Engineers Create Mirror-Like Material That Could Cool Buildings By Reflecting Heat Into Space

The mirror is built from several layers of wafer-thin materials. The first layer is reflective silver. On top of this are alternating layers of silicon dioxide and hafnium oxide. These layers improve the reflectivity, but also turn the mirror into a thermal radiator. When silicon dioxide heats up, it radiates the heat as infrared light at a wavelength of around 10 micrometres. Since there is very little in the atmosphere that absorbs at that wavelength, the heat passes straight out to space. The total thickness of the mirror is around two micrometres, or two thousandths of a millimetre.

Writing in the journal, Fan puts the installed cost of mirrors at between $20 and $70 per square metre and calculates an annual electricity saving of 100MWh per year on a three storey building.

Fan said that the mirror could cool buildings – or other objects – simply by putting it in direct contact with them. Coating the roof of a building with the mirror would prevent heating from sunlight but do little to remove heat from its interior. More likely, the mirror would be used to cool water or some other fluid that would then be pumped around the building.

Mirrors could replace air conditioning by beaming heat into space

Cheaper air conditioning, and possibly hazard of frying birds and planes alike, what is not to like of this invention

Perhaps they could improve those solar plants that cook the birds with this mirrors?

originally posted by: Indigent

The mirror is built from several layers of wafer-thin materials. The first layer is reflective silver. On top of this are alternating layers of silicon dioxide and hafnium oxide. These layers improve the reflectivity, but also turn the mirror into a thermal radiator. When silicon dioxide heats up, it radiates the heat as infrared light at a wavelength of around 10 micrometres. Since there is very little in the atmosphere that absorbs at that wavelength, the heat passes straight out to space. The total thickness of the mirror is around two micrometres, or two thousandths of a millimetre.

Writing in the journal, Fan puts the installed cost of mirrors at between $20 and $70 per square metre and calculates an annual electricity saving of 100MWh per year on a three storey building.

Fan said that the mirror could cool buildings – or other objects – simply by putting it in direct contact with them. Coating the roof of a building with the mirror would prevent heating from sunlight but do little to remove heat from its interior. More likely, the mirror would be used to cool water or some other fluid that would then be pumped around the building.

Mirrors could replace air conditioning by beaming heat into space

Cheaper air conditioning, and possibly hazard of frying birds and planes alike, what is not to like of this invention

Perhaps they could improve those solar plants that cook the birds with this mirrors?

You know, frying passing birds was the first thing that popped into my mind, too. You know you've become deeply cynical when something that should be good probably does have a dark consequence.



This could've also gone into the UFO/Aliens forum as well because, god knows all those heat beams going up into space are going to eventually hit a spacecraft. Forget sharks, we want skyscrapers with freaking laser beams.

Nope, birds are more likely to get fried first.

First think I thought about was, reflections would be very bad. Thinking about a plane flying by into a reflected sunlight would potentially blind a pilot. NOT GOOD. Then expanding that thought a bit more all that reflected sunlight back into space would blind satellites, possibly the space station, and astronauts.

Dah. most everyone knows to reflect and dissipate heat. Mirrors and white roofs have been used for years. Most peoples ceilings are not insulated either. There are lots of way to save and make energy out there. Most people are just too stupid to use or research that such things exist and work. Alternative energy included. Common sense is gone. Must be the fluoride in the water lol

Light can be reflected in many ways. With varying degrees of reflective mirrors and angles. Can be absorbed and used as energy before it heats the inside. The inside can be insulated from the outside. Lots of alternatives. It is endless. a reply to: Ceeker63

a reply to: roth1

It does not only reflect light it absorbs heat and emit IR, not a simple mirror

a reply to: Indigent

I see nothing in the "source" article about the reflections being focused. Actually, I would suspect that they could be deliberately unfocused to spread the reflected rays and not "fry birds and planes."

Greetings,
Having sold and installed reflective insulation in residential/commercial Buildings for over 30 yrs may I can put some light on this.

Aluminum and gold are the two most eff reflectors of radiant energy. both at 97% eff.
The amount of energy absorbed and reflected is equal.
Since heat energy always passes to the low energy object, cold, they are equally effective for both winter and summer.
See: fifoil.com
On the flip side insulation materials made from high energy absorbing materials such as glass and wood,paper are low eff insulations, absorbing and emitting about 90% plus of the energy. This is why the feds, utility companies etc promote them, more tax revenues, higher profits.
I'm attaching a pamphlet I use to distribute for those of you who might be interested in this subject

TROY, IL 62294 8393 HM 618 667 4222 e-m [email protected]

Information and opinions by George Himmeger : The chart data enclosed is taken from a mechanical engineering handbook along with
opinions from thirty years field experience

EXPLORING THE LEGITIMACY OF CLAIMS OF CHARACTERISTICS, TEST PROCEDURES AND “R” RATINGS FOR THERMAL INSULATIONS USING MECHANICAL ENGINEERING HAND BOOK DATA AND FORMULA

Fiber glass FG - Radiant Barriers RB

Confusion about the performance of various insulation materials is not a recent phenomenon. Some of the confusion comes from the fact that various materials control heat energy transfer according to the specific physical properties of the materials and their assembly for use. Another problem is that large manufacturers, with government sanction, literally control the methods used to test their product and competing products. This has been an ongoing fight for over fifty years in this country. Some products, commonly used here, are not allowed in other countries because of low performance and serious health issues. The most common testing problems are:

(1) The tests do not reflect actual “installed summer / winter conditions”, which can reveal up to fifty percent difference in performance compared to “accepted tests”.
(2) Most tests favor conductivity resistance and limit the effects of radiant energy. Most homes have about 12-15% conductive surfaces, about 7% is convection and air spaces accounting for up to 80% radiant energy gain or loss.
(3) Some tests do not reveal the serious performance degradation from condensation, actually storing and increasing heat flow, and how it affects the interior humidity levels.
(4) Some tests do not reveal possible mold and other problems.
(5) Some tests, or labeling, do not reveal the health problems due to toxic chemicals. This information is classified as proprietary information and given only to the government.
(6) The tests or labels do not reveal the ratio of material to air volume This ratio can be as low as 1% mass to 99% air volume allowing radiant energy to travel through like an open door, plus air infiltration. The exception to this is radiant barriers which rely on the air space to perform efficiently. If insulation tests were performed with the best interest of the consumer at heart, there would probably be only two insulations available to the consumer.
(7) The other subject ignored by the bulk insulation manufacturers is the approximate 80% heat gain/loss in buildings through radiant heat, infrared energy. This can be expected because most bulk insulations are only about 10 – 20% efficient in rejecting radiant energy, compared to about 97% for radiant barriers.
(8) The “R” factor for bulk insulations are based on the reciprocal of a “u” factor, a conductive test ( for a material that is about 99% air spaces?). The efficiency of RBS are based on a “k” factor. You cannot obtain a “R” value from a “k” factor.
The independent, non competitive, method presented here is based on long established data of energy exchange between two surfaces, ceiling/floor, at a given Delta T” (temperature difference between two surfaces) and will tell you what amount of heat energy is radiated into and out of the home summer and winter. This method depends on no tests and incorporates the characteristics of the insulation, building materials and the effects of any climate condition. It can be performed by anyone with a thermometer. Conventional “R” factor calculations cannot tell you this, due to the problems mentioned above and that the calculations are usually for material only. With “R” factors you can calculate for one set of condidtions and then find out the calculations had no reference to what is actually going on in the structure.

The common denominator for all insulations is; what is the temperature of the drywall and the floor it is radiating to? This “in situ” method incorporates all the variables because the drywall temperature determines your heating / cooling costs. You can use either Btu calculations or temperature calculations. You can see why the manufacturer of low efficiency insulation will not want to use this method. The drywall emission rate, about 90%+, is used in the following chart because that is the most commonly used material. The source of this information, and the following chart, is from an emissivity chart and formula of a mechanical engineering handbook. You may not be familiar with this source of information. It is a manual of materials charts, characteristics, formulas and numerous other factors used by engineers to manufacture most every thing you use. For many professional engineers it is the engineer’s “bible”.

THE HUMAN FACTOR The average person believes that the air temperature is the dominant factor in comfort. This might be true if it wasn’t for the energy radiating into and out of the building with its effects. It is this energy ratio between the interior surfaces and the surface of the body that ultimately determines the comfort factor and energy consumption.
For maximum energy savings you want the lowest rate of absorption and re-radiation of energy. Lower is better. The determining factors of any insulation’s performance are:
1 The rate of absorption and re-emittance ( radiating ) of energy. From the “bible” we see that wood (cellulose), and glass (fiberglass) is about 90%+ efficient in absorbing and re radiating energy. Base foam materials are about 20% efficient. Aluminum foil about .03%.
2 Other than the basic material and its construction features, moisture, either from humidity or condensations can cause substantial energy flow. Using the ratio or 5% increase per 1% of moisture by weight, data published by the National Bureau of Standards shows that fiberglass and cellulose can increase energy flow about 45 / 72% due to moisture in an uninhabited structure. Even the relative humidity can account for a dramatic increase in energy flow. Increased humidity levels in an inhabited structure can cause even more energy lose / gain along with the 1,000+ btu used to convert vapor to liquid. Since radiant barriers do not cause condensation and are superior vapor barriers, the interior humidity levels can be lower than with other insulations.
3 The low quality of installation can also be a detriment to the effectiveness of insulation.
The following chart shows Btu transfer for various ceiling temperatures. Calculations for infiltration, doors and windows are separate as they will be the same for any insulation installed.

Greetings, to cont,

To increase the envelope efficiency even more, Insulation Specialists has developed a simple method of installing RB to reduce to about 1% the conductivity surfaces of studs and ceiling joists from the normal 12-15 % surface area. In summer you can measure the drywall temperature which can reach up to 110 degs on a 95 deg day with the lower efficiency insulations and no roof shading. If the floor temperature is 75 degs the ceiling, using temperature figures, will radiate about 99 degs/sf/hr. The 110 deg ceiling temperature is about 25 degrees hotter than a winter radiant heat system, causing the air conditioner to run continuously to try to compensate. Without the air conditioner the interior temperature could exceed 100 degs. If the RB is 110 degs it will radiate about 2-3 degs /sf/hr. In a properly designed ranch home the interior temperature, with RB, will be about 80-81 degs without air-conditioning. The humidity levels can also be lower as the RB does not cause condensation which can be forced into the home by the high temperatures in the structure as with some of the lower efficiency materials. Question; if the indoor temperature can be hotter inside than outside without the air-conditioned, how can the manufacturer claim their material is insulation?
As you use the chart keep in mind these two questions;
1 If bulk insulations are about 99% airspaces and radiant energy travels through space at about the speed of light, and the base material absorbs and re-radiates the energy at about an 80-90 percent efficiency, how can a manufacturer claim their material is an insulator? More importantly how can an “R” value be assigned to them ?
2 If the function of a RB is to reflect energy, how can an “R” factor be assigned to it? How can the government and the manufacturers of bulk insulations legitimately force the use of “R” factors in evaluating radiant barriers? More importantly, why?
3 Why has the US Senate interfered with, at least twice, the governments fair trade polices, including FTC regulations, when it comes to insulations? Regulations which would have provided for a fair playing field. Answer: Over $100,000,000,000.00 tax revenue per year due to the excessive use of energy.
Because of this and other reasons the American home owners is using up to two to three times the amount of energy to heat a cool a home than what should be used.
In summer you can determine the temperature of your ceiling drywall by taping a thermometer to the drywall surface.
This chart is based on a 75 deg floor temperature. The chart can be validated by using the emissivity data and formula from Mark’s Mechanical Engineering Handbook. FG values are for insulation between joists and include joist heat transfer. The RB value is for the joists surfaces covered with the RB and a furring strip to separate the RB from the drywall. “A” is the dry wall temperature. “B” represents the Btu’s radiated for the FG installation. “C” represents the Btu’s radiated for the RB installation. “D” the Btu difference between the FG and RB.
Although the mechanics for side walls will be slightly difference this method can be used for approximate comparisons.

Summer Winter
“A” “B” “C” “D” “A” “B” “C” “D” 150 88 5 83 75 0 0 0
140 75 4 71 70 5 .3 5
130 61 3 58 60 14 1 13
120 49 3 48 50 22 1 21
110 37 2 35 40 31 2 29
100 26 1 25 30 38 2 36
90 15 1 14 20 45 3 42
80 5 .3 5 10 52 3 49
75 0 0 0 0 58 3 55

The 110 deg is high lighted to represent a 95 deg day. The 30 line is highlighted to show the similarities of the summer winter conditions. Note the jump when the temperature gets down to zero degs. Because of the rapid drop off in FG efficiency as the material thickness is increased it is difficult to extrapolate the RB and FG data for “R” value comparison. Compared to the advertised “R” value for FG the RB “R” factor could exceed “R”100 value by a considerable amount, and it is impossible to have a “R” value of 100 much less 100 plus.

Myth: Dust adversely affects the RB performance. A: Dust has little or no effect on a horizontally installed RB with airspace both sides. The top surface could be painted black and the bottom surface might emit 1 or 2 extra Btus. Most ceiling installations have one or more layers, so any increase in heat flow is doubtful. There is little or no dust on vertical installations. Even with dust present the RB is superior to other materials. These comments never reveal the test material type or test method, ( if actually tested )or actual performance differences.
Myth: Holes adversely affect the RB performance. A: Some RBs are manufactured with vapor escape holes. I know of no laboratory tests showing an increase in heat flow, particularly in multi layer installations. Obviously you don’t want large holes, these should be repaired.
Myth: RBs are not as efficient on up heat (winter) as summer. A: The engineering handbook does not make such a distinction. The mechanics of up heat vs down conductive heat flow are different; therefore any given material may exhibit slight differences for winter. However these comments never note that the RB is still superior to other materials.
Myth: Aluminum corrodes. A: Pure aluminum, such as the 99.9% pure foil used in RB, does not corrode under normal atmospheric conditions.
A light, invisible, oxidation does occur preventing any further oxidation. You would not want to breathe the fumes that could cause severe corrosion. Corrosion can and does occur in some unfinished alloy aluminum because of the dissimilar metals used for alloying the metal.
Myth: RB loses its insulation values over time. A: Since RBs do not corrode, the answer is self evident. I know of installations over 30 years old that work just fine.
Myth: You can’t use RB in very cold climates: A When Perry and other scientists went to the poles they use aluminum foil to insulate the structures. The Navy SEALS used multi-layer foil (mfg’d to mil spec HH I 1252) in 1964 in the Artic buildings where the mineral wool was failing. RB are used quite extensively and exclusively, in severely cold conditions, such as, cryogenics and space platforms.
Myth: RB are not very efficient in attic add-on application. If the application is not proper then this is a true statement. However, the retrofit tests so far conducted are not the most
effective application method. I have found that a double layer installation directly over the existing material can reduce a/c run time up to 30% or more. Why test the most inefficient method?

Energy saving reflective glass has been around for a while, so I guess this is just another further development of that technology. However when you use it, architectural considerations should be made in case there are inadvertent effects.

"Reflecting heat into space"? Surely not, as any reflected heat would be trapped by the ionosphere and thus have a "warming effect" both locally and eventually over a much wider area.

High density areas of habitation, with all those concrete and glass structures already create their own localized climate and on a sunny day can remain radiating heat throughout the cooler night hours. Thus artificially ramping up temperatures in the local area, whereas outside of that built up area, temperatures drop a lot more once the heat source, the sun, has set.

Now if it absorbs that heat and does something with it, without heating up the surrounding area, then that would be a lot better.

a reply to: Britguy

"Reflecting heat into space"? Surely not

I would think Nature reviewers would know what wavelengths are absorbed or not by atmospheric species

Passive radiative cooling below ambient air temperature under direct sunlight

Ill read it tomorrow when bored at work

it would heat the atmosphere long before the heat gets into space.

a reply to: ChesterJohn

The infrared atmospheric window is the overall dynamic property of the earth's atmosphere, taken as a whole at each place and occasion of interest, that lets some infrared radiation from the cloud tops and land-sea surface pass directly to space without intermediate absorption and re-emission, and thus without heating the atmosphere.

Infrared window

The bonds of H2O and NH3 absorb at wavelengths shorter than 8 µm. Except for the bonds in O3, no bonds between carbon, hydrogen, oxygen and nitrogen atoms absorb in the interval between about 8 and 14 µm, though there is weaker continuum absorption in that interval.

whats up with the stubbornness around these parts of the internet...

originally posted by: pauljs75
Energy saving reflective glass has been around for a while, so I guess this is just another further development of that technology. However when you use it, architectural considerations should be made in case there are inadvertent effects.

Saw that a while back. I guess that building will be coming down in it's own footprint some day soon...they'll "pull it"

Greetings,

The comments about reflected energy heating up the atmosphere are not correct. The earth radiates daytime heat energy back into space each night. You need a material of some sort that absorbs the radiant energy. There is nothing there.

Compare to a 20 deg cold sunny day. The energy is absorbed by your clothing, skin, etc, not the air. The air is cold but you are warm. This phenomena causers problems on space craft and reflective foils are used to control energy gain and losses.

The technology talked about here has been used since at least 1925 in residential and commercial buildings.
I have partial role of material that was manufactured about 1927.

In the 30 + yrs I sold and installed this type of material I never found anything that would equal it.