MY DIY project: solar air heater...
Posted: Fri Feb 12, 2021 12:18 pm
It is now nearly 10 years that I built and installed two solar air heater systems around the premises I rent, after I found out that the house is very damp, specially inside the cupboards. I bought ONE unit from a German producer (1,5 m2) in 2004 for my house in Italy, so I knew that they working perfect to reduce humidity in a big way. As I paid 2000 Euro that time for one single unit, I thought I could do that myself and much cheaper, as I wanted at least 10 m2 of the panels.
So I started my project with the idea to find out which type of solar collectors are most efficient and to built them cheap at the same moment.
I also thought that it would be a good business idea, to produce them in a larger scale here in Cyprus where the problem with damp houses is very common and for people which are not permanent in CY, a system like this, without electricity or maintenance would be great in their absence when the sun does the drying and heating for them.
My first attempt was that:
It would have been very cheap to produce, as it needed only 2 large trapezoidal sheets, painted black with fireplace paint, and mounted the 2 pieces, (the backs together), in order to achieve channels where air can transport the heat. But it failed: too much heat within minutes and the fan which moves the air into the house could not cope with a temperature of more than 70c and burnt. (outdoor temp was only 11c) So, as I could not find larger DC-fans to run with the solar module at higher performance, I stopped this idea.
I turned back to the more traditional version, which actually looks like the solar panels for hot water one can see on every Cyprus house roof. By luck I discovered that loads of old thermic panels were near my place dumped in a riverbed and piece by piece I transported 10 of them back to my house.
So I could even built 20 m2 of solar collectors with them not 10 which I planned in the first place.
I modified the inside of these old panels to make them more efficient by bending the coils and while open, I cut a 120 mm hole into the back in order to transport the hot air to the fan. Also some holes for the cold fresh air to enter, for circulation.
Panels where the glass was already broken, I used only the body and mounted the black sheets from my first project as collector.
Instead of the glass I found some special plastic sheets, however very expensive, 50 Euro one piece, but one can see how it looked ready, two different plastic quality and next to it the old modified panels.
In the end I came to the conclusion, after building another 6 units for the south side of the house, that the best way is the use of plastic sheets as a cover and to divide the panels in sections with several built in fans. I don't care that it does not look that pretty, but it does work and keeps the house dry and well ventilated and warmer than without. A warm bathroom, where the humidity after a shower is gone through the slightly open window in no time is perfect for me, no matter how it looks outside. Humidity in the whole house reduces from the start in the morning with more than 70 %RH on a sunny day within one hours or two, back to 45% RH which is great. So far in the last 10 years or so I had to replace only once more a heavy duty DC-fan, due to overheating in April... my fault not to cover the panels earlier for the summertime....
Max
So I started my project with the idea to find out which type of solar collectors are most efficient and to built them cheap at the same moment.
I also thought that it would be a good business idea, to produce them in a larger scale here in Cyprus where the problem with damp houses is very common and for people which are not permanent in CY, a system like this, without electricity or maintenance would be great in their absence when the sun does the drying and heating for them.
My first attempt was that:
It would have been very cheap to produce, as it needed only 2 large trapezoidal sheets, painted black with fireplace paint, and mounted the 2 pieces, (the backs together), in order to achieve channels where air can transport the heat. But it failed: too much heat within minutes and the fan which moves the air into the house could not cope with a temperature of more than 70c and burnt. (outdoor temp was only 11c) So, as I could not find larger DC-fans to run with the solar module at higher performance, I stopped this idea.
I turned back to the more traditional version, which actually looks like the solar panels for hot water one can see on every Cyprus house roof. By luck I discovered that loads of old thermic panels were near my place dumped in a riverbed and piece by piece I transported 10 of them back to my house.
So I could even built 20 m2 of solar collectors with them not 10 which I planned in the first place.
I modified the inside of these old panels to make them more efficient by bending the coils and while open, I cut a 120 mm hole into the back in order to transport the hot air to the fan. Also some holes for the cold fresh air to enter, for circulation.
Panels where the glass was already broken, I used only the body and mounted the black sheets from my first project as collector.
Instead of the glass I found some special plastic sheets, however very expensive, 50 Euro one piece, but one can see how it looked ready, two different plastic quality and next to it the old modified panels.
In the end I came to the conclusion, after building another 6 units for the south side of the house, that the best way is the use of plastic sheets as a cover and to divide the panels in sections with several built in fans. I don't care that it does not look that pretty, but it does work and keeps the house dry and well ventilated and warmer than without. A warm bathroom, where the humidity after a shower is gone through the slightly open window in no time is perfect for me, no matter how it looks outside. Humidity in the whole house reduces from the start in the morning with more than 70 %RH on a sunny day within one hours or two, back to 45% RH which is great. So far in the last 10 years or so I had to replace only once more a heavy duty DC-fan, due to overheating in April... my fault not to cover the panels earlier for the summertime....
Max