Home Cooling

[Zix]

Hello everyone,I have been glued to this board ever since I joined a few weeks ago.

Does anyone have any thoughts on cooling our homes.Most of the power comsumed in our home is the Air conditioning,it is very humid here so a swamp cooler is useless.

Thanks everyone this is a wonderful site.

Zix-----------------

[John II]

HI: That's one of my central focus points. I'm hoping to do it with about 3 kw worth of PV's wired to 120v dc and plan to drive a dc motor belted to a car airconditioner compressor.

I'm not there yet... but those are the plans.

John II

[rotornuts]

I had limited success cooling a greenhouse by running my intake ducts underground. Volume in a green house vs. heat gain was a problem. A house may be easier to cool this way.

Circulation fan only.

Mike

[whatsnext]

John II, Do you know haw many BTUs you can expect to get out of a car compressor? They don't seem to have very large evaporators, in cars, so I'd be curious to know how much output you think you'll get. Just looking at your numbers it looks like you could run a 6-8000btu AC 24-7.

John........

[wooferhound]

Have a look at these three sites

plenty of great ideas . . .

http://mb-soft.com/solar/intake.html

http://www.eere.energy.gov/consumerinfo/heatcool/hc_space_geothermal_types.html

http://www.bagelhole.org/article.php/Housing/337/

[Zix]

The ground loop sounds like a good idea,but a greenhouse just has too much heat to deal with.

I have access to a backhoe so it wouldnt be hard to install unless I hit rock.

I saw the other post about the car air compressor,I'm thinking a ground loop helped by a small unit would do it and help keep the moisture problem down.I'll keep reading tho,I have seen lots of great ideas on here.

Thanks everyone for your input.

Zix--------------

[Zix]

Great links Woof,Thanks..

Zix--------------------

[Zix]

Do ya think extending the tubing would affect the cooling much,,and how much would it take (in watts) to pull the compressor?

Zix----------------------------------

[gonedrovin]

I have been thinking, reading, studying, experimenting for over a year now, and I am convinced that the most efficient form of "solar" airconditioning would be the use of a ground source, or "earth coupled" system, importantly WITHOUT THE HEAT PUMP, and combined with a desiccant wheel to remove the insensible load.

With ground temperatures usually below 18 or 19 C, and a target temperature of 23-24C, there should be enough diferential for a decent heat exchanger, especially if the air has been dehumidified first....

I've had the devil's own trouble finding someone to sell me a desiccant wheel cassette, and in getting specs for plate and frame heat exchangers.

The other info about pipe fields etc is readily available.

If anyone else is interested, I'd be keen to pool my work.

[fishfarm]

I have considered this in the past but have not done anything as yet. I agree the most efficient option is the desiccant wheel dried by solar heat. If you get the air dry enough, it can be cooled by evaporation. I believe the best option is to build your own wheel using bulk silica gel beads. A simple round frame covered with window screen material on which the silica beads are laid could serve. Bulk silica gel beads are not too expensive, a 55 pound drum for $135 is one example. Available here:

http://www.veritemp.com/index.asp?sectionstr=Bulk+Silica+Gel&cat=155549&cartstep=minfo&p
rodid=1068095

[SpirckleM]

I found out by accident a way to keep my house from overheating on hot summer days.  My hood fan over the stove normally exhausts through a pipe in the roof, but when I installed an in-the-hood microwave, the exhaust vent came loose and is now venting right into the attic.  It was too hot to work in the attic at the time so I just left it and discovered that on hot days if I left the vent fan running it forced cooler air from the house into the attic and forced the hot air from the attic out through the attic vents.  Now my house stays a lot cooler with no air conditioning.  I have a small house in WA state so this works for me.  However this is probably not recommended for most people because a vent hood fan is just not powerful enough.

I've found out since that this same principle is used by whole-house fans to cool a house.  Think of the air in the attic at 125+ degrees as a hot blanket covering your living area.  Even if you insulate the attic, the heat is still warming up the wood in the rafters that your ceiling is attached to.  By forcing cool air into your attic your eliminating the hot blanket that your air-conditioning is fighting against.  If you use a forced air scheme you need to make sure you have plenty of outflow ventilation area in your attic to allow that air somewhere to go.

[Zix]

Hi Gonedrovin,

Your already in the"pool" this is a great place for sharing.

I'm not up on the wheel you refer to but i'm listening.

I'm wondering if ground water would help a ground loop(closed).

Zix-------------------------------

[Dave7F]

I would like to add a link to those that "wooferhound" posted on Aug 8th.

I think that this might warrant some further investigation:

http://www.motherearthnews.com/library/1975_September_October/Aces_Trump_In_Energy_Game_

Please post back here if you realize a practical application of an "Annual Cycle Energy System".  It would seem to be a version of a ground tied system with the added storage capability provided by a phase change.

Please talk among yourselves; I'm primarily a "lurker".

-Dave

[Aelric]

Cooling air with earth is a good idea, have seen a few articles on it.  Its called "earth tubes" might try a search on google.  They can be done with either a direct (air blown thru pipes underground) or an indirect (water or antifreeze circulating underground then coming to some kind of heat transfer coil)  on the direct system it was suggested to clean it every so often by pulling a old towel soaked in bleach thru the tube.  Would have to leave a pull rope in it at all times and they just used pvc pipe. These can also be straight down like a well then back up, or laterally like septic tank line style.  Also might try looking up geothermal air conditioning.

On the same subject, it seems even corporate america is looking into this, they have noticed that if they run the return end of the air conditioner that goes to the radiator thing outside (pardon my bad terminology) thru the ground at least a little bit before it enters the outide unit, that they get much better efficiency on the air conditioner.  

Interesting thing is earth really has a pretty low R value, its true potential lies in its thermal mass.  It functions as a giant thermal fly wheel to moderate tempratures, just like a shaded concrete slab will feel cool in the summer, or an exposed piece of masonry or dirt will feel warm even after the sun has gone down and it is cooler air around it.  This is why underground homes are so good, not because of great insulation (which is good too because it can help prevent water condensation on interior walls)  but it is because you have a consistant temprature the house is exposed to on the earth wall sides/top.  One of the big selling points for a Central heat & air system is to have even tempratures everywhere in the house, this is what earthsheltered homes do automatically.  

The same thing would apply to an earth tube air conditioning system, although it would not be quite as efficient.  Anyway thats just my two bits :-)

[ewitte]

This brings up a question.  If your doing this and designed a system to deliver 36,000 BTU of cooler air couldn't you just design it to charge a battery bank.  Hook up one side to a Stirling generator and your good to go.  What I've found is 3412 BTU is equal to 1KW/h.  With only 25 % efficiency a 36,000 BTU system can theoretically deliver over 2.6KW/h at any given time.  Create another set of pipes for cooling and you should never need that much energy.

Eric

[benjamindees]

Yes you could do that.  Stirling engines are still dependent on Carnot efficiency, though, which means the temperature difference must be high to get decent results.

And your figures are off.  

36,000 btu/hr == 10,550 Watts

You were probably thinking about air conditioners or heat pumps, which don't technically convert energy, just move it around.  They are usually at least 200% efficient, far more than a stirling engine could achieve.

[ewitte]

No.  I divided it by 4  "25 % efficiency".  I wasn't planning on getting all that much.  Couldn't you use the same technology they use in the newer low differential units?  The ones that activate by sitting on your hand.

[gonedrovin]

Hmm..Fishfarm..I hear what u say..from my understanding of desiccant wheels, in order to succeed, there needs to be a series of radial "fins" to prevent cross mixing  of process and regeneration air.

[gonedrovin]

Hi Zix..

From my reading...where available, gound water really imroves the efficiency of an earth-coupled system.

I Don't have the benefit of any significant amout of ground water, just several metres of most clay.

[thehairs]

If you live in a dry climate you might try using a swamp cooler on the intake of your ground tube and an attic exhaust to have the natural convection help move the air. If you try this I would really be interested with the results as that is the plan I was going to use when I move to SW Texas in a couple years.

David