Alternative Power sources - Low-E, was Cooling swimming pool in high temp

Author

Low-E, was Cooling swimming pool in high temp

Loren Amelang

2006-04-14, 5:21 pm

On Fri, 14 Apr 2006 13:55:21 -0400, "Solar Flare"
<solfart@hotomale.invalid> wrote:

>Low E is not made directional. It is made to block different
>wavelengths of infrared more than others.

My understanding is that "low emissivity" means just that - the
coating is not primarily a filter (though it does reduce transmission
of incoming radiant energy). The purpose of a low emissivity coating
is to reduce the heat re-radiated from the coated glass surface as a
result of the glass itself being hot.

In climates where you want to minimize summer cooling requirements,
you coat the second surface (counting from outside). The glass layer
that is touching the hot outdoor air then re-radiates less heat toward
the house. To minimize winter heat loss, you coat the third surface,
so the layer you've artificially heated doesn't radiate as much out
the window.

I've never seen an explanation of why you couldn't coat both
surfaces...

But in the original case of maximizing heat loss, you'd want to coat
your radiator with a "high emissivity" coating, like black paint or
its higher-tech derivatives.

Loren

clare at snyder.on.ca

2006-04-14, 6:21 pm

On Fri, 14 Apr 2006 12:18:17 -0700, Loren Amelang <loren@pacific.net>
wrote:

>On Fri, 14 Apr 2006 13:55:21 -0400, "Solar Flare"
><solfart@hotomale.invalid> wrote:
>
>
>My understanding is that "low emissivity" means just that - the
>coating is not primarily a filter (though it does reduce transmission
>of incoming radiant energy). The purpose of a low emissivity coating
>is to reduce the heat re-radiated from the coated glass surface as a
>result of the glass itself being hot.
>
>In climates where you want to minimize summer cooling requirements,
>you coat the second surface (counting from outside). The glass layer
>that is touching the hot outdoor air then re-radiates less heat toward
>the house. To minimize winter heat loss, you coat the third surface,
>so the layer you've artificially heated doesn't radiate as much out
>the window.
>
>I've never seen an explanation of why you couldn't coat both
>surfaces...

Never hheard of low-E-squared" or Low-E-^2" glass? Not on both
surfaces, but limits emissivity in both directions.
>
>But in the original case of maximizing heat loss, you'd want to coat
>your radiator with a "high emissivity" coating, like black paint or
>its higher-tech derivatives.
>
>Loren

*** Posted via a free Usenet account from http://www.teranews.com ***

Solar Flare

2006-04-14, 8:21 pm

Effectively the heat from the sun can enter the window but not get
back out due to the wavelength being changed.

The thermal radiation enters as one wavelength and is reradiated at a
different one that the Low E coating doesn't pass as well.

<clare at snyder.on.ca> wrote in message
news:ov2042t4ko4p2nuhdbgbldjrvcbt4sm9m4@4ax.com...
> On Fri, 14 Apr 2006 12:18:17 -0700, Loren Amelang
<loren@pacific.net>
> wrote:
>
transmission[color=darkred]
coating[color=darkred]
a[color=darkred]
layer[color=darkred]
toward[color=darkred]
surface,[color=darkred]
>
> Never hheard of low-E-squared" or Low-E-^2" glass? Not on both
> surfaces, but limits emissivity in both directions.
coat[color=darkred]
>
> *** Posted via a free Usenet account from http://www.teranews.com
***

Duane C. Johnson

2006-04-15, 12:21 am

Hi Solar;

Solar Flare <solfart@hotomale.invalid> wrote:

> Effectively the heat from the sun can enter the
> window but not get back out due to the wavelength
> being changed.

The sun does not transmit "heat" to us.
Heat is mechanical motion of atoms and molecules.
There are nearly none of these in space.
The sun sends us light or more properly
electro-magnetic radiation. Not heat.

> The thermal radiation enters as one wavelength

This is the problem there is no such thing as
"thermal radiation". There is infra red radiation
though.

Besides infra red radiation is only about 1/2 of the
power the sun delivers. The other half is visible
light.

> and is reradiated at a different one that the
> Low E coating doesn't pass as well.

Duane

--
Home of the $35 Solar Tracker Receiver
http://www.redrok.com/led3xassm.htm [*]
Powered by \ \ \ //|
Thermonuclear Solar Energy from the Sun / |
Energy (the SUN) \ \ \ / / |
Red Rock Energy \ \ / / |
Duane C. Johnson Designer \ \ / \ / |
1825 Florence St Heliostat,Control,& Mounts |
White Bear Lake, Minnesota === \ / \ |
USA 55110-3364 === \ |
(651)426-4766 use Courier New Font \ |
redrok@redrok.com (my email: address) \ |
http://www.redrok.com (Web site) ===

Solar Flare

2006-04-15, 12:21 am

The sun doesn't deliver anything. It doesn't even move closer to the
earth.

I prefer the plain infra radiation and it is never a form of power. It
is a form of energy.

Go back to sleep.

Please don't top post.

"Duane C. Johnson" <redrok@redrok.com> wrote in message
news:44405C0D.4070105@redrok.com...
> Hi Solar;
>
> Solar Flare <solfart@hotomale.invalid> wrote:
>
>
> The sun does not transmit "heat" to us.
> Heat is mechanical motion of atoms and molecules.
> There are nearly none of these in space.
> The sun sends us light or more properly
> electro-magnetic radiation. Not heat.
>
>
> This is the problem there is no such thing as
> "thermal radiation". There is infra red radiation
> though.
>
> Besides infra red radiation is only about 1/2 of the
> power the sun delivers. The other half is visible
> light.
>
>
> Duane
>
> --
> Home of the $35 Solar Tracker Receiver
> http://www.redrok.com/led3xassm.htm [*]
> Powered by \ \ \ //|
> Thermonuclear Solar Energy from the Sun / |
> Energy (the SUN) \ \ \ / / |
> Red Rock Energy \ \ / / |
> Duane C. Johnson Designer \ \ / \ / |
> 1825 Florence St Heliostat,Control,& Mounts |
> White Bear Lake, Minnesota === \ / \ |
> USA 55110-3364 === \ |
> (651)426-4766 use Courier New Font \ |
> redrok@redrok.com (my email: address) \ |
> http://www.redrok.com (Web site) ===

Duane C. Johnson

2006-04-15, 10:21 am

Hi Solar;

Solar Flare <solfart@hotmail.com> wrote:

> The sun doesn't deliver anything.

Ok, poor choice of words. It does radiate
power to Earth though.

> It doesn't even move closer to the earth.

Sure it does, well actually the Earth and Suns
distance does change throughout the year. We are
closest to the Sun about January 6th or so.

> I prefer the plain infra radiation and it is
> never a form of power. It is a form of energy.

Of course solar radiation is a form of power.
You can't store light to build up energy.

Solar energy is a misnomer.
Solar power can be collected and converted to
hear or other things that can be stored. However,
we can't tell where the power originated for
these stored energies.

> Please don't top post.

I didn't and usually don't.
I mostly use imbedded posting style.

Duane

--
Home of the $35 Solar Tracker Receiver
http://www.redrok.com/led3xassm.htm [*]
Powered by \ \ \ //|
Thermonuclear Solar Energy from the Sun / |
Energy (the SUN) \ \ \ / / |
Red Rock Energy \ \ / / |
Duane C. Johnson Designer \ \ / \ / |
1825 Florence St Heliostat,Control,& Mounts |
White Bear Lake, Minnesota === \ / \ |
USA 55110-3364 === \ |
(651)426-4766 use Courier New Font \ |
redrok@redrok.com (my email: address) \ |
http://www.redrok.com (Web site) ===

Loren Amelang

2006-04-15, 8:21 pm

On Fri, 14 Apr 2006 16:56:28 -0400, clare at snyder.on.ca wrote:

>On Fri, 14 Apr 2006 12:18:17 -0700, Loren Amelang <loren@pacific.net>
>wrote:
....
>
>Never hheard of low-E-squared" or Low-E-^2" glass? Not on both
>surfaces, but limits emissivity in both directions.

I hadn't. After about an hour of Googling, I still don't know exactly
what that term means. Some people seem to be using it to identify
"soft coat" or sputtered Low-E as opposed to "hard coat" (pyrolytic
CVD) Low-E. Several pages seemed to imply that the "Low-E^2" name is
proprietary to Cardinal Glass, while others use "Low-E2" and "Low-E^2"
interchangeably.

As I've heard some places before,
<http://www.cardinalcorp.com/data/Re...st-133_1020_0_0>
says:
-----
The U-factor does not change whether the coating is on surface 2 or 3.
-----

But their page on solar heat gain coefficient
<http://www.cardinalcorp.com/data/Re...st-133_1047_0_0>
gives numbers showing more summer heat gain with #3 coated., and
<http://www.arkema-inc.com/index.cfm?pag=84>
repeats the "surface matters" explanation:
-----
Low E glass coatings work by reflecting or absorbing IR light (heat
energy). The thickness of the Low E coating and the position in the
window (#2 or #3 surface) dictate how the window will perform.
When installed on the #3 surface of an insulated glass unit (IG), the
Low E coating will reflect IR heat from inside the room to help reduce
the energy loss during the cold months, thereby reducing heating
costs.
When installed on the #2 surface of an IG unit, the Low E coating will
reflect or absorb IR heat from the outside, thereby reducing solar
gain and cooling costs during the warm months.
-----

Back at the Cardinal site,
<http://www.cardinalcorp.com/data/Re...st-133_1007_0_0>
says:
-----
LoE² coatings on the other hand are solar selective, and will commonly
be referred to a low solar gain product. The multiple layers within
the LoE² coating block solar infrared while allowing the visible
energy to pass through the glass.
-----

Perhaps the confusion arises from companies using the term "Low-E" as
a generic identifier for "solar selective" coatings as well as for
coatings that modify long-wave IR (sensible) emissivity?

I could believe that when a high-emissivity surface and a low
emissivity surface face each other, the resulting long-wave sensible
heat transfer is the same regardless of the heat transfer direction -
limited by the lower of the two values. I believe that is the
"U-factor".

I could also believe that if more short-wave IR solar radiation is
reflected away by a coating on surface 2, less of it will hit surface
3 to be absorbed and raise the inner glass temperature. If surface 3
has the Low-E coating, the energy that is not reflected from it has
already contributed heat to the inner glass. The re-radiation from the
inner glass surface adds to the solar heat gain coefficient.

I haven't seen a standard quantity that identifies how much of the
solar heat gain coefficient is due to this re-radiation, and how much
is due to the overall transmission or reflection of solar IR,
regardless of which surface is coated. I suspect the larger component
of SHGC is due to the wavelength of the emissivity cutoff the coating
provides. Cold climate "Low-E" allows shorter (solar) IR wavelengths
to pass but traps longer (sensible) IR wavelengths indoors. Hot
climate solar selective coatings block both sensible and solar IR,
moving the cutoff up to allow only visible light through.

I guess companies feel they need to simplify this for the consumer...
Finding out what is really going on certainly isn't simple! I hope I'm
getting closer.

Loren

LinkBot