I had a system like this more than 10 years ago, sold by Sharper Image, you can still find them on eBay: https://www.ebay.com/c/1708057939 https://www.ebay.com

I had a system like this more than 10 years ago, sold by Sharper Image, you can still find them on eBay: https://www.ebay.com/c/1708057939 https://www.ebay.com/c/1708057939 It has metal plates that touch the sides of the neck and a Peltier heat exchanger with fan on the back. A pack of four C cells was worn on a belt at your waist or slung over your shoulder. It claimed to work by cooling the blood in the veins at the side of the neck, so your blood distributed the cooling throughout your body. When set to High it would cool you down about 5 to 10 degrees F (perceived air temperature, it wouldn't actually cool your body by that much or you'd be dead). The batteries would only last an hour or two at the high setting. At a lower setting they'd last much longer but the cooling effect was much less. It worked but I didn't use it often because it was uncomfortable to have cold metal plates touching the sides of the neck and the fan was noisy. After a years use it just stopped working. Perhaps there is a major vein at the base of the neck to transport the coolness to other parts of the body? Or maybe the spinal columns fluid does the heat transfer? There is indeed research showing that if you cool a persons wrist you can change their temperature perception, and it has been turned into a product: https://www.electronicsweekly.com/news/business/peltier-effect-beats-heat-2018-07/ https://www.electronicsweekly.com/news/business/peltier-effe... I don't think the principal is the same as this Sony device though. To change perception requires much less energy than that required to actually cool the body, and if they could do that on the wrist with a smaller device why build a bigger device that requires a special shirt to hold the device at the base of the neck? For energy efficiency a personal air conditioner makes a lot of sense, why cool a whole building when you can just cool the people in it? Everyone can adjust their own temperature then also.