Too busy just now to do a proper update on this project, but here's some photos of how things are going so far:

Super quick note to let you know that we're about halfway through actually building the first greenhouse out here at the Rainbow Valley community in Golden Bay, New Zealand.
Got a bunch of photos etc which will be going up as I get around to it.

A few photos of the setup:


20 litre oil drum, grabbed from a skip behind a car servicing centre. Hose and fittings bought new, can be a bit pricey, but Western Australia's a bit ridiculous price wise since they got rid of their manufacturing base.













Luckily the windows at my mum's place are pretty badly fitted, so there was a gap big enough to get the hoses through.
Just above is the car port, so the bank is shaded throughout the day. This seems to be important.














The very ghetto air pump housing. Taken from a old vacuum cleaner, stuck in some tupperware. Worked fairly well minus the fact that whatever plastic that is just does not want to adhere to any kind of glue, at all. Hence the tape and string, and it still leaked a bit.
Close enough is good enough.

RESULTS! (of cooling system prototype)

Actually got all this last week, but most of it was being gathered on the day I was flying out of Australia, so was gathered while running round packing, and this is the first chance I've had to get it down properly.

I did two basic experiments.

1.

Filled the 20 litre drum (30 cm tall, deepest point 1.1 m, shallowest 80 cm, in dry sand over sandstone) with hot water. This was in the form of 3 x 7 litres bought to boiling on the stove and poured into the tank through the connector hose. Should've measured the water temp at start and end of filling (took a minute or two to get it through the funnel) but I'm going to assume it was about 90 C. The ground temp was around 24.5 C.

So:

First 7 L volume at 9.40 am, second at 9.57, third at 10.12. Measured tank temp at 10.15 and was 77 C. This is a total of just on 5.75 mega joules.

Full data:

time water temp (C)

10:15	77
10:30	74
10:50	70
11:05	67
11:20	65
11:30	64
11:45	63
12:00	60
12:15	59
12:35	57
12:45	56
13:00	56
13:40	53
14:00	52
14:30	50
15:00	48
15:35	46
16:35	43
17:00	43
17:45	41
18:45	39
20:00	38
21:00	36
23:20	34
00:15	33
08:20	29
11:25	28
13:15	28
14:00	28
16:00	27
17:15	27
18:30	27
23:35	26
08:45	25

Graph!

And 2:

More relevant to the actual cooling system, I plugged the whole thing together and ran it for about 8 hours. The setup was: air being sucked from the top of the house through about 9 meters of 18mm garden hose into the air pump housing, which was a vacuum cleaner pump and motor inside a tupperware container with the attached electronics.

This meant the air was passed over the motor itself, which added a lot of heat to it. Dumb for a proper installation, but good for fully testing the system.

Air flow was about 2 litres / second, in that it took 20 seconds to fill a 40 litre bag.

The air then passed through 3 m hose, bubbled through about 30 cm vertical of water, and exited into the house through another 3 meters hose.

	Air In	Air Out	Air House
11:15	50	24	30
11:30	52	24.5	30
12:05	54	24.5	31
12:40	53.5	24	32
13:25	55.5	24	29
14:40	50	24.5	28
15:20	49	24.5	27
16:20	46	25	26
17:05	48	24.5	26
19:10	45.5	24.5	25

'Air in' being the temp coming out of the hose from the pump, ie just before it enters the tank. Pretty high due to the motor, the general air temp was about 34-36.

Air out is the air coming directly out of the tank.

Air house is the what came out into the house. At about 13:00 I wrapped the whole last length of hose in insulant and moved it out of the sun. I was surprised by how much heat the air picked up through only a couple meters of rubber hose, but there you go.

So I guess the two most striking things are that even with a fairly basic interface between the air and water (vague attempt at a diffuser, not really) the air dropped all it's heat, even at 55 C.

And that even with only 20 litres of water, which was only ever meant as a quick test, the water temp didn't really come up over the ground temp. True that 2 litres of air per second isn't much (I could've turned the motor up a lot more, but didn't want to 'splode it) but at an average of 50 C, the air was twice the temp above 24 that it would probably usually be running, so is therefor the same energy as 37 C at 4 litres per second, which is quick enough to replace 50 cubic metes of air in about 3.5 hours.

Which aint bad, frankly. It aint bad at all...

Thoughts?

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...

I've been thinking about ultra simple cooling systems.

The most available source of coolth seems to be ground temperature, which according to the internet deeper than a meter is about 10-16º year round worldwide, maybe up to 25º if it's real hot outside and you're on wet clay.

So, this idea would be to bury a water drum and pump the air through it. The hot air inlet would enter at the base so that the air bubbles up through the water dumping most of its heat and humidity. Cool air is then drawn out of the airspace at the top of the drum and piped into the building.

The pump can be driven by whatever is available, but a wind turbine would be easy enough and keep the whole system non electrical.

The growing space would have insulated walls and skylights with diffusers to bring the light levels down to about 30% of sunlight, which is optimal for most edible plants. Temperature would be regulated by airflow.

According to some quick, probably wrong, calculations on wolfram it looks like water is about 3000 times the thermal sink of air, ie taking 1º C out of 3000 litres of air would raise a litre of water 1º. Therefor a volume of air 2 meters by 3 by 4 would be balanced by 8 litres of water. So a 200 L steel drum would take care of just about anything, depending on the conductivity of the various walls.

This all seems extremely simple, which I guess means it's either already been done or there's something very wrong with the idea.

Here is the first basic design for the greenhouse. The main consideration is extreme ease of construction, and that it cost practically nothing in materials. Secondly that it maximise growable area and be easily customisable to different growing techniques, ie permaculture, hydroponics, aquaponics (combined plant and fish farming), bee hives, etc.

The design pictured has a side length of 16 meters, giving a 110 meter footprint and about 280-320 square meters of growing area, depending on use. The design is very scaleable and can be easily modified to whatever footprint is available.

Materials consist of 9 x 7 meter poles, about 262 meters of clear plastic mulch film, rope, and scrap wood for shelving, floors and stairs. All of this can be realistically recycled for free, or fairly cheap if paid for.

Click for larger view.

The greenhouse in 3d, wrapped and unwrapped. Click to view and install the player when prompted. Verified virus and spyware free.
Check http://www.3dvia.com for more information.