A Hot Air Conditioning idea

[Shadow Catcher]

I have been thinking of off grid AC ideas and have played around with small motor driven AC units using an automotive compressor. Suggested to me is using a heat absorption. Absorption refrigerators are a popular alternative to regular compressor refrigerators where electricity is unreliable, costly, or unavailable, where noise from the compressor, gas engine or generator is objectionable.
This could be done using solar, propane or even a campfire as heat sources. I am just starting to look into the idea and it well may be impractical or too complex to be viable but it will be an interesting exercise. One though was using a multifuel boiler that could also be used for heating.

[GPW]

What about a solar collector (Lens) on the absorption unit heater ... with a small solar panel for the fan... ??? Schmaybe' using old RV reefer guts ? Night would be another story ...

[Fishingtomatoseed]

Shadow Catcher love the idea.

From looking at the in-tro-net looks like there has been companies that have tried it before but no longer build them.....? Could one take an old reefer unit as GPW suggested and go from there. I wish I had the HVAC tools and experience to take such things apart and piddle. Can one buy individual parts say a good DC motor and a good compressor and put together a battery and solar panel friendly unit? Just rambling on....

[Ron Dickey]

Just take your ac out and turn it around and put it back in.

[Shadow Catcher]

The problem will be building one with enough Btu's that is not too big and bulky. Yes a solar heat source would work or could help, the problem is again getting enough Btu's. The components are available and I have just made the acquaintance of some one in the industry.
I am in the information gathering stage and so far all of the industrial systems I have found are far too big and the one residential system I found is sized for the whole house. One interesting article I found http://www.treehugger.com/culture/chall ... ioner.html which has a couple of interesting links including plans to build a simple Ammonia system.
From what I can find the typical RV gas refrigerator out put is about 400 Btu.

[mezmo]

Somewhat related --- heat source.

http://www.gizmag.com/hydroice-solar-po ... ine/25139/

Cheers,
Norm/mezmo

[GPW]

SC , I have an old 20” lens off a ships light ... creates intense heat when focused in the Sun .... sets paper afire immediately , vaporizes ants ... The thought of that focused on a small area should be enough to heat the ammonia (maybe? ) ... Or that with a huge parabolic reflector behind it too focused on the same spot... a Huge set up , not practical for a trailer ... Could be blinding , the light , and one could easily get seriously burned ... not the safest setup , but a small area of really intense heat ...


Just thinking along with the AC considerations , the Insulation is also a major factor ... so much less cooling would be required , as the Foamlings' have discovered...

[Shadow Catcher]

GPW there are solar AC units available now using hot water/antifreeze (polyethylene glycol) and the system pictured used an evacuated tube design. The research I am seeing uses a LiBr-H2O solution (Lithium Bromide).
I would think a solar mirror/lens system could be used but then you have to use solar tracking or use a tube system, not as critical. The difficulty with using solar for heat is in the level of complication...

[GPW]

It does get complicated pretty quick !!!

[Shadow Catcher]

You got that straight. Nothing like asking some one who has a clue, I just wrote the individual I met this weekend who is a consultant and very knowledgeable on all of the AC stuff and we will see what he says. A small engine driven system would probably be the easiest to cobble together, but I really like quiet!

[robfisher]

Many years back I was playing with the working part of a propane refrigerator/freezer. The unit was pretty large, I achieved cold, Too cold in fact. The problem I needed to solve was the unit icing up. Seemed to be just a matter of a heat exchanger. Maybe more air movement or maybe some kind of liquid.

Insulation is one factor but the other thing to remember is the amount of heat 2 people produce. Here's the numbers for one person. Double it.

The human body maintains a basic minimum rate of heat production at about 250 Btu/hr during sleep, the heat equivalent of about 75 watts, and about 400 Btu/hr (120 watts) when awake but sedentary. As bodily activity increases, the rate of oxidation of food, with its attendant release of energy, must increase. The level of heat production for light work will be about 650 Btu/hr (190 watts), the extreme value for heavy work, about 2400 Btu/hr (700 watts).

[Shadow Catcher]

I am making progress and this is the process I am looking at it is a LiBr-H2O (Lithium Bromide water) system no ammonia involved this is the description of an available unit http://www.yazakienergy.com/docs/OP-WFCS-0507.pdf

I am still in the information gathering stage and this is still well above my level of incompetence.
Description of how this works, Note that temps are well with in what can be harvested from a solar collector or from a boiler or water heater or...

Generator
When the heat medium inlet temperature exceeds 154.4oF (203oF max.) the solution pump forces dilute lithium bromide solution into the generator. The solution boils vigorously under a vacuum and droplets of concentrated solution are carried with refrigerant vapor to the primary separator. After separation, refrigerant vapor flows to the condenser and concentrated solution is precooled in the heat exchanger before flowing to the absorber.
Condenser
In the condenser, refrigerant vapor is condensed on the surface of the cooling coil and latent heat, removed by the cooling water, is rejected to a cooling tower. Refrigerant liquid accumulates in the condenser and then passes through an orifice into the evaporator.
Evaporator
In the evaporator, the refrigerant liquid is exposed to a substantially deeper vacuum than in the condenser due to the influence of the absorber. As refrigerant liquid flows over the surface of the evaporator coil it boils and removes heat, equivalent to the latent heat of the refrigerant, from the chilled water circuit. The recirculating chilled water is cooled to 44.6oF and the refrigerant vapor is attracted to the absorber.
Absorber
A deep vacuum in the absorber is maintained by the affinity of the concentrated solution from the generator with the refrigerant vapor formed in the evaporator. The refrigerant vapor is absorbed by concentrated lithium bromide solution flowing across the surface of the absorber coil. Heat of condensation and dilution are removed by the cooling water and rejected through a cooling tower. The resulting dilute solution is preheated in the heat exchanger before returning to the generator where the cycle is repeated.