It is getting hot this week in the east of North America, going up to to the high eighties (°F, 303°K, 30°C) in New York. Backpacks can make you feel even hotter, as they insulate your back and prevent evaporation of sweat, so you end up wet and sticky. So call up the Japan Trend Shop and order your Kucho Air-Conditioned Backpack Cooling Pack.
It is not actually a backpack; it is strapped onto your pack and sits between your pack and your back. And it's not really air conditioning; a fan powered by four AA batteries pushes air through vents in the cooling pack, which increases evaporation of sweat, which cools your back. Every four hours (at high setting) you need another four batteries.
The Thermographic photo shows that it is quite effective, although they do not tell us the relative humidity when the photos were taken. On a very humid day one will feel far less evaporation and cooling.
But I find it fascinating that they think one needs to throw batteries at a problem to solve it. I have a few German Deuter backpacks that I bought when a sporting goods chain went bankrupt a few years ago (they are expensive) ; they all have what they call an aircomfort cooling system where an open mesh sits against by back and the pack itself is a few inches away. It is very effective and comfortable; I have always wondered why every company didn't do this. Perhaps it is because the metal stays that curve the back of the pack away from my body take up space and add weight. But it still proves that there are alternatives to batteries.
We have shown other crazy Japanese inventions to keep cool, in related links below.