Conception of heat storage with Na2-SO4?

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Discussion Overview

The discussion revolves around the conception of heat storage using sodium sulfate (Na2-SO4) and explores various materials and methods for thermal energy storage. Participants consider the feasibility of using hydrated salts, alternatives like sodium acetate, gypsum, and activated carbon, and the engineering challenges associated with these materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Johann proposes using dry Na2-SO4 moistened with water to maximize energy release through solvation energy and questions the possibility of regenerating it with heat.
  • Some participants note that systems involving phase changes between liquid and solid are common in heat storage, suggesting that Na2-SO4 may be challenging to engineer effectively.
  • Alternatives such as sodium acetate, gypsum, and activated carbon are mentioned, with some participants expressing concerns about their capacity and competitiveness as heat storage materials.
  • One participant confirms that heating hydrated crystals can drive off water, making the chemistry sound, but questions the practical utility of this approach.
  • Another participant discusses a natural solution involving pine tree sap that can absorb and release energy, highlighting the potential of natural materials in heat storage.
  • Johann later evaluates sodium acetate as a more suitable option due to its higher melting point compared to Na2-SO4, while also expressing interest in gypsum and activated carbon, particularly regarding their thermochemical cycles.
  • A participant recalls magnesium sulfate heptahydrate being used for similar purposes, suggesting additional avenues for exploration.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement regarding the feasibility and practicality of using Na2-SO4 for heat storage. While some acknowledge the soundness of Johann's chemistry, others raise concerns about engineering challenges and suggest alternative materials. No consensus is reached on the best approach or material.

Contextual Notes

Participants highlight various limitations, including the challenges of managing the hydrated to anhydrous transition, the need for efficient water collection, and the potential corrosiveness or toxicity of materials. There is also mention of insufficient data on activated carbon's performance in heat storage applications.

Who May Find This Useful

This discussion may be useful for researchers and practitioners in the fields of thermal energy storage, materials science, and engineering, particularly those interested in innovative heat storage solutions and the exploration of alternative materials.

ovacs
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Hi,

Who could evaluate my conception of heat storage with Na2-SO4?

Idea:
Dry Na2-SO4 is moistered with water till max energy release (solvation energy?)
Has there been now Na2-SO4-10H20 produced?
Can this compound be regenerated (dried) with heat supply (sun radiation?) to dry Na2-SO4?


thanks taking time
Johann
 
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It's possible but something losing and gaining water is a bit tricky to engineer
Most systems using something going between liquid and solid form.

I think the small personal ones use Sodium Acetate - don't know what you would use on an industrial scale.
 


Thanks for your bringing Natrium Acetate. As a result, there are many other alternatives i found as gypsum, activated carbon. But it is challenging to bring any of them to a competitive technique as all are limited in capacity.
 


There is nothing conceptually wrong with what you describe. Heating up a hydrated crystal will drive the water off and make it anhydrous. I'm not sure how you make any of that useful, but your understanding of the chemistry is sound.
 


ovacs said:
As a result, there are many other alternatives i found as gypsum, activated carbon.
There is even a natural solution. Some pine tree (southern yellow pine?) has a sap that melts somewhere just below room temperature (15-20C) taking in energy and freezes below this temperature, thus giving out energy - natures air conditioner!
There were some people building homes in the US out of this - you need quite a lot obviously - I think the plan was basically log cabins with lots of insulation on the outside.

Your plan to hydrate a salt is workable as MagnetDave said, it's just a bit tricky to deal with the hydrated <-> crystal change in an engineering sense.
How do you collect the released water without using lots of power and how do you keep the resulting crystal in a compact form while still allowing water to get back into it? You also have to consider how corrosive / toxic the material is - it's no use having a free source of energy if you need some super expensive stainless steel or titanium alloy to contain it.
 


After some evaluation, natrium-sulfate is not any more a prior material for storaging sun energy. Actually, sodium-acetate would fit better due to its higher melting point of 58°C.
However, before looking closer into sodium-acetate, i focus more on gypsum and second on activated carbon. Related features of gypsum have been described within a patent in the 80's. As a result, there are sufficient data about gypsum in regard of heat storage and release but not yet from activated carbon run with water. If someone knows how to approache such a thermo-chemical cycle with activiated carbon and water at atmospheric conditions, that would be helpful. Thanks
 


I remember reading about using magnesium sulfate heptahydrate for the same purpose.
 

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