Energy Free Cooling through Physics

[freebeard]

Here is a metamaterials approach:

This Material Might Change How We Cool Our Houses Forever

A self-assembling aluminum foam. I should think that would be fairly durable.

Since there is a sintering phase to the process I doubt it will be made into a paint.

[aerohead]

Originally Posted by freebeard

Here is a metamaterials approach:

A self-assembling aluminum foam. I should think that would be fairly durable.

Since there is a sintering phase to the process I doubt it will be made into a paint.

1) I'm not seeing much daylight between this 'breakthrough' and flat white, titanium dioxide-based pigments.
2) Secondly, I see no discussion of 'latent' heat, which is typically the reason behind refrigerated air conditioning.
3)' Cooling' the inside of a home can 'kill' you, if you don't 'dehumidify' the air volume ( at high dewpoints, you could produce condensation on every internal surface of the living space, triggering 'black-mold') ).
4) The temperature of a roof and it's radiative load, downwards through an attic space can have 'zero' effect on the cost of cooling.

[freebeard]

1) It's at ?t=628. Ultrawhite paint is 88.6%, a silvered mirror is 89.5%.

2) Don't know

3) [citation needed]

4) Disagree. It's reflecting the heat load rather than cooling it.

The part significant to me is the mechanism, a three part precursor, a phase inversion, then washing one part, sintering away the other leaving an aluminum aerogel.

The resulting aluminum plate is white because of it's nanoscale structure not pigment. I suspect it's similar to the vacuum airship 'tic-tac' drones the Navy pilots are reporting offshore of California and Florida.

[Piotrsko]

Give the man a cigar for #4 reply.
WE had a white paint made of a calcium compound that supposedly reflected 90%. Lamp black in a suspension was the other heat control we used for space applications. Useful only for sunlight operations, otherwise everything got cold as outside space Everything external metal was polished

[freebeard]

Which paragraph? There are ~4 assertions?

There's a qualitative difference between 90% and 99.6%. Purdue University got to 97.9% with paint (Permalink #18). I think the cast aluminum parts will be more durable than paint.

[aerohead]

Originally Posted by freebeard

1) It's at ?t=628. Ultrawhite paint is 88.6%, a silvered mirror is 89.5%.

2) Don't know

3) [citation needed]

4) Disagree. It's reflecting the heat load rather than cooling it.

The part significant to me is the mechanism, a three part precursor, a phase inversion, then washing one part, sintering away the other leaving an aluminum aerogel.

The resulting aluminum plate is white because of it's nanoscale structure not pigment. I suspect it's similar to the vacuum airship 'tic-tac' drones the Navy pilots are reporting offshore of California and Florida.

2) When it's 'hot' and 'humid', the human body cannot reject heat through perspiration. The air is already saturated with water vapor, and your sweat just sits on your skin, never evaporating ( presently killing Guatemalan cane cutters by renal failure [ it was 119-F in Myanmar the other day ]). In order to 'cool' humans, you must dehumidify the air. The AC unit takes the air temp. down below dewpoint, the moisture collects on the evaporator coil, and drains out of the unit.
3) The American Society of Heating Refrigeration and Air conditioning Engineers ( ASHRAE ) publishes a HANDBOOK which contains all the necessary data from which to design HVAC systems.
Within the handbook, you'll find psychrometric charts, which allow you to study, and design for the amount of heat energy ( enthalpy )within a pound of dry air, for any given environmental condition. This is where you'll see the dewpoints ( temp at which water vapor condenses out of the air as liquid water ). By definition, the temp at the bottom of all 'clouds' is exactly at the 'dewpoint' temperature. If you cool without dehumidifying, you'll reach dewpoint, 100% relative humidity, and the water vapor will condense on the interior surfaces of the room, where 'killer' stachybotrys mold can take hold, requiring the building to be condemned.
4) If the temperature of the attic air in a ventilated attic, right at the top of the thermal insulation package above the ceiling, is no more than ten degrees above the outdoor temperature, then you're 'golden', as far as your AC system is concerned. It doesn't matter if the roof is a million-degrees!
The roof could be black and it might not make any difference.
Sure, your head might cook standing in there, but it doesn't make any difference to the house, as long as the attic is properly ventilated.
Insulation cannot 'see' infrared radiation that you feel standing there. Only delta-T. You could spend a fortune on roof coatings of extreme albedo, and see ultimately see zero difference in your air conditioning bill.
I used to see charlatans at HOME DEPOT all the time, deceiving uneducated home owners, with the infrared 'scam' hiding in plain view.

[freebeard]

While you think in terms of conventional attics, I think in terms of geodesic dome, with minimal material composition. Like aluminum plating weather shell with a tensioned fabric or foil inner shell.

Also I wonder whether the foamed aluminum can pass air or Nitrogen gases. If so it might be an ideal material to cast nose cones for atmospheric reentry.

edit:
To be clear, the space between the inner and outer shell replaces the attic. But it's a dynamic system (down on the shady side, up on the sunny side) instead of a stagnant pool. Don't get me started on engineered roofing trusses.

[Piotrsko]

Need a skin that tolerates, afaik 2500 degrees F. Aluminum gets all wonky at 1300. High nickle stainless is traditionally used.

[aerohead]

Originally Posted by freebeard

While you think in terms of conventional attics, I think in terms of geodesic dome, with minimal material composition. Like aluminum plating weather shell with a tensioned fabric or foil inner shell.

Also I wonder whether the foamed aluminum can pass air or Nitrogen gases. If so it might be an ideal material to cast nose cones for atmospheric reentry.

edit:
To be clear, the space between the inner and outer shell replaces the attic. But it's a dynamic system (down on the shady side, up on the sunny side) instead of a stagnant pool. Don't get me started on engineered roofing trusses.

Then, the reflectivity and R-Factor would really matter.
Where I am, R-45 is recommended for attics, so you'd be looking at 14-inch thick 'walls.'
Big shade trees, or outdoor shading of the structure would be good.
My dad and I constructed a full-length, rough-cedar, angled-slat sunshade for the west exposure of their Lubbock home.
R-19 on top of what they had in the attic. Lots of soffit vents, and 5, 12-inch wind turbine vents on the roof. Light colored shingles. 'Triple-glazed' windows with DIY heat-shrink clear vinyl. Weather stripping and caulk.
Summer utility bill took a $100/ month drop. Winter heating bill went south as well. ( mid-1970s Dollars ).

[freebeard]

Here's the story as a comic: www.stuartmcmillen.com/comic/chilling-domes/

Ten degree delta (first approximation), based on the shape. Theories on why and how: Buckminster Fuller’s Chilling Domes: the physics

I lived in a dome for seven years, and can confirm the effect.