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Jimmy

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Posts: 17
Reply with quote  #1 
Hi,

 I'm writing from Hungary and I've made my first steps in solar inspired by the projects written here and the builidtsolar.com homepage. (sorry if my english is not perfect)
So my garage has been recently built and as it has no heating I wanted to have a solar solution.
A friend has alredy built a can collector, but it is a bit complicated and one have to drink a lot of beer. [smile]
The screen collector was chosen as a solution, and I have tried to build a 'matrix' setup. The 1m x 2m frame has 4 0,6m x 1m screens inside. As the collector is mounted on the wall I have thought to tilt the 4 panels in a way that they are somewhat otrhogonal to the sun. But reading more and more I'm now not convinced that this is how it should be. Or If I have to change for a single big panel.
The wall is facing south, so it is perfect.
I have drilled 2 100mm wholes on the wall. Inside the garage there is a Suzuki Ignis heating motor which circulates the air. (with some filter)
I have programmed a small microcontroller to check the 2 temperature sensors (one in the garage, and one in the outcome of the collector) and if the output is at least 15C warmer than the input, turn the motor on. But I think I should increase this temp differenece.
 So collector is made of wooden frame, the back has some heat isolation, and the glasing is polycarbonate.

Here are some pics:

[collector] 
[collector_2] 

[motor] 

[out] 

It is 'working', it can heat up the garage by 1-2 degrees on a sunny day. (35m2, 80m3) (Which is nearly lost on a cold night.)
But I think I'm far away from perfect. I hope I can further increase the efficiency of the collector, or maybe I can even double the size.
So I'm really curious about your comments, hints, how to improve.
Many thanks.

solardan1959

Avatar / Picture

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Posts: 1,845
Reply with quote  #2 
Jimmy,
  Nice collector, controller, fan setup.  To bad about the size since you have more room, bigger would have been better.  Welcome to the site and thanks for the input.

Dan

added,
You mentioned,
Quote:
(Which is nearly lost on a cold night.)
  Of course things will cool off at night depending on the building and insulation but do you have any type of reverse flow protection?  With your set up the air will cool off at night and sink in the collector. This will pull in the warmer air from the building through the top vent and then come back in on the lower vent.  I do see the flaps on the output which will help quite a bit, just not sure how well they seal.

KevinH

Registered:
Posts: 547
Reply with quote  #3 
Jimmy,
Welcome to Simply Solar and congratulations on your first collector.  Do you have any pictures of the inside of the collector when you were building it?

Although there are things that can improve the performance, the output is mostly determined by the collector size.

Until you can build a larger (or second) collector, you could put a reflector below the collector.  It looks like you have plenty of room.  A reflector will increase the output temperature.  Do a Search for "reflector" here on Simply Solar or on BuildItSolar.

Kevin H
MN
Jimmy

Registered:
Posts: 17
Reply with quote  #4 
Thanks for the reflector idea.
I have give it an immediate try. [smile]

[reflector] 
I have used the tables on builidtsolar, to try to set the correct angle.
Size was limited on the parts I have found laying around. [smile]
This is a heat reflective foil used for roof isolating.
And as a first try it gave a very good improvement.
I was measuring the output temp of the collector, and the day before (without reflector) it was 35.5C peak, but today 40.9C. It was two very similar full sunny day. (Which is very rare in the last weeks.)
Jimmy

Registered:
Posts: 17
Reply with quote  #5 
Quote:
Originally Posted by solardan1959
Jimmy,

You mentioned,
Quote:
(Which is nearly lost on a cold night.)
  Of course things will cool off at night depending on the building and insulation but do you have any type of reverse flow protection?  With your set up the air will cool off at night and sink in the collector. This will pull in the warmer air from the building through the top vent and then come back in on the lower vent.  I do see the flaps on the output which will help quite a bit, just not sure how well they seal.



I only have those flaps.
How can I improve that?
Shall I build in similar flaps to the lower vent?
gbwillson

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Posts: 2,128
Reply with quote  #6 
Jimmy-

Nice experiment with the reflector. You may want it 3-4 times as wide so the sun will reflect throughout the day. Also, having the reflector on the ground may be a simpler solution, though you will have to move the reflector away from the house.

If I have only one flapper/damper or back flow valve, I put it on the low, or cold side. But nothing says you can't have one for both openings. Take a look at this damper.

http://simplysolar.supporttopics.com/file?id=1702485

Greg in MN[thumb]
Jimmy

Registered:
Posts: 17
Reply with quote  #7 
Thanks Greg for this advice.
I'll add something to the cold side also.

As the consturction of the garage has recently finished I do not have such a smooth ground where I can lay those reflectors. But now I see how much potential it has.

And I also have to take a step in air flow measurement. My feeling is that the current air flow is weak.
I do not have any info about the motor I use. (And it currently have some serial resistors in, becuase the power supply I have delivers only 4A)
I'll measure with a battery the full current need.

Should this air flow be matched to the size of the collector? Should I try to set it in a way (using PWM controll) to have a constant output temperature (like 30C more then the input)?
Or should it be matched to the air volume in the garage? And do not care too much about the temperature difference.

I have already read about the possible ways to measure flow. And I think the only applicable would be to measure the indicated voltage on a fan. But even I'd know that it indicates 2V or 3V I still don't know the exact flow. [frown]

And a last thing I've been thinking of if I should place the motor to the warm or to the cold side.

Thanks [smile]

(I have just both my first arduino board with lan shield to ba eble to collect temp. data and store them.)
KevinH

Registered:
Posts: 547
Reply with quote  #8 
A small mirror can be used to set the reflector angle.  Place the mirror flat on the reflector and you can easily see where that area is reflecting onto the collector.  The way you have the reflector at the bottom edge of the collector will give the best results.

Kevin H
MN
Jimmy

Registered:
Posts: 17
Reply with quote  #9 
Quote:
Originally Posted by KevinH
A small mirror can be used to set the reflector angle.  Place the mirror flat on the reflector and you can easily see where that area is reflecting onto the collector.  The way you have the reflector at the bottom edge of the collector will give the best results.

Kevin H
MN


Thanks again!
I'll take a mirror and try to set up the angle.
As a first guess the thither end of the reflector should be lower than as it is?
mclark999

Registered:
Posts: 165
Reply with quote  #10 
Quote:
Originally Posted by Jimmy


I have programmed a small microcontroller to check the 2 temperature sensors (one in the garage, and one in the outcome of the collector) and if the output is at least 15C warmer than the input, turn the motor on. But I think I should increase this temp differenece.
   
I.


I would use a snap switch mounted inside the collector near the output vent instead for turning the motor on. Any time it reaches around 37 degrees C, it turns on and runs until it drops by a few degrees.  


See this topic for more information. http://www.simplysolar.supporttopics.com/post/snap-disc-fan-switch-in-hot-air-collector-best-location-7127635?highlight=snap+switch&pid=1285440172#post1285440172



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Double screen hot air collector
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