http://www.smh.com.au/news/World/Japan-designer-makes-selfcooling-shirts/2007/08/19/1187462056200.html

Self-cooling clothes may seem like the stuff of science fiction, but for one Japanese company they are not only good business but a way to help the environment.

Shirts and jackets made by Kuchou-fuku - literally "air-conditioned clothes" - keep the wearer comfortable even in sweltering heat while using one-50th of the energy of a small air conditioner, said Hiroshi Ichigaya, the company's CEO.

"Until now, air-conditioning implied cooling the entire room. Now, we can cool just the body," Ichigaya said.

Two small fans sewn into the back of each garment and powered by a pocket-sized rechargeable battery pack circulate air across the wearer's skin, evaporating perspiration and keeping temperatures down - a welcome respite from Japan's mid-summer humidity and record-breaking heat in recent days.

But however cool the clothes, they seem unlikely to catch on any time soon. Because the fans puff out the garments with air, they give wearers a deceptively portly look.

one of my ideas was a self cooling hat.
Solar panels on top of the hat power the peltier devices inside it. It'ld cost about $400 to make.
Problems are the current supply from the solar panels (small ones) is too small for the peltier.
Powering a small fan takes less power, so would help lots.

Better to cool (move air) by vacuum than blowing.
So sucking air out of the hat/shirt is much more effective.
Most heat generated in head, cool that and it is ok.

The problem with using a vacuum is that the shirt would then stick to you and close of the airflow.

I've seen hats with solar powered fans on them. They are not cool.

prob have to have the fan inside the hat

Could put a digital thermoneter in it too, with the display outside. For the proud geeks :-)

Obviously never took off.

Can you get them in colours that match your propeller hat? Do they have a pocket protector?