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Yang Lab / University of Colorado at Boulder
The roof network that can cool a house with reduced energy consumption
US researchers have developed a new low cost system that could provide efficient cooling of homes while consuming very little electricity.
The team has developed a roof-sized set made of a highly reflective material made of glass and polymers.
During testing, the system kept the water about 10 ° C cooler than the ambient air when it was exposed to the midday sun in summer.
The approach could also be extended to cool power plants and data centers.
The system is based on what is called a cooling meta-material, which is essentially a technical film not found in nature.
Last year, US researchers at CU Boulder published a study on the extraordinary properties of the new film, which returns almost all the sunlight.
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But he also has another cooling tip that makes him quite special. If you use the film to cover the water, any heat contained in the liquid can escape into the air.
Thus, when the heat escapes and is not replaced because the material deviates from the sun's rays, temperatures fall rapidly.
Now, the scientists have improved the system and have built and tested a set of 13 square meters panels, small enough to fit most roofs.
"You can place these panels on the roof of a single-family home and meet its cooling needs," said Dongliang Zhao, senior author of CU Boulder's Department of Mechanical Engineering study.
What is the effectiveness of this material?
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Glenn J. Asakawa
The new material looks like aluminum foil but is slightly thicker
The system has been tested outdoors in various weather conditions. During experiments conducted in the summer of 2017, the reflection system allowed to keep a container of water colder than the ambient air during the hottest hours of the day.
"We can now apply these materials on building roofs and even build large-scale water cooling systems with considerable advantages over conventional air conditioning systems, which require large amounts of electricity to operate", said Associate Professor Gang Tan, another author of the University of Wyoming study.
What makes it work?
The key material consists of glass microspheres embedded in a polymer film, covered with a thin layer of silver.
At only 50 micrometers, it is slightly thicker than aluminum paper.
Another great advantage of this material is that it can be manufactured in rolls, which facilitates its application for residential and commercial applications.
For what is it likely to be used?
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Glenn J. Asakawa
The film can be made cheaply, say the authors
The authors say that one of the most effective uses of the new material would be to cool thermoelectric power plants. These facilities use large amounts of water and electricity to maintain the operating temperature of their machines. The use of new equipment could make them more efficient.
How much cooling does the world need?
In 2016, about 10% of global energy consumption was spent on air conditioning. According to the International Energy Agency, this tariff is expected to triple by 2050, with air conditioning consuming as much electricity as used in China today.
Besides all the CO2 produced in the form of electricity is created to power these devices, the air conditioning units also contain powerful greenhouse gases in the form of hydrofluorocarbons.
HFCs were introduced to protect the ozone layer, as the previous generation of chemicals for cooling exacerbated the hole that had developed in Antarctica in the 1980s.
Although HFCs are less damaging, they have significant global warming potential. In 2016, countries agreed to phasing them out over the next 15 to 20 years. If this happens successfully, it could have a significant impact on limiting future temperature increases.
The new study was published in the journal Joule.
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