Recovering solar energy by photochemical isomerisation - of a trans isomer to the cis form, then converting it back exothermically

摘要

Exploitation and recovery of solar energy comprises (i) exposing the trans isomer of a cpd. (I) to sunlight to convert much of it to the cis form. (ii) heating the cis-(I) to a sufficient temp. to initiate conversion back to trans-(I) with release of thermal energy and (iii) continuing the conversion without furtehr introduction of energy using a part of the liberated energy to effect the conversion while the rest is used elsewhere for other purposes. Trans-(I) is dissolved and/or dispersed in an aq. liq. contg. >=50 vol % water and is isomerised by exposure to light of wavelength 350-1200 nm. The absorption max. in sunlight, of trans-(I) is at 350-800 nm while at of cis-(I) is at shorter wavelengths. The photochemical reaction is efficient and occurs with min. deterioration. The solar energy can be stored as cis (I) until needed. Typical (I) include N,N'-diacetylindigo, stilbene or 3,3'-diethyloxacyanine iodide.