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Forum Index : Other Stuff : Thermal Cold storage

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Davo99
Senior Member

Joined: 03/06/2019
Location: Australia
Posts: 297
Posted: 04:54pm 01 Dec 2019
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So as not to derail another thread....

  Quote  I have been toying with the idea of using a 5000L water tank I have as a thermal storage bank.  Circulate the water through a radiator during the day for cooling the house. Run the water through an external radiator at night to cool the water back down. Here it's common for a 20o temp drop and more over night.  Bit of a water spray wouldn't hurt the cooling effect either.

10o Difference in 5KL of water is almost 60 Kwh of energy.  That's worthwhile.
If I could get the tank temp down to 15o, I'd really be laughing.  That said, even having 30o air blowing in here many days would be a help.


Looking into this a bit more today I see things are better than I realised here.

This week the Highest Nightly temp is predicted to be 15oC. The lowest is predicted to be 11 and that's on the hottest day of 35.  That gives a nice 20O temp difference to 30oC and an opportunity to cool the water down to a temp that would be very useable for cooling.

At 20o difference, The tank I'd use beside the house which I remembered is 3000L not 5000, still gives a significant 66KWh of Cold. If I pulled that down over 5 Hours, I would get a reasonable 10 Kw cooling capacity. At the flow rate required, that should only take 200W of power for the pump and maybe 50 for a fan.

I also wonder what sort of chilling effect I could get with a water spray at 15oC and how low that would allow me to get the tank? I'm thinking If I ran the pump 2 Hours before dawn, that should be the coolest time but I should be able to look that up anyway.
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2915
Posted: 08:04pm 01 Dec 2019
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  Quote  I also wonder what sort of chilling effect I could get with a water spray at 15oC and how low that would allow me to get the tank? I'm thinking If I ran the pump 2 Hours before dawn, that should be the coolest time but I should be able to look that up anyway.

That depends on the wet bulb temperature (or humidity).
Its certainly coldest just before dawn, but the humidity is highest then too.
When humidity approaches 100% you get dew.

Water spray evaporative cooling is still an excellent way to reduce the temperature of anything, but it works best when humidity is low.
It should be possible to get wet bulb temperatures for your region from the weather bureau. That will tell you exactly the lowest temperature your spray can reach.
Cheers, Tony.
 
SimpleSafeName

Regular Member

Joined: 28/07/2019
Location: United States
Posts: 86
Posted: 02:06am 02 Dec 2019
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Around here it makes more sense to bury your water lines, especially if you plan on putting in a septic tank and leach field. The advantage to the "Geo" system is that your ground is going to be about 18C in the summer and around 13C in the winter. You get this heat/cool assist 24/7/365. You can use the delta for heating and cooling.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 297
Posted: 05:50am 02 Dec 2019
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I was thinking of a system that comprised of 2 x 1000L tanks buried and using car AC driven by a diesel engine and an oil burner as a cooler/ heater with thermal storage. I have crunched the numbers on this and it seems more than viable.  It's also a lot of work to set up so I was thinking of something Cheap and cheerful in the mean time.

I have a 3000L tank of water right beside the house with another 2 IBC's. I could easily add another 4 IBC's to give me 5000L in them and the 3000 In the tank.

Given this hairbrained Idea would need 2 car radiators with fans ( have them)  a Pump for Circulation ( have that) and some hoses and fittings ( have probably 80%  of that)
This could be a cheap and easy to set up practical system for my home and it's layout.

My thought with the tanks was to in fact insulate them with sheets of Styrofoam and bury them 6 Ft down where the ground temp is most stable. I also thought of locating a greenhouse over the top to take advantage of any  lost heat in winter and protect from heat rise in summer.

I would burn oil or have a co-gen setup for winter heating and having the storage would be a big advantage. I am also looking at replacing the buried tanks with a spa for the thermal storage in winter.  5000L of water would store a lot of heat and I could take it pretty warm as well to give max energy storage for the night when I don't want to run a burner or engine.

For now, I'm sure there would be a lot I could learn with using the tank I have where I have it with some easily reusable materials I already for the most part have.
 
zeitfest
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Joined: 31/07/2019
Location: Australia
Posts: 20
Posted: 08:10am 02 Dec 2019
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just a thought -
With a bit of luck, a water solar heater panel could double-duty as a thermal radiator at night. It would have to be un-insulated though.
If there are no clouds at night, the only thing radiating heat back to the panel  is the upper atmosphere which gets very (too) cold. Some panels are set up with a small flow at night so that they don't freeze.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 297
Posted: 01:16pm 02 Dec 2019
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That is an interesting thought.
I don't propose to know much about water heating panels but I believe they have a glass covering over the absorber to insulate them and trap the heat as it's gathered.
If this glass was removed then I think they would radiate a lot better.  Put a fan blowing across them and they would give up lots of heat.

The thing then is, what's going to be easier and cheaper to set up, a car radiator with a fan or a solar panel that's been modified?

I would also question where the best cold Might be, right down at ground level or 3 M up on your roof?  On real hot days it may be the roof as the ground itself may still be radiating heat. Question would be how long would it take the roof to cool down as well?
Before down I'd say it's energy had been given up as would that of the ground.

I'd tend to think lower down would be cooler but in reality, probably not enough height difference to matter.
 
renewableMark

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Joined: 09/12/2017
Location: Australia
Posts: 1423
Posted: 09:07pm 02 Dec 2019
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Go to youtube and type  DIY geothermal
heaps of ideas you'll most likely find interesting.
Cheers Caveman Mark
Off grid eastern Melb
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2915
Posted: 07:56pm 03 Dec 2019
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The Europeans are pretty much into ground sourced heat pumps. Their problem is a bit different to ours, being a much colder climate.
Cheers, Tony.
 
Davo99
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Joined: 03/06/2019
Location: Australia
Posts: 297
Posted: 11:32pm 03 Dec 2019
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There are some very interesting ideas with Geo but they mostly look very expensive and require ripping up ones yard.

For me, cooling isn't much of a problem just using the AC powered from my panels.
My preference for winter would be to fuel my heating one way or another with waste oil.

The idea with the tank was just an idea for a cheap and cheerful low power draw cooling setup that actually has some promise in the amount of energy stored and the low power to run it.  The weather where I am is also quite accommodating to the idea as well.

I don't need to do this but I like pondering DIY ideas with things I could easily and cheaply Implement.
TBH, I didn't think there would be the amount of energy storage available in this till I crunched the numbers. I'm generally pretty good at estimating this sort of thing now and while I knew there had to be some potential, I would not have guessed as much as there is.

The slimline tanks like I have are popular and usualy located beside buildings which put s them in a convinent spot.  Couple of radiators and fans, a pump hoses and fittings and one is there.  Maybe get out of it for $200 decreasing on what you have in your collection of Treasure.  Only thing I may not have is all the hose fittings but then again, I do have 2 bread crates full so.....

Also pondering the idea I was thinking a couple of Fleabay controllers may help this along nicely as well. I'm thinking a temprature controller like for a solar pool heater. 2 thermo couples, one for air and one for water temp.  When the air temp exceded a certain temp, the system kicks in until the water temp reaches a certain level and then switches off. May even need an inside air temp monitor in case the place gets too cold.  With a small well insulated house, that could be quite possible.

At night a similar controller could activate the cooling cycle but probably just a timer would do as the coolest part of the night is going to be pretty predictable.

I couldn't find wet Bulb humidity for my area or a temp/ time chart but probably no matter. One will get what one would get and that's pretty much it. Unlike what a lot of people believe these days, one cannot control the weather.

One thing that also occurred with the water spray/ humidity question was how Dry things have been here. I cannot miss a day watering my plants or they wither.  I am trying to raise a bunch of offcuts for hedging. I have them in small seedling containers in trays with some water.  The evaporation rates I see here are unreal. Even the birdbath looses a very significant amount of water when I haven't seen a single bird in it some days. In any case, the ones I do see tend to drink rather than splash around and they aren't Drinking THAT much water.  the evap may be occurring through the day but I still feel looking at the Humidity figures I can find that a bit of water spray would be effective.  

I know very well that spraying the condenser on my AC makes a Huge difference to the output any time I do it so I don't think this idea would be much different.

I think I'll start pulling together the Bits I need and give this a go.
The weather has been very mild here latley, all I have been doing is running the AC on fan to move some air about or kicking in the AC for an hour and the place has been nice. I think the thick Smoke blanket is helping keep things cooler.  Was bad here yesterday and I was out in the yard  on the tractor and saw a Piece of ash/ char  settle on the bonnet.  Looked closer and it was clearly a leaf that had been burnt and carried along.  Not good.

Right now some sort of DIY air purifier would be a winner.  I was thinking about  Bubbling air through water and wondering how effective that might be at removing at least some of the smoke in the air.  I have a fairly High pressure blower that will blow a decent amount of air to a reasonable Depth, at least that of a 200L Drum and through a 2" Pipe but no idea of the effectiveness. Would at least add some humidity to the place which wouldn't be a bad thing.

I don't think for a minute this tank idea is the best or most efficient thing for cooling a place, just a cheap and simple one that would lend itself easily to my circumstances but does have good and worthwhile potential.

As soon as Christmas is Over, I'll start working on setting up my oil burning spa heater conversion for winter.
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 2915
Posted: 02:10am 04 Dec 2019
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If heating is your game, and you have plenty of acreage out in the country, how about a solar pond ?
https://energyeducation.ca/encyclopedia/Solar_pond

Basically you bulldoze out a suitably large dam. A clay soil is ideal, or a clay layer if your soil is sandy. Then line the dam with black plastic to make it watertight.
Fill the dam with water in layers, starting with the top layer of pure water first.

Then slowly and very carefully with a minimum of introduced turbulence, add a second layer below the first layer of slightly higher salinity.
Keep going with a third layer below the second with even higher salinity.
The bottom layer will end up as incredibly thick brine.

The layers will remain stratified, and that traps the heat. It may take a year or two to finally reach full maximum operating temperature, but the lowest layer will be almost at boiling temperature.
It will stay pretty hot right through winter, and depending on the mass of stored water will have a huge amount of stored heat right through winter.

Its not going to be practical for most of us here, but its something people out in the bush might care to do a bit of research on.
Edited 2019-12-04 12:11 by Warpspeed
Cheers, Tony.
 
Davo99
Senior Member

Joined: 03/06/2019
Location: Australia
Posts: 297
Posted: 07:48am 04 Dec 2019
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A friend of Mine just put in an average size dam.  The pond liner cost him $15k.
The salt to give it anywhere near the levels needed I would say would cost many more thousands unless you can buy the stuff like top soil in a dump truck.

It's a very novel idea though! I wonder if it could be adapted to use solar collectors  to heat the water and then pump it back under the fresh water layer.  

Other thought is use another liner to isolate the fresh and the salt water. May give some insulative properties as well.

I think the cost of this method in setup and ongoing would be non viable for a home but maybe a small hotel or something may work out Ok.
 
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