Here is such a simple, but very useful fan we will do.
I took 4 120 mm coolers. I had two and two I bought.
Glued the whole thing for 10 minutes with super glue.
Powered by charging a cell, i.e. from 5 volts.
Lovely! A wonderful breeze immediately pleased me. I tried to connect to 12 volts - and I thought that it was too much - the wind is like a normal fan at maximum power, i.e. pretty strong. I decided to stay at 5 volts.
This design has a number of advantages compared to a conventional fan. The main thing is small-sized, put it in a bag and carry wherever you want. Put in the window, you want to blow, you want to blow. I actually did it from the very beginning for a window leaf and did.