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Old 10-08-21, 09:33 AM   #1
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Default 2 million btu thermal heat storage powered by the sun.

I'm in the process of designing a heat storage system for our home. One of my design criteria is the be able to buffer 3 days of no sun on the coldest days. I've calculated that 2 million btus of storage to be my target capacity.

I'm planning on using water and paraffin wax and a large tank. I've collected 3000 lbs. of wax so far but still need to find its melting temperature and design around that.

I'm in the process of sourcing a 2000 gallon stainless steel tank for the project.

Is this of interest to the group?


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Old 10-08-21, 03:18 PM   #2
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Hi Sparky!

Sounds like a great plan!

Storing heat/energy is important, and using phase changing materials will increase the storage capacity.

Some links in this board to check out:
Heat accumulator (not sure why my pics disappeared, but most are also here)
useing frig for ac post #14
Phase change materials

Please update us with your project!
Ecorenovation - the bottomless piggy bank that tries to tame the energy hog.
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Old 10-11-21, 04:13 PM   #3
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Well I tested the melting point of my paraffin wax and its somewhere around 138-140 farenheit. It was hard to get it narrowed down.

One of the ways that I'm looking to input heat into my hot water storage tank is with an air to water heat pump similar to what some here have done with their homemade heat pump water heaters. I was thinking of starting with a 5 ton system.

my question is how high of a water temperature can I achieve and what refrigerant would I be looking at using?

I currently have a 5 ton mr cool universal system for my home and it is working well. It claims to be rated to -22 f with full output. time will tell.

One of my goals is to get off of using natural gas and just use our solar system that I installed 5 years ago. we currently have 24-305 watt panels and 36- 325 watt panels with 2 solaredge 7600 inverters.

So the question is how hot of water hopefully 160-180??? in my climate.

let me know what you think, thanks
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Old 11-10-21, 06:55 PM   #4
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The melting point of your paraffin sounds too high for a heat pump based system to run well at high efficiency.
You would be better off with a lower temperature wax unless you were to use solar thermal to melt it, which may well be a better option if you have sunny winters.
Have you thought about your heat exchanger design for your thermal store?
I've heard of people using PET bottles filled with paraffin stacked inside of a large water store.
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Old 11-10-21, 06:55 PM   #5
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Here is how I solved it.
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Old 12-19-21, 04:28 PM   #6
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Default Project update

Yesterday I picked up my tank. It was brand new old stock. It is 1600 gallons with its length around 10'. It was made to be used horizontally but I will be standing it up on end. There are so many modifications to be made to it but we will map it out and check off each item as we go. It will need legs and also the manhole moved from the side to the new top.
I will start the digging for the pit that it will sit in. The pit will be 8' x 8' and 3' deep.
My ceiling height in the garage is 11' 3" , so if I go 3' into the ground I will have nice room to work above this room.

I'm planning on insulating the room and not the tank and as I was driving yesterday I realized that this may be hard on electrical equipment that might reside inside the room. I will do more thinking on that.

Right now I'm planning on dividing the upper portion of the tank from the bottom with the top portion holding the 3000 lbs. of paraffin wax and the lower section holding the water.

Slow progress but it is progress.

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