conception of heat storage with Na2-SO4?

ovacs

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

NobodySpecial

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.

ovacs

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.

MagnetDave

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.

NobodySpecial

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.

ovacs

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

Borek

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