[Avodah] Solar oven

[Micha Berger via Avodah]

On Sun, Mar 06, 2016 at 01:40:10PM +0000, D Rubin via Avodah wrote:
: Looks like proper toldoth chamoh bishul, so surely not de'oirayso.
: It's maybe similar to the machloketh between R. OY and R. SZ about
: dud shemesh..

Water that was in the dud from before Shabbos:

One has to be choleiq as to whether the food is getting heated directly
from the sun, in which case it's mutar, or if the device it being heated
by the sun and then /it/ heats the food.

RSZA (quoted in SSK 1:45) holds that a dud shemesh is heating the water
direcly by the sun, and therefore mei'iqar hadin mutar. (Ad kan SSK 1st
ed. Later editions of the SSK end up with "tov lehimana" because the
typical dud shemesh will draw from an electric boiler if there is more
hot water.)

Similarly the Tzitz Eliezer (7:19) and the rumor mill says R ZP Frank.

The other tzad is to say that the fact that it takes a dud shemesh to get
the water that hot, even though the heat is direct, it has the din the
gemara gave indirect heat.

Pulling more water into the dud on Shabbos because you're using the water
already in it:

ROY holds (YO 4 OC 34) holds that it's pesiq reishei delo nicha lei that
new water would enter the dud shemesh, so it's mutar for Sepharadim, but
tov lehachmir. (Lo zakhisi lehavin; unless it's a minute left to Shabbos,
it's having another batch of warm water nicha lei?) RZPF (OC 188) and
the TE (9:19) call it gerama, so Ashk would be off the hook too.

In any case, THIS device uses "the latent-heat capacity of our proprietary
PCM (short for Phase Change Material) encapsulated within an aluminum
extrusion". (It seems their thermal battery is this, a batter for
heat, not an electric battery that uses heat.) It therefore is quite
intentionally not using direct sunlight, and would be assur.

Tir'u baTov!
-Micha

-- 
Micha Berger             I always give much away,
micha at aishdas.org        and so gather happiness instead of pleasure.
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