Porous Polymers with Switchable Optical Transmittance for Optical and Thermal Regulation

Mandal, Jyotirmoy; Jia, Mingxin; Overvig, Adam; Fu, Yanke; Che, Eric; Yu, Nanfang; Yang, Yuan

doi:10.1016/j.joule.2019.09.016

Cited by 237 publications

(187 citation statements)

References 28 publications

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“…For the realization of high solar reflectance, the densely stack of the fibers in the electrospun membrane could bring plenty of interfaces between air and PVDF/TEOS, and since PVDF/TEOS scarely absorbs light in solar region, the numerous interfaces would lead to a high solar reflectance of the membrane . Therefore, higher thickness and fiber density would cause higher membrane reflectance, which was confirmed by the simulation results as shown in Figure S5a,b (Supporting Information).…”

Section: Resultssupporting

confidence: 57%

“…The concept of radiative cooling is that a substance (referred as radiator) on earth could spontaneously reduce its temperature without any energy input, by sending excessive heat to outer space in the form of infrared thermal radiation through the atmospheric window (8–13 µm) . This environmentally‐friendly technology could be put into practical applications via two ways: 1) directly attach radiators on the surfaces of objects (e.g., building rooftop) which need to be cooled; 2) Use radiators to cool heat‐transfer (e.g., water) fluid which could be integrated into other thermal systems (e.g., air conditioner or condensers) . Particularly, daytime radiative cooling has attracted intense interest in recent years.…”

Section: Introductionmentioning

confidence: 99%

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Scalable Flexible Hybrid Membranes with Photonic Structures for Daytime Radiative Cooling

Wang

Liu

et al. 2019

Adv Funct Materials

281

185

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Passive radiative cooling technology can cool down an object by reflecting solar light and radiating heat simultaneously. However, photonic radiators generally require stringent and nanoscale-precision fabrication, which greatly restricts mass production and renders them less attractive for large-area applications. A simple, inexpensive, and scalable electrospinning method is demonstrated for fabricating a high-performance flexible hybrid membrane radiator (FHMR) that consists of polyvinylidene fluoride/ tetraethyl orthosilicate fibers with numerous nanopores inside and SiO 2 microspheres randomly distributed across its surface. Even without silver back-coating, a 300 µm thick FHMR has an average infrared emissivity >0.96 and reflects ≈97% of solar irradiance. Moreover, it exhibits great flexibility and superior strength. The daytime cooling performance this device is experimentally demonstrated with an average radiative cooling power of 61 W m −2 and a temperature decrease up to 6 °C under a peak solar intensity of 1000 W m −2 . This performance is comparable to those of state-of-the-art devices.

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Section: Resultssupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Scalable Flexible Hybrid Membranes with Photonic Structures for Daytime Radiative Cooling

Wang

Liu

et al. 2019

Adv Funct Materials

281

185

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“…The heating and cooling performance of a bilayer (500 µm thick SPDMS2.0 + 200 µm thick CBP) was evaluated by well-established methods ( Figure S21, Supporting Information). [23] In cold weather, the bilayer achieves a neat increase of ≈18 °C in subambient temperature from 9:00 am to 12:00 noon under an average solar intensity (I solar ) of ≈795 W m −2 at an ambient temperature of ≈10 °C (Figure 4a). The same sample was then converted to the porous state for cooling in hot weather with an ambient air temperature of ≈35 °C (see Figure S22 in the Supporting Information for the measurement setup).…”

Section: Doi: 101002/adma202000870mentioning

confidence: 99%

“…All-day radiation constitutes a powerful energy-saving method for summer cooling. [19][20][21][22][23][24][25] Recent studies have suggested that introducing light scattering particles/cavities into a polymer matrix can increase passive daytime radiative cooling by reflecting solar radiation. [26][27][28][29] Such materials should be designed to reflect the light in the wavelength (λ) range of ≈0.3-2.5 µm but allow thermal emission into the cold outer space through the atmospheric longwave infrared (LWIR) transmission window (λ ≈ 8-13 µm).…”

Section: Doi: 101002/adma202000870mentioning

confidence: 99%

Switchable Cavitation in Silicone Coatings for Energy‐Saving Cooling and Heating

et al. 2020

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Space cooling and heating currently result in huge amounts of energy consumption and various environmental problems. Herein, a switching strategy is described for efficient energy‐saving cooling and heating based on the dynamic cavitation of silicone coatings that can be reversibly and continuously tuned from a highly porous state to a transparent solid. In the porous state, the coatings can achieve efficient solar reflection (93%) and long‐wave infrared emission (94%) to induce a subambient temperature drop of about 5 °C in hot weather (≈35 °C). In the transparent solid state, the coatings allow active sunlight permeation (95%) to induce solar heating to raise the ambient temperature from 10 to 28 °C in cold weather. The coatings are made from commercially available, cheap materials via a facile, environmentally friendly method, and are durable, reversible, and patternable. They can be applied immediately to various existed objects including rigid substrates.

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“…Once the liquid solidifies, radiation can no longer escape to space, so the cooling effect is cut off. And last October, Mandal and Yang reported another way to stop overcooling 10 . If they fill the pores of their polymer coating with isopropanol, the coating starts to trap heat rather than shed it.…”

Section: Keeping Their Coolmentioning

confidence: 99%

The super-cool materials that send heat to space

Lim¹

2019

Nature

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W hen businessman Howard Bisla was tasked with saving a local shop from financial ruin, one of his first concerns was energy efficiency. In June 2018, he approached his local electricity provider in Sacramento, California, about upgrading the lights. The provider had another idea. It offered to install an experimental cooling system: panels that could stay colder than their surroundings, even under the blazing hot sun, without consuming energy. The aluminium-backed panels now sit on the shop's roof, their mirrored surfaces coated with a thin cooling film and angled to the sky. They cool liquid in pipes underneath that run into the shop, and, together with new lights, have reduced electricity bills by around 15%. "Even on a hot day, they're not hot," Bisla says. The panels emerged from a discovery at Stanford University in California. In 2014, researchers there announced that they had created a material that stayed colder than its surroundings in direct sunlight 1. Two members of the team, Shanhui Fan and Aaswath Raman, with colleague Eli Goldstein, founded a start-up firm, SkyCool Systems, and supplied Bisla's panels. Since then, they and other researchers have made a host of materials, including films, spray paints and treated wood, that stay cool in the heat. These materials all rely on enhancing a natural heat-shedding effect known as passive radiative cooling. Every person, building and object on Earth radiates heat, but the planet's JYOTIRMOY MANDAL A thermal image of a panel with a 'super-cool' coating outside Columbia University in New York City.

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Porous Polymers with Switchable Optical Transmittance for Optical and Thermal Regulation

Cited by 237 publications

References 28 publications

Scalable Flexible Hybrid Membranes with Photonic Structures for Daytime Radiative Cooling

Scalable Flexible Hybrid Membranes with Photonic Structures for Daytime Radiative Cooling

Switchable Cavitation in Silicone Coatings for Energy‐Saving Cooling and Heating

The super-cool materials that send heat to space

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