Sun warming system

[Finn Beardman]

I am living in an old country house 50 miles north of Helsinki. I have built a solar air collector to my sauna, and now I am building a sun warming system to the main house. The idea is to run the house warming system with the solar energy.
Here is a picture of my "sun collector" on my sauna. The other project is on the making, I hope to get it ready before the snow season.

 

[offgriddle]

How many watts will your house warming system require?

 

[gnubie]

Solar thermal, watts but of a different kind. I can appreciate wanting to do it with PV but I think black surfaces as a heat trap to heat up the air is a better idea if there isn't a specific need to produce electricity.

 

[svetz]

Hey Finn! Welcome to the forums!

What a great project!

Solar thermal, watts but of a different kind. I can appreciate wanting to do it with PV but I think black surfaces as a heat trap to heat up the air is a better idea if there isn't a specific need to produce electricity.

Hmm, is there a way to get both? PV Panels only convert ~20% to electricity, so the other 80% must be heat, right?

 

[Finn Beardman]

I use glass fiber cloth painted matt black (fire extinguishing sheet) as a heat trap. It would be easy to adjust a solar panel to trap heat, but...BUT... they can get very hot. I have reached 111C or 232F.

Check the end of my video as I measure it with a steak meter (all other meters failed)

 

[svetz]

That's impressive! Thanks for posting it! I've seen stuff with Mylar film (space blankets) in a parabolic reflector, but I'm unfamiliar with what you're doing there. How exactly does a solar air collector work?

 

[Supervstech]

That's impressive! Thanks for posting it! I've seen stuff with Mylar film (space blankets) in a parabolic reflector, but I'm unfamiliar with what you're doing there. How exactly does a solar air collector work?

They are similar to solar water heaters... without the water.
I have seen them made with ductwork tubes, soda cans, glass panels, plywood etc.

 

[Finn Beardman]

That's impressive! Thanks for posting it! I've seen stuff with Mylar film (space blankets) in a parabolic reflector, but I'm unfamiliar with what you're doing there. How exactly does a solar air collector work?

From outside to inside I use folloving materials:
Prices for one frame:
First: 4,5 mm thick dual wall polypropylene sheet, that is used in greenhouses. Price in Finland 45€
Second: Old window, 3mm glass Price in Finland free
Third: glass fiber sheet, painted matt black. Price in Finland 8,50 € + paint 2X 4.90€ (instead of matt black paint you can use laser printer black powder and some sprayable fixative.)
Plywood, 6mm Price in Finland 45€
Styrofoam 50mm Price in Finland 49 €
Wooden frame should be covered with thermal insulation also, use bubble wrap or whatever.
Cold Air is pumped down between the first and second, then up THROUGH the sheet. The blower fan should be assembled in the cold end.

Simple, cheap and easy to build.

 

[svetz]

So, your fiber sheets in the third layer look something like this? You sprayed the backs with the black matte, as described above? I know you said the first layer was 4.5mm deep; how deep is the 3rd layer?

Have you ever tried putting a PV panel at the 4th layer rather than spraying the backs black? Since the fiber sheets are used in green houses they should be transparent to much of the radiation a panel uses; I wonder what sort efficiency you might see from them?

 

[Finn Beardman]

The first layer only is made of this green house plastic board, the second layer is glass window, the third layer behind the window is glass fiber sheet, it is rather thin, maybe 1 mm only. The idea is to force the air through this mat painted sheet, air gets warm and goes to the "exhaust pipe". In my case I am going to steer the warm air to the air source heat pump (MITSUBISHI ELECTRIC LN 25) which is powered by solar or grid, depending on how I can get electricity stored.

 

[Finn Beardman]

Today I assembled a temporaly duct fan to one of the screens. Result, with a fan ON, it blows 61C or 142F. The weather is sunny, thin clouds. Outside temperature is +6C or 43F

 

[gnubie]

Very nice.

 

[Supervstech]

The first layer only is made of this green house plastic board, the second layer is glass window, the third layer behind the window is glass fiber sheet, it is rather thin, maybe 1 mm only. The idea is to force the air through this mat painted sheet, air gets warm and goes to the "exhaust pipe". In my case I am going to steer the warm air to the air source heat pump (MITSUBISHI ELECTRIC LN 25) which is powered by solar or grid, depending on how I can get electricity stored.

View attachment 1105

That is brilliant!
Have the solar heat air fed to the condenser.
It should help the unit output more heat in low ambients.

 

[Finn Beardman]

All the components except batteries have been bought. I wonder if these solar cells are too much to my Solar Charge controller. I have three of these:

 

[gnubie]

Can you post the make & model of the SCC?

 

[Finn Beardman]

My "solar shed" looks like this today.


These are my components so far:

 

[Finn Beardman]

Can you post the make & model of the SCC?

Epever 4210AN 12/24v
current 40A
max pv 100V
max pv input power 520w/12v 1040w/24v

 

[gnubie]

In series those panels exceed the solar input voltage rating of the Epever but in parallel they are OK. The output rating of the Epever is based on the battery voltage.

If you have a 12 volt battery you will potentially be discarding a lot of the panel's output (930 watts peak) as the Epever can only supply 520 watts into a 12 volt battery. The Epever will current limit at 40 amps.

If you have a 24 volt battery the full output of the panels can be delivered.