Maximizing Heat Storage in Water: Photovoltaic vs Radiator

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Discussion Overview

The discussion centers around comparing the heat storage capabilities of photovoltaic solar panels versus radiator systems, specifically focusing on the use of water as a heat storage medium. Participants explore the potential effects of adding salts to water to enhance its heat storage capacity, while also addressing misconceptions about boiling point elevation and specific heat.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants inquire about specific salts that can be added to water to increase its heat storage capacity without raising the boiling point.
  • Others suggest that sodium or magnesium sulfate or chloride could be potential candidates, but note that these may raise the boiling point.
  • A participant shares a graph indicating that the specific heat of NaCl in water decreases as salt is added, raising questions about the implications for thermal storage.
  • There is a discussion about whether it is advantageous to raise or lower the specific heat of water for thermal storage, with some suggesting that a higher specific heat is generally preferable.
  • One participant mentions a specific case of a greenhouse using a salt formulation that reportedly stores significantly more heat than water, but expresses uncertainty about its relevance to their own experiment.
  • Another participant clarifies that their focus is on using water for convenience and scale, rather than exploring solid materials like concrete or sand.
  • There is a suggestion that the participant might be thinking of molten-salt thermal storage, which involves phase changes at higher temperatures.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the effectiveness of adding salts to water for heat storage. Multiple competing views are presented regarding the implications of specific heat and the suitability of different materials for thermal storage.

Contextual Notes

Participants express varying levels of understanding and familiarity with the concepts discussed, which may affect the clarity of the conversation. There are references to specific graphs and articles that may not be universally accessible or interpretable.

camerart
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Hi,
I'm going to make a comparison test between Photovoltaic solar panels and the radiator type.

I intend to store all heat with an insulated water tank.

Many years ago, I heard about water bottles in a green house with some kind of salts in the water, which allowed the water to store more heat than plain water. I'm not talking about raising the boiling point!
Any ideas as to what this salt is please?
Camerart
 
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camerart said:
I'm not talking about raising the boiling point!
Any ideas as to what this salt is please?
Sodium or magnesium sulfate or chloride, however you will be raising the boiling point.
 
Hi B,
Ah, thanks.
Can you explain a little more what happens please, and how much difference it makes?
Als how much works best?
Thanks, Camerart
 
Tom.G said:
Here is a graph of the specific heat of NaCl in H2O. It looks like the specific heat decreases as salt is added to water.

https://www.engineeringtoolbox.com/docs/documents/1187/sodium-chloride-water-specific-heat.png

Above found with:
https://www.google.com/search?&q=specific+heat+sodium+chloride

Cheers,
Tom
Hi Tom,
Thanks for the links. (While I appreciate the links to Google, it doesn't make things simpler) I've searched myself and find this very difficult route to understanding. I'm not lazy!

Can I point out that I'm slightly Dyslexic, so what may be obvious to some may not be obvious to me. I keep searching and find similar questions, where they may be answered by comparing a block of Iron compared to a 'block' of water, this complicates things.

If a litre of water, 'A' has salt in it, from the graph link, I see it will have a lower specific heat, than litre of water 'B'

For thermal storage, is it better to raise or lower the specific heat of a volume of water?
In other words, is it an advantage to add salt to store more heat in a known volume of water?

C
 
Last edited:
camerart said:
For thermal storage, is it better to raise or lower the specific heat of a volume of water?
In other words, is it an advantage to add salt to store more heat in a known volume of water?
Well, you asked the initial question and it comes with an implied answer: it is often better to have a higher specific heat because that means you need less of the storage medium. So, additives are often there because of boiling or freezing point concerns.

So I think then the answer to the original question is no, it's not really the way it works that you add something to water to make it store more heat, you just use more water.
 
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Hi R,
Thank you for a clear answer.
I wonder what it was that was done to those greenhouse bottles of water? Maybe the idea was simply incorrect.
Cheers, C.
 
  • #10
Usually, stuff is added to water to lower the freezing point, to prevent water lines from getting clogged, and bursting from ice expansion. And also, usually, it lowers the heat-capacity.

For a greenhouse, it'd be neat if you could raise the freezing point of a ballast.
 
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  • #11
Perhaps you read this article:

Chill: out! Storing heat inside a greenhouse using salt
...
The salt formulation used inside Carmenia's greenhouse is capable of storing 62 times the amount of heat by weight as water.
...

I'm late for a very important date, so I don't have time to figure out if this is nonsense or not. See you next week!
 
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  • #12
Hi O,
I think it may be true, but not what I'm asking. The salt is a solid, like sand or concrete, and can store more heat than water, but for my experiment, I specifically need to use water, for convenience, and scale.

I could have tried a ton of concrete, then found that a ton of this salt would be better, then I would have to get rid of the concrete, so water it is :)

I'll start another thread about my idea, and see what you think. Note: I prefer simple words of what you think, rather than Google links or deep science.
C.
 
  • #13
I don't think you need another thread ; rather to define what you're trying to accomplish with your experiment.

You might be thinking of molten-salt thermal storage, which is a phase change for higher temperatures than boiling water.

Or, you might not.
 

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