Molecular solar thermal energy storage in Dewar pyrimidone beyond 1.6 megajoules per kilogram
Upon excitation at 300 nm, pyrimidones underwent valence isomerization to form the corresponding Dewar isomers.
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Addition of hydrochloric acid (HCl) to Dewar pyrimidone (107 mg in 0.46 ml of water) increased the solution temperature to 100°C and induced boiling within 1 s, demonstrating rapid macroscopic heat transfer to an environmentally benign medium under ambient conditions.
There's an article circulating about a new way of long-term energy storage which just about might be practical enough to gain traction. :)
An isomer of pyrimidone is charged with 300 nanometer UVB light, and energy is released in a water solution by changing the pH of the solution.