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Rick H Parker

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Reply with quote  #11 
"Is this every 11°f above ambient room temperature?"

For calculating usable (transferable) heat ... the answer is Yes.
You can only transfer heat from a higher temperature to a lower temperature.

Example:
Ambient temperature = 70°F
Water temperature = 150°F

(150 - 70)/11 = 7.27.
~ equivalent to 7 hours run time of a 1500W space heater.

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Rick H Parker
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stmbtwle

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Reply with quote  #12 
Agree but it's not quite that simple, and certainly not linear.  You'll get a LOT of heat transfer when you have an 80 degree temperature difference, but as the water cools and the air warms the transfer will be slower. 

This "front end loading" can be a good thing if you're trying to heat up a cool room.

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Willie, Tampa Bay
littlecreek

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Reply with quote  #13 
Thanks, this is great info. Just wondering about a solar batch heater for an unheated basement. One barrel outside collecting heat during the day, at night drains into a barrel in the basement to release the heat.
littlecreek

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Reply with quote  #14 
IMG_20181115_141320.jpg 

something along this line for a collector, simple drain to let gravity empty it at the end of day.

myk3y

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Reply with quote  #15 
I’ve been researching wax as a storage medium.

Using 300mm PET drink bottles, filled with wax, closed and stacked in the water tank, storing heat all day. The wax can store immense amounts of heat and release it all night.

Industrial wax is cheap.

There’s been a bunch of scholarly articles on the ability of wax to store heat, as well as wax/glass beads, wax/steel ball bearings, etc. Even wax and washed gravel.
stmbtwle

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Reply with quote  #16 
As you're effectively building a drainback system, instead of the batch collector I think you'd be better served with a large flat tube collector. Irrigation tubing will work IF you keep water flowing through it. With no water flow it may melt. The heat drum or drums in the basement would double as your drainback tank. You could power a DC pump with a pv panel, or control an AC pump with a timer or snap switch.
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
myk3y

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Reply with quote  #17 
Quote:
Originally Posted by stmbtwle
As you're effectively building a drainback system, instead of the batch collector I think you'd be better served with a large flat tube collector. Irrigation tubing will work IF you keep water flowing through it. With no water flow it may melt. The heat drum or drums in the basement would double as your drainback tank. You could power a DC pump with a pv panel, or control an AC pump with a timer or snap switch.


How does a snap switch (what we call a microswitch?) work in a scenario like that? What triggers the switch?
stmbtwle

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Reply with quote  #18 
Sorry, I used the wrong term. I meant a snap disc thermostat, similar to this.
https://www.ebay.com/itm/Supco-AT021-Adjustable-Airflow-Thermostat-Fan-Control-Snap-Disc-Close-on-Rise/173213260368?epid=2255529293&hash=item2854509a50:g:SFUAAOSwzgRWzif~&redirect=mobile

They work by a temperature sensitive disk that "snaps" the switch open or closed. Commonly used for attic fans, etc. Available in several types and settings. Some are adjustable. Not terribly precise but cheap and reliable.

There's also a digital type:
https://www.ebay.com/itm/Inkbird-All-purpose-Digital-Temperature-Controller-110V-Thermostat-50-210-F-Fan/222076874307?hash=item33b4d02e43:g:qRgAAOSwiylXBNTg:sc:ShippingMethodExpress!33570!US!-1&redirect=mobile

I've done some reading on wax as a storage medium and it sounds really promising, though I haven't tried it.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
myk3y

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Reply with quote  #19 
Thanks for that.

There are so many terminology differences across the anglophone countries.

‘Nations divided by a common language’ :D

Yes, wax is promising, especially as the ability to store it safely in PET bottles that would otherwise be trash fill.

The coefficient of expansion is something to watch for with different types of wax - some increase hardly at all, some by quite a few percent.

Steel ball bearings offset the tendency to float and store a tonne of heat.
Rick H Parker

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Reply with quote  #20 
Quote:
Originally Posted by myk3y
I’ve been researching wax as a storage medium.

Using 300mm PET drink bottles, filled with wax, closed and stacked in the water tank, storing heat all day. The wax can store immense amounts of heat and release it all night.

Industrial wax is cheap.

There’s been a bunch of scholarly articles on the ability of wax to store heat, as well as wax/glass beads, wax/steel ball bearings, etc. Even wax and washed gravel.


There are a couple of engineering problems to over come. Wax is a PCM it absorbs and releases large amounts of heat as it changes from solid to liquid and vice versa. You need some kind of thermal buffer to make it a practical heat storage.

Wax is a flammable, there are serious safety issues that need to be addressed.  

Waste of time for residential when water storage does the job economically and without serious safety issues.



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Rick H Parker
Kansas, USA
Electronics Engineering Technologist
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