We have investigated the switching mechanisms of photochromic systems that are relevant for harvesting,storing, and releasing solar energy. We consider storage of solar energy in the form of energeticchemical bonds via light-induced isomerization reactions. The approach concerns photoswitches thatupon irradiation isomerize to high-energy metastable isomers and through the corresponding back-reaction will release the stored energy. Thereby, we have considered molecular closed-cycle energystorage systems that do not involve the release of CO2. We present potential energy surfaces for groundstates and excited states and discuss the roles that these states play when harvesting, storing, andreleasing solar energy. Furthermore, we have illustrated new approaches for obtaining synergy betweentheoretical modeling and future experimental work.