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High Throughput Virtual Screening of 230 Billion Molecular Solar Heat Battery Candidates

preprint
revised on 08.07.2020 and posted on 08.07.2020 by Mads Koerstz, Anders S. Christensen, Kurt V. Mikkelsen, Mogens Brøndsted Nielsen, Jan H. Jensen
The dihydroazulene/vinylheptafulvene (DHA/VHF) thermocouple is a promising can- didate for thermal heat batteries that absorb and store solar energy as chemical energy without the need for insulation. However, in order to be viable the energy storage capacity and lifetime of the high energy form (i.e. the free energy barrier to the back reaction) of the canonical parent compound must be increased significantly to be of practical use. We use semiempirical quantum chemical methods, machine learning, and density functional theory to virtually screen over 230 billion substituted DHA molecules to identify promis- ing candidates. We identify a molecule with a predicted energy density of 0.38 kJ/g, which is significantly larger than the 0.14 kJ/g computed for the parent compound. The free energy barrier to the back reaction is 11 kJ/mol higher than the parent compound, which should correspond to a half-life of about 10 days - 4 months. This is considerably longer than the 3-39 hours (depending on solvent) observed for the parent compound and sufficiently long for many practical applications. However, the main conclusion of this study is that there are no molecules among the 230 billion with a storage density approaching 1 kJ/g.

Funding

Swiss National Science Foundation

VILLUM Foundation

History

Email Address of Submitting Author

jhjensen@chem.ku.dk

Institution

University of Copenhagen

Country

Denmark

ORCID For Submitting Author

0000-0002-1465-1010

Declaration of Conflict of Interest

no conflict of interest

Version Notes

New data and more or less rewritten

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