I bought a simple D10cm USB fan some time ago. I was surprised at the air flow from this rather cheap high quality fan was so good. At times when the heat is to high. A fan is absolutely necessary.
Since there exist larger diameter fans. From 10,13 to 18 cm. I wonder if they could be used in emergency situations. For field hospital like situations. Where there is no access to reliable electricity. These fans can run on a limited amount of solar power. Rated at 2.5watts 0.5A 5V. I could have 3x18cm USB fans on separate powerbanks. Thats a 54cm fan on battery power.
Hmm could this work?