Alternative roof air conditioning systems, availability and fitment

[ducksface]

I was in Phoenix today and noticed some very sleek, low profile, AC units on school busses. Some were carrier, some were other brands. Long and wide, maybe four feet long and three feet wide, but only about 8 inches high.

I also saw the old school system in the picture.
On line info is sporadic and sparse, as if I'm expected to have background information.

What powers these, where can I find a selection, are they sensical to install, has anyone installed one?

[16ACE27]

Google is your friend:

https://www.webasto-comfort.com/int/...g-35-to-62-kw/