Heat and mass transfer in hygroscopic hydrogels

Díaz‐Marín, Carlos D.; Zhang, Lenan; Fil, Bachir El; Lu, Zhengmao; Alshrah, Mohammed; Grossman, Jeffrey C.; Wang, Evelyn N.

doi:10.1016/j.ijheatmasstransfer.2022.123103

Cited by 31 publications

(27 citation statements)

References 46 publications

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“…Since no change in the hydrogel weight was monitored at this stage, the temperature reduction was mainly attributed to the sensible heat required to raise hydrogel temperature. 22 For the following over 5 h, the cooling effect was maintained mainly by the latent heat of water evaporation. Because although the hydrogel temperature kept increasing, the increase rate was very small (∼1.5 °C/h).…”

Section: Composite Backplatementioning

confidence: 99%

“…In comparison, the heating plate attached with a 4 mm thick PAm/alginate-CaCl 2 hydrogel showed significantly lower temperature in the initial period (Figure c and Figure S7b). Since no change in the hydrogel weight was monitored at this stage, the temperature reduction was mainly attributed to the sensible heat required to raise hydrogel temperature . For the following over 5 h, the cooling effect was maintained mainly by the latent heat of water evaporation.…”

Section: Fabrication and Characterization Of The Composite Backplatementioning

confidence: 99%

“…As illustrated in Figure 1d, we used a hydrogel containing hygroscopic salts (hygroscopic hydrogel) as the sorbent material, mainly due to its good scalability, low cost, and outstanding absorption capacity over a wide range of relative humidity (RH). 22 The hydrogel serves as a porous and hydrophilic substrate, providing numerous channels for moisture transport and storage of water and hygroscopic salts.…”

Section: Composite Backplatementioning

confidence: 99%

“…18−20 Due to the large evaporation enthalpy (>2000 J/g), water vapor could efficiently carry heat to the surroundings. 21,22 More importantly, the cooling capacity could be regenerated by capturing moisture from the ambient. This makes evaporative cooling require no water and energy input and thus become lightweight yet efficient, which has been demonstrated in the thermal management of electronic devices, 18,23 lithium-ion batteries, 24 buildings, 25,26 and PV panels.…”

mentioning

confidence: 99%

“…Motivated by mammals and plants that cool themselves by evaporating water, in recent years evaporative cooling technologies based on atmospheric water vapor adsorption materials get increasing attention. − Due to the large evaporation enthalpy (>2000 J/g), water vapor could efficiently carry heat to the surroundings. , More importantly, the cooling capacity could be regenerated by capturing moisture from the ambient. This makes evaporative cooling require no water and energy input and thus become lightweight yet efficient, which has been demonstrated in the thermal management of electronic devices, , lithium-ion batteries, buildings, , and PV panels .…”

mentioning

confidence: 99%

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A Hygroscopic Composite Backplate Enabling Passive Cooling of Photovoltaic Panels

et al. 2023

ACS Energy Lett.

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Cooling photovoltaics (PV) matters since elevated temperature reduces efficiency and lifetime, but it is a great challenge when simultaneously pursuing effective cooling, low material cost, and light extra components. We herein propose a composite backplate for the passive cooling of PV panels, which consists of hygroscopic hydrogels with an adsorption-evaporative cooling effect and protective membranes. Besides, instant tough bonding with conventional PV backsheet allows for the composite backplate ease of implementation. Consequently, the composite backplate demonstrates nondegrading cooling performance during multiday field tests. Compared to a normal PV panel with good ventilation conditions, the average temperature reduction of each day varies from 1.5 to 6.4 °C under different climate conditions, indicating the absolute energy yield would increase by 0.57% to 2.43% of the yield under 25 °C. Considering the nearly unchanged appearance, moderate weight increase, and low raw material costs, this composite backplate facilitates benefiting from cooling PV panels attainable.

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Section: Composite Backplatementioning

confidence: 99%

Section: Fabrication and Characterization Of The Composite Backplatementioning

confidence: 99%

Section: Composite Backplatementioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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A Hygroscopic Composite Backplate Enabling Passive Cooling of Photovoltaic Panels

et al. 2023

ACS Energy Lett.

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Moisture Absorbing and Water Self‐Releasing from Hybrid Hydrogel Desiccants

Nah,

Lee,

et al. 2023

Adv Funct Materials

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Atmospheric moisture is a valuable resource for fresh water and potentially sustainable energy. However, direct harvesting water from moisture (the vapor form) remains the most challenging. Hybrid desiccants made from hydrogels embedded with salt offer promise in absorbing moisture. However, the desorption process often requires additional energy to heat the samples. Here, poly(acrylic acid) (PAA) hydrogels embedded with lithium chloride are prepared, demonstratng simultaneous moisture absorption and self‐release of liquid water at room temperature with 50–90% relative humidity. The water self‐releasing process can be separated into two distinct stages: 1) surface release, where water droplets grow on the hydrogel surface due to differences in nucleation and diffusion rates, and 2) bulk release, triggered by the collapse of polymer chains, subsequently releasing water from the hydrogel network. Factors such as salt concentration, hydrogel crosslinking density, and film thickness are investigated to better understand the moisture absorption and water‐releasing processes. Moreover, hydrophobic domains are introduced onto the salt‐embedded PAA films, creating an edge effect that enhances the droplet growth rates. When the hydrophobic domains are patterned, the movement of released water can be guided, resulting in a threefold increase in water removal rate attributed to gravitational force.

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Unusual Temperature Dependence of Water Sorption in Semicrystalline Hydrogels

et al. 2023

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Water vapor sorption is a ubiquitous phenomenon in nature and plays an important role in various applications, including humidity regulation, energy storage, thermal management, and water harvesting. In particular, capturing moisture at elevated temperatures is highly desirable to prevent dehydration and to enlarge the tunability of water uptake. However, owing to the thermodynamic limit of conventional materials, sorbents inevitably tend to capture less water vapor at higher temperatures, impeding their broad applications. Here, an inverse temperature dependence of water sorption in poly(ethylene glycol) (PEG) hydrogels, where their water uptake can be doubled with increasing temperature from 25 to 50 °C, is reported. With mechanistic modeling of water-polymer interactions, this unusual water sorption is attributed to the first-order phase transformation of PEG structures, and the key parameters for a more generalized strategy in materials development are identified. This work elucidates a new regime of water sorption with an unusual temperature dependence, enabling a promising engineering space for harnessing moisture and heat.

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Heat and mass transfer in hygroscopic hydrogels

Cited by 31 publications

References 46 publications

A Hygroscopic Composite Backplate Enabling Passive Cooling of Photovoltaic Panels

A Hygroscopic Composite Backplate Enabling Passive Cooling of Photovoltaic Panels

Moisture Absorbing and Water Self‐Releasing from Hybrid Hydrogel Desiccants

Unusual Temperature Dependence of Water Sorption in Semicrystalline Hydrogels

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