Photochemical Phase Transitions Enable Coharvesting of Photon Energy and Ambient Heat for Energetic Molecular Solar Thermal Batteries That Upgrade Thermal Energy
Journal article, 2020

Discovering physicochemical principles for simultaneous harvesting of multiform energy from the environment will advance current sustainable energy technologies. Here we explore photochemical phase transitions - a photochemistry-thermophysics coupled regime - for coharvesting of solar and thermal energy. In particular, we show that photon energy and ambient heat can be stored together and released on demand as high-temperature heat, enabled by room-temperature photochemical crystal↔liquid transitions of engineered molecular photoswitches. Integrating the two forms of energy in single-component molecular materials is capable of providing energy capacity beyond that of traditional solar or thermal energy storage systems based solely on molecular photoisomerization or phase change, respectively. Significantly, the ambient heat that is harvested during photochemical melting into liquid of the low-melting-point, metastable isomer can be released as high-temperature heat by recrystallization of the high-melting-point, parent isomer. This reveals that photon energy drives the upgrading of thermal energy in such a hybrid energy system. Rationally designed small-molecule azo switches achieve high gravimetric energy densities of 0.3-0.4 MJ/kg with long-term storage stability. Rechargeable solar thermal battery devices are fabricated, which upon light triggering provide gravimetric power density of about 2.7 kW/kg and temperature increases of >20 °C in ambient environment. We further show their use as deicing coatings. Our work demonstrates a new concept of energy utilization - combining solar energy and low-grade heat into higher-grade heat - which unlocks the possibility of developing sustainable energy systems powered by a combination of natural sunlight and ambient heat.


Zhao Yang Zhang

Shanghai Jiao Tong University

Yixin He

Shanghai Jiao Tong University

Zhihang Wang

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Kasper Moth-Poulsen Group

Jiale Xu

Shanghai Jiao Tong University

Mingchen Xie

Shanghai Jiao Tong University

Peng Tao

Shanghai Jiao Tong University

Deyang Ji

Tianjin University

Kasper Moth-Poulsen

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Kasper Moth-Poulsen Group

Tao Li

Shanghai Jiao Tong University

Journal of the American Chemical Society

0002-7863 (ISSN) 1520-5126 (eISSN)

Vol. 142 28 12256-12264

Subject Categories

Energy Engineering

Energy Systems

Building Technologies





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9/1/2020 7