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The Zen of Passive Solar Heating Panel Design (2010)

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Re: The Zen of Passive Solar Heating Panel Design (2010)

#21

Post by WalterBright »

dboreham wrote: post #9

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…

> How to ensure snow does not cover the panel/solar heat collector is also a potential problem.

Mount the panels vertically.

Re: The Zen of Passive Solar Heating Panel Design (2010)

#22

Post by imaginenore »

anotheryou wrote: post #8
imaginenore wrote: post #4

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…

maybe you can build a "plug" for the half-open window?

That would be challenging, we try to keep windows air tight for the winter to avoid any leaks.

Re: The Zen of Passive Solar Heating Panel Design (2010)

#23

Post by imaginenore »

rzzzt wrote: post #11
imaginenore wrote: post #4

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…

Some people build these with painted beer can columns on the inside serving as air ducts, see this video for an example: https://youtu.be/nuxanLdtwZQ They also tend to install it on the side wall; it doesn't get that much sunshine in the summer, but it becomes more efficient in the winter when the Sun stays at lower angles. External circulation of air is still required and is usually done by using an electric fan.

Yeah, I'm fully aware of that design. I've seen tests of it against a much simple design with the sheet of fabric in the middle, and there's basically no difference. Cutting so many cans' tops and bottoms is actually not an easy task, I had tried.

Re: The Zen of Passive Solar Heating Panel Design (2010)

#24

Post by Retric »

maxerickson wrote: post #16
themartorana wrote: post #14

Earlier quoted context omitted.

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?

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.

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.

Re: The Zen of Passive Solar Heating Panel Design (2010)

#25

Post by pinko »

WalterBright wrote: post #21
dboreham wrote: post #9

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…

> How to ensure snow does not cover the panel/solar heat collector is also a potential problem. Mount the panels vertically.

Not always sufficient!

http://c8.alamy.com/comp/D0DG83/stop-sign-covered-in-snow-du...

Re: The Zen of Passive Solar Heating Panel Design (2010)

#26

Post by andrewwhartion »

Retric wrote: post #24
maxerickson wrote: post #16

Earlier quoted context omitted.

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.

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.

> 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.

Re: The Zen of Passive Solar Heating Panel Design (2010)

#27

Post by gvb »

devenson wrote: post #18

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?

Efficiency.

The black box surface and vanes maximize the conversion of light into heat. The construction with the airflow traps and chimney effect maximize the transfer of the heat into the building while minimizing the heat transfer out of the building when the sun isn't shining.

Windows are not nearly as efficient because the material behind the windows is not optimized to convert light into heat (see his section on the design of the black vanes) and the airflow spreading the heat throughout the building will be poor compared to the design in the article.

Re: The Zen of Passive Solar Heating Panel Design (2010)

#28

Post by lucio »

nkurz wrote: post #20
devenson wrote: post #18

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?

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 ex…

How about Double Glazed Windows and shades?

Re: The Zen of Passive Solar Heating Panel Design (2010)

#29

Post by devenson »

gvb wrote: post #27
devenson wrote: post #18

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?

Efficiency. The black box surface and vanes maximize the conversion of light into heat. The construction with the airflow traps and chimney effect maximize the transfer of the heat into the building while minimizing the heat transfer out of the building when the sun isn't shining. Windows are not nearly as efficient because the material behind the windows is not optimized to convert light into heat (see his section o…

You're right about the airflow traps preventing the heat transfer out at night. However, I think windows will trap the heat from incoming sunlight as well as the black vanes since a window allows the light to reach farther into the building and get absorbed by the floor (or opposite wall). Ultimately he wants the heat in the floor anyway, so it's best to get it there via radiation. Not much of it will be radiated back out the same window. In fact the black vanes and the rest of the collector should radiate more of the energy back out to the world because they're hotter than the interior space.

Re: The Zen of Passive Solar Heating Panel Design (2010)

#30

Post by nkurz »

lucio wrote: post #28
nkurz wrote: post #20

Earlier quoted context omitted.

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 ex…

How about Double Glazed Windows and shades?

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...

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/

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.

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