Saturated Salt Solutions

Thanks for the prompt response. It's very close to what I was after and has given me some good leads.

"Water soluable. Non Toxic in normal conditions and as disolved."

Glauber's Salt for Thermal Energy Storage Check out the characteristics of the Glauber's salt. Any salt that changes state will have more storage than a simple salt solution.

That's the stuff that I'm after. "Phase change materials". The energy involved in phase change is "completely" recovered in the reversal of the phase change. In my zeal, I had not considered "phase separation" and what I would call stratification of the salt/fluid interface which would create problems as the material repetitively cycles hot/cool.

Glauber's salt sounds great, now to find a salt with phase change around 75 Deg C.

The mention of the organic alternatives like parafin and such gives me another alternative to review.

Looks like I'm off to google PCMs.

Thanks heaps.

Aye, There's the rub.:

"In my zeal, I had not considered "phase separation" and what I would call stratification of the salt/fluid interface which would create problems as the material repetitively cycles hot/cool."

Its kinda/sorta like memory effect in nicad rechargeable batteries. (to my way of thinking)

milo

Hi - I remember reading about heat pump technologies some years ago that were using salt solutions as their energy storage medium - There are as I understand several commercial models available. Anyhow look up heat pumps and you will be amazed!

Cheers

Water solubile, non-toxic, and cheap. Hmmm...three limiting factors. Any particular reason why one or more of these requirements can't be relaxed? It should widen the range of possibilities...

When I posted the initial question, I was faced with a decision of how long to make it without boring everybody.

The interest and responses coming warrant further expansion. (Again thanks for the interest.)

Water soluable was a constraint imposed by me. (I remember reading a novel some 30 years ago and an aside in the novel was about bed warmers that contained water based solutions that were heated in the carriages and then provided to the travellers.)

Non-toxic is imposed as the intended end result is for domestic and camping water heating. (Making smaller hot water systems with the same thermal storage capacity.) I didn't want leaks or spills to pose any difficulty in containment or decontamination or damage to waste treatment equipment. Heating the storage with solar concentrator and oil as the transport media and then heating water for showers, washers and such. Yes, it's a double coil heat exchanger with the solution as the intermediate material.

"Cheap" is again imposed to support mass supply to housing and camping. I suppose here I wanted to imply "readily available" in adequate quantity around the world. (Or more simply "Not some exotic laboratory material".)

I'm wanting to make two prototypes. One for household water heating using solar collector and the other for camping using waste heat from the car engine as you drive to the camping areas.

The key factor is the phase change temperature. I want that to be close to the current setpoints used in domestic hot water systems so these can become a "drop in" replacement.

Another contributor has already "opened my eyes" to other options with phase change in that zone that is not water based (Thanks to that contributor) and while my initial experiments will be on the water based system, I think there will also be experiments with other materials.

Should keep me busy through the winter down here.