I meant collect natural sunlight, like a solar panel, and then have a controlled release/burn; so set up a spell on a carryable object to collect sunlight naturally (day duration), and then have it release it at the same rate once night falls. Or alternately release it all at once - but that would probably require some sort of watching ward. Personally, I allow non-ritual watching wards (as the effect specifically says that the ritual part is due to the non-deterministic nature of the ward) - so if you wanted to make a Concentration or Circle/Ring watching ward, you could; or even one that releases it all at a certain time of the evening.