solar thermal heating
- Thread starter forgeblast
- Start date
GaryGary
New member
OP
forgeblast
Elite Member
The screen will tend to spread the inlet air out over the full surface as there is a bit of pressure drop across the screen, but it seems like you are asking a lot of the screen.
**should I then use the soffit along with the screen?
I'd think about doing two collectors with the dividing line extending down from the center of the window. The inlets for the two collectors could be a common inlet under the center of the window and down by the floor. The collector outlets could be upper right and upper left. It seems like this might give a better chance of getting good flow to the full collector?
I like this idea, It would be an easier sell, I think, to my wife.
, this level of airflow will give you about a 50 to 60F temp rise with good sun.
***Is this from the outside air temp? or what is already inside?
If you want the fan to be quiet, then bigger (larger diameter) is generally better.
With the fans pulling the air out, would i be able to then get away with using a heavier dampner, ie dryer vent as opposed to the plastic that you have used?
Thank you so much for all your info already. I was talking to the wife and she said "make sure you post that im skeptical and I want to see pictures of what it will look like on the inside".
I went to build it solar and she has a much better idea, ty again. I am also going to try to find wooden cover for the fans.
The fans should I be looking at bathroom vent fans or a different type of fan?
ty once again.
**when you use the screening do you also use baffles to control the direction of the air flow. how do you control the flow with the al soffit?
these are two fan styles that i found.
http://compare.ebay.com/like/230511...ff16e93&itemid=230511560762&ff4=263602_304662
http://www.hvacquick.com/products/r...-Register-Boosters/Suncourt-Room-to-Room-Fans
**should I then use the soffit along with the screen?
I'd think about doing two collectors with the dividing line extending down from the center of the window. The inlets for the two collectors could be a common inlet under the center of the window and down by the floor. The collector outlets could be upper right and upper left. It seems like this might give a better chance of getting good flow to the full collector?
I like this idea, It would be an easier sell, I think, to my wife.
, this level of airflow will give you about a 50 to 60F temp rise with good sun.
***Is this from the outside air temp? or what is already inside?
If you want the fan to be quiet, then bigger (larger diameter) is generally better.
With the fans pulling the air out, would i be able to then get away with using a heavier dampner, ie dryer vent as opposed to the plastic that you have used?
Thank you so much for all your info already. I was talking to the wife and she said "make sure you post that im skeptical and I want to see pictures of what it will look like on the inside".
I went to build it solar and she has a much better idea, ty again. I am also going to try to find wooden cover for the fans.
The fans should I be looking at bathroom vent fans or a different type of fan?
ty once again.
**when you use the screening do you also use baffles to control the direction of the air flow. how do you control the flow with the al soffit?
these are two fan styles that i found.
http://compare.ebay.com/like/230511...ff16e93&itemid=230511560762&ff4=263602_304662
http://www.hvacquick.com/products/r...-Register-Boosters/Suncourt-Room-to-Room-Fans
Last edited:
hr3
Veteran Member
The inside of mine looks like any other warm air grill you see in the floor or ceiling.. Do you have a cellar window near where you want to put your panel...If so look at the pic I posted,, Supply and return both through the window opening ..
OP
forgeblast
Elite Member
I did see your pic hr3, i wish i had a basment window there, it would have helped, but we have no windows on that side (basement wise).
So you ran yours through the basement window and then up through the floor?
So you ran yours through the basement window and then up through the floor?
hr3
Veteran Member
Yes ,, The basement on this side of the house is finished off and there are three rooms all part of the master bedroom above .. The cold air supply comes from the exercise room out to the panels then back into the hot tub room as soon as this area is warm enough a damper closes and supply's heat to the master bedroom .. It does very well,, Also in the summer I will run it manually to cool the bedroom at night.. Mine are vertical and do not get hot in the summer and in the winter the sun is so low they work fine,, even better with snow on the ground..
I used a fantech fg series very quiet and fully speed adjustable..
Even if you don't have windows on the side you want to put it you should still have rim joist space enough to exit and enter..
GaryGary
New member
Hi,
Some comments embedded below at the --> marks:
The screen will tend to spread the inlet air out over the full surface as there is a bit of pressure drop across the screen, but it seems like you are asking a lot of the screen.
**should I then use the soffit along with the screen?
--> I'd say probably not.
I think you would be better off with dividing the collector in two.
If the top of the collector was not interrupted by the window, I'd say an alternative would be to have plenums either along the top and bottom or vertical ones at the right and left edges, but the window makes either of those questionable.
You might think about adding a third layer of screen this might improve the thermal efficiency a bit, and would give a little more pressure drop that would help spread the air better.
Bear in mind that there is just not a lot of material out there on how air really behaves in these collectors -- about the best you can do is make an educated guess.
I'd think about doing two collectors with the dividing line extending down from the center of the window. The inlets for the two collectors could be a common inlet under the center of the window and down by the floor. The collector outlets could be upper right and upper left. It seems like this might give a better chance of getting good flow to the full collector?
I like this idea, It would be an easier sell, I think, to my wife.
, this level of airflow will give you about a 50 to 60F temp rise with good sun.
***Is this from the outside air temp? or what is already inside?
--> That's along the lines of room air enters the inlet at about 65F, and leaves the collector at about 120F in good sun conditions. You won't get that kind of temp rise in part sun, or in the early morning or late afternoon, and you don't want the temp rise to get so low that the air feels cool because its moving. But you also don't want too much temperature rise, as this means the absorber is running hot, and is losing a lot of heat out the glazing -- this is important as this heat loss out the glazing is most of the reason that collectors run at 50% or so efficiency rather than 90%.
With the fans pulling the air out, would i be able to then get away with using a heavier dampner, ie dryer vent as opposed to the plastic that you have used?
--> Yes, I think so.
Either pushing or pulling, fan forced collectors can use dampers that require more pressure to open than thermosyphon collectors.
You just want to make sure the inlet and outlet vents and the damper opening are not too small as this will cause pressure drop and less flow.
Thank you so much for all your info already. I was talking to the wife and she said "make sure you post that im skeptical and I want to see pictures of what it will look like on the inside".
I went to build it solar and she has a much better idea, ty again. I am also going to try to find wooden cover for the fans.
--> On the making the collector look better front:
- If you have clear glazing like SunTuf or glass, you will see the screens, and to some degree the color of the back wall of the collector.
The screens actually look pretty good -- kind of a nice soft look.
The screen collectors (I think) look better if you don't paint the back wall black, but choose some medium dark color that matches the house.
On my barn screen collector, you can in the pictures that it does not have the "big black square" look because you see the siding color a bit through the screen. The collector would likely be just a bit more efficient with the black back wall, but (for me) the aesthetic gain outweighs the small efficiency increase.
- Another option is to use twinwall glazing. I think it has a really nice look, and you don't see the internals of the collector through it. If you are in a cold climate it also adds a bit of efficiency. If you can find a good local source, it does not add all that much to the cost -- a good price is about $1.80 a sqft. I'd use 10mm thick or thicker.
greenhouse cover glazing materials at reasonable cost
Shipping is a killer on this stuff, so local is best if you can.
- The trim around the outside of the collector makes a big difference
on how the collector looks. I kind of like the PVC wood or deck wood, as they look pretty good, and they have a good life.
-- Couple of examples of (I think) nice looking collectors:
This is my new solar water heating collector glazed with twinwall:
A Simple DIY Solar Space and Water Heating System
The page is not done yet, but there are a few pictures that show the look.
This is Knick's collector:
A $1K Solar Water Heating System that Looks Great
twinwall with a nice frame.
The fans should I be looking at bathroom vent fans or a different type of fan?
ty once again.
**when you use the screening do you also use baffles to control the direction of the air flow. how do you control the flow with the al soffit?
--> the vented alum soffit and the screen collectors work the same way. The vent holes in the soffit act the same way as the holes in the screen.
I guess that the ones I've seen (not that many large ones) did not use baffles, and I'm not sure how you would use baffles with flow on both sides of the screen/soffit? They tend to rely on the pressure drop across the screen or soffit to distribute the air. Again, I've not seen anyone who has actually done the work to see exactly where the flow does go, but it does make some sense.
I've actually ordered 16 small thermistor temperature sensors that I can glue to the absorber screen on my 4 by 8 test collector to see how much variation there is in absorber temp -- areas not getting much airflow should show up as hot spots on the absorber.
these are two fan styles that i found.
http://compare.ebay.com/like/2305115...=263602_304662
HVACQuick - residential
--> I could not find a fan curve for either of these. The first one looks promising -- I did email them to ask for a fan curve and/or flow at 0.2 inches of water pressure drop.
Someone mentioned the Fantech FG -- this is the brochure:
http://fantech.net/docs-resi/450286-fg-brochure.pdf
There is a fan curve in the brochure -- it looks like the FG6 would have plenty of grunt -- maybe more than is really needed for your collector? I think it was mentioned that its a quiet fan, and that's a big plus.
Gary
Last edited by forgeblast; Today at 10:08 AM.
Some comments embedded below at the --> marks:
The screen will tend to spread the inlet air out over the full surface as there is a bit of pressure drop across the screen, but it seems like you are asking a lot of the screen.
**should I then use the soffit along with the screen?
--> I'd say probably not.
I think you would be better off with dividing the collector in two.
If the top of the collector was not interrupted by the window, I'd say an alternative would be to have plenums either along the top and bottom or vertical ones at the right and left edges, but the window makes either of those questionable.
You might think about adding a third layer of screen this might improve the thermal efficiency a bit, and would give a little more pressure drop that would help spread the air better.
Bear in mind that there is just not a lot of material out there on how air really behaves in these collectors -- about the best you can do is make an educated guess.
I'd think about doing two collectors with the dividing line extending down from the center of the window. The inlets for the two collectors could be a common inlet under the center of the window and down by the floor. The collector outlets could be upper right and upper left. It seems like this might give a better chance of getting good flow to the full collector?
I like this idea, It would be an easier sell, I think, to my wife.
, this level of airflow will give you about a 50 to 60F temp rise with good sun.
***Is this from the outside air temp? or what is already inside?
--> That's along the lines of room air enters the inlet at about 65F, and leaves the collector at about 120F in good sun conditions. You won't get that kind of temp rise in part sun, or in the early morning or late afternoon, and you don't want the temp rise to get so low that the air feels cool because its moving. But you also don't want too much temperature rise, as this means the absorber is running hot, and is losing a lot of heat out the glazing -- this is important as this heat loss out the glazing is most of the reason that collectors run at 50% or so efficiency rather than 90%.
With the fans pulling the air out, would i be able to then get away with using a heavier dampner, ie dryer vent as opposed to the plastic that you have used?
--> Yes, I think so.
Either pushing or pulling, fan forced collectors can use dampers that require more pressure to open than thermosyphon collectors.
You just want to make sure the inlet and outlet vents and the damper opening are not too small as this will cause pressure drop and less flow.
Thank you so much for all your info already. I was talking to the wife and she said "make sure you post that im skeptical and I want to see pictures of what it will look like on the inside".
I went to build it solar and she has a much better idea, ty again. I am also going to try to find wooden cover for the fans.
--> On the making the collector look better front:
- If you have clear glazing like SunTuf or glass, you will see the screens, and to some degree the color of the back wall of the collector.
The screens actually look pretty good -- kind of a nice soft look.
The screen collectors (I think) look better if you don't paint the back wall black, but choose some medium dark color that matches the house.
On my barn screen collector, you can in the pictures that it does not have the "big black square" look because you see the siding color a bit through the screen. The collector would likely be just a bit more efficient with the black back wall, but (for me) the aesthetic gain outweighs the small efficiency increase.
- Another option is to use twinwall glazing. I think it has a really nice look, and you don't see the internals of the collector through it. If you are in a cold climate it also adds a bit of efficiency. If you can find a good local source, it does not add all that much to the cost -- a good price is about $1.80 a sqft. I'd use 10mm thick or thicker.
greenhouse cover glazing materials at reasonable cost
Shipping is a killer on this stuff, so local is best if you can.
- The trim around the outside of the collector makes a big difference
on how the collector looks. I kind of like the PVC wood or deck wood, as they look pretty good, and they have a good life.
-- Couple of examples of (I think) nice looking collectors:
This is my new solar water heating collector glazed with twinwall:
A Simple DIY Solar Space and Water Heating System
The page is not done yet, but there are a few pictures that show the look.
This is Knick's collector:
A $1K Solar Water Heating System that Looks Great
twinwall with a nice frame.
The fans should I be looking at bathroom vent fans or a different type of fan?
ty once again.
**when you use the screening do you also use baffles to control the direction of the air flow. how do you control the flow with the al soffit?
--> the vented alum soffit and the screen collectors work the same way. The vent holes in the soffit act the same way as the holes in the screen.
I guess that the ones I've seen (not that many large ones) did not use baffles, and I'm not sure how you would use baffles with flow on both sides of the screen/soffit? They tend to rely on the pressure drop across the screen or soffit to distribute the air. Again, I've not seen anyone who has actually done the work to see exactly where the flow does go, but it does make some sense.
I've actually ordered 16 small thermistor temperature sensors that I can glue to the absorber screen on my 4 by 8 test collector to see how much variation there is in absorber temp -- areas not getting much airflow should show up as hot spots on the absorber.
these are two fan styles that i found.
http://compare.ebay.com/like/2305115...=263602_304662
HVACQuick - residential
--> I could not find a fan curve for either of these. The first one looks promising -- I did email them to ask for a fan curve and/or flow at 0.2 inches of water pressure drop.
Someone mentioned the Fantech FG -- this is the brochure:
http://fantech.net/docs-resi/450286-fg-brochure.pdf
There is a fan curve in the brochure -- it looks like the FG6 would have plenty of grunt -- maybe more than is really needed for your collector? I think it was mentioned that its a quiet fan, and that's a big plus.
Gary
Last edited by forgeblast; Today at 10:08 AM.
OP
forgeblast
Elite Member
Thank you Gary! I know i will need to make an enclosed unit, it will be installed over t-111. The grooves/texture would make it almost impossible to seal out the outside air.
I am thinking too, that If i do make the unit out of 2x6 or even a 2x8 i can mount the fan in the box itself cutting down on the amount you can see in the house.
Building a Simple Solar Air Heating Collector
(this shows a system on t-111 and its insulated which is probably what i will do)
Building an inexpensive solar heating panel | Mobile Home Repair shows an example of the baffles.
The screen collectors (I think) look better if you don't paint the back wall black, but choose some medium dark color that matches the house.
That is a good idea, the house is a dark brown, and i still have the stain i can match the outside, and then use a dark brown to match the grey of the screen.
roll covering - double wall continuous greenhouse cover looks very promising, its already in a 4' width also.
(How would this be attached, would you use a u channel? or just staple and put a flashing over the ends. Or tape the ends with the aluminum tape)
Solar Collector Glazing Materials (i was spending a lot of time here to check on various materials)
I am thinking too, that If i do make the unit out of 2x6 or even a 2x8 i can mount the fan in the box itself cutting down on the amount you can see in the house.
Building a Simple Solar Air Heating Collector
(this shows a system on t-111 and its insulated which is probably what i will do)
Building an inexpensive solar heating panel | Mobile Home Repair shows an example of the baffles.
The screen collectors (I think) look better if you don't paint the back wall black, but choose some medium dark color that matches the house.
That is a good idea, the house is a dark brown, and i still have the stain i can match the outside, and then use a dark brown to match the grey of the screen.
roll covering - double wall continuous greenhouse cover looks very promising, its already in a 4' width also.
(How would this be attached, would you use a u channel? or just staple and put a flashing over the ends. Or tape the ends with the aluminum tape)
Solar Collector Glazing Materials (i was spending a lot of time here to check on various materials)
GaryGary
New member
That Solexx material is polyehthylene. Polyethylene is normally only good to about 130 or 140F, so that seems pretty low for a solar collector. I think I'd stick with the plycarbonate (SunTuf or the twinwall polycarbonate) -- its good for about 270F.
When stagnated, my vertical barn collector gets up to 185F -- tilted collectors can go well above this.
The mobile home collector is a backpass collector (all flow on the back side of the absorber), and these typically do use baffles to get the flow to spread over the absorber. Not sure how you would accomplish this on a collector with a flow through absorber.
At the inlet on the flow through screen collector, you do want a deflector or plat that keeps the room air from impinging directly onto the glazing -- this should be about half an inch from the glazing. In that same are near the inlet you might want to try some form of baffle that deflects the air out to the sides a bit rather than letting it short cut straight toward the outlet -- but, I'd not overdo it.
Gary
OP
forgeblast
Elite Member
I think i know what was confusing me.
The screen collectors will slow the air allowing it to heat up and then with the fans they will pull the air through the unit.
Units such as the can and soffit units, heat up the can/soffit and in return the air that is traveling around them.
(i have heard some people not able to get temps as hot because the air flow is down.)
So on the unit with the screens, does it need a fan? or does the fan give more air flow which in turn gives a better heat return....or am I still confused...lol
The screen collectors will slow the air allowing it to heat up and then with the fans they will pull the air through the unit.
Units such as the can and soffit units, heat up the can/soffit and in return the air that is traveling around them.
(i have heard some people not able to get temps as hot because the air flow is down.)
So on the unit with the screens, does it need a fan? or does the fan give more air flow which in turn gives a better heat return....or am I still confused...lol