Thread: Heat Storage

Hi everyone,

I've got a question I hope you can help with, my aplogies if this is in the wrong section. To cut it short I'm currently designing a vehicle system for my college project. Part of the system is to store heat produced from the engine to be used at a later time.

I'm finding it quite difficult to find clear information regarding suitable heat storage information.

I know it's possible as the Toyota Prius uses a container to store heated engine coolant at temperature for up to three days.

From what I can gather, water is the most efficient for storing heat energy, and a vacuum flask(?) is the best for insulating the heat.

The average coolant temperature of an engine is around 100 degrees C, and ideally I'd like to keep this heat stored for the longest possible period within reason (regarding practicality for price and space available in a car).

I've heard about some kind of salt that is good for storing heat but couldn't find any more information on the subject.

If anyone has any ideas or knows of any more suitable materials/containers it would be really helpful.

Thanks,

Laurence

Why srore the heat?

http://en.wikipedia.org/w/index.php?...=thermal+salts

Molten salt is a good method for storing high temperature heat but the melting point is way higher than 100C so it doesn't appear to be useful in your application.

You should be looking for a material that changes phases within your operating temperature range and has a high latent heat of fusion. From the Wiki link below it looks as if lauric acid might be a good bet.

http://en.wikipedia.org/wiki/Phase_change_material

Hi, thanks for the replies. theoretically i could capture the heat from other sources while the engine is running to get a higher temperature, so those materials could be useful.

As I understand it from that wiki article, the process of it melting allows it to absorb a far greater amount of heat than water.

However, i was planning to use a system where the fluid was passed around the engine in order to absorb the heat, then pumped back into a vacuum tank where its kept insulated, and pumped on to other systems later on. i think this would be an issue if i was to use a material that becomes solid as it cools down as it would just be stuck in the rest of the system.

Does that last bit sound right or am I missing the point?

all input is greatly appreciated, thanks

I've just had a thought actually

I know that sodium acetate remains liquid (and cold) until you apply pressure(?) to it which causes it to solidify and release the heat. however, its not quite enough heat for my liking.

Do all of the PCMs behave like this or do they just react to the ambient temperature? ideally i'd like something that i could store heat in, leave uninsulated and then just activate it to release the heat like those sodium acetate pads. would need to be one that I could store more energy in though.

apologies for noobish questions

Originally Posted by Laurencemayo

As I understand it from that wiki article, the process of it melting allows it to absorb a far greater amount of heat than water.

You are storing latent heat rather than sensible heat.

However, i was planning to use a system where the fluid was passed around the engine in order to absorb the heat, then pumped back into a vacuum tank where its kept insulated, and pumped on to other systems later on. i think this would be an issue if i was to use a material that becomes solid as it cools down as it would just be stuck in the rest of the system.

Does that last bit sound right or am I missing the point?

all input is greatly appreciated, thanks

You would circulate a conventional coolant such as glycol/water, not the phase change material. The phase change material would be in an insulated vessel containing a coil that would transfer heat from the hot glycol, which would become cooler and go back to the engine block, to the phase change material which would absorb the heat as both sensible and latent heat.

You would circulate a conventional coolant such as glycol/water, not the phase change material. The phase change material would be in an insulated vessel containing a coil that would transfer heat from the hot glycol, which would become cooler and go back to the engine block, to the phase change material which would absorb the heat as both sensible and latent heat.

ahhh got ya mate thats really helpful, thanks!

since you don't explain WTF you are doing most answers are a guessing game. bye and good luck