Author Topic: Phase Change [heating with solar]  (Read 12038 times)

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Bruce S

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Phase Change [heating with solar]
« on: August 16, 2017, 02:30:37 PM »
With winter just a few short months away, the plants I have growing in pots will begin their annual back into the green house. The blue & black barrels can hold a whole lot of heat , but there's no real way for me to slow the heating without going into full insulation of those barrels ( very space constrained at this point).

I've been looking into different ways of storing more latent heat from our water barrels.

Being that my wife happens to be a chef, I also know first hand how well beef fat stores heat ( I've made a few tallow candles even). Tallow seems to be close to paraffin in heat/cold qualities, being that I can get it free thought I would try it first.
 
I went searching our forum and found that Madscientist267 had done some Phase change tests (for cooling) with salt water. I also saw where dnix71 has a link for Phase Change materials.

I'm wondering if anyone had thought about using the latent heat holding abilities of fats to slow down the cooling effect of the water or rather allowed the solar heating time to melt the fats to a liquid then release the heat while it converted back to a solid.

My thoughts are to use cases of canning jars, stacked in various arrangements,while sitting down in the barrels full of water; to absorb the heat from the water, melting the fats , then during the night the fats revert back to their solid state warming the water backup keeping the area warm. It may just be better to burn the tallow candles than all these other steps. BUT this seems to be a better cyclic route.

Any thoughts?

Thanks
Bruce S

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Amish_Fighter_Pilot

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Re: Phase Change [heating with solar]
« Reply #1 on: August 17, 2017, 11:09:00 PM »
That is an interesting line of thinking. Its sort of the opposite of the way some cooling systems are being designed now, and yet works somewhat the same way. They make ice at night and let it thaw during the day.

I would strongly recommend separating the fats from the water completely if possible. They should be able to share heat across a radiator or something, but mixing them together is a recipe for unwanted anaerobic bacteria(and the smell associated with it).

MattM

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Re: Phase Change [heating with solar]
« Reply #2 on: August 18, 2017, 12:42:46 AM »
Is this to hold thermal heat from the day-time into the night?  (Because sunlight is already at a premium during the day on quite a few winter days.)

It would probably work through the fall until the real cold sets in and then you can burn the fat when sunlight isn't so abundant.

I can't help but to think getting heat into the system is much easier than a recovery system.  Once the cooled down grease coagulates and shields the remaining liquid from exchanging heat, then what?

Amish_Fighter_Pilot

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Re: Phase Change [heating with solar]
« Reply #3 on: August 18, 2017, 02:13:22 AM »
They make blender blade attachments that fit right on jars. Maybe he can rig some of them up as low-speed agitators?

electrondady1

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Re: Phase Change [heating with solar]
« Reply #4 on: August 18, 2017, 08:13:26 AM »
your making the supposition that animal fat can retain its heat energy longer that an equal mass of other material ? how does that work?

mbouwer

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Re: Phase Change [heating with solar]
« Reply #5 on: August 18, 2017, 09:01:26 AM »
Bruce,

It's not so easy to store heat for a long time.

I gave my green house 3 layers of glas with a big cavity between them.
Even in high winds and at severe frost a 60 watt lamp ensures a pleasant temperature inside.

Regards Rinus



DamonHD

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Re: Phase Change [heating with solar]
« Reply #6 on: August 18, 2017, 09:05:10 AM »
This is the way I would choose to store heat, with phase change, if possible:

https://www.sunamp.com/

They're also up to about 30,000 cycles of the storage with no loss of capacity so far.

Rgds

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Bruce S

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Re: Phase Change [heating with solar]
« Reply #7 on: August 18, 2017, 11:30:08 AM »
mbower1:
Keeping the green house warm can be an exercise in futility  :o.
Where I'm located we can get weeks of -12C weather during the coldest parts. AT that time any plants that are not in the house will be put in the composter. The green house was an inexpensive one and setting it up for extended winter projects will take some time.

elecrtondady1;
Not really sure what you mean about equal mass, however in side by side tests with tallow, tap water and salted tap water each at 500mL ALL warmed up to 150F , the tallow will hold it's heat 2x longer than either waters. This I did just in our kitchen using room temperature at about 78F. Along with using a no-touch infrared temp gun with the fluids being held in glass canning jars. I'd would've really like to have had a constant temp monitoring going on with all three.

IF by equal mass you mean the same amounts in weights, then no I did not test it like that.

DamonHD:
 that stuff looks a lot like the stuff we get for sore shoulders, they can be reused a bunch of times. I'll certainly be reading up on that stuff.
 
MattM;
Yes this is to grab any heat the sun can provide, setting up those beer can heaters are pretty easy, this is kinda like that , but in the water barrels it heats up the water instead of just air. Works pretty well, the green house keeps the wind and snow/ice stuff off of them and when the sun shines, the inside can get toasty ( not scientific term but,,, ).

Having the candles to burn could help, but I'd be a little worried about the fire ( I could always have my local FD engine house come by and give me tips  8), but then they would want to stay , hang out, drink my coffee  ;))

Another issue I'm worried about is the expansion rate of the tallow, since I do not want this and the water to mix, I need to keep the containers air tight.

This idea may turn out to be more work than it's worth :-(.
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Amish_Fighter_Pilot

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Re: Phase Change [heating with solar]
« Reply #8 on: August 18, 2017, 12:52:07 PM »
I still think the idea has merit, but your choice of material may need some revision.

Bruce S

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Re: Phase Change [heating with solar]
« Reply #9 on: August 18, 2017, 02:29:50 PM »
I still think the idea has merit, but your choice of material may need some revision.

I agree, but , this is why I post these things here. More than just starting a journal, beginning a test phase then spending loads of time or $$$, I can get very honest useful input.

Tallow, until humans become totally vegans (NOT in my lifetime I'm sure) will be around. A visit to a farmer's market only 10mins away can net me 20Kg for far less than buying paraffin.
The candles are neat to burn, and much much cheaper than making soy candles. Plus as an added bonus they're easy to burn in the chimney.

The Phase change link DamonHD sent is an interesting one too.

Cheers
Bruce S

 
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OperaHouse

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Re: Phase Change [heating with solar]
« Reply #10 on: August 18, 2017, 04:18:26 PM »
SUNAMP.......

Companies like this drive me nuts.

 It takes the storage capacity of a giant hot water tank into an appliance around the size of a domestic refrigerator.

Well.............How big is that water tank?

Weighs 50% than the same amount of water.

Doesn't exactly sound exciting.  Of course there are advantages, but they won't tell you anything till you talk to a salesman.  There is a new Australian PV to water heat box.  A lot of fluff in their video, but they couldn't tell me anything about how it worked when I asked, like how efficient is it when the panels are only putting out 20%.  It does make sense.  They are trying to market to the uneducated.

DamonHD

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Re: Phase Change [heating with solar]
« Reply #11 on: August 18, 2017, 04:50:13 PM »
I know Sunamp and its CEO reasonably well.

A huge virtue of the Sunamp solution is that is is far more compact and has far lower losses than an equivalent tank of water.

One version can take diverted power from PV, but other versions can be used as thermal stores for heating and hot water with other heat sources such as heat pumps.

Rgds

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Mary B

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Re: Phase Change [heating with solar]
« Reply #12 on: August 18, 2017, 09:33:36 PM »
SunampPV price... GASP 1,800 pounds??? yikes! This page has some heat storage rates for various materials(no fats though...)

http://www.engineeringtoolbox.com/sensible-heat-storage-d_1217.html


Amish_Fighter_Pilot

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Re: Phase Change [heating with solar]
« Reply #13 on: August 18, 2017, 11:06:08 PM »
I think since the tallow gets so hard to work with and non-conductive as it freezes into a solid that what you should do is run coils of pipe through the jars and circulate the water through that. Its a fat radiator, only the radiator is radiating in to the fluid instead of out because of the temperature differentials. The water doesn't change phase, so make the water the thing that moves, not the fat.

MattM

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Re: Phase Change [heating with solar]
« Reply #14 on: August 19, 2017, 08:30:38 AM »
If the fat is mixed with something like used engine oil, would it be easier to transfer heat?

Solidified fat just doesn't migrate well.  I fear pulling heat from the fat will clump fat around the condenser and leave most of it uncooled.

MattM

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Re: Phase Change [heating with solar]
« Reply #15 on: August 19, 2017, 08:39:43 AM »
SunampPV price... GASP 1,800 pounds??? yikes! This page has some heat storage rates for various materials(no fats though...)

http://www.engineeringtoolbox.com/sensible-heat-storage-d_1217.html

I had no idea iron had such potential.  Railroad track scrap used to be easy to come by and they paid me to take it.  It would have been easy to bury several tons - and I mean TONS - and run PEX in contact with it.  Its a damn shame I don't have the 20' flatbed around any more.  If I'd only knew its other potential other than as a quick buck.

DamonHD

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Re: Phase Change [heating with solar]
« Reply #16 on: August 19, 2017, 12:05:02 PM »
A significant problem is the amount of insulation you need around it to stop heat leaking away too fast...

A nice feature of the Sunamp gear is its vacuum insulated panels.

Rgds

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Amish_Fighter_Pilot

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Re: Phase Change [heating with solar]
« Reply #17 on: August 19, 2017, 12:13:13 PM »
Yeah, it would either have to be vacuum panels or aerogel. Nothing else is likely insular enough.

dnix71

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Re: Phase Change [heating with solar]
« Reply #18 on: August 19, 2017, 10:56:02 PM »
His idea of storing low grade heat in a sealed phase change box for compactness is a great idea, esp. the part about making it portable, so it doesn't have to be piped.

There are refrigerators that do the opposite of this, Eutectic fridges 'store' cold in a phase change.
This will allow for operation without a battery in many cases.
http://www.ozefridge.com.au/

Bruce S

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Re: Phase Change [heating with solar]
« Reply #19 on: August 22, 2017, 10:57:23 AM »
As a test before I go mainstream.
I'm going to make a few of these tallow units, I'll either seal it up in tin cans or beer cans. Beer cans will swell easier and let me know if how much to put in the cans that will allow the heating. For the water container I'll be using the large 1.4Kg Coffee containers that will also be painted black. These I get for free from work and will get hot enough to cook the roots of the plants that are (or were) growing in them.
The cheap $1/can black paint cans will cover about 2 containers with two coats that have lasted 2 years now outside.
Some of these have worked out nicely sitting inside in the southern windows of our grow room. This is where I also found the roots getting cooked from all the extra heat. The African violets didn't mind, but the basil flat out died.
 

I'll get pics as I go. I have just enough tallow ready for about two 350mL beer cans.

Cheers
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george65

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Re: Phase Change [heating with solar]
« Reply #20 on: August 25, 2017, 02:32:54 AM »

I'm not exactly sure what you are planning to do in the actual application here ( put jars of fat in a drum of water to slow heat release?)  However, whatever it is, be aware that using fat ( or oil ) will LOOSE you heat capacity.

You mention you are space limited and it would seem you want all the thermal storage you can get. By replacing water with fat or oil, the total BTU capacity of your system will be decreased for the same Volume. Fats and oils have significantly lower thermal capacity than water. Water is in fact one of the best thermal storage mediums with common materials and is hard to beat in Practicality.
If say for instance you are storing 5 Kw of heat now, You may only be able to stores 3 Kw depending on how much fat you use.

The advantage of a fat or oil over water would be in elevated temps over 100oC. At that point water will boil  but you could take fats or oils to 200oC . Be on the edge and they would be smoking at that point but they would do it.  Of course then you need the containers and piping etc that will handle that.  For the sort of temps you are going to want, water will be the best medium by far.

I want to do a greenhouse before next winter and will look at water storage and burning oil. This will elevate the co2 levels and provide heat. Unlike what many think, oil can be burned perfectly clean and even set up to provide constant heat with a simple controller.  There is around 10Kw of energy in ever litre of veg oil ( I imagine fat would be similar as it's a fraction higher in energy content than oil but would vary) so you wouldn't need a lot to heat a decent greenhouse I'd Imagine. In any case a decent restaurant would have 100L a week or so which would be more than enough.

I'm just going to build a real simple 2 stage burner to start with, Idle and heat. With a simple thermostat, once the heat is needed a fan will kick in and a valve open and the thing will ramp up. once it is at temp it will go back to the standby idle mode. That will provide some heat in itself anyway.
Co2 could be monitored and exhaust Vented in or out.
I'm thinking to make just a little baby 5Kw burner or at least program one to that and see how it goes. The variables of the thermal properties of the greenhouse would be infinite but 5 Kw would  easily heat any enclosed space backyard greenhouse size and would kick in and out as needed on the thermostat.

I'll try a direct heating setup first and see how that goes and if the Co2 is too high then I'll look at a hydronic  setup.
I think you'd be far better off burning the fats than trying to use them as a storage medium.

frackers

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Re: Phase Change [heating with solar]
« Reply #21 on: August 25, 2017, 07:09:27 AM »
I'm surprised nobody has mentioned supersaturated sodium acetate solutions as used in heat pads. Uses the heat of recrystalisation to store energy.
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DamonHD

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Re: Phase Change [heating with solar]
« Reply #22 on: August 25, 2017, 05:40:37 PM »
That's what Sunamp is doing, and their secret sauce is keeping the reaction under control.

Rgds

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Bruce S

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Re: Phase Change [heating with solar]
« Reply #23 on: August 28, 2017, 09:03:55 AM »
Georeg65;
Because I'm hardheaded and I like a challenge  :o. That is what I'm trying to do.
I knew that displacing the water by the sealed glass or tins of tallow would lower the amount of heat by the volume of displaced water.
Since I'd also like to extend the growing season into the freezing months (squash, beets, turnips, Kale, etc) I also need to thing about freezing issues.
Likewise, burning the oil directly could be a nice solution, but then I have to stay around as a just in case the burn gets out-of-hand.
I have tested the floating candle thingy, and cute and practical. I have some chicken-of-the-sea tins that I'll be trying this out with.

Frackers:
That is intriguing, I do have couple of those snap heaters, but thought it would be too pricey even for me to try out.

Damon;
I wonder if they use a membrane to keep the solution regulated. Like Mary B said: At $2Gs per it a little out of my greenhouse range.

Cheers
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OperaHouse

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Re: Phase Change [heating with solar]
« Reply #24 on: August 28, 2017, 08:38:57 PM »
I'm surprised nobody has mentioned supersaturated sodium acetate solutions as used in heat pads. Uses the heat of recrystalisation to store energy.

I have one of those and it is a pain in the ass to use. You would need a load of cells and magic twangers to start it.  Do  they stop id a temperature is maintained?

DamonHD

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Re: Phase Change [heating with solar]
« Reply #25 on: August 29, 2017, 04:07:36 AM »
AFAIK, yes.
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Bruce S

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Re: Phase Change [heating with solar]
« Reply #26 on: September 12, 2017, 11:47:48 AM »
It's been a little while since my last post.
I thought I would post a short update.

Here's a pic of the Tallow donors (but don't tell them  ;) ).
For my French friends,, YES these are those lovely tasting Charolais cattle.
   
After reading the suggestions here and doing more online research , I've decided the idea of Phase change might be do-able, but using the tallow as a fire would be better while I test the Phase change method.

I did some research on using the tallow along with Paraffin based candles to keep the green house warm for a much longer period without the worry of fire or spillage.

The real interesting setup is to use the paraffin based candle to buffer the tallow. I'll also setup the internet sensation (using clay pots as radiant heat) instead of merely a fire that could burn something.

More to come
Cheers
Bruce S
 
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Bruce S

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Re: Phase Change [heating with solar]
« Reply #27 on: November 09, 2017, 02:35:52 PM »
Now that overnight temps are in or near the kill the tomato plants' temps
I wanted to post a small update.
The idea of using tallow is still a valid one, however since most of our days have been overcast enough to not heat up the water in blacken containers and not even close enough to warm the little bit of tallow .
The test plant has taken some pretty big hits. 1/3 of the plant is pretty much dead.
On a brighter note I've been getting vegetable shortening ( the stuff knock-off Crisco ) that is either expired or rancid.

Here's a picture of how I built them. I place these in a #10 can that is filled with water 1/2 way. 3 of these have been great for keeping the cold away from the plants.

We are still getting tomatoes too ;-)
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OperaHouse

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Re: Phase Change [heating with solar]
« Reply #28 on: November 09, 2017, 02:49:38 PM »
Have you tried the underground sewer pipes with a small fan blowing air through through them?

Bruce S

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Re: Phase Change [heating with solar]
« Reply #29 on: November 09, 2017, 04:05:18 PM »
Not yet, that will need to wait until spring/summer dig time.

I do know that the composter helps keep the little plants warm too. I covered a volunteer tomato plant with a sheet blanket and that plant did better than the ones trying to stay warm using water/tallow combo.

We tend to run our compost bins hot due to "critters".

 
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george65

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Re: Phase Change [heating with solar]
« Reply #30 on: November 09, 2017, 06:41:04 PM »

Looks like a Wick in the middle of it.  Have you been making giant candles? Might be a viable solution!

I'm having trouble with my Tomato and other seedlings.  They either get burnt to a crisp in one hot day and are dried out or the things are drowning with too much water.
An old upright freeze died in flames the other week so I moved it up the back and am using it for seed raising.

I put a large LED Lightbar I wasn't using on the top shelf and have that connected to a battery charger and a broken solar panel on the roof behind.
During the day, the panel makes all the power and the charger amps drop to nothing. as the sun goes, the charger takes over.  Just direct connected and seem to work fine.  I thought the panel would take power from the charger when not generating but the amps are the same and I remembered, like the charger the panel has diodes which should prevent that.

At night I close the fridge door as the temps drop pretty well here and that keeps everything nice and toasty and then let the warmth and air in during the day.  Had it going about a week now and the seedlings are coming on great and the seed is germinating nicely.
Was thinking of a small fan to move the air and warmth around and also maybe put a fogger in there on a timer.

I saw some small cheap heater elements off Fleabay that are 12V so was also wondering about putting them  in some water at the bottom of the freezer for when winter comes.  They are constant temp, anything from 120 to 250C  but with a 25L drum of water I can't see them getting near boiling it.  If they do I'll add more water for lower temps and more thermal mass.
The freezer did have excellent insulation,  l When it died the food was still properly frozen ( even the ice cubes didn't melt) for 3 days.

I had 3 tomato plants in 25L drums that were 3 years old. Unfortunately last year I went away for a couple of weeks and it rained the whole time. Poor things must have drowned because I lost them all which I was really peeved about.  Going to put some more in shortly and see how long I can keep them going. I put my LED's on them at night  which probably threw enough warmth to keep the frost off, give them much needed light and annoyed my mongeral neighbour as well.

Kinda miss not having the mongeral around to upset. Neighbors here are good so I have all these fiendish ideas going to waste now.  :0)

Got the new controller finished for the aeroponic system so have to put some lettuce in and get that going.  I actually prefer that to gardening with soil.
I want to do a whole wall of grow towers but first I have to get a handle on the climate and weather here.

Bruce S

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Re: Phase Change [heating with solar]
« Reply #31 on: November 10, 2017, 10:43:16 AM »
I was doing something similar with a min-fridge that I rescued from work 3 years ago ( had a blown start relay). It died of a opened internal winding .
New neighbors complained of "open storage" plants are now inside in an old galvanized wash tub ( free) along side 1M kale plant. Shock is over and cute new snow pea sized tomatoes showing up.

Lights= I went with 0.99/ea 21CM USB based LEDs built for plants. These are 5Vdc1.0A units that I run at 5.vdc 0.8A ( I use a USB 110VAC) adapter so I can make use of mechanical timer for 16 hours of light. The backs get warm even at lower power but plants and moth eggs love 'em.

Moth worms all but destroyed the kale!Seems the extra warmth interrupted their winter sleep and they chowed down.

YES, I built over sized paraffin / solid veggie oil candles  ;) , not sure just how long they burn but they're still on in the morning. Solid veggie shortening was nearly free paraffin candles we can get pretty cheap at thrift stores last snag was 50 for $1.
I use wife's cooking time to melt shortening.

I got the idea from a U-tuber in the UK.
https://www.youtube.com/watch?v=jRehAKZ7uHU
 I might try it as big as he did , but the little ones allow me to make them while oven is on. Tins are recycled canned fishes empties

My little morningstar solar controller finally went belly up and near killed my 65Ahr 12Vdc battery. So I'm now baby sitting it until new and improved unit arrives. I went with a higher end 30A 12/24 Vdc unit this is programmable to cut off power at a setable voltage.

Basil is weak in hydroponics so I use a hybrid system similar to a dutch bucket system for them. Could be the stems are too heavy for it. Wife's school grows them using hydroponics and they'res are huge
Containers are free coffee containers PVC tubing is free from worksites, all I buy is elbows and grommets.

I may start a separate thread for those


 

 
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george65

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Re: Phase Change [heating with solar]
« Reply #32 on: November 10, 2017, 07:09:37 PM »

Moth worms all but destroyed the kale!
 

Geez, there is a scary similarity!!

Had the exact same problem this last couple of weeks! Kale was disappearing before my eyes! It was in pots under the verandah waiting to be planted out.
I'd get the grubs and there would be more the next day and more the day after that. My god those things can eat!
When they stopped on the kale because I put veggie dust on it, they decimated my Mint that was doing so well. 
I have learned, everything has a bit of veggie dust now. it's only sulfur and some other natural compound I forget so not worried about it on the plants and it keeps those green eating machines away.

In suburbia I threw seeds in dirt or in my aeroponic system I made and stuff grew like no tomorrow. When I moved to this rural area I had I ideas of growing enough to do a farmers market once in a while just for the satisfaction of it.
Reality is I can barely get seedlings up and going out here.  It's either too hot and kills them in a day or not hot enough and they get over watered and drowned or something else.  Thought it was me till the next door neighbour with the big greenhouse and the netted patch complained during an over the fence conversation that his veggies were amounting to nothing this year and he didn't know why.
Thats why I set the old fridge up, more of a controlled environment.

Do you have a link for the LED'S?
I really need to put something down the sides of the fridge so they all get light. Haven't got much in it atm so it's OK but when I do add more I'm going to need more than a single light source.

As for the candles, I can't see them warming anything larger than my fridge and If I had LEDS in there, especially with the controller, the heat output from those would be more significant. I think one would need a LOT of those to make any difference to an outside greenhouse even big enough just to walk in. The burn time is a direct relationship to the heat output, more fuel consumed in a shorter time, the better the heat output. That candle while a clever enough idea to be sure, is basically a glorified match with the same heat output. Great for long term lighting but not for heating.  A Tail light globe from a car would have far higher thermal output than that candle.  One could do the maths on the thermodynamics but I'd be guessing its around  3-4W Maximum!
Pint of wax/shortening has less than 6 Kw of energy. He burned that over 120+ hours.  Not a lot of power. First giveaway to me was he picked the jar up. Does not have to be too hot to touch to produce heat but if it's that cool...... Ya.

 Maybe the candle Idea comes from people that think 4 tealights with an upside down flower pot will warm a room?
Placebos cure a lot of medical problems too I spose. Maybe someone should market "Warming Tablets" to these people.  Take one and never be cold for 12 hours.  Active ingredient, 100% chalk.

If you can get the shortening for free, then making a candle with a thicker  wick  or a bit of rope like sash cord would work better. Faster burn, much better heat.  I'd Imagine unless you did them in a bucket you'd be having to do more every day but at least the greenhouse would stay warm.
A small smudge pot burner design running on veg oil I think would be a better alternative. Not something orchard sized but scaled down to where it gave enough heat for the job at hand without being over the top. Last one I did was a 4L saucepan with a 4" Pipe welded in the top and drilled for secondary air and 4x 1" holes in the lid for primary air.
With a 6ft flue that thing would throw enough heat to keep people back 4 ft and still had a jet flame out the top.
With the same 4L saucepan and something like a 1"  flue/ secondary air mix chamber and a 1/2" primary air control that had a bit of metal over the top that could be moved to regulate it, You could tune the thing to do the sort of output needed for a greenhouse.

An electronics Boffin like yourself could probably use a small carburetor off something like a chainsaw  linked to an arduino for primary air control.  Set the " Idle " on the carb to allow enough air to keep the heater just going and link the arduino to a thermostat. 
When the greenhouse cools off, arduino uses a servo to open the carb ( just want the carb for an accurate air metering) allowing more air and greater heat. When it's warm enough,  the carb closes off the air and the thing idles.
All the fuel oil is in the pot. There is NO need to drip feed like you see on a lot of designs. It works just perfect in batch mode.  All you need to do is control the primary air and it burns just fine.  Refill and Light at night  and shut off in the morning. If the servo could be set to hold an idle air setting, It could close the burner off all together when a set temp was reached or exceeded for a time or a CDS sensed it was daytime...... Or leave the thing burning all the time apart from top ups which you could do when lit if you had a cap on a refill port.

Haven't done anything with hydroponics but my aeroponics system made from a plastic drum, a fountain pump and a timer works a treat on Lettuce, rocket, Kale and similar leafy greens.