Thread: Battery idea

I posted this in the electrical section, but someone told me that it would work better here.

Is it possible to have an endothermic reaction absorb heat, then remove the energy of the heat as electricity? My idea is to have an endothermic reaction that produces two salts in a higher energy state than the two(or more) original chemicals. When the energy is used, the salts should reverse the reaction, resetting it to absorb more heat.
I'm not very good at chemistry, preferring physics instead, so any help you can give me would be appreciated.

Originally Posted by TheUnknowable

I posted this in the electrical section, but someone told me that it would work better here.

Is it possible to have an endothermic reaction absorb heat, then remove the energy of the heat as electricity? My idea is to have an endothermic reaction that produces two salts in a higher energy state than the two(or more) original chemicals. When the energy is used, the salts should reverse the reaction, resetting it to absorb more heat.
I'm not very good at chemistry, preferring physics instead, so any help you can give me would be appreciated.

What you describe is not a battery, though, is it?

A battery reversibly stores and releases electricity, whereas your proposed device converts heat to electricity, i.e. a one-way process.

Perhaps what you mean is to set up a suitable endothermic reaction in the form of an electrochemical cell? But then you would consume the ingredients.

The problem I see with making such a thing reversible is thermodynamic. An endothermic reaction only proceeds because the entropy increase is strong enough to overcome the energy absorption: ΔG = ΔH - TΔS so if ΔH is +ve then the TΔS term has to be big enough to outweigh this, to allow G to decrease during the reaction. This is by definition an irreversible process, it seems to me, i.e. you will never be able to drive it backwards to recover your starting ingredients.

But let's see what others think.

I tried. Crystals dissolve endothermic. Repeated crystallization, the discharge
With sodium acetate, sodium chloride, sodium sulfate. . . . . . . . .

Originally Posted by pingguo002

I tried. Crystals dissolve endothermic. Repeated crystallization, the discharge
With sodium acetate, sodium chloride, sodium sulfate. . . . . . . . .

Can you give a little more detail? Did you just put salt between two metal plates and can "recharge" it by melting the salt?
Personally, I'm looking for a way to turn low temperature heat (even room temperature) into electricity, but that's a start.

Originally Posted by TheUnknowable

Originally Posted by pingguo002

I tried. Crystals dissolve endothermic. Repeated crystallization, the discharge
With sodium acetate, sodium chloride, sodium sulfate. . . . . . . . .

Can you give a little more detail? Did you just put salt between two metal plates and can "recharge" it by melting the salt?
Personally, I'm looking for a way to turn low temperature heat (even room temperature) into electricity, but that's a start.

I recommend reading up on your thermodynamics before you waste too much time on this.

Low temperature heat is the highest entropy form of energy it is possible to have. As such, it cannot, ever, be converted into work unless a significant portion of it is rejected as waste heat at an even lower temperature.

You cannot escape the efficiency limitations of the Carnot cycle merely by interposing electricity, I'm afraid. Any energy conversion that starts with heat is subject to it.

Crystallization can only get a very small micro-current.
Ingredients: water, glass, copper, iron, sodium thiosulfate
Excess sodium thiosulfate, in copper, iron tablets produce crystals, with micro-current.


Six months ago, the details of tests forgotten.
Suggested adding a catalyst, manganese dioxide. Should crystallization, recrystallization affected.
Try using carbon as electrode
Magnets, with iron powder, can promote crystallization
Try adding sodium hydroxide, potassium hydroxide


I did not realize orderly crystals, can not provide efficient power.

Originally Posted by pingguo002

Crystallization can only get a very small micro-current.
Ingredients: water, glass, copper, iron, sodium thiosulfate
Excess sodium thiosulfate, in copper, iron tablets produce crystals, with micro-current.


Six months ago, the details of tests forgotten.
Suggested adding a catalyst, manganese dioxide. Should crystallization, recrystallization affected.
Try using carbon as electrode
Magnets, with iron powder, can promote crystallization
Try adding sodium hydroxide, potassium hydroxide


I did not realize orderly crystals, can not provide efficient power.

BUT, I am sure any current you obtain will be due to irreversible consumption of ingredients, NOT from reversible absorption of ambient heat.

This is because of the thermodynamics - you have no heat sink into which you can reject a portion of the heat you are attempting to convert to electricity.

Won't the battery itself shed some of the heat? You would probably have to cool it, but that can be done with a TEC.

heat to electric current can be done with a bi metal loop, (I have forgotten the name for this effect). But a heat sink is required. One bimetal interface needs to be warm and the other cold. If you are hoping to get energy out of room temp air the the other end of the loop must be someplace cooler, say down a well, in ground water. This is not a battery however just an energy source. It is not rechargeable.

Originally Posted by Sealeaf

heat to electric current can be done with a bi metal loop, (I have forgotten the name for this effect). But a heat sink is required. One bimetal interface needs to be warm and the other cold. If you are hoping to get energy out of room temp air the the other end of the loop must be someplace cooler, say down a well, in ground water. This is not a battery however just an energy source. It is not rechargeable.

Seebeck effect. It's what drives thermocouples and TEC units.

Energy comes from the freedom movement of water. Thermal power generation is the difference between non-renewable, free movement of water molecules is the norm. Providing free movement of molecules heat. Free movement into the crystals were converted into electricity. My experiment failed, crystallization is difficult to control. Abandon electricity generated mainly crystallized too weak