Phase Change Materials (PCM) temperature control

[AeroDude]

Has anyone used or considered using Phase Change Materials (PCM) to control the temperature of your Tear's interior? I mean this stuff:
http://energain.co.uk/Energain/en_GB/index.html
and
http://www.puretemp.com/industries.html
I especially like the Dupont Energain panel solution. It was used by the Stanford University team in their Solar Decathlon competition entry (http://solardecathlon.stanford.edu/desi ... lectrical/), but as far as I know, the 1/4" thick panels are not sold in the US (yet). Basically the PCM panels store heat (or cold) much better than a solid material and depending on the PCM chosen, it will maintain a certain temperature about 3 times as long. I've been hearing many stories about warm days, followed by (too) cold nights here in Northern California. PCM panels may help use daytime heat to make the nights a little more comfortable without using external energy or a heater.

[KCStudly]

Interesting concept.

Let's have a little closer look. From the specifications the 5.2 mm panels weigh about 10 lbs per sq meter, or (if my math is correct) about 44 lbs for an equivalent 4 x 8 sheet size. That's in the same territory as 3/4 inch ply and, unless I missed something, it's not a structural member. Just foil over paraffin cells.

And it works on the concept of collecting solar gain. Hmm, not very many windows in a traditional TD.

I'd rather go the other way, rather than adding weight, replace the traditional plywood with hard board insulation and thin wall skins. Foam is lighter, presumably much less expensive, and can be made into a structural panel, foamie style.

[AeroDude]

You're pretty much right except for the fact that these panels don't require any direct sunlight. As long as they heat up during daytime, for the Dupont panels above 75F, they should work. I haven't seen any pricing information, but I do expect them to be rather expensive. So it should really make a difference if I decided to try them out. Will go for a more traditional build for now.
Thanks!

[KCStudly]

My solar gain comment was from the perspective of a foamie builder who will be using small-ish tinted glass windows in my doors. Lots of insulation and almost no window "effect", so not much solar gain expected on any count.

It is interesting, and it is not my intent to discourage experimentation; far from it. Just looking at the (presumed) cost to benefit ratio and a little further past the marketing.

[AeroDude]

I appreciate your comments and insights. Will let you know if I find new information and/or change my mind

[mezmo]

Sorry, - no time to read the links now, but just
a fast question.

Do they work absorbing heat from conducted heat or
from radiant heat ? - Just wondering if sitting close to
it would draw out a person's body heat ? And also, does it
need some kind of fire retarding covering when installed ?

Cheers,
Norm/mezmo

[eamarquardt]

Sorry, - no time to read the links now, but just
a fast question.

Do they work absorbing heat from conducted heat or
from radiant heat ? - Just wondering if sitting close to
it would draw out a person's body heat ? And also, does it
need some kind of fire retarding covering when installed ?

Cheers,
Norm/mezmo

Ya gotta think of these panels as a form of "ice" that melts and thaws at different temperature than water. When a substance undergoes a phase change it can absorb or release far more heat than if it just changes temperature and remains in the same phase (liquid, solid, gas). For example to change the temperature of water one degree C it takes about two calories per gram. To change water from a liquid to ice it takes 80 calories per gram. To change water to a gas takes about 540 calories per gram. Heat is heat and it doesn't matter how the panels are heated or cooled they will absorb and release energy in greater amounts during phase changes. In the case of these panels it's from a solid to a liquid.

Hope this helps.

Cheers,

Gus