Posted by Rob Dekker on September 15, 2005, 5:42 am
[...]
>> Aluminum frame, all-copper absorbers/tubing and tempered glass covers.
>> A 4'x10' (3.5 m^2) collector goes for $26, which is about $50/m^2.
>> We are getting close (for my target $000 system)...
> Better, but still only 1" insulation. ;-)
I know. But I wonder how important the insulation material is.
Common sense tells that the (single-pane) 3mm glass glazing should loose
a lot more heat by radiation and transmission/convection than even 1/2" of
good insulation material on the backside of the collector..
> And: does a Poly-Isocyanurate
> persist two decades of the temperatures that the collectors have? The max
> temperature of that insulation material is about 300 deg F (150 deg C) -
> pretty near to the stagnation temperature, or even below it for good
> collectors.
Mmm. Yeah, that is kind of tightly designed isn't it...
> Christian
>
Posted by Christian Kaiser on September 15, 2005, 6:07 am
>>> Aluminum frame, all-copper absorbers/tubing and tempered glass covers.
>>> A 4'x10' (3.5 m^2) collector goes for $26, which is about $50/m^2.
>>> We are getting close (for my target $000 system)...
>>
>> Better, but still only 1" insulation. ;-)
> I know. But I wonder how important the insulation material is.
> Common sense tells that the (single-pane) 3mm glass glazing should loose
> a lot more heat by radiation and transmission/convection than even 1/2" of
> good insulation material on the backside of the collector..
Sounds sound :) But as I once said here in Germany you only get money for
the collectors from the state if they fulfill that logo program "blue angel"
(who invents these?!), which means they have to be able to produce 525
W/m^2 --- and all of them have at least 6 cm insulation... I don't know
whether that's the reason, but when the collector surface is about 100 to
110 deg C when in operation at noon, there's 80 degrees (to 20 deg C
environment) in temperature difference at the insulation.
I don't know the insulation constants, maybe Polyisocyanurate is so much
better than mineral wool that that makes no difference. But then there's the
problem of temperature stability of that stuff. It seems the manufacturers
don't learn from the experience of others.
I found a few collectors with a layer of mineral or glass wool, backed up by
another layer of polyurethane. But most have one thick layer of mineral
wool.
Christian
Posted by nicksanspam on September 15, 2005, 9:26 am
>...does a Poly-Isocyanurate persist two decades of the temperatures
>that the collectors have? The max temperature of that insulation
>material is about 300 deg F (150 deg C) - pretty near to the stagnation
>temperature, or even below it for good collectors.
When Gary sent me the nice solar pond water heater model he tested in
Montana, I put it together in partial sun with the pump unpowered and
had a meltdown :-) The 2" Styrofoam cover (under a layer of EPDM under
2 layers of polycarbonate) developed multiple 1" hills and 2" valleys.
A 2" double-foil polyiso replacement with foil-taped edges has worked
fine so far. One polyiso ap engineer says it's good to at least 350 F,
when the surface starts to develop cosmetic wrinkles. But I think we
should replace both polycarbonate layers with greenhouse polyethylene
to lower the cost and assembly complexity and stagnation temperature.
I put some polyiso on top of a toaster oven, and it deformed badly...
Nick
Don't miss this opportunity to have every solar question you ever asked
answered in three different ways...
Join PE Drew Gillett and PhD Rich Komp and me for a workshop on Solar House
Heating and Natural Cooling Strategies at the first Pennsylvania Renewable
Energy Festival at 9 AM on Saturday September 24, 2005 near Allentown. See
http://www.paenergyfest.com/workshop-info.shtml
Posted by Gary on September 15, 2005, 9:29 pm
nicksanspam@ece.villanova.edu wrote:
>
>
>>...does a Poly-Isocyanurate persist two decades of the temperatures
>>that the collectors have? The max temperature of that insulation
>>material is about 300 deg F (150 deg C) - pretty near to the stagnation
>>temperature, or even below it for good collectors.
>
>
> When Gary sent me the nice solar pond water heater model he tested in
> Montana, I put it together in partial sun with the pump unpowered and
> had a meltdown :-) The 2" Styrofoam cover (under a layer of EPDM under
> 2 layers of polycarbonate) developed multiple 1" hills and 2" valleys.
Here are some additional (unintended) thermal sculptures.
http://www.builditsolar.com/Experimental/pinkfoam.htm
>
> A 2" double-foil polyiso replacement with foil-taped edges has worked
> fine so far. One polyiso ap engineer says it's good to at least 350 F,
> when the surface starts to develop cosmetic wrinkles. But I think we
> should replace both polycarbonate layers with greenhouse polyethylene
> to lower the cost and assembly complexity and stagnation temperature.
I like polycarbonate on the outside layer for weathering, durability,
impact resistance, AND the dog can't chew a hole through it to get to
a warm spot (like she did on my poly film sunspace) :-)
>
> I put some polyiso on top of a toaster oven, and it deformed badly...
>
> Nick
>
> Don't miss this opportunity to have every solar question you ever asked
> answered in three different ways...
>
> Join PE Drew Gillett and PhD Rich Komp and me for a workshop on Solar House
> Heating and Natural Cooling Strategies at the first Pennsylvania Renewable
> Energy Festival at 9 AM on Saturday September 24, 2005 near Allentown. See
>
> http://www.paenergyfest.com/workshop-info.shtml
>
--
Gary
www.BuildItSolar.com
gary@BuildItSolar.com
"Build It Yourself" Solar Projects
----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
Posted by nicksanspam on September 15, 2005, 10:09 pm
>I like polycarbonate on the outside layer for weathering, durability,
>impact resistance, AND the dog can't chew a hole through it to get to
>a warm spot (like she did on my poly film sunspace) :-)
That's OK too. Does your dog get to vote?
Nick
XML site map
>> A 4'x10' (3.5 m^2) collector goes for $26, which is about $50/m^2.
>> We are getting close (for my target $000 system)...
> Better, but still only 1" insulation. ;-)