Solar chimney + unpowered swamp cooler

[Eric]

Eric's format does indeed work. However, Google is smart enough to know the site needs either "http://" or "https://" before the site domain. Per Google's own instructions the correct format is:

[search phrase] site:eplaya.burningman.org

See, ya learn something every day. I was taught the long format by an IT guy years ago (mid 2000s), and had never even thought about seeing if it had changed - though I did drop the "www" part years ago. I'll take the saved keystrokes, and that format also makes it much less frightening looking when you're showing it to people.

[EspressoDude]

so, what if the wind blows in such a direction that the swamp cooler is on the leeward, low pressure side of the structure? would this create a lower negative pressure than the solar chimney? thus when it is windy ( hot afternoons ) the chimney would suck in dust. unless the water based evaporative cooler was always on the upwind side...... swiveling yurt with a weather vane, and a weather cock on top ?

[The CO]

Best advice I can offer is this: Make it work in Default world. You have to get this idea to work in any form of the real world before worrying about if it can be done at the burn. Right now you are at a hypothesis stage. Time to build a functional test version and objectively measure input/output. Good luck.

[Token]

so, what if the wind blows in such a direction that the swamp cooler is on the leeward, low pressure side of the structure? would this create a lower negative pressure than the solar chimney? thus when it is windy ( hot afternoons ) the chimney would suck in dust. unless the water based evaporative cooler was always on the upwind side...... swiveling yurt with a weather vane, and a weather cock on top ?

Now you are talking!

Lets throw in airfoils into the design and my personal favorite: The Venturi!

You might be right on the pressure gradient near the base of the hexayurt. It will likely be in the "low pressure" region most of the time, regardless of where the wind comes from. Any time you have a right angle and air flow ... low pressure spot.

[SageV]

It's an interesting idea. I had tried this in a CAD simulation about ten years ago but determined that having enough thermal mass to make it work effectively pretty much obviated it as a practical idea. An alternative that's easier is just a solar powered swamp cooler. There's a few popular designs on eplaya and the interwebs, but you can get about 75% of the cooling efficiency of those designs for about a 25% of the resources (power/water) by tweaking with the evaporative medium and trying different pumps. Many pumps run off DC power, but not all of them are specifically designed for low power applications.

[some seeing eye]

Sparr, are you an experimenter and maker? The http://ae-zone.org/ has an old school mail exploder with archives. They are a good on-playa resource too. Most wild ass ideas they have tried or know what not to try and why.

[GreyCoyote]

This is burningman. Channel the vibe, dude. You want some thermally-induced airflow? Nuke this solar-hippie-tree-hugger bullshit and go big!

Set a 50k BTU propane burner about 1/3rd of the way up the stack. Aim it upwards. Ignite. Throttle it back to where you can balance propane flow to best effect. Insulate it. Instant draft. Far more than you could ever manage going solar along. And it'll look cool at night. Double-extra style points if you put a poofer function on it. And you can smoke a major bomber joint inside your foam dome and all those incriminating smells get combusted on their way out.

[FIGJAM]

Loooooooooong sticks and wienies???

[SageV]

This is burningman. Channel the vibe, dude. You want some thermally-induced airflow? Nuke this solar-hippie-tree-hugger bullshit and go big!

You're giving me flashbacks to the 2008 burn...where they put way too much fuel under the man. Then there was that oil derrick thing.

[Canoe]

... Then there was that oil derrick thing.

Burned/blew more fuel than everybody getting to, being at and then getting home.

[Madgirl]

Loooooooooong sticks and wienies???

And marshmallows!

[GreyCoyote]

... Then there was that oil derrick thing.

Burned/blew more fuel than everybody getting to, being at and then getting home.

You say that like its a BAD thing...

[SageV]

One followup, these folk seem to have done a ton of work beyond what I could as a DIY hobbyist in answering your question plus their research is fairly current:

http://www.journal-ijeee.com/content/pd ... 2-4-45.pdf

For relative measures, a solar chimney pointed directly at the sun during sunup in the Burn Season could potentially absorb about 287 W/m2 in solar radiation, so in theory you could get it to a comfortable temperature if your structure was really tight and the ambient temperature was under 86 F. Their argument is that the thermal mass flow rate has to be within a certain range, and as the temperature goes up that range gets narrower and the flow rate increases and that makes it more difficult to control effectively. Too fast and you lose the benefit of evaporative cooling. They are talking 2-7 air changes per hour (ACH) for temperatures below 86F and since the playa can run much hotter than that, the structure would need to be very tight but not too tight.

So it *is* possible in theory, but I think pragmatically it still would be difficult to get the infrastructure out there to control the thermal mass, and as the paper points out, for it to be practical heavily depends on environmental factors like temperature, wind, and humidity. When I originally looked at this a long time ago, I was thinking a small dome with structural insulation panels suspended between the bars, but I quickly came to the conclusion that wasn't pragmatic just to do passive solar cooling for a small dome.

[sparr]

Their argument is that the thermal mass flow rate has to be within a certain range, and as the temperature goes up that range gets narrower and the flow rate increases and that makes it more difficult to control effectively. Too fast and you lose the benefit of evaporative cooling. They are talking 2-7 air changes per hour (ACH) for temperatures below 86F and since the playa can run much hotter than that, the structure would need to be very tight but not too tight.

It had not occurred to me that it might ever be too fast. I had planned to make an adjustable vent to disable the system at night, maybe that could be used to regulate effectiveness during the day, too?

[Captain Goddammit]

I really do admire your creative thinking and build-your-own mentality.
But I also think you're kinda' reinventing the wheel... If I were you I'd go ahead and build the solar chimney setup. Burning Man isn't all about being practical, a lot of stuff is just for the challenge or sport of it.
But I'd also bring a well-tested and playa-proven FIGJAM battery-powered bucket swamp cooler, so you can have a comfortable dwelling.
I bring spare everything. It's all about having backup, a Plan B.
But good on ya' for experimenting and trying stuff!

[SageV]

Their argument is that the thermal mass flow rate has to be within a certain range, and as the temperature goes up that range gets narrower and the flow rate increases and that makes it more difficult to control effectively. Too fast and you lose the benefit of evaporative cooling. They are talking 2-7 air changes per hour (ACH) for temperatures below 86F and since the playa can run much hotter than that, the structure would need to be very tight but not too tight.

It had not occurred to me that it might ever be too fast. I had planned to make an adjustable vent to disable the system at night, maybe that could be used to regulate effectiveness during the day, too?

There's some handy charts in that paper. I actually calculated the W/m2 for convenience in reading the charts (since everyone else likes Kwh/m2/day).

[desiredlogin]

I was thinking of a passive cooling system like this for this year. I've gone in an uncooled hexayurt the past 2 years and it was fine. The way I've been thinking of it, a passive system might not pump as much air as a powered system, but since I'm comfortable with no system, a passive set up should still be fine. The one thing that has me reconsidering is the point about lowering the air pressure in the yurt (passive) vs raising it (powered), especially in terms of keeping dust out...

[unjonharley]

I was thinking of a passive cooling system like this for this year. I've gone in an uncooled hexayurt the past 2 years and it was fine. The way I've been thinking of it, a passive system might not pump as much air as a powered system, but since I'm comfortable with no system, a passive set up should still be fine. The one thing that has me reconsidering is the point about lowering the air pressure in the yurt (passive) vs raising it (powered), especially in terms of keeping dust out...

A short (say) 1m wont suck. It will remove expanded(warm air) and leave the more dense cool air.. Or a longer pipe for more air movement and add a damper.. Stove pipe is easiest to work with..

[Token]

I really do admire your creative thinking and build-your-own mentality.
But I also think you're kinda' reinventing the wheel... If I were you I'd go ahead and build the solar chimney setup. Burning Man isn't all about being practical, a lot of stuff is just for the challenge or sport of it.
But I'd also bring a well-tested and playa-proven FIGJAM battery-powered bucket swamp cooler, so you can have a comfortable dwelling.
I bring spare everything. It's all about having backup, a Plan B.
But good on ya' for experimenting and trying stuff!

+1

Admiral is wise.

Have a plan B that is proven and reliable.

[Toe]

Has anyone gone ahead and done a proper thermal chimney or reverse stack yet?

[Token]

Has anyone gone ahead and done a proper thermal chimney or reverse stack yet?

If you have a hexayurt, why don’t you be the mad scientist?

Wait for a nice sunny warm/hot day.

Install and flash a proper 4” vent in the apex of the yurt.

Stick 8’ of black single-wall stove pipe on the vent.

Seal the yurt door real good.

Use a Hudson sprayer to wet down the inside base of all the interior walls.

Measure Inside temperature with a cheap logger.

See how simple it can be ... make the whole yurt a giant swamp cooler at the footprint which is never sealed that well to begin with.

Then tinker to improve.

[unjonharley]

The pipe will not draw if the wind is taking the (sun) heat away .. An old Mother Earth magazine suggest : Surround and seal the (stove) pipe with a clear plastic .. The sun heat escapes through the inside of the pipe.. The heat in the pipe go's up, causing a draw from inside the hut/enclosure.. Removing the warm-expanded air .. This would work with a Figjam bucket cooler .. Add a spinning vent cap to stop any blow back (of dust).. Embroidery hoop would give you a good circle pattern for a clear plastic tube ..

[Canoe]

The pipe will not draw if the wind is taking the (sun) heat away .. An old Mother Earth magazine suggest : Surround and seal the (stove) pipe with a clear plastic .. The sun heat escapes through the inside of the pipe.. The heat in the pipe go's up, causing a draw from inside the hut/enclosure.. Removing the warm-expanded air .. This would work with a Figjam bucket cooler .. Add a spinning vent cap to stop any blow back (of dust).. Embroidery hoop would give you a good circle pattern for a clear plastic tube ..

Or clear pipe with black felt hanging inside. Absorbs solar and other heat, heat transfers to air, hot air rises.

But air doesn't naturally flow. Heat or heat differences doesn't make air flow. Pressure differences makes air flow. Hot air expands and becomes less dense than the air around it, so it gets pushed up by the cooler/denser air coming in the bottom of the pipe to displace it. Are you just going to be drawing fresh ambient air (still hot) from outside the structure through the structure to go up the pipe. Chill that ambient air as it drawn into the structure (chilled by whatever means) by the low pressure created by the lower density hot air in the stack, and now it's denser than both the heated stack air and incoming ambient. The heated stack air is getting displaced up, the dense chilled air inside wants to go down (if sealed, that means back out the swamp cooler). So where is the pressure and where's the resulting airflow...

You've got to get heated stack air displaced upwards, a very well sealed structure, with incoming ambient getting chilled then mixing with the air inside the structure but with a tendency to sink to the bottom, and the air inside that warms from absorbing heat through the structure's envelope (and from occupants) rises to the top of the structure and the intake to the stack...
I'd expect key would be to have the air from the swampcooler going into the structure from high up, so the coolest air that pools to the floor doesn't have a place to flow out.

Stacks work great for a solar-heated stack for removing fumes from outhouses.

[Canoe]

I want "to believe", but for something that requires a negative envelope pressure that's on a hot dusty playa... you're going to end up sucking some hot dusty air indoors.

You could do a closed system, where the swamp-cooler air runs through sealed duct loop just below the ceiling (where it will absorb the most heat from the interior air) and then it exhausts out the stack. No where near as efficient. That lets you keep the interior at a floating pressure independent of the stack and swamp-cooler. A lot of work just to avoid what is a very small electrical load. And you lose one of the main benefits of the swampcooler: it provides fresh air, dust-free and at a positive pressure, keeping casual blown hot dusty air out of the structure, while over time replacing any dust/dusty-air that does get in.

[FIGJAM]

With almost a constant breeze, or real wind on the playa, blowing across the top pipe create some suction?

[Jackass]

venturi effect.

[Token]

venturi effect.

Hey now! Didn’t I say that back in July 2015

[Jackass]

It seems you did, I hadn't read back that far...recently.