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myk3y

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Reply with quote  #21 
Wax, sealed in a container, inside a water-filled vessel, presents less of a ‘serious safety issue’ than does the polypropylene tubing used in most heat-transfer systems.

It takes longer to change phase, along with its greater specific, makes it a superior medium for storing heat, and releases it in a slower manner as it returns to solid, than a water reservoir.

If a simple method of creating a nanoemulsion at home can be fabricated, that would be even better at slow gain/slow release thermal storage, with a much higher specific heat than water alone.

There are many combination materials to increase thermal storage - such as wax and sand, which would reduce any safety issues to a negligible concern.

stmbtwle

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Reply with quote  #22 
Sand isn't a good heat storage medium, and if mixed with water could wreck a pump. Wax is interesting, particularly an emulsion, but how do you make it? Detergent?
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myk3y

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Reply with quote  #23 
Sand on its own isn’t, mostly because it’s hard to heat it. Silica granules in a phase-change medium is.

It’s going to be a heck of a job to get unbound from wax and out of a PET bottle into water and find its way into a pump...

Items usually unable to be used as thermal mass, such as ball bearings, glass beads, rocks, sand, scrap metal, are mostly because of the difficulty in heating unusual shapes due to all the air. By encapsulating them in a phase-change material, such as wax, there’s no air to insulate. There’s no rust, or dirt, or dust, to foul your water.

Emulsification itself isn’t enough, it needs to be Nano emulsification, otherwise th emulsion breaks down under heat. The process is usually to use ultrasonic actuators, such as you find in fish finders, ultrasonic baths, etc. Cheap enough as a unit ($6-10 for a decent high-powered one) and building an ultrasonic signal generator and amp isn’t difficult. Something to play with later, I think. Much easier to use straight wax or wax with glass or PET beads.

The specific heat of water is around 4, much higher than wax at around .9, but it’s the phase change point that is the advantage - the change from solid to liquid happens at a much higher temperature than with water, such that the circulating water gives all of its heat to the wax right up until it hits the melting point. This keeps the water at a much lower average temperature than if water alone had been used.

There’s no argument that water has a higher latent heat storage capacity than nearly any other medium, and it’s easy, but you need big quantities to effect a decent storage system. Wax can hold the same amount of heat in 1/4 the space. You could, for example, make small storage reservoirs in multiple places around the house using containers of water filled with bottles of wax.

Is wax less safe than water? Sure. At what point does a minimal threat to safety cease to be an issue? Is it more complicated and more expensive than water to use? Yep. That’s why commercial wax thermal storage tanks for heating cost ~$5000.

I’m sure you can find any number of reasons not to do something, if you try.

I thought it offers another method for harvesting calories that has some benefits.

Most housing in most of the world doesn’t have a basement, so storage for large water reservoirs is more problematic than a multi-story North American house with ample underground storage. We’ve lived in around forty houses around the world, only three of which had basements - one in the UK and two in the US. Thinking of alternative methods that suit my particular environment won’t suit all implementations.

We will be building a new house when we move off the equator and that will have concrete floors with embedded heating and a solar thermal capture system. But, until we complete the build we will likely be living somewhere that doesn’t have that and so looking at a simple, compact and easily-implemented system was my design criteria.

And it’s an interesting concept.

Finding space for a 200 litre storage reservoir for a bedroom vs a 50L reservoir in our much smaller houses would be problematic. 2M x 1M x 1M vs 350mm^3.


stmbtwle

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Reply with quote  #24 
I had thought of simply letting the wax float on top of the water with vertical copper (aluminum?) conductors to transfer the heat. Or possibly with hot water coils in the wax. Never pursued it though.

Finding space for the reservoir was my problem as I don't have a basement either (Florida). The cost of building an outdoor shelter for it was also problematic...I did the math, and scrapped the idea.

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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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Posts: 31
Reply with quote  #25 
Quote:
Originally Posted by stmbtwle
I had thought of simply letting the wax float on top of the water with vertical copper (aluminum?) conductors to transfer the heat. Or possibly with hot water coils in the wax. Never pursued it though.

Finding space for the reservoir was my problem as I don't have a basement either (Florida). The cost of building an outdoor shelter for it was also problematic...I did the math, and scrapped the idea.


Similar problem to us - slab floor, house plonked on top :)

We do usually have plenty of space under the house, as the older ones are on pilings, but that’s mostly been because all of our houses so far have been in hilly areas, and where were moving ng to is likely to be flat(ish... not much flat land in NZ north island when you move from the coasts).

I hadn’t thought about floating wax - seems like it is fraught with peril o.0
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