer.

If you wanted to move air upwards during the winter, why not bury a length of pipe in the earth? It should be warmed by the earth and then gradually drift upward? I am thinking of an inlet close to the ground and an outlet up high. I am not sure it would even be noticeable though. Or it could even be something wider and more well-like.

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