Ground temperature data.

To check the ground temp for the previously mentioned cooling system I rigged up a simple temperature probe consisting of a meter length of garden hose taped to a stick (to keep it straight) and plugged at the bottom end. I buried this to a depth of about 90 cm (3 feet, as far as my arm can reach into the ground), put in a small amount of water for conductivity, and lowered in a glass thermometer on a thread. I then plugged the open end of the hose to prevent air exchange.
Every so often I pull out the thermometer and record the ground and air temperatures.
The ground is dry sand on a 45 degree incline, shaded throughout the day. Initially I measured a spot beside the house which got direct sun most of the day, and it was about 7 C hotter


Results:

	Ground (C)	Air (C)
January 14th
14.24	22	21.5
22.30	22	22
Jan 15th
10.10	21	26
12.00	21.5	26
14.00	21.5	25
17.15	21.5	24
Jan 16th
8.30	21	25
13.30	21.5	35.5
15.15	21.5	30
16.45	21.5
23.00	21	22
Jan 17th
10.45	21	29.5
Jan 24th
09.00	21.5	18

This shows that even an air temp of 35.5 C (96 F) doesn't affect the ground temperature at that depth at all, making this cooling system potentially quite viable.

Once I get a chance (after the solar device is going) I'll take a crack at piecing this together.


Mild update: overnight temperature went down to 13 at about 3.30 am, but ground temp measured at 9.15 am hadn't budged 0ff 21.5. At this point I'm going to call this conclusive.

Nother update; ground temp is up to a steady 23, so guess there's seasonal variation. February is generally the hottest month round here.

Update the third; I suspect the increase may be due to the sun shifting on to it as it gets lower in the sky. Also have had an air temp of 38 C, ground temp unaffected.

Update IV; had a cloudy day, and the temperature was still 23, so if that's due to increased direct sunlight, it's at least a couple days averaged. In other news the ground temp has now gone up to 24, the maximum air temp has been 39.5, and the probe has been removed to make way for the cooling tank as I actually make this thing.
A 1.5 meter deep hole involves more digging that you'd think...