Solar heating of common materials.
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Solar heating of common materials.
I'm not sure where to post this. I didn't want to hijack another thread.
Somebody may find the following useful:
Solar temperature gain and insulation has interested me for many decades.
In my youth it was the fear of global cooling. Now it has swung the other way.
Our observatories and observing spots are subject to local, solar heating.
Which can spoil the view of the sun due to rising heat tremors. Convection currents.
The local seeing is considered as poor to bad.
There is a very simple and inexpensive test:
Prop some sheets or objects of different metals and materials out in the sunshine.
Size doesn't matter much. This test will shock you at the difference in temperature achieved.
You can use a "pistol" remote reading thermometer. These now cost as little as £10/$10/10€.
One of these handy tools [toys] may save you a trip to the ER or A&E!
I wanted to see which material would be most suitable for covering a dome/observatory walls for solar work.
Note that I am not allowed traditional white. My rural situation would make it far too visible from a distance.
I prefer the anonymity and invisibility of green. Despite the very obvious, thermal drawbacks.
There are temporary measures planned for excluding solar heating.
Objects and sheets of brass, mild steel, stainless steel and copper are easily found and placed out in the sun.
Several will soon be far too hot for human touch.
All my own test samples were "shiny." Shiny [green] fibreglass soon soars well over 100F.
As does [green] painted, birch plywood. Only the plywood cooled rapidly when clouds passed over the sun.
Even the open slit of a cool, white dome can act as a solar collector.
Early solar heating experiments employed simple, open boxes.
If the sunlight falls on black painted walls inside an observatory they will heat up.
They won't even enjoy the cooling effect of a breeze inside a dome.
Beware aluminium, foil-faced insulation!
I bought some after seeing people use it on their mounts. It is anything but cool!
White, lightweight tarpaulins do remain cool. As does white, woven "big bag" material.
This would be a dirt cheap way of temporarily shading hot ground surfaces around your solar telescope.
Or draped on the south facing walls of your roll off roof observatory?
Most of the world's roofs are covered in materials which soar in temperature in summer sunshine.
Which is why those who can afford it will choose a trendy black roof and air conditioning.
Replacing all the dark, south-facing roofs with white materials could "save the planet!"
Ask your architect why they insist on a red hot roof surface when you are having bedrooms fitted into the attic.
I have regularly toured builders merchants', open air, roofing displays.
Just testing which material is coolest for a southerly exposure.
We have had attic bedrooms for decades in several different homes and know about unwanted solar heating.
Only pure white, fibre reinforced, corrugated cement sheeting remains cool so far.
After the "Great Danish Storm" of 1999 most damaged roofs were replaced with black.
The misery this must have caused homeowners should be properly investigated as homeowners are bribed to fit heat pumps.
These can be used in summer as very inefficient, air conditioning. This is unlikely to reduce their CO2 burden.
Somebody may find the following useful:
Solar temperature gain and insulation has interested me for many decades.
In my youth it was the fear of global cooling. Now it has swung the other way.
Our observatories and observing spots are subject to local, solar heating.
Which can spoil the view of the sun due to rising heat tremors. Convection currents.
The local seeing is considered as poor to bad.
There is a very simple and inexpensive test:
Prop some sheets or objects of different metals and materials out in the sunshine.
Size doesn't matter much. This test will shock you at the difference in temperature achieved.
You can use a "pistol" remote reading thermometer. These now cost as little as £10/$10/10€.
One of these handy tools [toys] may save you a trip to the ER or A&E!
I wanted to see which material would be most suitable for covering a dome/observatory walls for solar work.
Note that I am not allowed traditional white. My rural situation would make it far too visible from a distance.
I prefer the anonymity and invisibility of green. Despite the very obvious, thermal drawbacks.
There are temporary measures planned for excluding solar heating.
Objects and sheets of brass, mild steel, stainless steel and copper are easily found and placed out in the sun.
Several will soon be far too hot for human touch.
All my own test samples were "shiny." Shiny [green] fibreglass soon soars well over 100F.
As does [green] painted, birch plywood. Only the plywood cooled rapidly when clouds passed over the sun.
Even the open slit of a cool, white dome can act as a solar collector.
Early solar heating experiments employed simple, open boxes.
If the sunlight falls on black painted walls inside an observatory they will heat up.
They won't even enjoy the cooling effect of a breeze inside a dome.
Beware aluminium, foil-faced insulation!
I bought some after seeing people use it on their mounts. It is anything but cool!
White, lightweight tarpaulins do remain cool. As does white, woven "big bag" material.
This would be a dirt cheap way of temporarily shading hot ground surfaces around your solar telescope.
Or draped on the south facing walls of your roll off roof observatory?
Most of the world's roofs are covered in materials which soar in temperature in summer sunshine.
Which is why those who can afford it will choose a trendy black roof and air conditioning.
Replacing all the dark, south-facing roofs with white materials could "save the planet!"
Ask your architect why they insist on a red hot roof surface when you are having bedrooms fitted into the attic.
I have regularly toured builders merchants', open air, roofing displays.
Just testing which material is coolest for a southerly exposure.
We have had attic bedrooms for decades in several different homes and know about unwanted solar heating.
Only pure white, fibre reinforced, corrugated cement sheeting remains cool so far.
After the "Great Danish Storm" of 1999 most damaged roofs were replaced with black.
The misery this must have caused homeowners should be properly investigated as homeowners are bribed to fit heat pumps.
These can be used in summer as very inefficient, air conditioning. This is unlikely to reduce their CO2 burden.
http://fullerscopes.blogspot.dk/
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Solar heating of common materials.
Hi
Just bought some of this. Not tried it yet.
https://www.ebay.co.uk/itm/154277688540
Cement sheet would make a heavy observatory.
Cheers. Andrew.
Just bought some of this. Not tried it yet.
https://www.ebay.co.uk/itm/154277688540
Cement sheet would make a heavy observatory.
Cheers. Andrew.
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Re: Solar heating of common materials.
Good luck with that.AndiesHandyHandies wrote: ↑Fri Aug 20, 2021 7:40 am Hi
Just bought some of this. Not tried it yet.
https://www.ebay.co.uk/itm/154277688540
Cement sheet would make a heavy observatory.
Cheers. Andrew.
A major paint manufacturer was told to stop advertising its "insulating" paint.
Because it simply didn't work as claimed.
White corrugated cement could be used on a south facing facade or roll-off roof.
It is strong, so needs only a simple, wooden, support structure.
It is considered one of the lightest roofing materials.
It regularly replaces thatch without needing roof reinforcement.
There are also thinner, flat sheets of this material available for wall cladding.
This would need much greater care when fixing to avoid damage.
Being fairly brittle it could crack between screw fixings on corners.
http://fullerscopes.blogspot.dk/
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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- Bob Yoesle
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Re: Solar heating of common materials.
What you're apparently looking for is high emissivity materials - meaning these materials release heat more effectively than low-emissivity materials.
Cool-roof materials and paints are the best for solar work, and are used on most all professional solar telescope protective buildings and telescope structures. I found this quite effective in dealing with poor daytime seeing coming from a standard green metal roll-off-roof: Henry Co. 687 Enviro-White elastometric roof coating rated nearly as good as the DKI Solar Telescope's ACS Acu-Shield paint, way less expensive, and much more readily available at the local Home Depot. It can be thinned with water to a paint consistency and applied in multiple coatings. If I had to do it over again I would skip the meatal roofing altogether and just cool-roof paint the plywood underlayment.
The Cool roof Rating Council figures comparing the two products shows them to be essentially identical in reflectance, emittance, and SRI at 1 and 3 years:
* The Solar Reflectance Index (SRI.) is a measure of the ability to reject solar heat, as shown by a small temperature rise. It is defined so that a standard black (reflectance 0.05 [5%], thermal emittance 0.90 [90%]) is 0 and a standard white (reflectance 0.80 [80%], emittance 0.90 [90%]) is 100. Materials with the highest SRI values are the coolest. Due to the way SRI is defined, especially hot materials can take slightly negative values, and particularly cool materials can exceed 100.
Cool-roof materials and paints are the best for solar work, and are used on most all professional solar telescope protective buildings and telescope structures. I found this quite effective in dealing with poor daytime seeing coming from a standard green metal roll-off-roof: Henry Co. 687 Enviro-White elastometric roof coating rated nearly as good as the DKI Solar Telescope's ACS Acu-Shield paint, way less expensive, and much more readily available at the local Home Depot. It can be thinned with water to a paint consistency and applied in multiple coatings. If I had to do it over again I would skip the meatal roofing altogether and just cool-roof paint the plywood underlayment.
The Cool roof Rating Council figures comparing the two products shows them to be essentially identical in reflectance, emittance, and SRI at 1 and 3 years:
* The Solar Reflectance Index (SRI.) is a measure of the ability to reject solar heat, as shown by a small temperature rise. It is defined so that a standard black (reflectance 0.05 [5%], thermal emittance 0.90 [90%]) is 0 and a standard white (reflectance 0.80 [80%], emittance 0.90 [90%]) is 100. Materials with the highest SRI values are the coolest. Due to the way SRI is defined, especially hot materials can take slightly negative values, and particularly cool materials can exceed 100.
Last edited by Bob Yoesle on Sun Aug 22, 2021 7:34 pm, edited 2 times in total.
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Re: Solar heating of common materials.
Thanks Bob.
Very useful information.
Flexible materials, which show no solar gain, are most useful to the amateur observatory builder like myself. Those who must adhere to local norms [partners and neighbours] for appearance, may be denied permanent finishes. However desirable they may be from a theoretical viewpoint.
Temporarily draping an offending surface or building, to avoid thermal issues, can have great value IMHO. A temporary tarpaulin, as a sun screen, can be rapidly folded and stored in a corner. Or, the back of a dome could be finished in green and parked, to face that way when not in use. While the active shutter side may be a more desirable white. Drop down, white blinds could cover green shutters only when required for observation and imaging.
It is also an incredibly easy way to asses the visual impact of any planned observatory. A mock-up of posts and battens, or even bent, PVC plumbing pipe to simulate a dome, can be draped with a lightweight tarpaulin. Green and white are commonly available at low cost. Each colour will provide an instant valuation of social acceptability in any situation. Preferably before typically large sums are invested in such a structure. Only to become a cause of local hostility.
An alternative might be tall shrubs or conifers in pots. To be easily moved about on inexpensive trolleys. Or even a sack truck. To provide solar shade. Or visual shielding from neighbours' glares.
Very useful information.
Flexible materials, which show no solar gain, are most useful to the amateur observatory builder like myself. Those who must adhere to local norms [partners and neighbours] for appearance, may be denied permanent finishes. However desirable they may be from a theoretical viewpoint.
Temporarily draping an offending surface or building, to avoid thermal issues, can have great value IMHO. A temporary tarpaulin, as a sun screen, can be rapidly folded and stored in a corner. Or, the back of a dome could be finished in green and parked, to face that way when not in use. While the active shutter side may be a more desirable white. Drop down, white blinds could cover green shutters only when required for observation and imaging.
It is also an incredibly easy way to asses the visual impact of any planned observatory. A mock-up of posts and battens, or even bent, PVC plumbing pipe to simulate a dome, can be draped with a lightweight tarpaulin. Green and white are commonly available at low cost. Each colour will provide an instant valuation of social acceptability in any situation. Preferably before typically large sums are invested in such a structure. Only to become a cause of local hostility.
An alternative might be tall shrubs or conifers in pots. To be easily moved about on inexpensive trolleys. Or even a sack truck. To provide solar shade. Or visual shielding from neighbours' glares.
http://fullerscopes.blogspot.dk/
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Solar heating of common materials.
Totally agree. In a 'deprived inner city area' - where I live, it also must not be something that jumps out at the local 'hoodlums' and 'thieves' as the potential next spot for a burglary so they can raise a few quid selling 'scrap' to get the next fix to shoot up their arm...
This is what 've done around and over the pier that's permanently installed in my garden, they form a roof with an eye over it. I'll get some pics up when i'm back home again...
In addition to the sun screens careful 'shrubbage' surrounding the perimeter of the pier hides from prying eyes. The pier and mount head (no scopes are left mounted outside) are covered with a tarpaulin bbq style cover held on with bungee cords which to the untrained eye makes it look like a rotary washing line folded down and covered up.
http://brierleyhillsolar.blogspot.co.uk/
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Re: Solar heating of common materials.
Ok, back home now, and some sun, so the scopes were out. Here's some pics to illustrate the use of 'sails' for screening the scope and surrounding area both thermally and visually.
Pier sits behind sails infront of the greenhouse:
P1010482 by Mark Townley, on Flickr
Gates from the front of the garden - 'nothing to see here...'
P1010493 by Mark Townley, on Flickr
Internally the scope peeps through the gap. Gap position easily adjusted by moving sail anchor points.
P1010483 by Mark Townley, on Flickr
P1010485 by Mark Townley, on Flickr
View from above, shrubs also provide screening...
P1010489 by Mark Townley, on Flickr
Peeping out...
P1010492 by Mark Townley, on Flickr
I'm pleased with the results and 2 sails cost a few tens of pounds... Easy to put up, easy to take down.
Pier sits behind sails infront of the greenhouse:
P1010482 by Mark Townley, on Flickr
Gates from the front of the garden - 'nothing to see here...'
P1010493 by Mark Townley, on Flickr
Internally the scope peeps through the gap. Gap position easily adjusted by moving sail anchor points.
P1010483 by Mark Townley, on Flickr
P1010485 by Mark Townley, on Flickr
View from above, shrubs also provide screening...
P1010489 by Mark Townley, on Flickr
Peeping out...
P1010492 by Mark Townley, on Flickr
I'm pleased with the results and 2 sails cost a few tens of pounds... Easy to put up, easy to take down.
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
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Re: Solar heating of common materials.
Very nice implementation of screening Mark! And I love the urban green-scaping.
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Re: Solar heating of common materials.
Thanks Bob! It's all a balance. In the perfect world I wouldn't have greenhouses anywhere near where I observe from, but it's all a balance, not just my better half, but also neighbours of which I have no control of...
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Re: Solar heating of common materials.
Excellent screening Mark!
The sun can't heat where the sun don't shine.
The sun can't heat where the sun don't shine.
http://fullerscopes.blogspot.dk/
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
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Re: Solar heating of common materials.
Due to global warming, we are faced with excessive heating of the roof of our houses. This was a problem because, on sunny days, the temperature in the house rose to critical levels. My friend contacted one company, saying that this is the top Indianapolis roof company for you and the roofers offered me a cheap and simple solution to the problem. For these purposes, mineral or glass wool is installed immediately under the roofing material, after the vapor barrier. Thanks to its presence, it can restrain the penetration of heat inside.
Last edited by Sandrogoewey on Wed Sep 07, 2022 6:59 am, edited 1 time in total.
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Re: Solar heating of common materials.
reminder
this is a solar astronomy forum.
this is a solar astronomy forum.
Stephen W. Ramsden
Atlanta, GA USA
Founder/Director Charlie Bates Solar Astronomy Project
http://www.solarastronomy.org
Atlanta, GA USA
Founder/Director Charlie Bates Solar Astronomy Project
http://www.solarastronomy.org