In an effort to find efficient ways to keep buildings cool in hot weather and warm in cold weather, researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME) have been able to hold copper particles in liquids. We have developed a shape-changing material that Or solid form. The material uses very low currents to switch between the two states, but this is only a fraction of the energy that can be saved through passive heating and cooling.
The non-combustible material consists of multiple layers including polyurethane film, graphene sheet and gold grid. But the real action happens thanks to the aqueous electrolyte and the copper particles.
When the material is in heating mode, copper particles are deposited on the film forming a solid layer that is good at absorbing solar heat. After passing a low current through the material, the particles disperse in the electrolyte and the material enters a cooling mode where the sun’s warming infrared energy is reflected instead of absorbed. In a study, the material he managed to switch back and forth for 1,800 cycles.
“We’ve basically come up with a low-energy way of treating the building like a person: adding layers when it’s cold and taking them off when it’s hot,” said lead researcher Ast. Professor Po-Chun Hsu. “This kind of smart material allows us to maintain the temperature inside the building without using a lot of energy.”
In fact, researchers found that the material can retain 93% of the infrared energy it touches when it is in a solid heating mode configuration. Liquid cooling mode can reflect up to 92% of this energy. Even factoring in the meager current required to activate the shift, this translates to savings of up to 8.4% on his HVAC cost for the building, the researchers say.
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“Once you switch states, you don’t need to add any more energy to stay in either state,” Hsu said. “Thus, buildings that don’t need to switch between these states very often are actually using a negligible amount of electricity.”
In addition, materials can be programmed to change in desired temperature, so they can be tuned to work differently in disparate climates.
In addition, the material is transparent in cooling mode, so in addition to providing temperature regulation benefits, it can also provide an interesting design element. Pigment applied on the bottom layer in transparent cooling mode, while in solid warming mode it gives a coppery appearance.
Materials that change color in response to electrical current in this way are known as electrochromics, and I saw a very similar material developed two years ago by scientists at Duke University in North Carolina. You can also see materials developed for window films and sunglasses.
So far, the researchers have created pieces of material about 6 cm (about 2.4 inches) in diameter, which they say could be used in a shingles-like configuration to build a covering. Their next step is to investigate methods of fabricating the materials and how using them between liquid and solid states can be valuable in terms of passive thermal control. .
A study was published in a journal natural sustainability.
Source: University of Chicago
