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Author Topic: Small solar air heater  (Read 6762 times)

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phpenguin

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Small solar air heater
« on: December 19, 2014, 08:23:47 AM »
Hi,

I've been testing it for a week so far. Temperature of the heat chamber rises upto 50 Celsius degrees when it's sunny, drops near zero Celsius degree when it's cloudy and cold weather. Basically this type of solar air heater is supplementary device that reduces overall heating cost in a house or structure.   

The beauty of the solar air heater is it's very easy to build, relatively cheap under $50 USD at most. You can use any metal objects as the heating element coated with black paint. For thermal insulation to improve performance of the heater I chose a roll of radiant barrier and card board boxes which were cheap. I didn't put these yet.

Dimension of the solar air heater is width 50 cm, height 80 cm, depth 11 cm.

Bill of Materials

1x Black oil paint, 1L ? 5,000 KRW (Currency of South Korea)
1x Silicon paste, 250mL ? 2,000 KRW
2x 500mm x 400mm, thickness 5mm glass plate ? 20,000 KRW
40+x Aluminium can
(Collected aluminum cans on the streets and from recycle bin)
2x L-shape metal bracket ? 600 KRW
1x metal exhaust port ? 1,000 KRW
1x Small paint brush

6x square wooden block
12x M6x60 bolt
12x M6 nut
12x M6 lock washer
24x M6 washer
12x Wood screw

2x wooden bar
2x M6x60 bolt
2x M6 nut
4x M6 washer

1x 12V fan
1x 12V@2A power supply
13mm thickness of MDF board
(used previous door panel)













cheerio

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Re: Small solar air heater
« Reply #1 on: December 20, 2014, 22:21:34 PM »
if you use it in winter you should seal it up perfectly and suck out all the air you can get out of the box. this would help you to get a good result even on cloudy days.
actually i am surprised it works as good as it does right now O_O

phpenguin

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Re: Small solar air heater
« Reply #2 on: December 21, 2014, 02:37:41 AM »
I'll use the radiant barrier and cardboard as thermal insulation.





cheerio

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Re: Small solar air heater
« Reply #3 on: December 24, 2014, 04:50:14 AM »

kam

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Re: Small solar air heater
« Reply #4 on: December 29, 2014, 00:03:58 AM »
I saw this post, looked at the mirror and saw this light bulb above my head... I think an idea popped out! In Greece we have sun like almost all year. Its time to do some calculations...

phpenguin

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Re: Small solar air heater
« Reply #5 on: January 17, 2015, 22:58:20 PM »
It's in full operation! :)

I added insulation on it with cardboard and radiant barrier.

Layer of cardboard


Layer of radiant barrier




I used pairs of washer and screw instead glue to secure the insulation materials.






It's pumping out warm air around twenty three Celsius degrees.


The outdoor temperature was between two and four Celsius degrees.


Food of thoughts:

Solar panel to supply power to the fan during blackout situation
How to improve heat efficiency?
I think close loop air circulation system generates warmer air than heating up cold air all the time.
I'll post simple drawing to do it.

cheerio

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Re: Small solar air heater
« Reply #6 on: January 18, 2015, 18:28:48 PM »
nice one!

kam

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Re: Small solar air heater
« Reply #7 on: January 19, 2015, 21:55:31 PM »
Definitely close loop. Also, I'd like to see some calculations on the efficiency of the system. You can do this by assuming that most of the heat energy is transferred by heating the water (moisture) in the air. So, you can calculate how much energy the system provides by knowing the temperature difference (in your case i think it is about 20oC), the humidity and the air volume you pump out. The heat capacity of water is 4.2 kJ/kg.K (or 1.167 Wh/kg.K), which means that you have to provide 4.2KJ of energy to heat one kilo of water for one degree K (or Celsius).

If relative humidity is say 30% and you pump 1000 liters per hour of air, this means that every hour you heat up 300 liters of water (roughly 300 kg) for 20 degrees. So the power that you pump out of the system is 1.167 x 300 x 20 = 7KW,which is a ridiculously high amount of power for such a small system. So, what is the catch?



Please correct my calculations if i'm wrong because lately i make a lot of mistakes... It seems that i'm getting old :///

phpenguin

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Re: Small solar air heater
« Reply #8 on: January 21, 2015, 05:21:14 AM »
@kam

Your question is out of my head honestly. The solar air heater barely warms up the small room which I converted into a workshop. I consider it as a small stove under few hundred watts of power at most. My guess is that three to four of the air heaters can produce enough air flow that increase the room temperature five to six degrees at most.

When ambient temperature is near zero degrees, i.e. 2 Celsius degrees, to heat up one liter of water requires additional energy that needs to compensate heat loss caused by surrounding environment, which is many times bigger than water heating. I think running a 2kW of electric stove in my workshop wouldn't raise the room temperature above 15 Celsius degrees. And I'll have outrageous electric bill over few hundred dollars per month.  :o The power company charges five to six times higher rate to house owners.

According to Miachael Rynolds thermal mass is secret of sustainable building.

Earthship by Michael Reynolds. (http://earthship.com/)



Earthships on Democracy Now!
http://youtu.be/Qy6cs0h4_74

Mike Reynolds Garbage Warrior
http://youtu.be/QVX2wdDH19Y

cheerio

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Re: Small solar air heater
« Reply #9 on: January 22, 2015, 01:19:23 AM »
i like your spirit!
Where do you live?