How to Cool Buildings Without Electricity? Beam Heat into Space

[Dubious]

by Charles Q. Choi, Live Science Contributor | November 28, 2014 09:27am ET

In this illustration, a reflective panel is coated with a material designed to help cool buildings without using air conditioning.

A new superthin material can cool buildings without requiring electricity, by beaming heat directly into outer space, researchers say.

In addition to cooling areas that don't have access to electrical power, the material could help reduce demand for electricity, since air conditioning accounts for nearly 15 percent of the electricity consumed by buildings in the United States.

The heart of the new cooler is a multilayered material measuring just 1.8 microns thick, which is thinner than the thinnest sheet of aluminum foil. In comparison, the average human hair is about 100 microns wide. [Top 10 Craziest Environmental Ideas]

This material is made of seven layers of silicon dioxide and hafnium dioxide on top of a thin layer of silver. The way each layer varies in thickness makes the material bend visible and invisible forms of light in ways that grant it cooling properties.

Invisible light in the form of infrared radiation is one key way all objects shed heat. "If you use an infrared camera, you can see we all glow in infrared light," said study co-author Shanhui Fan, an electrical engineer at Stanford University in California.

One way this material helps keep things cool is by serving as a highly effective mirror. By reflecting 97 percent of sunlight away, it helps keep anything it covers from heating up.

In addition, when this material does absorb heat, its composition and structure ensure that it only emits very specific wavelengths of infrared radiation, ones that air does not absorb, the researchers said. Instead, this infrared radiation is free to leave the atmosphere and head out into space.

"The coldness of the universe is a vast resource that we can benefit from," Fan told Live Science.

The scientists tested a prototype of their cooler on a clear winter day in Stanford, California, and found it could cool to nearly 9 degrees Fahrenheit (5 degrees Celsius) cooler than the surrounding air, even in the sunlight.

"This is very novel and an extraordinarily simple idea," Eli Yablonovitch, a photonics crystal expert at the University of California, Berkeley, who did not take part in this research, said in a statement.

The researchers suggested that their material's cost and performance compare favorably to those of other rooftop air-conditioning systems, such as those driven by electricity derived from solar cells. The new device could also work alongside these other technologies, the researchers said.

However, the scientists cautioned that their prototype measures only about 8 inches (20 centimeters) across, or about the size of a personal pizza. "We are now scaling production up to make larger samples," Fan said. "To cool buildings, you really need to cover large areas."

The scientists detailed their findings today (Nov. 26) in the journal Nature.

How to Cool Buildings Without Electricity? Beam Heat into Space



Pakistan govt offices are known not to pay electricity bills they should invest in such a system!

 

[TheNoob]

You sure? Cuz i'm about to order some few thick mirriors.....

 

[Dubious]

You sure? Cuz i'm about to order some few thick mirriors.....

Did you read before commenting?

This material is made of seven layers of silicon dioxide and hafnium dioxide on top of a thin layer of silver

Dont know any mirrors made of that

This material is made of seven layers of silicon dioxide and hafnium dioxide on top of a thin layer of silver. The way each layer varies in thickness makes the material bend visible and invisible forms of light in ways that grant it cooling properties.

serving as a highly effective mirror.

prototype measures only about 8 inches (20 centimeters) across, or about the size of a personal pizza

 

[TheNoob]

Did you read before commenting?


Dont know any mirrors made of that

but but... I wanted to contact the aliens...

 

[Dubious]

but but... I wanted to contact the aliens...

Stop trolling we have enough indians filling that job!

 

[gslv]

Stop trolling we have enough indians filling that job!

Haan ji , aapne yaad kiya is nacheez ko.
On the topic cool. Even painting the roof white reduces the temp a lot.

 

[syedali73]

Well, I am not sure if the heat will be able to leave the atmosphere though. Any data on that?

 

[Dubious]

Well, I am not sure if the heat will be able to leave the atmosphere though. Any data on that?

Need to find the article...

The scientists detailed their findings today (Nov. 26) in the journal Nature.

 

[ashok mourya]

A team of researchers at Stanford University have developed a new type of solar structure that can provide cooling for buildings, even in direct sunlight, which could lead to air conditioning units that require no electricity.

The solar cooling device designed by the team reflects most of the sunlight hitting it, while also taking heat from the buildings or structures it is installed on and radiating it out into space, thereby improving the cooling efforts of those structures.

"People usually see space as a source of heat from the sun, but away from the sun outer space is really a cold, cold place. We've developed a new type of structure that reflects the vast majority of sunlight, while at the same time it sends heat into that coldness, which cools manmade structures even in the daytime." - Shanhui Fan, professor of electrical engineering

According to the team, the challenge of creating such a device is in developing a reflector capable of reflecting as much sun as possible, while also efficiently emitting thermal radiation within a specific range of wavelengths, so the heat energy can escape the Earth's atmosphere.

The solution came from using nanostructured photonic materials that can either enhance or suppress certain wavelengths of light, enabling the team to combine the reflector and thermal emitter in one device that has no moving parts and no external energy demands. The team engineered nanophotonic materials from quartz and silicon carbide, which are both weak in absorbing sunlight, to build their device.

According to the research results, the new panel can achieve a net cooling power of over 100 w per square meter, and that a typical single-family house with only 10% of its roof covered with the panels could see about 35% of its cooling needs in the summer offset by the device.

Because these radiative cooling panels use passive technology, there is no external energy input required, and the lack of moving parts to wear out or break on the panels would lead to a longer useful life and low maintenance costs.

"We can foresee applications for radiative cooling in off-the-grid areas of the developing world where air conditioning is not even possible at this time. There are large numbers of people who could benefit from such systems." - Fan

 

[syedali73]

Need to find the article...

Some will leave the atmosphere into the space but not all. The atmosphere is made up of gases and when we direct radiation at them, the gas molecule will absorb it and begin to warm up. I am saying this because total solar radiation that falls on our planet, only 29% is reflected back into space whereas 23% is absorbed by the atmosphere and 48% by the earth surface.

 

[!eon]

You can reduce heating up of your building but you still need electricity to cool it.

 

[Dubious]

Some will leave the atmosphere into the space but not all. The atmosphere is made up of gases and when we direct radiation at them, the gas molecule will absorb it and begin to warm up. I am saying this because total solar radiation that falls on our planet, only 29% is reflected back into space whereas 23% is absorbed by the atmosphere and 48% by the earth surface.

Yea...but so far it is still a prototype and a small one...I am sure if they continue work they will have it figured out

A cool idea
New materials may change the way temperatures are regulated

AIR conditioning is a transformative technology. It has made the world’s torrid climes pleasanter to live in, and enabled the siesta-free working habits of the temperate regions to move closer to the equator. But cooling buildings takes a lot of energy. Heat must be pumped actively from their interiors to their exteriors. Fully 15% of the electricity used by buildings in the United States is devoted to this task. If an idea dreamed up by Aaswath Raman of Stanford University and his colleagues comes to fruition, that may change. Dr Raman has invented a way to encourage buildings to dump their heat without the need for pumps and compressors. Instead, they simply radiate it into outer space.

The idea, described in this week’s Nature, is both cunning and simple. Outer space is very cold (about 3°C above absolute zero) and very big, so it is the perfect heat sink. Earth radiates heat into it all the time. But this is compensated for by the heat the planet receives from the sun. To encourage one part of Earth’s surface (such as an individual building) to cool down, all you need do in principle is reflect the sunlight which falls on it back into space, while also encouraging as much radiative cooling from it as possible.

To try to turn principle into practice Dr Raman has made a material which reflects 97% of sunlight while itself radiating at a wavelength of between eight and 13 microns (or millionths of a metre), which is where the atmosphere is most transparent. Production of the material is made possible with modern manufacturing methods. It consists of four layers of silicon dioxide interspersed with three of hafnium dioxide. Each of these seven layers is of a different, precisely defined thickness, ranging from 13 to 688 nanometres (or billionths of a metre). It is backed by a layer of silver 200 nanometres thick, to act as a mirror.

The result, a sheet with a total thickness of less than two microns, is the photonic equivalent of a semiconductor: it does to light what a semiconductor does to electricity, namely manipulates its energy levels. Since, optically speaking, energy levels correspond to wavelengths, such an arrangement can be tweaked to reflect some wavelengths and preferentially emit others. And that, in choosing the layers’ pedantically exact dimensions, is just what Dr Raman and his colleagues have done.

Polythene plan
They worked out on a computer how thick those layers needed to be to reflect pretty much the entire solar spectrum while, at the same time, shedding infra-red light at the frequency which can most easily escape from Earth into outer space. And then they made it, to see if it works.

It does. Mounted on a silicon wafer to keep it flat, held in a specially designed box made of Mylar, polythene, polystyrene, acrylic and wood, to minimise the conduction of heat into it from its surroundings, and then left outside on a sunny, albeit rather wintry Californian day, the photonic sheet settled down to a temperature 4.9°C cooler than its surroundings. If it were thermally connected to those surroundings, rather than isolated from them, that temperature difference would disappear—but the result would be to cool the surroundings slightly.

Turning this discovery into a useful device will be a journey down a long road. Dr Raman and his colleagues have, however, taken the first step by working out that they should be able to replace the hafnium dioxide (which is expensive) with titanium dioxide (which is cheap). They will probably need to replace the silver, too—though the cost of silicon dioxide, also known as sand, is not so much of a problem.

The process will also have to be scaled up. And it will work only on those parts of a building (mainly the roof) that have a clear view of the sky, and thus of outer space, so it will not replace air conditioning completely. But the idea of even part of a building’s cooling system being electricity-free is an attractive one, so this may be the start of something really cool.


http://www.economist.com/news/scien...ange-way-temperatures-are-regulated-cool-idea

You can reduce heating up of your building but you still need electricity to cool it.

Yes but it "technically speaking" would reduce the reliance on air conditioning

 

[forcetrip]

Its called therma sheets and I am in the process of putting them on my roof as well. Its definitely not going to throw the heat into space or so it seems with my limited knowledge of how light works. It is going to cool the house by minimum of 2c and maximum of 5c. That means if you have air conditioning it wouldn't have to work the extra degrees to cool the room.

 

[Dubious]

Its called therma sheets and I am in the process of putting them on my roof as well. Its definitely not going to throw the heat into space or so it seems with my limited knowledge of how light works. It is going to cool the house by minimum of 2c and maximum of 5c. That means if you have air conditioning it wouldn't have to work the extra degrees to cool the room.

You have them in Pakistan? but their prototype is only a small thing and it was only published last year...

their prototype measures only about 8 inches (20 centimeters) across, or about the size of a personal pizza.

 

[Thəorətic Muslim]

Green roof - Wikipedia, the free encyclopedia

Passive Cooling: Responding to Electricity Demand in the UAE | Carboun: Advocating Sustainable Cities in the Middle East

In Hong Kong apparently researchers found out that the massive use of Air Conditioners raised the temperature of the City by ~3 degrees. Article was on BBC back in 2009-2011. I cant seem to find the article.