5 ms·

The Zen of Passive Solar Heating Panel Design (2010)

153 points by mpatobin 10y ago

tonyarkles 10y ago
That's pretty amazing! Clearly a lot of thought and effort went into getting the design nailed down.
samcheng 10y ago
Here's the payout: > This installation was completed in 2007 - and has been adequate to maintain the indoor temperature above 65°F/18°C since that time – even though outdoor temperatures in winter dropped below -20°F/-29°C and even though the nine-foot by nine-foot overhead door has been opened every morning and every evening. > Before the end of 2009 the panels had saved more than their purchase price in fuel costs and the owner expects that the future savings will exceed the original cost of the entire structure. He told me he really likes starting every day (checking his livestock) in a nice warm truck.
- themartorana 10y ago
  So what's stopping a setup like this becoming standard? It's obviously generally superior, at least for new construction that's well-insulated. Right?
  - swampthinker 10y ago
    Because this is better than building code, and builders really don't have a huge incentive to go beyond code.
  - maxerickson 10y ago
    They won't work very well when they don't have good southern exposure, they won't circulate a lot of heat if you have rooms and doors. Meanwhile, the direct operating costs for natural gas heat aren't all that high.
    - Retric 10y ago
      Inserting something like this into the duct work of a normal heating or cooling system is fairly simple. The real issue is they increase construction costs and most buildings are built by people that don't use them. Further, they don't look like something out of a Norman Rockwell painting.
      - andrewwhartion 10y ago
        > most buildings are built by people that don't use them Having rented for the past 6 years in 4 different houses, I've become convinced that this is one of the most significant factors for why so many house aren't enjoyable to live in. Even if the overall design and layout of the house is good (I'm talking about the Christopher Alexander sense of good design), there are always small and not-so-small features that would never have been built that way had the person designing or building the house been intending to occupy it. Or had they moved in, said problems would be remedied in short order.
      - redtexture 10y ago
        A problem of insertion into ductwork of a passive-design system component, is that when the heating system runs at night, it will cause air to pass through the panels, and thus cool the building at night in winter. Since the solar panel-system is passive in design, insertion into ductwork would be a new design issue.
    - GoToRO 10y ago
      "good southern exposure". In which case you can fit normal windows and achieve the same or better.
      - redtexture 10y ago
        No, windows fail, as can be seen by reviewing the linked pages. Windows are not the same: - Windows do not passively aid circulation of warmed air, which the panels are particularly designed to do. - Windows also do not passively reduce or eliminate overnight-losses of energy (heat) on a cold night (consider negative-centigrade temperature or less), which the linked-to design does do, by passively preventing circulation of air that would cool the building overnight The design linked-to is specifically designed to passively deal with the prevention of the transfer of heat outside on a cold night, among other things, including limited cost, simple construction, and rapid payback over the life of the building in a cold winter environment. Windows fail as a passive solar source. Diurnal intervention required for windows.
imaginenore 10y ago
I actually built a similar system as an experiment, basically a 1 x 2 x ¼ meters (multi-layered) cardboard box painted all black inside and covered with a sheet of transparent plastic on one of the larger sides. It was really cheap, around $10-15 in materials. Then I added two holes (in and out), and put some cheap flexible air duct hoses with some old CPU fan, which was another $8. On a sunny day it heats up the air incredibly well, where it actually could be beneficial during the winter season. Unfortunately there are big problems that I encountered that I couldn't solve cheaply. 1) Mounted on the roof, it has to be sturdy enough to resist heavy rains and strong winds. We get winter windstorms, and one winter it got up to 55 knots with 70 knot gusts. I have no idea how to cheaply mount this box on the roof so it doesn't fly off and kill someone. 2) Intake and exhaust hoses would have to go either through the walls or through the windows. And since I don't own the house, my only real option would be to cut circular holes in the windows, and then replace the glass when we move out. Again, not cheap. 3) For the winter months I would have to also insulate these hoses, or they would lose most of the heat on the way to the house. EDIT: I also think if you don't care about what your house looks like, you can either paint it black or wrap it in black plastic.
- heisenbit 10y ago
  > I also think if you don't care about what your house looks like, you can either paint it black or wrap it in black plastic. Such heating will work during the day but transporting the energy from the heated plastic into the house is another matter. The hot surface also would radiate a lot of heat immediately away. And when the night comes you heat the sky with what you have stored up. The article is fascinating as it shows what can be achieved on a system engineering level. As an engineer however I would also like to see some performance measurements like air flow and temperature deltas going beyond the anecdotal story keeping the build warm in the northern US. Did not see anything on his homepage. There have been related posts on HN that showed advances on material science level where the absorption and radiation wavelengths of surfaces have been optimized. > Unfortunately there are big problems that I encountered that I couldn't solve cheaply. PV system cost these days is dominated by other costs than the solar cells. Engineering something that can withstand weather for a sustained period is both non-trival and not cheap. There may be some overlap in what PV systems require and what a passive heating system requires. Maybe the massive investments in the PV space make passive heating systems these days more practical?
intrasight 10y ago
Curious if anyone sells such panels
- freerobby 10y ago
  Mostly smaller outfits but you can find them. See e.g. http://sunmatesolarpanels.com/content/view/2/31/ http://sunmatesolarpanels.com/content/view/2/31/
  - intrasight 10y ago
    Thanks
deleted 10y ago
[deleted]
dboreham 10y ago
Very interesting. I live in a place where we have significant issues with ice build up on roof surfaces, gutters, etc. One way to deal with this is to electrically heat the roof and gutters. This of course is expensive (very!). So I had the ideal that one could use the available solar energy (it is reasonably sunny in winter here) to melt the ice. My idea is not to use PV panels and restive electrical heating but to directly transfer the solar energy as heat to the ice. This would be done with some sort of heating panel, coupled to the metalic gutters with a heat pipe. Sometime I need to do some analysis to see if it is a viable idea. How to ensure snow does not cover the panel/solar heat collector is also a potential problem.
- WalterBright 10y ago
  > How to ensure snow does not cover the panel/solar heat collector is also a potential problem. Mount the panels vertically.
  - pinko 10y ago
    Not always sufficient! http://c8.alamy.com/comp/D0DG83/stop-sign-covered-in-snow-during-a-blizzard-D0DG83.jpg http://c8.alamy.com/comp/D0DG83/stop-sign-covered-in-snow-du...
    - redtexture 10y ago
      Not an insulated capture point. Backside of the example metal sign always cooled on backside by low temperature air.
- cellularmitosis 10y ago
  You could also wait until it stops snowing and then throw a large piece of black fabric (think black woven nylon like a trampoline) over the snow. Automating the black fabric deploy would be an interesting project :)
dttocs 10y ago
See also http://www.builditsolar.com http://www.builditsolar.com for more recent improvements and ideas for simple passive solar.
dorfsmay 10y ago
I knew about vacuum tube, but they are expensive, require a pump and something to convert the heat back from liquid to air. This on the other hand has zero moving part and requires no maintenance. Amazing!
samatman 10y ago
For a next-level extension of this idea, check out this paper on solar closets: http://www.ece.villanova.edu/~nick/solar/solar.html http://www.ece.villanova.edu/~nick/solar/solar.html
devenson 10y ago
If he just made large windows out of the same double walled polycarbonate panels, wouldn't they collect just as much heat from the sun during the day? The problem with windows however is they don't insulate as well. Perhaps just doubling up or tripling their thickness would achieve the same result in the end, and be much simpler. What am I failing to understand?
- nkurz 10y ago
  What am I failing to understand? You might be missing that maximizing heat collection while the sun is shining is not the goal, that too hot in the day can be just as bad as too cold at night, that each layer of "clear" polycarbonate (ie, 2 for twinwall) blocks about 10% of the light, and that gaping curtainless windows are not always a desirable architectural feature. How many buildings have you been in that have expansive south facing windows? How many of them have been comfortable day-and-night year-round in a harsh climate without mechanical heating and cooling? Very few buildings achieve this, and I'd guess that none of them have large windows. The Introduction to to the article is a good "introduction" to the issues. The rest of the article explains the introduction. If you are interested in the issues, it's a good article, worth reading in depth. But as the author says in the preface, "I’d suggest reading this when you’re in a “learn” mode – because if you’re in “skim” mode, you’ll just be wasting your time."
  - lucio 10y ago
    How about Double Glazed Windows and shades?
    - nkurz 10y ago
      It depends on your goals. One saying is that "a good window is still a poor wall". A quality double glazed window still has about 10x the heatloss of a well built wall. Here's a summary with a link to more: http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/55519/A-Good-Window-Is-Still-a-Poor-Wall http://www.energyvanguard.com/blog-building-science-HERS-BPI... Shades can help with privacy, but what if you want the privacy at the same time you want to be capturing heat? And if requires active control --- well, that's by definition not passive. Interestingly, the new movement in high efficiency houses is frequently for low solar gain windows: well insulated windows with special coatings to admit less heat while still admitting light. From another standpoint, gigantic expanses of windows are rarely the best way to build a pleasant room. As well as being a rare crossover between Computer Science and Building Architecture, Christopher Alexander's "A Pattern Language" has lots to say on this. Some excerpts here: http://kk.org/cooltools/a-pattern-language/ http://kk.org/cooltools/a-pattern-language/ Which is to say that opaque heat-gathering walls serve a purpose that is separate than that served by windows. Both have their place, and they don't tend to replace each other directly.

153 points by mpatobin 10y ago

That's pretty amazing! Clearly a lot of thought and effort went into getting the design nailed down.

Here's the payout: > This installation was completed in 2007 - and has been adequate to maintain the indoor temperature above 65°F/18°C since that time – even though outdoor temperatures in winter dropped below -20°F/-29°C and even though the nine-foot by nine-foot overhead door has been opened every morning and every evening. > Before the end of 2009 the panels had saved more than their purchase price in fuel costs and the owner expects that the future savings will exceed the original cost of the entire structure. He told me he really likes starting every day (checking his livestock) in a nice warm truck.

themartorana 10y ago
So what's stopping a setup like this becoming standard? It's obviously generally superior, at least for new construction that's well-insulated. Right?
- swampthinker 10y ago
  Because this is better than building code, and builders really don't have a huge incentive to go beyond code.
- maxerickson 10y ago
  They won't work very well when they don't have good southern exposure, they won't circulate a lot of heat if you have rooms and doors. Meanwhile, the direct operating costs for natural gas heat aren't all that high.
  - Retric 10y ago
    Inserting something like this into the duct work of a normal heating or cooling system is fairly simple. The real issue is they increase construction costs and most buildings are built by people that don't use them. Further, they don't look like something out of a Norman Rockwell painting.
    - andrewwhartion 10y ago
      > most buildings are built by people that don't use them Having rented for the past 6 years in 4 different houses, I've become convinced that this is one of the most significant factors for why so many house aren't enjoyable to live in. Even if the overall design and layout of the house is good (I'm talking about the Christopher Alexander sense of good design), there are always small and not-so-small features that would never have been built that way had the person designing or building the house been intending to occupy it. Or had they moved in, said problems would be remedied in short order.
    - redtexture 10y ago
      A problem of insertion into ductwork of a passive-design system component, is that when the heating system runs at night, it will cause air to pass through the panels, and thus cool the building at night in winter. Since the solar panel-system is passive in design, insertion into ductwork would be a new design issue.
  - GoToRO 10y ago
    "good southern exposure". In which case you can fit normal windows and achieve the same or better.
    - redtexture 10y ago
      No, windows fail, as can be seen by reviewing the linked pages. Windows are not the same: - Windows do not passively aid circulation of warmed air, which the panels are particularly designed to do. - Windows also do not passively reduce or eliminate overnight-losses of energy (heat) on a cold night (consider negative-centigrade temperature or less), which the linked-to design does do, by passively preventing circulation of air that would cool the building overnight The design linked-to is specifically designed to passively deal with the prevention of the transfer of heat outside on a cold night, among other things, including limited cost, simple construction, and rapid payback over the life of the building in a cold winter environment. Windows fail as a passive solar source. Diurnal intervention required for windows.

imaginenore 10y ago

I actually built a similar system as an experiment, basically a 1 x 2 x ¼ meters (multi-layered) cardboard box painted all black inside and covered with a sheet of transparent plastic on one of the larger sides. It was really cheap, around $10-15 in materials. Then I added two holes (in and out), and put some cheap flexible air duct hoses with some old CPU fan, which was another $8. On a sunny day it heats up the air incredibly well, where it actually could be beneficial during the winter season. Unfortunately there are big problems that I encountered that I couldn't solve cheaply. 1) Mounted on the roof, it has to be sturdy enough to resist heavy rains and strong winds. We get winter windstorms, and one winter it got up to 55 knots with 70 knot gusts. I have no idea how to cheaply mount this box on the roof so it doesn't fly off and kill someone. 2) Intake and exhaust hoses would have to go either through the walls or through the windows. And since I don't own the house, my only real option would be to cut circular holes in the windows, and then replace the glass when we move out. Again, not cheap. 3) For the winter months I would have to also insulate these hoses, or they would lose most of the heat on the way to the house. EDIT: I also think if you don't care about what your house looks like, you can either paint it black or wrap it in black plastic.

heisenbit 10y ago
> I also think if you don't care about what your house looks like, you can either paint it black or wrap it in black plastic. Such heating will work during the day but transporting the energy from the heated plastic into the house is another matter. The hot surface also would radiate a lot of heat immediately away. And when the night comes you heat the sky with what you have stored up. The article is fascinating as it shows what can be achieved on a system engineering level. As an engineer however I would also like to see some performance measurements like air flow and temperature deltas going beyond the anecdotal story keeping the build warm in the northern US. Did not see anything on his homepage. There have been related posts on HN that showed advances on material science level where the absorption and radiation wavelengths of surfaces have been optimized. > Unfortunately there are big problems that I encountered that I couldn't solve cheaply. PV system cost these days is dominated by other costs than the solar cells. Engineering something that can withstand weather for a sustained period is both non-trival and not cheap. There may be some overlap in what PV systems require and what a passive heating system requires. Maybe the massive investments in the PV space make passive heating systems these days more practical?

intrasight 10y ago

Curious if anyone sells such panels

freerobby 10y ago
Mostly smaller outfits but you can find them. See e.g. http://sunmatesolarpanels.com/content/view/2/31/ http://sunmatesolarpanels.com/content/view/2/31/
- intrasight 10y ago
  Thanks

deleted 10y ago

[deleted]

dboreham 10y ago

Very interesting. I live in a place where we have significant issues with ice build up on roof surfaces, gutters, etc. One way to deal with this is to electrically heat the roof and gutters. This of course is expensive (very!). So I had the ideal that one could use the available solar energy (it is reasonably sunny in winter here) to melt the ice. My idea is not to use PV panels and restive electrical heating but to directly transfer the solar energy as heat to the ice. This would be done with some sort of heating panel, coupled to the metalic gutters with a heat pipe. Sometime I need to do some analysis to see if it is a viable idea. How to ensure snow does not cover the panel/solar heat collector is also a potential problem.

WalterBright 10y ago
> How to ensure snow does not cover the panel/solar heat collector is also a potential problem. Mount the panels vertically.
- pinko 10y ago
  Not always sufficient! http://c8.alamy.com/comp/D0DG83/stop-sign-covered-in-snow-during-a-blizzard-D0DG83.jpg http://c8.alamy.com/comp/D0DG83/stop-sign-covered-in-snow-du...
  - redtexture 10y ago
    Not an insulated capture point. Backside of the example metal sign always cooled on backside by low temperature air.
cellularmitosis 10y ago
You could also wait until it stops snowing and then throw a large piece of black fabric (think black woven nylon like a trampoline) over the snow. Automating the black fabric deploy would be an interesting project :)

dttocs 10y ago

See also http://www.builditsolar.com http://www.builditsolar.com for more recent improvements and ideas for simple passive solar.

dorfsmay 10y ago

I knew about vacuum tube, but they are expensive, require a pump and something to convert the heat back from liquid to air. This on the other hand has zero moving part and requires no maintenance. Amazing!

samatman 10y ago

For a next-level extension of this idea, check out this paper on solar closets: http://www.ece.villanova.edu/~nick/solar/solar.html http://www.ece.villanova.edu/~nick/solar/solar.html

devenson 10y ago

If he just made large windows out of the same double walled polycarbonate panels, wouldn't they collect just as much heat from the sun during the day? The problem with windows however is they don't insulate as well. Perhaps just doubling up or tripling their thickness would achieve the same result in the end, and be much simpler. What am I failing to understand?

nkurz 10y ago
What am I failing to understand? You might be missing that maximizing heat collection while the sun is shining is not the goal, that too hot in the day can be just as bad as too cold at night, that each layer of "clear" polycarbonate (ie, 2 for twinwall) blocks about 10% of the light, and that gaping curtainless windows are not always a desirable architectural feature. How many buildings have you been in that have expansive south facing windows? How many of them have been comfortable day-and-night year-round in a harsh climate without mechanical heating and cooling? Very few buildings achieve this, and I'd guess that none of them have large windows. The Introduction to to the article is a good "introduction" to the issues. The rest of the article explains the introduction. If you are interested in the issues, it's a good article, worth reading in depth. But as the author says in the preface, "I’d suggest reading this when you’re in a “learn” mode – because if you’re in “skim” mode, you’ll just be wasting your time."
- lucio 10y ago
  How about Double Glazed Windows and shades?
  - nkurz 10y ago
    It depends on your goals. One saying is that "a good window is still a poor wall". A quality double glazed window still has about 10x the heatloss of a well built wall. Here's a summary with a link to more: http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/55519/A-Good-Window-Is-Still-a-Poor-Wall http://www.energyvanguard.com/blog-building-science-HERS-BPI... Shades can help with privacy, but what if you want the privacy at the same time you want to be capturing heat? And if requires active control --- well, that's by definition not passive. Interestingly, the new movement in high efficiency houses is frequently for low solar gain windows: well insulated windows with special coatings to admit less heat while still admitting light. From another standpoint, gigantic expanses of windows are rarely the best way to build a pleasant room. As well as being a rare crossover between Computer Science and Building Architecture, Christopher Alexander's "A Pattern Language" has lots to say on this. Some excerpts here: http://kk.org/cooltools/a-pattern-language/ http://kk.org/cooltools/a-pattern-language/ Which is to say that opaque heat-gathering walls serve a purpose that is separate than that served by windows. Both have their place, and they don't tend to replace each other directly.