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DANSAGE

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Posts: 3
Reply with quote  #41 
I have not done much since an earlier post in this thread about proposed collectors for our new house, due to monetary and time constraints.  I did purchase some duct board for use in the back of the collectors before it could go obsolete.  It is about 1" thick high temperature insulation with aluminum foil on one surface.  I tested it for high temperature behavior and got up to 400+ degrees  F. with just some charring and a bad smell.  I needed to know what would happen, if the power or the fans failed. 

Has anyone had any experience with the semi-selective paint Solkote?  I figured it might give as good or better performance on the backpass collectors as you are seeing on the screen types, since it would limit the heat loss through the glazing on the front of the collectors. 

Attached are a couple of house pictures (one with the 60 degree slanted solar collector wall).  

Dan Sage HV04.JPG  HV94.JPG

netttech

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Posts: 720
Reply with quote  #42 
I've not used the Solkote paint or heard of anyone using it. I viewed a video of the stuff on their website.

It may be better, but it depends on it's price. I've used the cheapest flat black to the hi-temp rustoleum paint. If there's a difference it's very minor.

Jeff
Central IL
Solar air & water
Garage_Hermit

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Reply with quote  #43 
@Julian for #40

Your phenomenon sounds very similar to one that I have noticed also, that I call OSCILLATION...

Namely, even in "constant sun", the temperature inside my vertical slate facade seems to "go up and down by a few degrees",
over a period of between two and five minutes.

(at least when the thermometer is not maxed out...)

So this a vertical collector, unglazed, with an air space behind the slates, where I have an alcohol thermometer on a one-meter stick.  Very scientific test set-up, I think you'll agree !

This is the "static temp" (no air is being extracted)
I have a second thermometer in proximity, that gives the ambient temp, and that one would not change at all, for the sake of comparison.

============

I get the exact same phenomenon on the roof SLOPE, namely oscillation.

(and we are talking about Several Tons of slate)
http://www.simplysolar.supporttopics.com/post/garagehermits-projects-6221962?pid=1279772148&highlight=tons+slate#post1279772148

This time, the temperature is dynamic, because I am pumping air.
Nonetherless, even in "constant sun", the temperature goes up and down over a two-minute period, by about one degree " - I refer to this as HUNTING.

I guess in scientific terms it is HYSTERESIS.

=========

I would hypothesize that ANY collector will produce the same phenomenon, due to natural period.
All materials vibrate, and some vibrate more than others, and most have a natural frequency, and I reckon a plate of glass or perspex is the same.

Even a road bridge will vibrate as traffic moves over it...

======== Added =====

In addition, quite apart from any collector-related phenomenon as suggested, there is wind, as you suggest, and I suppose there is also "irradiance quality"...

While we refer to "constant sun" in fact we can only *guess* (or rather the common mortals amongst us - bereft of laboratory equipment etc. -- can only guess -- that is why I use quotes...
In effect, I have no idea at all as to the actual amount of IR or wavelengths or UV etc. arriving at a given time, even if the sky "looks nice and unchanged" ,  I have read some place that the density of the solar flux changes also (like, the sun emits more energy at certain times of the year, solar bursts..., it goes daft for an afternoon (a bit like my kids sometimes...)

G_H


__________________
(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilĂ " unless talking musical instruments...
Julian Jameson

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Posts: 152
Reply with quote  #44 
I think GPS can be used to help determine atmospheric effects on electromagnetic radiation (at least to some extent). Not sure about the exact equipment requirements or how easy it would be to set it up, but if you know your exact location, you can compare that with what the GPS tells you it is. Any differences can imply signal scattering or diffusion somewhere between the receiver and the 20,000km high orbit of the GPS satellites.

I believe I have some detailed information about this, in a text book somewhere. I'll have to look it up when I get the chance. If it's something I can figure out and make good use of, I might be able to add it to the smartphone app I've been working on.

Quote:
Originally Posted by Garage_Hermit
@Julian for #40
In effect, I have no idea at all as to the actual amount of IR or wavelengths or UV etc. arriving at a given time, even if the sky "looks nice and unchanged" ,  I have read some place that the density of the solar flux changes also (like, the sun emits more energy at certain times of the year, solar bursts..., it goes daft for an afternoon (a bit like my kids sometimes...)

G_H

mattie

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Reply with quote  #45 
Not much to add here apart from i love that house and location.
Julian Jameson

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Posts: 152
Reply with quote  #46 
Here's some data from the last couple of weeks.

It's all based on averaged output per hour of each heater. Also, a couple of side-notes, I've been fiddling with the heaters and software during this time, so some differences may have been made by those alterations. And the weather has been, to put it bluntly, "crap". It's that time of the year, where the usual November gloom casts an undesirable shadow on ideal conditions for solar heating!


A table detailing the outputs in BTU/h:

DateHeater 1 (BTU/h)Heater 2 BTU/hTotal BTU
11/21/201412375.612951.825327.4
11/22/201414518.515137.129655.6
11/23/201411765.710339.122104.8
11/24/2014 280.3280.3
11/25/20149261.27924.517185.7
11/29/201413683.714393.928077.6
11/30/201463.21081.41144.6
12/1/20145527.34874.110401.4
12/2/20145993.68120.914114.5
12/4/201410874.613831.624706.2
    
Total (BTU/h):84063.388934.8 
Runtime(h)5153 


A graph that shows how the heaters compare with each other (it maps in to the days listed above):
H1vsH2Nov2014.jpg 

And here's a live stream of the current performance of the heaters (currently 10:10am here, with some cloud but a good amount of blue sky, 21.2F and some light snow is falling!):





netttech

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Posts: 720
Reply with quote  #47 
You mentioned clouds & agree that may the issue.

The weather has been crappy here also for solar heaters, projects.

This week I conducted a test of copper tubing for a parabolic project.I noticed a shift in recorded temps 1 minute apart between the 2 copper tubes. One lost 6 degrees, the other gained 5 degrees.

After 2-3 minutes the shift occurred again, only reversed. I then noticed I had hi-wispy clouds that wasn't visibly noticeable on the panel. I think even though the clouds didn't cast a 'shadow' it interacted with the materials of the tubing I was testing.

I wonder if that is what's occurring for you?
hi clouds.JPG 
Jeff
Central IL
Solar air & water

Julian Jameson

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Posts: 152
Reply with quote  #48 
This weekend, I implemented a light meter, which indicates sunlight strength in watts per sq. meter, to the Android App that I've been working on recently (which, believe me, is very exciting!). 

Hopefully, this will provide some usable data to indicate if it's variance in sunlight or other factors (e.g. variance in ambient temperature, or wind effects).

Quote:
Originally Posted by netttech


I wonder if that is what's occurring for you?
hi clouds.JPG 
Jeff
Central IL
Solar air & water
solardan1959

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Posts: 1,845
Reply with quote  #49 
Julian,
   This uses the light sensing stuff on the phone to determine sunlight strength and should work on most Android phones?  If so it does sound neat.

Dan
Julian Jameson

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Posts: 152
Reply with quote  #50 
That's right! It'll work with any android phone or tablet that has a light sensor (which is usually used to automatically adjust the brightness of the screen).

I'm also implementing all the other calculator functions (Celsius-Fahrenheit conversion, rise calculation, CFM from FPM/area, outlet area from dimensions, power output in BTUs or Watts, emissivity factor, output versus sun strength comparison, as well as wireless connectivity to my control system). It should be quite a useful tool!


Quote:
Originally Posted by solardan1959
Julian,
   This uses the light sensing stuff on the phone to determine sunlight strength and should work on most Android phones?  If so it does sound neat.

Dan
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