re: fireplace heat recovery
11 dec 2001
>so, basically nick, you seem to be saying that licl (lithium chloride?)
>can store about 13 times as much energey as water.
something like that. consider the difference between a drumful of water
on top of a basement woodstove and a drumful of 50% licl solution.
evaporate water when the woodstove is running, and absorb water vapor
from a damp basement floor when it is not, as a chemical heat pump,
making the floor colder and the drum warmer. to work at a reasonable
rate, this probably needs additional heat exchange surface for the
absorption part, eg a layer of plastic film under the basement ceiling,
and we only get 1300 btu/lb with infinite dilution, so the real yield
is less, given a finite tank volume to hold the weak solution and
the fact that weaker solutions provide lower temp heat at lower rates.
>question is, how expensive is the raw product.
cyprus foote-mineral sells dry licl in 55 gallon drums for $4/lb.
a 2:1 mix of cacl2 (an ice-melting salt at about 50 cents/lb) and
licl can work almost as well.
>i seem to remember seeing balls? of pcm that were fairly pricey, but
>then, so is insulating 13 times as big of a storage area. i see licl
>mentioned in a lot of your posts, is this because it is one of the
>better pcm's, or because it is a cheaper product?
it's a desiccant (water absorbing) salt, vs a pcm. another advantage
is that it can store heat forever with no loss of heat over time and
no need for insulation. there's no risk of fire, it doesn't get tired
of changing phase, and it can be used in a simple heat pump.