Debunked by EEV Blog and Thunderfoot, et al.

Isn’t this likely to add to global warming by adding huge amounts of heat into the atmosphere at night, when it would normally be radiating it away?

It also has the potential to disrupt local ecosystems with light and heat pollution.

Yup, you're essentially unbalancing the surface area of the planet that gets hit vs that radiates the heat away on the night side. It will decrease the albedo of the planet significantly if it is ever deployed at scale.

Solar panels do this a little bit already, since they're dark and they collect a lot that is reflected back out, turning it into heat by using it.

More space trash sure doesn't seem the solution to sustainability