Passive thermal management using thermoresponsive hydrogel

Patent metadata

Field	Value
Publication number	US-11999152-B2
Application number	US-202117554177-A
Country	US
Kind code	B2
Filing date	Dec 17, 2021
Priority date	Dec 17, 2021
Publication date	Jun 4, 2024
Grant date	Jun 4, 2024

Abstract

A passive thermal management system and methods of using a thermoresponsive hydrogel coating configured to autonomously switch between a heating state and a cooling state based on ambient temperature. At temperature greater than a lower critical solution temperature of the thermoresponsive hydrogel, the thermoresponsive hydrogel coating becomes solar reflective and has enhanced radiative cooling ability to achieve daytime radiative cooling. At temperatures less than the lower critical solution temperature, the thermoresponsive hydrogel coating becomes transparent to facilitate absorption of solar radiation by sun absorber.

First claim

What is claimed is:

1. A passive thermal management system, comprising:
a substrate; and
a thermally responsive multilayer structure on the substrate, the thermally responsive multilayer structure including:
an inner porous layer on the substrate, wherein the inner porous layer serves as a water reservoir, and
an outer composite layer on the inner porous layer, the outer composite layer being composed of a thermally switchable sublayer and an optically absorptive sublayer, the thermally switchable sublayer configured to autonomously transition between a heating absorbing state and a heat dissipation state in response to a change in ambient temperature, the optically absorptive sublayer configured to absorb solar radiation; and

one or more encapsulating layers on the multilayer structure, wherein the at least one encapsulating layer is composed of an optically transparent material;
wherein the thermally switchable sublayer comprises a thermally responsive polymer hydrogel, and wherein the optically absorptive sublayer comprises a carbon-based material;
wherein at a temperature less than a lower critical solution temperature of the thermally switchable sublayer, the thermally switchable sublayer absorbs water from the water reservoir, and
wherein at a temperature greater than the lower critical solution temperature of the thermally switchable sublayer, the thermally switchable sublayer releases water to be absorbed by the water reservoir.

2. The passive thermal management system of claim 1 , wherein:
the thermally responsive polymer hydrogel comprises a thermochromic Poly(N-isopropylacrylamide (PNIPAM) hydrogel, and
the carbon-based material comprises graphite.

3. A passive thermal management system, comprising:
a substrate; and
a thermally responsive multilayer structure on the substrate, the thermally responsive multilayer structure including:
an inner porous layer on the substrate, wherein the inner porous layer serves as a water reservoir;
an outer composite layer on the inner porous layer, the outer composite layer being composed of a thermally switchable sublayer and an optically absorptive sublayer; and

an encapsulating layer comprising an optically transparent material formed on the multilayer structure;
wherein the thermally switchable sublayer comprises means for autonomously transitioning between a heating absorbing state and a heat dissipation state in response to a change in ambient temperature;
wherein the optically absorptive sublayer comprises means for absorbing solar radiation;
wherein at a temperature less than a lower critical solution temperature of the thermally switchable sublayer, the thermally switchable sublayer absorbs water from the water reservoir, and
wherein at a temperature greater than the lower critical solution temperature of the thermally switchable sublayer, the thermally switchable sublayer releases water to be absorbed by the water reservoir.

Assignees

• Toyota Eng & Mfg North America
• Univ Illinois

Inventors

• Joshi Shailesh N
• Xie Dajie
• Braun Paul

Classifications

• B32B5/18 Primary

  characterised by features of a layer {of} foamed material · CPC title

• B32B5/32

  at least two} layers being foamed {and next to each other · CPC title

• B32B37/14

  characterised by the properties of the layers · CPC title

• B32B2264/108

  Carbon, e.g. graphite particles · CPC title

• B32B2266/0257

  Polyamide · CPC title