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Author Topic: Nebraska retiree uses earths's heat to grow oranges in snow  (Read 1158 times)

EvilFruit

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Moh'd

SoCal2warm

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #1 on: June 13, 2018, 10:26:42 AM »
It's not just the earth's heat. Heat that builds up in the greenhouse during the daytime is pumped down, using the earth below as a heat bank. The temperatures down there aren't very warm, but it's enough to keep the plants from freezing during the night. Instead of venting the heat out in the day, a fan circulates air down into pipes. A depth as shallow as 12 feet is enough to be functional.

Florian

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #2 on: June 14, 2018, 01:50:06 AM »
Have you read the manual that he sells on his website? I really do wonder why this method isn't used more if it is as easy and cheap as he claims..

Ilya11

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #3 on: June 14, 2018, 04:15:53 AM »
From what I read in other forums, the main problem with such systems is water condensate being formed underground. It should be drained somehow and it is not an easy task in heavy soils and high water levels.
Best regards,
                       Ilya

SoCal2warm

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #4 on: June 15, 2018, 11:40:09 PM »
Designing a system to drain out condensation in the pipes shouldn't be too complicated.

I don't see any reason why above ground (or shallow in ground) heat banks couldn't be used, assuming they were well insulated.
It could just be as simple as multiple stacked plastic brick containers of water, encassed in a double layer of pumice-rich concrete (low thermal conductivity). It would probably need to be  somewhere around a fourth of the ground surface space of the greenhouse though, in size.
« Last Edit: June 15, 2018, 11:41:52 PM by SoCal2warm »

SoCal2warm

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spaugh

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #6 on: June 23, 2018, 01:07:55 AM »
I am surprised the dirt below the GH can store the heat for more than a day or two.  I wonder how long the elevated temps in the soil exist if the fan is shut off during the day?  At least if you get down deep enough you can probably get rid of any frost just from the earths natural temps many feet down.

He also mentioned they have bananas growing year round.  I need to see some banana racks to believe that.
Brad Spaugh

Walt

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #7 on: June 23, 2018, 01:05:43 PM »
I used to have  a greenhouse sunk about 1 1/2 M into the ground.  This was in cenrtral Kansas, USA, zone 6.  Tomatoes survived the winters in it without any extra heat.  Just sun and heat stored in the walls and floor.
Tomatoes didn't grow during December until late March.  But green fruit stayed good through that time and began growing again and  ripened when longer days arrived in late March.
My fig also did fine in that greenhouse.
I think many citrus would do fine in such a greenhouse. 
The greenhouse only had automatic vent openers.  No fans.  In fact no electricity or gas.

SoCal2warm

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Eutectic Salts
« Reply #8 on: October 16, 2018, 02:48:19 PM »
A well-designed greenhouse can maintain temperatures in the night using just barrels of water as the thermal mass.

You can look at the temperature data for the SunCatcher design greenhouse here:
https://s3.amazonaws.com/sfc-dynamic-content/uploadfiles/212/Terry%20Carroll.pdf

The nighttime temperatures inside tend not to go below about 58 F, even thought the ambient outside temperatures are going down to between 2 to 15 degrees F.
The parts of the greenhouse not facing the angle of the winter sun to collect sunlight are well insulated. Both the inside and outside of the greenhouse is painted white, to reflect maximum light inside, and help avoid heat loss at night on the outside, and prevent overheating in Summer.

Another technology that exists is to use special eutectic salts instead of water as the heat mass. These eutectic salts can store 62 times the amount of heat by weight as water. The salts undergo a phase change from liquid to solid at a particular temperature.

Farmers have long been using barrels of water, often painted black, to warm a greenhouse. Water does an excellent job of storing and releasing heat, but it canít match the capabilities of eutectic salts.

Like using water as a thermal mass, eutectic salts can be used to store the heat generated by light coming through the greenhouse during the daytime and allow it to be stored so that it can be released back at night. Unlike using water over its liquid range, however, the use of eutectic salts involve freezing or phase change to bank heat.

http://smallfarmcanada.ca/2016/chill-out-storing-heat-inside-a-greenhouse-using-salt/

Quote
The salt formulation used inside Carmeniaís greenhouse is capable of storing 62 times the amount of heat by weight as water. In this trial the salt based PCM stored 260 kilojoules of heat per kg of PCM whereas water stores 4.19 kj per kg. In order to realize the 6-8 degree Fahrenheit increase in nighttime temperature gain achieved in the trial, Carmenia Farm would have had to place 33 45-gallon barrels of water inside its 200 square foot greenhouse. This would have been impossible as 33 barrels would not even fit. A major benefit of the salt-based phase change medium PCM was that it presented a minimal intrusion into growing space.

The principles of heat generation and storage in off-grid greenhouses are laid out in easy to understand terms by James McCullagh in The Solar Greenhouse Book.  Written in 1978, McCullagh mentioned the up-and-coming technology of eutectic salts. Now 37 years later, there are only two companies with salt-based energy storage products on the market. I first reached out to one of them, RGEES, in the U.S.,

I purchased the amount of phase change medium (PCM) product with a phase change temperature of 6C (43F) as recommended by the manufacturer.
The beauty of this technology is that different formulations of the salts produce different phase change temperatures, so farmers in colder climates are able to also use the technology, simply with a phase change temperature that is appropriate for the local climate. The manufacturer produces salt based storage products that change phase at a number of different temperatures, as low as -26C.

Of course, water itself has a phase change temperature of 0 C, so barrels of water are very effective at keeping temperatures inside a greenhouse from going much below freezing, since the water will begin to freeze first before the temperature goes down.

Keep in mind though the night temperature inside the greenhouse will still likely be a few degrees lower than the temperature maintained by the phase change medium.


Dr. Maria Telkas, University of Delaware, proved that Glauber's Salt technology was sound and economical some 30 years ago. She had a couple of patents in that regard. She built a home based on same at the U. of Delaware, and it was a nice practical validation. This technology could have a major impact on how we deal with energy.

Thermal storage is a fundamental problem in solar designs and phase change materials make tremendous logical sense when you go through the numbers. For example, stone, brick and the like have about 0.2 cal./gram/deg C heat capacity. The different mixtures of Glauber's salts, for example, have about 50 to 80 cal./gram during the phase change. Water is 1 cal./gram/deg C. So if you cycle brick, for example, through about 5 degree Celsius change, you only have 1 cal./gram. In this case you have an advantage of 50 to 80 times the thermal storage with Glauber's salts as you do with brick.
As described on our web site, I can heat the north side of our home (passively) with these salts. Because of Dr. Telka's patented techniques, the salts cycle indefinitely. I have had mine for about 20 years.

My salt tubes are about 2 1/2 inches in diameter and 36 inches long and are black-heavy PVC -- sealed with caps on the ends. They work well. As you can see on our web site, I have them on the South side so that the winter sun gives them good exposure -- melting them during the day time, so that they will give off 90 degree F heat at night. If you had them in a circulating water bath, that would probably work as well.

The salts that I have melt at 90 degrees F and have a heat capacity of about 80 calories per gram.
As shown by Dr. Telkas, you cannot use straight Glauber's salt. She came up with a patented mixture to make them work properly.
She used borax to act as a seed to keep the salts from super cooling, and she added clay (I believe bentenite) to stabilize the mixture. The deca-hydrate water bond to the sodium sulfate is a week bond, and if it breaks then you loose the heat-of-fusion properties of about 80 calories per gram. The melting point is about 90 degrees F. The salts I have in our home came from England. Some companies in the states tried her idea, but bypassed the patents and they all failed.

We built our home in 1992 with no furnace and it often gets to -20 degrees F here. It did last us through the winter.

http://www.allanstime.com/SolarHome/Eutectic_Salt/

One such phase change salt material is NaCl∑Na2SO4∑10H2O, which has a melting point at 64 F, phase change heat of 286 kJ/kg

That's simply a mix of regular salt and sodium sulfate hydrate (Glaubers salt), in a ratio of 0.18 g of salt to 1g of Glaubers salt.


Greenhouses can get quite hot inside when the sun is out and the skies are clear, even though it may be cold outside, due to what has been termed the "Greenhouse Effect". However, during the night, temperatures are usually only a few degrees above the outside temperature without some sort of thermal mass. (Although being sheltered from the wind may have some additional benefit protecting the plants from wind chill, movement of air carrying away heat at a rapid rate)


 



SoCal2warm

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #9 on: October 19, 2018, 04:57:26 AM »
Here's a little data about how much heat water can store, just to help you do the calculations.
1 gallon of water = 3.7 liters
1 liter of water = 1 kilogram
1 liter of water can store 4184 Joules per kilogram per degree Celsius
A difference of 1 degree F would is only 5/9 the difference of 1 degree C
1 Joule = 1 watt per second.
There are 3600 seconds in an hour.

If we assume a daytime-nighttime difference of 60 degrees F (which wouldn't be uncommon inside a greenhouse), and 24 gallons of water, and that the water is going to be releasing its heat over an 8 hour period...
4184 x 3.7 x 60 x 5/9 /8 /3600 x 24 = 430

The amount of heat energy stored in the water would be equivalent to running a 430 watt heater for those 8 hours.
And I suspect that's about how much energy you'd need to keep a small 6 foot by 8 foot greenhouse warm enough, assuming the outside temperature was 35 degrees F.

forumfool

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #10 on: October 22, 2018, 10:52:37 AM »
Walt very interesting about your greenhouse. What were the dimensions and orientation to the sun? What was the glazing? There was another guy in Kansas who did something similar.
http://www.greenfingardens.com/2015/07/our-new-fish-housebanana-house.html?m=1

citrange

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #11 on: October 22, 2018, 05:48:26 PM »
After reading this topic I contacted a UK company that supplies Phase Change Materials (PCM) packed into plastic 'icepacks' and available to change phase at a temperature of your choice.
I have a 24' x 10' glass greenhouse lined with twin-wall polycarbonate sheeting. Heating is provided by a 3kw electric heater set to maintain temperature at around 8C.
On the very coldest winter nights here this heater runs continuously and the temperature inside can still fall to around freezing.
From their figures for energy stored per icepack, I calculated I needed about 50 of them to reduce the load on the heater by about 50% on these cold nights - providing the previous daytime temperature had been warm enough to re-charge the packs.
They suggested a PCM of 13C would be best. Unfortunately the estimated cost of around £1000 (US$1300) is way outside my budget - but it would have been an interesting experiment!
See http://www.pcmproducts.net/

forumfool

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #12 on: October 23, 2018, 10:09:17 AM »
Did you do a math estimate of how much the pcm would save you each year? If it took 130$ off your yearly bill thatís a ten year payoff not bad. It must be worth it for some applications or they wouldnít sell the Stuff

Walt

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #13 on: October 24, 2018, 02:48:41 PM »
Walt very interesting about your greenhouse. What were the dimensions and orientation to the sun? What was the glazing? There was another guy in Kansas who did something similar.
http://www.greenfingardens.com/2015/07/our-new-fish-housebanana-house.html?m=1


Thanks for the link.
My greenhouse was a 20 ft. square.  That's a bit more than 6m. per side.  It was dug into a south-facing side of a valley.  The walls were railroad ties I got 4 for $1, from a railroad that had been abandonded.  Top was 4 ft. by 8 ft sheets of glass from an abandonded solar heater for a school gym, delivered free.
I couldn't afford to build a greenhouse like that using new materials, then or now.

forumfool

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Re: Nebraska retiree uses earths's heat to grow oranges in snow
« Reply #14 on: October 25, 2018, 07:22:54 PM »
Very nice. Assuming you donít have pictures of it but it sounds like the slope of the land helped a lot and the only glazing was the angled south wall. Nice that you made it out of salvage

 

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