Yup, PV=nRT, ideal gas law. If you increase the pressure of air and hold the volume constant, then the temperature will go up. When you lower the pressure, the temperature goes back down.
This can help in the situation you are describing because when you increase the temperature of your incoming air it is causing a larger temperature difference between the air and the ground, increasing the amount of heat you can transfer. When the pressure lowers on the other side, you end up with cooler air. But the heat still needs to go somewhere, just increasing and then decreasing the pressure does not make the heat disappear. You also need to put energy in to increase the pressure in the form of some fans that can push a very high static pressure.
Topic: Thoughts On Geo Cooling An Off-Grid Location (Read 212 times)
Its tough as Vegas gets really hot. I have been there when it was 117F.
There are some passive tricks that cool air.
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>>>>>>>>>
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The tunnel above is neutral.
the tunnel below compresses the air then expands it this will cool the air.
But the math needed to design it properly. Is a bit past my pay level.
To say make the tunnel 3 feet shrink it to 2 feet expand it to 3 feet. Could be undersized a lot.
Also How fast do you size it down how long do you keep it at 2 feet and how fast do you flare it back to 3 feet.
But this is a compression effect followed by expansion and it will drop the temps on that air. At no extra cost.
I have done this technique in building a cooler 1 board s9 and it worked but that is on a 300 watt miner. not a 20 foot container.
If you can get good air cool enough the ideas do work, but it is really hot in Vegas at times.
There are some passive tricks that cool air.
_________
>>>>>>>>>
_________
The tunnel above is neutral.
the tunnel below compresses the air then expands it this will cool the air.
But the math needed to design it properly. Is a bit past my pay level.
To say make the tunnel 3 feet shrink it to 2 feet expand it to 3 feet. Could be undersized a lot.
Also How fast do you size it down how long do you keep it at 2 feet and how fast do you flare it back to 3 feet.
But this is a compression effect followed by expansion and it will drop the temps on that air. At no extra cost.
I have done this technique in building a cooler 1 board s9 and it worked but that is on a 300 watt miner. not a 20 foot container.
If you can get good air cool enough the ideas do work, but it is really hot in Vegas at times.
I'd guess that Phil is correct about a flow-through system vs a closed loop, but it does depend on exactly what the temperature rise is through the miner. There is some max input temperature that the miner can operate at, and at whatever that temperature is, the exhaust temperature would need to be higher than ambient for a flow-through system to beat out a closed loop. This would probably only be an issue on the hottest days of the year.
Shading the input is going to make 0 difference especially when you're pulling several thousand CFM though. It may feel cooler in the shade, but the air temperature isn't actually lower. I guess it could make a measurable difference on a windless day if your intake was in the middle of an asphalt parking lot...
Dry soil has a pretty low thermal conductivity which will limit the amount of heat you can extract from your incoming air. So you may need hundreds of feet of pipe per miner to operate on the hottest days of the year.
So let's say the maximum input temperature a miner will work at is 90 deg F at full fan speed of 200cfm. On a 105deg day, it would require 3240btu/hr to take 200cfm of air down to 90 deg, so if the efficiency is similar to a liquid system you'd need 324 feet of pipe per miner. If the temp on the hottest day of the year was 115deg, then you'd need 5400btu/hr or around 540ft of pipe per miner. That might be the case for a 1200W S9. Newer generation miners use more air, so numbers would be larger.
btu/hr = 1.08 * Temperature Drop * CFM
Shading the input is going to make 0 difference especially when you're pulling several thousand CFM though. It may feel cooler in the shade, but the air temperature isn't actually lower. I guess it could make a measurable difference on a windless day if your intake was in the middle of an asphalt parking lot...
Dry soil has a pretty low thermal conductivity which will limit the amount of heat you can extract from your incoming air. So you may need hundreds of feet of pipe per miner to operate on the hottest days of the year.
So let's say the maximum input temperature a miner will work at is 90 deg F at full fan speed of 200cfm. On a 105deg day, it would require 3240btu/hr to take 200cfm of air down to 90 deg, so if the efficiency is similar to a liquid system you'd need 324 feet of pipe per miner. If the temp on the hottest day of the year was 115deg, then you'd need 5400btu/hr or around 540ft of pipe per miner. That might be the case for a 1200W S9. Newer generation miners use more air, so numbers would be larger.
btu/hr = 1.08 * Temperature Drop * CFM
Thanks for the visuals... helps me a LOT.
Question... if the miners were exhausting into a separated "hotbox" or hot zone... and THAT space was being sucked out (basically as you've drawn)... and the "intake" for the miners was the inside air on the "cool" side... assuming the building has some form of insulation, would it not be better to flip your intake inside, so you're shooting the room air into the U vs. the outside air. I'm just wondering if you'd be starting at something slightly cooler than the shaded outside air.
Or maybe the whole building, insulated or not, is a virtual hotbox, so your design makes more sense. Hmm.
We have begun to talk about a 20' shipping container, with a "lean to" of solar panels that go over the container's roof height to provide some building shading.
Question... if the miners were exhausting into a separated "hotbox" or hot zone... and THAT space was being sucked out (basically as you've drawn)... and the "intake" for the miners was the inside air on the "cool" side... assuming the building has some form of insulation, would it not be better to flip your intake inside, so you're shooting the room air into the U vs. the outside air. I'm just wondering if you'd be starting at something slightly cooler than the shaded outside air.
Or maybe the whole building, insulated or not, is a virtual hotbox, so your design makes more sense. Hmm.
We have begun to talk about a 20' shipping container, with a "lean to" of solar panels that go over the container's roof height to provide some building shading.
You do not want a loop system.
If you run air into that u underground it will be cooler air.
just use exhaust fans to pull air.
I shade the entrance to the hole in the ground.
That air enters at non desert temps. at least 10 f cooler then the outside air.
the key is the shading tarp and the hole.
note the circle that covers the air hole into the mine that is a filter
If you run air into that u underground it will be cooler air.
just use exhaust fans to pull air.
I shade the entrance to the hole in the ground.
That air enters at non desert temps. at least 10 f cooler then the outside air.
the key is the shading tarp and the hole.
note the circle that covers the air hole into the mine that is a filter
Some good points here, and worth looking into. My only reluctance to an evaporative cooler would be that we'd need to have some sort of ongoing water source onsite. I'm not sure if that's an option at some of these sites we're looking at. Literal 40-160 acre flat parcels in the desert. I suppose drilling a well at some point could be a "phase two" option during a later build out.
If the intention is to somewhat cool the room, does the cooled-air system need to match the exact CFM of the miner fans? I more or less thought of it as a way to bring the ambient temperature of the room down a few degrees. I'm sure my lack of an engineering degree is shining right about now... but I more or less thought of this as "injecting" some cooler air into the situation, not necessarily providing ALL of the air that's being exchanged in the room? Or is that dumb?
If the intention is to somewhat cool the room, does the cooled-air system need to match the exact CFM of the miner fans? I more or less thought of it as a way to bring the ambient temperature of the room down a few degrees. I'm sure my lack of an engineering degree is shining right about now... but I more or less thought of this as "injecting" some cooler air into the situation, not necessarily providing ALL of the air that's being exchanged in the room? Or is that dumb?
Yeah, I saw articles on systems like you are describing. It's trading off efficiency for simplicity. It's just a lot more efficient to transfer the heat from a liquid to the surroundings than from air, and liquid holds way more heat per unit volume so you don't have to move it as fast. Keep in mind that you'll need to push around 200cfm of air per miner through your pipe, so you'll need very large pipes and an air system that can handle very big static pressures. So for the scale you're talking about, I think the liquid one with a heat exchanger is probably going to end up simpler in the end. But in my opinion, neither will be as inexpensive or as simple as an evaporative cooling system.
But I'd love to see the results of a test. Just set up a single air loop with a single miner, and bury 50 or 100 feet of 6 or 8" pvc.
But I'd love to see the results of a test. Just set up a single air loop with a single miner, and bury 50 or 100 feet of 6 or 8" pvc.
Am I missing something in the part of forcing hot air in the ground (down) and pulling cold air out (up) with small fans?
Wouldn't it be easier to simply force the air from the outside at ground level though this pipe network and in your shack at floor level and let the hot air simply go up and out with a single fan?
Wouldn't it be easier to simply force the air from the outside at ground level though this pipe network and in your shack at floor level and let the hot air simply go up and out with a single fan?
No you're right... I wasn't more clear about that. I'd probably still build a "hot box" for the miners to spout hot air into, and vent that out separately.
So the intake for the geo system would be ambient temp air from the non-hot box part of the room, and then the outflow "geo cooled" air would be directed more closely towards the intake on the miners themselves.
I'm probably not explaining this well, but I definitely wasn't implying running the hot miner air through that.
Don't think geothermal works very well with air directly, they normally use liquid and heat exchangers. And you might need 1000s (maybe 10s of 1000s...) of feet of pipe with liquid buried pretty deep in the desert to support the # of miners you can pack into a 900 sq ft shack.
I'm kind of reluctant to use the term "geo thermal" because it tends to invoke a more involved system like you're saying with exchangers and such. The system I saw on this TV show was simply air in / air out. Maybe this worked better for this person because of where they were located (they definitely were not out in the middle of the desert)... but it seemed like it would provide a solid temperature year-round, cooler for sure, even if not perfect.
Don't think geothermal works very well with air directly, they normally use liquid and heat exchangers. And you might need 1000s (maybe 10s of 1000s...) of feet of pipe with liquid buried pretty deep in the desert to support the # of miners you can pack into a 900 sq ft shack.
I think you'd probably be better off using an evaporative cooling system, they work really well in dry places and can be made DIY pretty cheap.
edit: one estimate of pipe length per BTU I found after a little googling was 10 BTU per ft for dry soil. So for a closed system (with perfect insulation from the outside air), you'd need about 1000 feet per 3KW miner. Probably better to take the 105deg air from outside and pass it through the heat exchanger to bring it down to the temperature required and then just exhaust back outside, but even if it only required half the pipe, that's still a lot of digging for each miner...
I think you'd probably be better off using an evaporative cooling system, they work really well in dry places and can be made DIY pretty cheap.
edit: one estimate of pipe length per BTU I found after a little googling was 10 BTU per ft for dry soil. So for a closed system (with perfect insulation from the outside air), you'd need about 1000 feet per 3KW miner. Probably better to take the 105deg air from outside and pass it through the heat exchanger to bring it down to the temperature required and then just exhaust back outside, but even if it only required half the pipe, that's still a lot of digging for each miner...
Am I missing something in the part of forcing hot air in the ground (down) and pulling cold air out (up) with small fans?
Wouldn't it be easier to simply force the air from the outside at ground level though this pipe network and in your shack at floor level and let the hot air simply go up and out with a single fan?
Wouldn't it be easier to simply force the air from the outside at ground level though this pipe network and in your shack at floor level and let the hot air simply go up and out with a single fan?
...
Does anyone think this is do-able for a 700-900 sq foot mining shack out in the desert?
the square footage is irrelevant. What matters is how many BTU's (watts*3.412142) you are moving. The more BTU's the more thermal mass (the dirt around longer tubes) needed. Does anyone think this is do-able for a 700-900 sq foot mining shack out in the desert?
I'm currently entertaining the idea creating an off-grid solar-powered farm in the desert southwest. In the summer when the outside temp are 105 (F) / 40 (C) I'm wondering if a geo cooling option would work.
I recently saw a TV show where the builder used this to cool an off-grid home that was roughly 2500 sq ft.
From what I gathered, you send some air tubes down 8-12 feet below the ground where theair ground temperature is a consistent 55 degrees or so. You pull warm air in from one part of the property, shoot it down the tubes, where it naturally cools down, and then back up and into the property at roughly 65-70 degrees.
The electricity draw involved is much lower than air conditioning, obviously, because you more or less are running small fans on the intake/outflow ends of the tube system.
Does anyone think this is do-able for a 700-900 sq foot mining shack out in the desert?
I recently saw a TV show where the builder used this to cool an off-grid home that was roughly 2500 sq ft.
From what I gathered, you send some air tubes down 8-12 feet below the ground where the
The electricity draw involved is much lower than air conditioning, obviously, because you more or less are running small fans on the intake/outflow ends of the tube system.
Does anyone think this is do-able for a 700-900 sq foot mining shack out in the desert?
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