I believe there are "sun sensors", and they come down to block the sun and the heat, to make the building more "energy efficient" so you don't use as much A/C.
I'd also assume there are manual overrides in each unit, just in case you don't like living in the dark, and having to turn on lights during the day, if you're home.
Quite a few buildings have them, but I've never heard of them being forced upon a residential building
Singapore Changi Airport uses them to prevent the big glass terminal from becoming (more of) a Greenhouse.
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