Efficient cycling utilization of solar-thermal energy for thermochromic displays with controllable heat output

Yang, Weixiang; Feng, Yiyu; Si, Qianyu; Yan, Qinghai; Peng, Long; Dong, Liqi; Fu, Linxia; Feng, Wei

doi:10.1039/c8ta05333b

Cited by 91 publications

(60 citation statements)

References 46 publications

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“…For ideal solar heating, it is expected the material has high absorption in 200-2500 nm and low emissivity in >2500 nm 7 . Prior research efforts for both solar heating [8][9][10][11] and radiative cooling [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] have yielded both high technological performance and deep scientific understanding, which spans from a variety of fields, including materials science, photonics and plasmonics, and heat transfer. However, they are mostly static or quasi-dynamic devices, which cannot completely solve the dynamic heating and cooling demand problem effectively, especially in the daytime [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] .…”

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confidence: 99%

Integration of daytime radiative cooling and solar heating for year-round energy saving in buildings

et al. 2020

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The heating and cooling energy consumption of buildings accounts for about 15% of national total energy consumption in the United States. In response to this challenge, many promising technologies with minimum carbon footprint have been proposed. However, most of the approaches are static and monofunctional, which can only reduce building energy consumption in certain conditions and climate zones. Here, we demonstrate a dual-mode device with electrostatically-controlled thermal contact conductance, which can achieve up to 71.6 W/m2 of cooling power density and up to 643.4 W/m2 of heating power density (over 93% of solar energy utilized) because of the suppression of thermal contact resistance and the engineering of surface morphology and optical property. Building energy simulation shows our dual-mode device, if widely deployed in the United States, can save 19.2% heating and cooling energy, which is 1.7 times higher than cooling-only and 2.2 times higher than heating-only approaches.

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confidence: 99%

Integration of daytime radiative cooling and solar heating for year-round energy saving in buildings

et al. 2020

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“…The broad exothermic peak in a heating curve arose from the thermally induced cis→trans isomerization in the melt, which revealed ΔHisom of 160-190 J/g (consistent with the molar enthalpy of 52 kJ/mol), falling in the range of the attainable energy density by azobenzene compounds (< 200 J/g). [5a,6a,18] Little exothermicity was observed below 80 o C and the exothermic peak temperatures were as high as ~135 o C, manifesting the very high storage stability of our molecular materials compared to that of the reported solar thermal batteries, including small-molecule azobenzenes, [18] azopolymers, [19][20][21][22] nanocarbon-templated azobenzene hybrids, [23] and phase-changeable ionic azo materials. [16] The sharp exothermic peak in a cooling curve represents the rapid transition from trans-liquid to trans-crystal, and it provides ΔHcryst of about 140-210 J/g.…”

Section: Resultsmentioning

confidence: 93%

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

Zhang¹,

2019

Preprint

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Solar energy and ambient heat are two inexhaustible energy sources for addressing the global challenge of energy and sustainability. Solar thermal battery based on molecular switches that can store solar energy and release it as heat has recently attracted great interest, but its development is severely limited by both low energy density and short storage stability. On the other hand, the efficient recovery and upgrading of low-grade heat, especially that of the ambient heat, has been a great challenge. Here we report that solar energy and ambient heat can be simultaneously harvested and stored, which is enabled by room-temperature photochemical crystal-to-liquid transitions of small-molecule photoswitches. The two forms of energy are released together to produce high-temperature heat during the reverse photochemical phase change. This strategy, combined with molecular design, provides high energy density of 320-370 J/g and long-term storage stability (half-life of about 3 months). On this basis, we fabricate high-performance, flexible film devices of solar thermal battery, which can be readily recharged at room temperature with good cycling ability, show fast rate of heat release, and produce high-temperature heat that is >20<sup> o</sup>C higher than the ambient temperature. Our work opens up a new avenue to harvest ambient heat, and demonstrate a feasible strategy to develop high-performance solar thermal battery.

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“…The solar energy storage of the composite in this study is driven by azobenzene‐based isomerization and phase change. Compared with the pure azobenzene derivatives as solar thermal fuel, this energy density is higher [13b,c,14,25] (Figure 4b). The approaches to improve the energy density by grafting and polymerization increase the energy barrier of isomerization, as a result decreasing the isomerization extent (Δ ξ ) and isomerization speed (release speed).…”

Section: Resultsmentioning

confidence: 99%

“…a) Energy release obtained by DSC and calculated on the charged C 14 OH@C 14 Azo with various mole ratios in the exothermic and endothermic process, including of phase change and isomerization. b) A comparison of the energy density from the latest reports: ○ , Azo‐based hybrid; [10b,c,11b,13a] □ , mono‐Azo‐based material; [13b,c,14,25a] ▽ , composites of Azo and PCM; [5a,6a] ☆ , this paper. c) Possible energy storage mechanism.…”

Section: Resultsmentioning

confidence: 99%

“…Color directly endows a visual representation for the information transmission, e.g., traffic light and battery indicator on the phone. The color change has been applied to monitor the specific temperature during energy release, [ 14 ] while monitoring energy state at any given time remains significantly challenging for developing STF. Thus, a visible solar thermal fuel (VSTF) is presented, which is defined as a STF with a visual parameter for monitoring energy state, throughout the charging and discharging process.…”

Section: Introductionmentioning

confidence: 99%

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A Visible Energy Management by Photochromic Solar Thermal Fuel Using a Color Display

et al. 2020

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Photocontrolled solar thermal fuel offers enormous potential for light harvesting, storage, and thermal management. Monitoring energy storage process still remains significantly challenging with an evident and convenient display. Inspired by the battery indicator on the phone with color variation, a visible solar thermal fuel (VSTF) is designed by compositing photochromic azobenzene with organic phase change materials. This is an efficient strategy for improving renewable energy storage capacity without solvent assistance, and displaying the energy storage process. The photochromic dopant enables color change due to varying light‐absorption wavelengths with the conformational change. Notably, the energy release situation of charged composite under sunlight stimuli is demonstrated to heat water, showing about 4 °C higher than that of the uncharged one. The color difference depends on the isomerization extent (trans %) which links to the energy storage parameters. It has potential to display the energy storage process and utilize the energy more efficiently.

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Efficient cycling utilization of solar-thermal energy for thermochromic displays with controllable heat output

Abstract: Photo-thermal energy cycles for thermochromic displays with control of heat output.

Cited by 91 publications

References 46 publications

Integration of daytime radiative cooling and solar heating for year-round energy saving in buildings

Integration of daytime radiative cooling and solar heating for year-round energy saving in buildings

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

A Visible Energy Management by Photochromic Solar Thermal Fuel Using a Color Display

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