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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-
by rcthompson 14y ago
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.
- Splines 14y agoOn that topic, does anyone know how these things work? http://www.amazon.co.uk/Magic-Gel-Reusable-Hand-Warmer/dp/B000MU4IJ2 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.
- hexagonal 14y agoSodium Acetate. https://en.wikipedia.org/wiki/Sodium_acetate https://en.wikipedia.org/wiki/Sodium_acetate
- limmeau 14y agoI think there's a saturated solution of sodium acetate inside. The metal clickie causes the solution to crystallize, which happens to happen exothermically. (IANAchemist)
- vlisivka 14y agoCan 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?
- xutopia 14y agoIt's most likely unwieldy. Sometimes you can cause the exothermic effect to occur without you wanting it by a vibration or shock.
- excuse-me 14y agoThey 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
- eigenvector 14y agoI 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.
- dllthomas 14y agoI 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).
- mtmcannon 14y agoWhat 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.
- samstave 14y agoCan you give me some examples of how this can be used?
- julian37 14y agoThe 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 http://en.wikipedia.org/wiki/District_heating
- rsanchez1 14y agoThis 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.
- excuse-me 14y agoRecharging 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?
- Zaak 14y agoI wonder if you could incorporate a wire mesh into the zeolite to improve the heat distribution.
- olefoo 14y agoIf 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.
- gte910h 14y agoA drum dryer like you use for clothing sounds built to take water out of these things (with grates smaller than the pellets of course).
- DanBC2 14y agoNoisy as hell though. Also, how robust are the pellets? Tumbling them may create a lot of dust. Damp dust would be tricky to control. I used to have to dry silica gel bags. We'd put them in a temperature controlled oven for a few hours, it'd ramp the heat up and fans would pull air through. That worked quite well, but was only for small quantities. I guess you could have many mesh racks with heating at the base (or even through the mesh) and fans at the top to extract moist air. Drying that air and re-using it would handy.
- 14y ago
- samstave 14y agoIf they could use a similar process to how aerogel is made, creating a foam structure of the zeolite, then surface area would be considerable.
- cheatercheater 14y agohow 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?