Citrus Growers Forum

Millet · Posted: Wed 31 Dec, 2008 2:18 am

You also want to place your greenhouse north and south (unless it is a solar greenhouse). This direction reduces the solar pull on you crops. Further you want to make your north wall a solid insulated wall. North walls do not provide light, but rather lose light. My north wall is solid with the inside painted white, which reflects sun light back into the greenhouse. This helps allot with the low winter sun. Joe, just like you wrote, I have been in hundreds and hundreds of commercial greenhouse throughout Colorado, New Mexico and southern California. Used to be my business when I sold greenhouse supplies, and I never seen even one commercial grower growing in the ground. Growing in the ground would be a really big disaster for any commercial grower.- Millet

dauben · Posted: Wed 31 Dec, 2008 2:57 am

JoeReal wrote:

Phillip:

Here's my gift to you, I initially promised this with a crude drawing or diagram, and it still is, but here it is for you to improve my design.

Wow Joe,
Looking at your design closer, you put a lot of thought into it.

A couple of questions:
1) What's the oil for on the intake?
2) I've forgotton most of my termodynamics from college, but do you think there would be any benefit of having a water (or other fluid) system below ground with a heat exchanger to heat/cool the air? My thought is some other fluid may absorb/dissipate heat faster than air would and maybe reduce the amout of piping required. Likewise, the backfill material around the pipe may be a different material that's more suitable for holding/dissipating heat.

Phillip

JoeReal · Posted: Wed 31 Dec, 2008 6:53 am

dauben wrote:

JoeReal wrote:

Phillip:

Here's my gift to you, I initially promised this with a crude drawing or diagram, and it still is, but here it is for you to improve my design.

Wow Joe,
Looking at your design closer, you put a lot of thought into it.

A couple of questions:
1) What's the oil for on the intake?
2) I've forgotton most of my termodynamics from college, but do you think there would be any benefit of having a water (or other fluid) system below ground with a heat exchanger to heat/cool the air? My thought is some other fluid may absorb/dissipate heat faster than air would and maybe reduce the amout of piping required. Likewise, the backfill material around the pipe may be a different material that's more suitable for holding/dissipating heat.

Phillip

I have started playing with soil physics calculations and finite element analysis. Very laborious, for I think not much gain because the corrugated flexible drainage pipe from Home Depot or Lowes are so cheap. They sell like $32 for 100 feet and cheaper if you buy the "contractor" rolls of 1000 feet. I intentionally avoided the smooth pipes because the heat exchange would be slower due to laminar flow inside, better to have those corrugations.

1) The oil is NON-Volatile. this is the classic dust trap setup, which is actually similar to your vehicles dust trap. Non-volatile oil so that it doesn't evaporate and no smell of that stuff inside your greenhouse. The setup is done in such a way you change the direction of air flow very abruptly, and thus the heavier dust particles will stick into the oil and be relatively dust free as the air is drawn into the geotubes.

2) Moistening the soil will improve its heat capacity. No need to "liquefy" the material around the tubes. It will be messy. By having plenty of tubes that are very long, the air will have plenty of travel time to have excellent heat exchanges with the moistened soil mass.

And about the water reservoir along the sidewall of the greenhouse, I haven't finished drawing those in MSPaint! I don't have AutoCAD, so bear with the slow output. Anyway, yes, if you run a circulating water system to the top of the greenhouse and to this water reservoir, it will improve the heat exchanges and stability of the temperature by a lot, for the price of a low power water pump. I've read some designs about that one.

I have come across various scientific and engineering publications about these kinds of setup from India and other energy poor countries that wanted to save on heating and cooling.

In fact, if I can find a micro-excavator, I would love to install the geotubes under my front and back lawns. I'll have fresh air that is properly cooled or heated, going into the house, and then venting off through the port holes on the attic, all driven by a fan and not compressors. That is less than 1/10th the power consumption of either the AC or the heater, plus you have very fresh air the entire year. Not the very humid air during summer and very dry air during the winter, but perfectly fresh air all the time, at least, that's how the theory works.

Major problem with today's houses is that they spend tons of money on insulation then create port holes on the roof for the air to flow in and out, along with heat!!! This is somewhat a stupid design, and can't believe it found its way into the construction regulation. So we end up moving heat around. We generate heat during the winter using massive amounts of energy in our heater, and then pump the heat out using massive amounts of compressor energy during the summer! But if you find clever way of averaging out the extreme temperature using massive objects like the soil that you're standing on, the average annual temperature is the ideal temperature, and thus the purpose of these geotubes.

Now if you draw outside air from those geotubes, you actually have fresh air with a nice moisture content going into your house, and you wouldn't need heating and cooling, it is stable temperature, like living inside a cave but without the moldy stale air feel to it. The energy expense would only be for the price of a fan blower! Using geotubes is precisely like living in a basement or inside a cave, but instead of stale air, it is always fresh. Since we cannot bury our current houses under the soil to simulate a basement or a cave, or have plenty of money to install super massive annualized insulation on the current house, the geotubes and the excavating to put them in is the cheapest alternative. And it saves on a lot of energy expenses that can have paybacks in a couple of years.

dauben · Posted: Wed 31 Dec, 2008 1:51 pm

JoeReal wrote:

Major problem with today's houses is that they spend tons of money on insulation then create port holes on the roof for the air to flow in and out, along with heat!!! This is somewhat a stupid design, and can't believe it found its way into the construction regulation. So we end up moving heat around. We generate heat during the winter using massive amounts of energy in our heater, and then pump the heat out using massive amounts of compressor energy during the summer! But if you find clever way of averaging out the extreme temperature using massive objects like the soil that you're standing on, the average annual temperature is the ideal temperature, and thus the purpose of these geotubes.

Actually, what's funny is there's a battle going on in San Diego over port holes in attics. People come in for their plan checks to the fire department with all kinds of attic ventilation required by the County. The fire department doesn't want any because that's where embers enter in from brush fires. The poor customer is stuck between two agenices trying to battle it out.

Phillip

JoeReal · Posted: Wed 31 Dec, 2008 2:14 pm

dauben wrote:

Actually, what's funny is there's a battle going on in San Diego over port holes in attics. People come in for their plan checks to the fire department with all kinds of attic ventilation required by the County. The fire department doesn't want any because that's where embers enter in from brush fires. The poor customer is stuck between two agenices trying to battle it out.

Phillip

Yes, I hear you! And we have politicians to decide it all for us. An average politician typically falls asleep in science and mathematics classes, how much more when it moved over to Physics and engineering thermodynamics? And yet, there they are, deciding it all out for us, acting smarting than all the engineers and scientists combined, but with nary a clue!

JoeReal · Posted: Wed 31 Dec, 2008 2:26 pm

dauben wrote:

Joe, does your gift include professional installation? Smile

Thanks,

Phillip

If I am nearby, I'd be glad to help with the installation. But, you have great access to cheaper labor down there! With the construction industry going bust, left and right, you can independently get a hired hand to help you in your projects at the rate of $75 to $120/day depending on the skill level. And we know very well that during the housing boom, you can only get contractors to help you and will be charged by the contractor for the same type of laborers, the price of engineer's salary, between $40 to $100/hour.

Millet · Posted: Wed 31 Dec, 2008 6:59 pm

Joe,I am certainly not an engineer, so I ask, in cold areas such as Colorado, where the underground geotubes will be drawing in cold out side air with a temperature range from 0-F to -20F, then this air traveling through the geotubes warms by heat exchange from the surrounding earth, and finally injecting the warmer air into the greenhouse, eventually cause the earth in close proximity to the geotubes to cool? In Colorado, the system would run almost constantly during the worst of the winter months, and therefore, begin to expel air that is cooler and cooler air into the greenhouse? - Millet

JoeReal · Posted: Wed 31 Dec, 2008 9:01 pm

Millet wrote:

Joe,I am certainly not an engineer, so I ask, in cold areas such as Colorado, where the underground geotubes will be drawing in cold out side air with a temperature range from 0-F to -20F, then this air traveling through the geotubes warms by heat exchange from the surrounding earth, and finally injecting the warmer air into the greenhouse, eventually cause the earth in close proximity to the geotubes to cool? In Colorado, the system would run almost constantly during the worst of the winter months, and therefore, begin to expel air that is cooler and cooler air into the greenhouse? - Millet

That is why I specifically mentioned California for the applicability. Actually most Mediterranean type climates where there is extreme difference between night and day temperature are good candidates.

As a rule of thumb, the equilibrium or stable temperature of the ground is equal to the temperature of the water in the deep well. I have a map that details the various deep well water across the entire US of A. If your groundwater temperature is ideal, like between 60 to 75 deg F, the geotubes would be great.

There are calculations involved from the geotubes and your ground properties. I have not finalized those yet. The trick as you have said is to prevent the cooling, that is why I have suggested in my design, some programmable thermostatically controlled blowers to minimize the extremities.

The main idea of the geotube is to have enough mass so that you can average your temperature on annualized basis. For the data as to what temperature that it would approach, look to the water temperature of the deep well. As soon as I find the map, I'll post it here. I'll be scooting over to San Francisco to spend new year with family.

Happy New Year to All!

Millet · Posted: Wed 31 Dec, 2008 10:20 pm

I have three wells on the farm, they are (1) 240-ft. deep, (2) 175-ft. deep, and the third well is an agricultural deep well at 980-ft.. The 980 foot deep well, has the pump located at 500 feet deep. I have never measured the temperature of the water, so I will have to measure it to see what the water temperature is. However, I would not want to run the well on a constant basis to run water through the geotubes. It is a 10 horsepower motor, plus I would have a flood very quickly. So how do I over come such a problem. - Millet

JoeReal · Posted: Thu 01 Jan, 2009 11:05 pm

Here's the Stable Soil Temperature Map as promised.

By joereal at 2009-01-01

JoeReal · Posted: Thu 01 Jan, 2009 11:25 pm

And for you Millet, a better suited but more expensive design would be a closed loop vertical geotubes that is run through the well. This has better thermal exchange and truly take advantage of the water inside the well. There is a cheaper way to dig vertically deeper, would require only 2 day job per 150 ft hole, by able bodied people, using a soil auger. Will discuss it more if interested, but the idea is illustrated below:

By joereal at 2009-01-01

Millet · Posted: Fri 02 Jan, 2009 12:20 am

Actually, such a vertical hole could be dug rather easily by a well company. My deep well (980-ft. deep) was dug and then a 6-inch steel casing was inserted into the hole. Geothermal tubing could just as well be inserted as an iron casing. I'll have to inquire what the well company would charge to do this. Out here in the country, every body know every body, and the owner of the well company is a friend of mine. (However, being a friend does not lower the cost. BTW I am in the 50F geo area of your map. - LOL). -Thanks Joe, I appreciate all your efforts. Very kind of you. Millet

JoeReal · Posted: Fri 02 Jan, 2009 3:44 am

Phillip and Millet:

the MAIN concept is that the geotube is the heat exchanger. You only need to run air through them. The length of the pipe is that it will facilitate the crappy heat exchange coefficient of the plastic pipe with the moist soil (in case of Millet, the water in the well). There is ever no need to pump water around from any distance, so the energy required to move air is just that of the fan. The fan should draw air from the tubes, and not push air through the tubes.

Major reason why PVC or high density corrugated plastic tubing are needed: Condensation can form, and the air that condensed could contain carbon dioxide which will form carbonic acid. Some air contains sulfur, especially if there are nearby coal plants, so that you will have acidic condensate either way. The metal tubes while have good thermal conductivity, will get corroded in time, so they are never ever recommended for use as the heat exchanger in geotube. Remember, the geotubes are your heat exchanger and are designed for slower heat exchanges, and are compensated by the pipe length. To give time for annualized temperature averaging and temperature stability. The way the tubes were arranged, either vertically or horizontally have very specific reasons why they are arranged that way. Pay particular attention as you will have to maintain the geotubes as well, that is why part of the design included its maintenance operations such as flushing the geotubes. But as always, the geotubes are designed for air heat exchanges, never for water or other fluids. I hope this will give very clear intent of why things were designed that way. I can site you specific designs and other research studies if so desired.

Joe

hardyvermont · Posted: Sun 10 Feb, 2013 12:33 am

People have installed tubing underneath the floor of their greenhouses and blown the warm air of the greenhouse into the ground during the day for cooling and used the fans at night to remove the heat and warm the air.

One of the better sources is here:
http://www.sunnyjohn.com/indexpages/shcs.htm

The largest orange grove in Nebraska
http://www.altenergymag.com/emagazine.php?issue_number=03.08.01&article=finch