# US 10,865,336 B2 · Polymer based solid-state solar thermal fuels

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- Number: US 10,865,336 B2
- Document ID: US10865336B2
- Status: Granted
- Kind: B2
- Application number: 16/060,944
- Filed: 2016-12-11
- Published: 2018-12-13
- Granted: 2020-12-15
- Earliest claimed: 2015-12-10
- Assignees: Massachusetts Institute of Technology
- Applicants: Massachusetts Institute of Technology
- Inventors: Jeffrey C. Grossman; David Zhitomirsky
- Web page: https://patentgrep.com/patent/US10865336B2

## CPC

- C09K 5/14: Solid materials, e.g. powdery or granular
- F24S 21/00: Solar heat collectors not provided for in groups F24S10/00-F24S20/00
- F24S 60/00: Arrangements for storing heat collected by solar heat collectors (working fluids forming pools or ponds F24S10/10)
- F24S 60/20: using chemical reactions, e.g. thermochemical reactions or isomerisation reactions
- F24S 80/20: Working fluids specially adapted for solar heat collectors
- F28D 20/003: {using thermochemical reactions}
- Y02E 10/40: Solar thermal energy, e.g. solar towers
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- F24S: SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS (for producing mechanical power from solar energy F03G6/00)
- F28D: HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT (fluid heaters having heat generating means and heat transferring means F24H; furnaces F27; details of heat-exchange apparatus of general)
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A polymer consisting of small functional molecules can be integrated into solar thermal fuels in the solid-state for solar energy harvesting and storage. In certain embodiments, a solar energy storage device can include one or more layers of photoswitchable moieties associated with a polymer. Such solar thermal fuel polymers can be used to enable deposition from low concentration solutions, resulting in uniform and large-area thin-films. This approach enables conformal deposition on a variety of conducting substrates that can be either flat or structured and control over film growth via electrodeposition conditions and results in highly uniform and large-area thin films.

## Claims

### Claim 1

An energy storage device comprising a solar thermal fuel including one of more layers of a plurality of photoswitchable moieties associated with a first polymer, wherein the plurality of photoswitchable moieties include a plurality of azobenzene moieties, a plurality of stilbene moieties, a plurality of norbornadiene moieties, or a plurality of spiropyran moieties, wherein the first polymer is a polystyrene or a polyolefin and wherein the energy storage device is in solid state.

### Claim 2 (depends on 1)

The energy storage device of claim 1, wherein the plurality of photoswitchable moieties are covalently linked to first polymer.

### Claim 3 (depends on 1)

The energy storage device of claim 1, wherein the first polymer is polystyrene.

### Claim 4 (depends on 1)

The energy storage device of claim 1, wherein the plurality of azobenzene moieties have formula (I):
wherein:
each R1, independently, is H, halo, hydroxy, nitro, cyano, amino, alkylamino, dialkylamino, —SO3H, alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy, cycloalkoxy, heterocyclyl, aryl, heteroaryl, heterocyclylalkyl, arylalkyl, heteroarylalkyl, —C(O)-alkyl, —C(O)-alkenyl, —C(O)— cycloalkyl, —C(O)-cycloalkenyl, —C(O)-alkoxy, —C(O)-cycloalkoxy, —C(O)-heterocyclyl, —C(O)-aryl, —C(O)-heteroaryl, —C(O)-heterocyclylalkyl, —C(O)-arylalkyl, or —C(O)-heteroarylalkyl;
each R2, independently, is H, halo, hydroxy, nitro, cyano, amino, alkylamino, dialkylamino, —SO3H, alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxy, cycloalkoxy, heterocyclyl, aryl, heteroaryl, heterocyclylalkyl, arylalkyl, heteroarylalkyl, —C(O)-alkyl, —C(O)-alkenyl, —C(O)— cycloalkyl, —C(O)-cycloalkenyl, —C(O)-alkoxy, —C(O)-cycloalkoxy, —C(O)-heterocyclyl, —C(O)-aryl, —C(O)-heteroaryl, —C(O)-heterocyclylalkyl, —C(O)-arylalkyl, or —C(O)-heteroarylalkyl;
a is 0, 1, 2, 3 or 4;
b is 0, 1, 2, 3, 4, or 5; and
- represents an optional covalent link to the first polymer.

### Claim 5 (depends on 1)

The energy storage device of claim 1, wherein the photoswitchable moieties are converted from a lower-energy state to a higher-energy metastable state upon UV illumination.

### Claim 6 (depends on 1)

The energy storage device of claim 1, wherein the photoswitchable moieties are reverted from a higher-energy metastable state to a lower-energy state by a trigger.

### Claim 7 (depends on 6)

The energy storage device of claim 6, wherein reverting from a higher-energy state to a lower-energy metastable state upon an external trigger induces heat release.

### Claim 8 (depends on 7)

The energy storage device of claim 7, wherein reverting from a higher-energy state to a lower-energy metastable state includes isomerization of the photoswitchable moieties.

### Claim 9 (depends on 1)

The energy storage device of claim 1, wherein the first polymer is incorporated into a second polymer matrix.

### Claim 10

An energy storage device comprising a solar thermal fuel including one of more layers of a plurality of photoswitchable moieties associated with a first polymer, wherein the plurality of photoswitchable moieties include a plurality of azobenzene moieties, a plurality of stilbene moieties, a plurality of norbornadiene moieties, or a plurality of spiropyran moieties, wherein the energy storage device is in solid state, wherein the first polymer is incorporated into a second polymer matrix and wherein the first polymer and the second polymer are crosslinked.

### Claim 11 (depends on 9)

The energy storage device of claim 9, wherein the second polymer includes acrylate.

### Claim 12 (depends on 1)

The energy storage device of claim 1, wherein the thickness of the one or more layers is between 100 nm and 100 μm.

### Claim 13 (depends on 1)

The energy storage device of claim 1, wherein the photoswitchable moieties are functionalized.

### Claim 14 (depends on 1)

The energy storage device of claim 1, wherein a plurality of ionizable moieties are associated with the first polymer.

### Claim 15 (depends on 14)

The energy storage device of claim 14, wherein the ionizable moieties includes carboxyl groups.

### Claim 16 (depends on 1)

The energy storage device of claim 1, further comprising a substrate, wherein the substrate is coated with the solar thermal fuel.

### Claim 17 (depends on 16)

The energy storage device of claim 16, wherein the substrate includes a conducting material.

### Claim 18 (depends on 16)

The energy storage device of claim 16, wherein the substrate includes a metal wire.

### Claim 19 (depends on 18)

The energy storage device of claim 18, wherein the metal wire is incorporated into a fabric.

### Claim 20 (depends on 16)

The energy storage device of claim 16, wherein the substrate includes indium tin oxide.

### Claim 21 (depends on 1)

The energy storage device of claim 1, wherein the solar thermal fuel further includes a binder.

### Claim 22

A method of storing cyclable energy comprising:
providing an energy storage device comprising a solar thermal fuel including a plurality of photoswitchable moieties associated with a first polymer, wherein the plurality of photoswitchable moieties include a plurality of azobenzene moieties, a plurality of stilbene moieties, a plurality of norbornadiene moieties, or a plurality of spiropyran moieties, wherein the first polymer is a polystyrene or a polyolefin and wherein the energy storage device is in solid state;
illuminating the plurality of photoswitchable moieties, thereby converting the photoswitchable moieties to from a lower-energy state to a higher-energy metastable state;
storing the plurality of photoswitchable moieties in the higher-energy metastable state for a period of time; and
providing a trigger to cause the plurality of photoswitchable moieties to revert to the lower-energy state.

### Claim 23 (depends on 22)

The method of claim 22, further comprising releasing heat.

### Claim 24 (depends on 22)

The method of claim 22, wherein converting the photoswitchable moieties to from a lower-energy state to a higher-energy metastable state includes isomerization of the photoswitchable moieties.

### Claim 25

A method of manufacturing an energy storage device comprising:
providing a substrate;
depositing a layer of a first polymer solution on the substrate, a plurality of photoswitchable moieties associated with the first polymer, wherein the plurality of photoswitchable moieties include a plurality of azobenzene moieties, a plurality of stilbene moieties, a plurality of norbornadiene moieties, or a plurality of spiropyran moieties, wherein the first polymer is a polystyrene or a polyolefin; and
solidifying the layer.

### Claim 26 (depends on 25)

The method of claim 25, further comprising repeating depositing a layer of a first polymer solution on the substrate, a plurality of photoswitchable moieties associated with the first polymer and solidifying the layer.

### Claim 27 (depends on 25)

The method of claim 25, further comprising charging the device with UV illumination.

### Claim 28 (depends on 25)

The method of claim 25, wherein solidifying includes UV curing.

### Claim 29 (depends on 25)

The method of claim 25, wherein the first polymer solution further includes a second polymer, wherein the first polymer and the second polymer form crosslinks upon UV illumination.

### Claim 30 (depends on 25)

The method of claim 25, wherein depositing includes tape-casting, drop-casting or spin-coating.

### Claim 31 (depends on 25)

The method of claim 25, wherein depositing includes electrodeposition.

### Claim 32 (depends on 31)

The method of claim 31, wherein the first solution is dissolved in an electrolyte.

### Claim 33 (depends on 32)

The method of claim 32, wherein the first solution further includes water.