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A comment on Zeolite retains heat indefinitely, absorbs 4x more heat than water.

Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by rcthompson on Wednesday June 06, 2012 @02:41PM (#4075407)
Short version of the science: The heat is released via an exothermic chemical reaction between the Zeolite and water. However, unlike the one-time-use chemical-reaction heating pads you can buy in a pharmacy, this reaction is reversible, so you can "recharge" the Zeolite by heating it and removing the water as it is released in order to force the reaction to reverse itself. The reaction goes something like this:

Zeolite + water <-> Zeolite & water complex + HEAT

The reaction happens at the surface of the zeolite, so the storage capacity is proportional to the surface area of the pellet. If you make the pellet highly porous, this can be proportional to its volume.

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by eigenvector on Wednesday June 06, 2012 @02:50PM (#4075451)
I don't see how this can translate to the title "Zeolite retains heat indefinitely". After the cycle of heating and cooling has been repeated some finite number of times, parasitic heat loss to the environment will eventually remove all of the heat added at the beginning.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by rcthompson on Wednesday June 06, 2012 @07:53PM (#4076811)
When you use water as a heat storage medium, you are storing the heat in the kinetic energy of the water molecules. In common parlance, you are increasing the temperature of the water. Obviously, over time the water's temperature will gradually revert to the ambient temperature, and you will lose all the heat you stored in it.

In contrast, when you store heat in Zeolite, you are not storing it as kinetic energy, you are driving an endothermic chemical reaction that stores the energy in high-energy chemical bonds. After you are done heating the Zeolite to "charge" it, it will return to the ambient temperature, but it still has (lots of) energy stored in the chemical bonds. This energy does not dissipate in the way that the kinetic energy of a high-temperature substance would. The energy can only be released by reversing the chemical reaction, so it is securely stored. You can then transport the Zeolite at ambient temperature to a location in need of heat, and then add water, which reverses the chemical reaction and releases the heat again.

So it doesn't actually store "heat", it takes in heat (i.e. molecular kinetic) energy and stores it in a different form (chemical bond energy).

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by kenrikm on Wednesday June 06, 2012 @09:21PM (#4077096)
So then it could be used to store heat created from a reactor then transported where the heat is needed?
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by rcthompson on Wednesday June 06, 2012 @10:52PM (#4077377)
Yes, that is the general idea.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by CirstoiuRadu on Thursday June 07, 2012 @05:46AM (#4078228)
You would always lose heat as black body radiation for the period of time the Zeolite is hotter than the environment!
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by dllthomas on Wednesday June 06, 2012 @03:00PM (#4075528)
I assume it means that, because it is stored in the chemical structure rather than actual heat, it's not leaking to the environment while the pellet is sitting on a shelf (if not exposed to the elements).
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by mtmcannon on Wednesday June 06, 2012 @03:01PM (#4075535)
What they mean is that when the Zeolite is "heated", then it can be stored indefinitely without "cooling down". If you heat water and put it in a tank, it will lose its heat relatively quickly. The Zeolite stores the energy from heat in (stable) chemical bonds, so it won't lose energy over time.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by samstave on Wednesday June 06, 2012 @03:38PM (#4075732)
Can you give me some examples of how this can be used?
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by mtmcannon on Wednesday June 06, 2012 @04:20PM (#4075976)
You can heat Zeolite using solar power during the day and release the energy at night. Current thermal energy storage techniques use stuff like molten salt (http://en.wikipedia.org/wiki/Thermal_energy_storage), which is a lot harder to work with than pellets.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by deelowe on Wednesday June 06, 2012 @05:35PM (#4076350)
Yeah, but once you do that, how do you get the water back out? It sounds like this stuff doesn't do that very easily.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by phn on Wednesday June 06, 2012 @06:45PM (#4076589)
From what I understood, the water comes out when you heat it.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by julian37 on Wednesday June 06, 2012 @04:03PM (#4075895)
The article gives one example: you could charge them with waste heat at plants and factories, then transport them to homes and offices where (I suppose) they could be used for heating and hot water, at some later point in time.

Sounds more efficient than teleheating via insulated pipes: http://en.wikipedia.org/wiki/District_heating

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by rsanchez1 on Wednesday June 06, 2012 @09:43PM (#4077161)
This is a great application. It could be particularly useful in the New England states. Manufacturing could store their waste heat in the zeolite, and resell it to homes and businesses who can use it to heat up during the winter. It could be a major disruption to utility companies.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by ramchip on Thursday June 07, 2012 @12:21AM (#4077594)
Considering the transport cost and equipment needed, I'm not convinced that would be economically viable...
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by JoeAltmaier on Thursday June 07, 2012 @07:33AM (#4078439)
Water heater in your home. Deliver heat when needed by pouring water on stones, comes out hot. Doesn't have to keep water hot and ready; so probably save 90% of the energy currently leaked away due to Newton cooling (hot water heater cooling off all day while you're at work).
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by MaysonL on Wednesday June 06, 2012 @04:20PM (#4075975)
Think of it as a rechargeable heat battery.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by samstave on Wednesday June 06, 2012 @03:34PM (#4075713)
If they could use a similar process to how aerogel is made, creating a foam structure of the zeolite, then surface area would be considerable.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by Splines on Wednesday June 06, 2012 @03:28PM (#4075676)
On that topic, does anyone know how these things work?

http://www.amazon.co.uk/Magic-Gel-Reusable-Hand-Warmer/dp/B0...

I've seen them in person and they're remarkable if you've never encountered them before.

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by limmeau on Wednesday June 06, 2012 @03:35PM (#4075722)
I think there's a saturated solution of sodium acetate inside. The metal clickie causes the solution to crystallize, which happens to happen exothermically.

(IANAchemist)

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by vlisivka on Thursday June 07, 2012 @05:21AM (#4078178)
Can I use sodium acetate to heat my energy passive home (which I will build soon) by heating it at day in Trombe wall and discharging it at night?
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by xutopia on Thursday June 07, 2012 @09:37AM (#4078935)
It's most likely unwieldy. Sometimes you can cause the exothermic effect to occur without you wanting it by a vibration or shock.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by hexagonal on Wednesday June 06, 2012 @03:35PM (#4075719)
Sodium Acetate.

https://en.wikipedia.org/wiki/Sodium_acetate

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by excuse-me on Wednesday June 06, 2012 @03:38PM (#4075738)
They are a supersaturated Sodium acetate solution. Liquids give off energy when they freeze and take energy in when they melt.

When you heat these and melt them they can stay stable as a saturated liquid until you create a small site for them to start freezing around - they then give off energy when they freeze. The 'clicker' is all that's required to localy concentrate it enough to form a single crystal seed to start the freezing

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by excuse-me on Wednesday June 06, 2012 @03:32PM (#4075699)
Recharging it isn't that simple

We use zeolite as a water scavenger in high vacuum systems, it's tremendously good at grabbing onto water BUT because it's so porous and very low thermal conductivity it's a real pain to heat it enough to get all the water out again. We have a heater resistor at the bottom of a small can of this and the top of the pellets a few cm away is cool enough to touch. You might do better with a microwave system but then the inefficiencies are going to hurt.

Why not use one of the many phase change salt solutions that are also used for rechargeable heater packs?

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by rcthompson on Wednesday June 06, 2012 @06:53PM (#4076618)
Is it such a major problem that it leads to major efficiency losses (measured as joules of output energy over joules of input energy required to "recharge")?
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by gte910h on Wednesday June 06, 2012 @06:23PM (#4076521)
A drum dryer like you use for clothing sounds built to take water out of these things (with grates smaller than the pellets of course).
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by excuse-me on Wednesday June 06, 2012 @06:53PM (#4076617)
The stuff is fragile (or at least the 5nm molecular sieve type)- if you shake it too much you make dust which blocks the pores
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by Zaak on Wednesday June 06, 2012 @03:46PM (#4075794)
I wonder if you could incorporate a wire mesh into the zeolite to improve the heat distribution.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by olefoo on Wednesday June 06, 2012 @06:39PM (#4076568)
If you could figure out a good way to integrate the heating element and the the zeolite on a surface like a menger sponge you would have a very high surface area and good thermal response characteristics.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by nwmcsween on Thursday June 07, 2012 @03:41AM (#4078000)
> ..microwave system but then the inefficiencies are going to hurt.

What inefficiencies? A microwave should be more efficient due to it only energizing H2O bonds.

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by rcthompson on Thursday June 07, 2012 @03:52AM (#4078017)
Surely a microwave oven is not 100% efficient in converting the input electrical energy into output heat in the object to be heated? I'm not sure how near 100% it is.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by AnthonBerg on Thursday June 07, 2012 @05:16AM (#4078160)
Hey good question. Kitchen microwaves: ~64%

– http://en.wikipedia.org/wiki/Microwave_oven#Heating_efficien...

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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by debacle on Thursday June 07, 2012 @11:20AM (#4079406)
That's actually pretty good.
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Re:Zeolite retains heat indefinitely, absorbs 4x more heat t... by cheatercheater on Thursday June 07, 2012 @02:35AM (#4077870)
how is that stuff similar to the (salt?)-based cooling pads that you would crack to start the endothermic reaction, and then put in a freezer to "charge" them up?
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