fred greek

Sounds like an interesting project.  I've visited the aquaponics set up at the local collecge multiple times, which has the plants & fish in the same greenhouse.  It's never smelled bad to me.  

Greetings from Tucson Arizona, where we will hopefully soon have daytime high temperatures under 80...

Is there anyone in my area with experience in constructing the earthbag type of buildings with whom I might meet and perhaps see how it works?  

kathleen, obviously do your own due deligence, check with your doc, etc., but I read that sweet potatoes are not a member of the nightshade family, rather they are in the convolvulaceae family.

We are in Tucson, AZ.  Our primary calorie crops are several varieties of sweet potato.  With them, the leaves and young stems are edible.  

If you are still in the Tucson area and looking for rain collection info, see the folks at Watershed Management Group.

https://watershedmg.org/

Decades ago, we bought isolated acreage outside of Kingman, AZ, put in a well, foundation, other infrastructure.  It was going to be our retirement homestead.   But, on a visit when I was alone, I climbed one of the hills, and near the top felt chest pain.  I took out my cell to call 911. But, I realized that as isolated as we were, by the time an ambulance could get there (miles of dirt road off any paved road) the coyotes would be fighting over my carcass.

I went home, and put the property up for sale.  For retirement, we bought a small home within the City of Tucson.  It is a small house, small lot, but close to all pre-crash services.  We are doing our best to make the property self-reliant, and an urban permaculture site.

Comments re atmospheric condensers, based upon notes I’ve collected over the years.

Basically it is necessary to cool the air to the "Dewpoint".  All of the devices on the web appear to rely on night cooled mass to provide the needed temperature difference, yet leave the device open to daytime heating by the sun.  Granted, I find indications that even in the daytime in certain conditions it might be possible to radiate to the sky 100 to 200 BTU per hour, which strictly in math could represent 1 pint or so of operation for every 10 square foot or radiation area.

But.  

Once the water has condensed the "dry" air, now cool, needs to be exhausted.  This points out the flaw in all of the “air well” devices I have seen. None of them provide for heat exchange directly between the incoming and outgoing air , therefore the "coolness", essential to precipitation, imparted to the incoming air is directly exhausted, and rapidly eroded.

Ideally, there should be sufficient heat exchange between intake and exhaust air that at the pipe open ends, they are virtually at the same temperature, despite being cycled thru a chilled spot.  The transition between liquid and vapor water is, absent unknown science or magic, a matter of the transfer of 970 BTU per each pint condensed.  (7760 BTU per gallon)  

Assume a Tucson fall day with a relative humidity of 7%. There is roughly 7% of 8.8 grams of water in each cubic meter of air (.616 gram).  Lower the temperature to 66 F, and relative humidity doubles to 14%.  Lower the temperature to 48 F, and relative humidity again doubles, now to 28%.  

If we cool air without changing its moisture content, eventually we'll reach a temperature at which the air can no longer hold the moisture it contains. Then water will have to condense out of the air, forming dew or fog. The dewpoint is this critical temperature at which condensation occurs.

But, water does not immediately change state as the temperature reaches the "right" point.  The "Latent heat of condensation" (Lc) refers to the heat that must be removed from water vapor for it to change into a liquid. Lc=2500 Joules per gram (J/g) of water or about 600 calories per gram (cal/g) of water.

Specific heat is defined as the amount of heat energy required to raise 1 g of a substance by 1° Celsius.  If the specific heat of air is .25 calories per gram of air per degree C change, then each degree C change in a cubic meter represents 323 calories.  The specific heat of water is 1 calorie per gram per degree C.  In our Tucson fall day above there was .616 grams of water in a cubic meter of air.  Air and water vapor together take a change of about 324 calories per degree C.  We need to lower the temperature by around 40 C, or get rid of 12,960 calories of heat to reach the dew point.  An additional 379 calories of heat needs to be removed to compensate for the latent heat of condensation, for a total of 13,339 calories.

Presenting numbers for perspective.  Assume a daily water need of 174 gallons (658.6 liters) - 658,660 grams of water.  In a Tucson fall day, each of us would need to "wring" all of the water out of more than a million cubic meters of air  (1,069,252) - a cube 100 meters on a side.  If the cross section of the cooling tube is a meter, and the device operates 24/7, and the device is 100% efficient, the required flow rate is 12 meter per second.  DON’T panic, that’s only about 28 mph.  At that speed though, the air must stay in the chilled zone long enough for the vapor to condense.  

The heat to be moved is about 14 billion calories.  (55.6 million BTU) The water portion of this number is about 450 million calories (1.8 million BTU).  Depending on device efficiency, SOME part of the other 1 billion calories should be able to be conserved in a heat exchanger.

Another approach.

Increasing the pressure also changes the dew point.  Double the pressure and relative humidity doubles.  Assume normal atmospheric pressure of 14 PSI.  Pump the fall Tucson air into a tank at 28 PSI and the relative humidity inside is now 14%.  Make it 56 PSI - 28%.  102 PSI - 56%.  204 PSI - 102%, and you've got water accumulating in the bottom of the tank.  

We’ve been in our present home in Tucson for around a year now.  The modest lot is covered in several inches of small rock, and the “soil” underneath is rock-hard.  I’ve been willing to chip my way thru the “soil” to put in trees, but not yet at least dig to put in a garden.  Trees include six moringa.  I begun looking for perennial plants, with a deep taproot, so digging a hole for them is worth the effort.

Suggestions?

Our “staples” are primarily sweet potatoes in self-watering containers, similar to the commercial “Earthbox” product.  We have six different varieties growing, to see which does the best at our location.  Sweet potatoes have the advantage over potatoes, in that sweet potato leaves and young vines are edible.  Those for a potato are not.  

Are there any permaculture groups in Tucson that actually meet to exchange ideas?

I understand the Native Seeds Search (NSS) folks, on Campbell in Tucson, have a seed swap program where you can get some seeds at no cost, I gather with a promise you will return more seeds later.  I’ve not used their program.

The Pima County library system has a program where you can obtain free seeds.
https://www.library.pima.gov/browse_program/seed-library/

Even if your local branch does not have seeds on hand, you can submit a request to have the seeds you want delivered to you at your local branch.  You do not have to return seeds.  You can get up to ten packages each month.  

During the cooler months, the local Community Food Bank conducts gardening related classes, check their schedule at:
http://www.communityfoodbank.org/Our-Work/Programs/Garden-Workshops/Workshops